_On to the Asteroid_ by Travis Taylor and Les Johnson

[Lynn McGuire]

_On to the Asteroid_ by Travis Taylor and Les Johnson
https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/

Book number two of a two book space opera series. I read the
excellently printed and bound MMPB by Baen.

In the middle of the 2020s, there is a space race going on with China,
NASA, and an American private space touring firm. Another firm seeks to
get into the space business by secretly bringing a metals rich asteroid
to Earth using an electric thruster system. The electric thruster
system fails midway to Earth and the asteroid will hit the Earth rather
than going into orbit around it since there is not a backup thruster
system. Since the asteroid is a mile long by a quarter mile in
diameter, the asteroid's path must be changed.

Please note this little series is very hard science fiction. All of
this is possible today using today's technology and materials. And, a
LOT of money.

My rating: 4.4 out of 5 stars
Amazon rating: 3.5 out of 5 stars (21 reviews)

Lynn

[Robert Carnegie]

Post by Lynn McGuire
_On to the Asteroid_ by Travis Taylor and Les Johnson
https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/
Book number two of a two book space opera series. I read the
excellently printed and bound MMPB by Baen.
In the middle of the 2020s, there is a space race going on with China,
NASA, and an American private space touring firm. Another firm seeks to
get into the space business by secretly bringing a metals rich asteroid
to Earth using an electric thruster system. The electric thruster
system fails midway to Earth and the asteroid will hit the Earth rather
than going into orbit around it since there is not a backup thruster
system. Since the asteroid is a mile long by a quarter mile in
diameter, the asteroid's path must be changed.
Please note this little series is very hard science fiction. All of
this is possible today using today's technology and materials. And, a
LOT of money.

Does this book include the lawsuits arising from the action
depicted, or is that what volume three will be about?

[Lynn McGuire]

Post by Robert Carnegie

Post by Lynn McGuire
_On to the Asteroid_ by Travis Taylor and Les Johnson
https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/
Book number two of a two book space opera series. I read the
excellently printed and bound MMPB by Baen.
In the middle of the 2020s, there is a space race going on with China,
NASA, and an American private space touring firm. Another firm seeks to
get into the space business by secretly bringing a metals rich asteroid
to Earth using an electric thruster system. The electric thruster
system fails midway to Earth and the asteroid will hit the Earth rather
than going into orbit around it since there is not a backup thruster
system. Since the asteroid is a mile long by a quarter mile in
diameter, the asteroid's path must be changed.
Please note this little series is very hard science fiction. All of
this is possible today using today's technology and materials. And, a
LOT of money.

Does this book include the lawsuits arising from the action
depicted, or is that what volume three will be about?

Just the arrest warrants in various states for killing 10,000+ people
across the USA. And the space asteroid entrepreneur is not even a USA
citizen or inhabitant. The key phrases here are "no backup thruster
system" and "secretly".

Lynn

[James Nicoll]

Post by Lynn McGuire
_On to the Asteroid_ by Travis Taylor and Les Johnson
https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/
Book number two of a two book space opera series. I read the
excellently printed and bound MMPB by Baen.
In the middle of the 2020s, there is a space race going on with China,
NASA, and an American private space touring firm. Another firm seeks to
get into the space business by secretly bringing a metals rich asteroid
to Earth using an electric thruster system. The electric thruster
system fails midway to Earth and the asteroid will hit the Earth rather
than going into orbit around it since there is not a backup thruster
system. Since the asteroid is a mile long by a quarter mile in
diameter, the asteroid's path must be changed.
Please note this little series is very hard science fiction. All of
this is possible today using today's technology and materials. And, a
LOT of money.

Oh, yes? How do they explain nobody noticing the geezy huge amount of
waste heat from the propulsion system required?

[Lynn McGuire]

Post by James Nicoll

Post by Lynn McGuire
_On to the Asteroid_ by Travis Taylor and Les Johnson
https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/
Book number two of a two book space opera series. I read the
excellently printed and bound MMPB by Baen.
In the middle of the 2020s, there is a space race going on with China,
NASA, and an American private space touring firm. Another firm seeks to
get into the space business by secretly bringing a metals rich asteroid
to Earth using an electric thruster system. The electric thruster
system fails midway to Earth and the asteroid will hit the Earth rather
than going into orbit around it since there is not a backup thruster
system. Since the asteroid is a mile long by a quarter mile in
diameter, the asteroid's path must be changed.
Please note this little series is very hard science fiction. All of
this is possible today using today's technology and materials. And, a
LOT of money.

Oh, yes? How do they explain nobody noticing the geezy huge amount of
waste heat from the propulsion system required?

From the rocket from the Earth to the asteroid ? From the electric
thrusters on the asteroid ?

Lynn

[James Nicoll]

Post by Lynn McGuire

Post by James Nicoll

Post by Lynn McGuire
_On to the Asteroid_ by Travis Taylor and Les Johnson
https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/
Book number two of a two book space opera series. I read the
excellently printed and bound MMPB by Baen.
In the middle of the 2020s, there is a space race going on with China,
NASA, and an American private space touring firm. Another firm seeks to
get into the space business by secretly bringing a metals rich asteroid
to Earth using an electric thruster system. The electric thruster
system fails midway to Earth and the asteroid will hit the Earth rather
than going into orbit around it since there is not a backup thruster
system. Since the asteroid is a mile long by a quarter mile in
diameter, the asteroid's path must be changed.
Please note this little series is very hard science fiction. All of
this is possible today using today's technology and materials. And, a
LOT of money.

Oh, yes? How do they explain nobody noticing the geezy huge amount of
waste heat from the propulsion system required?

From the rocket from the Earth to the asteroid ? From the electric
thrusters on the asteroid ?

Both, but esp the second.

[Lynn McGuire]

Post by James Nicoll

Post by Lynn McGuire

Post by James Nicoll

Post by Lynn McGuire
_On to the Asteroid_ by Travis Taylor and Les Johnson
https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/
Book number two of a two book space opera series. I read the
excellently printed and bound MMPB by Baen.
In the middle of the 2020s, there is a space race going on with China,
NASA, and an American private space touring firm. Another firm seeks to
get into the space business by secretly bringing a metals rich asteroid
to Earth using an electric thruster system. The electric thruster
system fails midway to Earth and the asteroid will hit the Earth rather
than going into orbit around it since there is not a backup thruster
system. Since the asteroid is a mile long by a quarter mile in
diameter, the asteroid's path must be changed.
Please note this little series is very hard science fiction. All of
this is possible today using today's technology and materials. And, a
LOT of money.

Oh, yes? How do they explain nobody noticing the geezy huge amount of
waste heat from the propulsion system required?

From the rocket from the Earth to the asteroid ? From the electric
thrusters on the asteroid ?

Both, but esp the second.

Space is big. Telescopes are small.

Lynn

[James Nicoll]

Post by James Nicoll

Post by Lynn McGuire

Post by James Nicoll

Post by Lynn McGuire
_On to the Asteroid_ by Travis Taylor and Les Johnson
https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/
Book number two of a two book space opera series. I read the
excellently printed and bound MMPB by Baen.
In the middle of the 2020s, there is a space race going on with China,
NASA, and an American private space touring firm. Another firm seeks to
get into the space business by secretly bringing a metals rich asteroid
to Earth using an electric thruster system. The electric thruster
system fails midway to Earth and the asteroid will hit the Earth rather
than going into orbit around it since there is not a backup thruster
system. Since the asteroid is a mile long by a quarter mile in
diameter, the asteroid's path must be changed.
Please note this little series is very hard science fiction. All of
this is possible today using today's technology and materials. And, a
LOT of money.

Oh, yes? How do they explain nobody noticing the geezy huge amount of
waste heat from the propulsion system required?

From the rocket from the Earth to the asteroid ? From the electric
thrusters on the asteroid ?

Both, but esp the second.

Wait, no: even before that: what are they powering the electric thrusters
with and how did they cram it into a rocket nobody seems to have taken
particular notice of, in a competitive environment? Because I get a mass
for the rock roughly 4x10^9 tonnes. They seem to be able to change its
velocity pretty quickly: let's say .01 m/s/s as a handwave. And
lets say the electric drive has an exhaust velocity of 100 km/s because
round number. In the first second, they throw 400 kg, each kg of which
has 5x10^9 J of Ek, for a total of 2x10^12 J. But they do this every
second so that's a power plant that even if it's perfectly efficient
at turning electricity into kinetic energy of reaction mass is significantly
more powerful than the most powerful reactor currently on Earth.

You can reduce the power demands by dialing down the exhaust velocity
but then you have to use more of the asteroid as reaction mass, if using
the asteroid as reaction mass is an option for this drive. At 10 km/s
they have to huck 4000 kg at 10,000 m/s and that only takes 5x10^7 J/kg
for a total of 2x10^11 J. I think. Doing this in my head. If they
do that every second, it's only about 200 GW so merely 20, 25 times
the power output of the largest nuclear reactors? Unless I dropped a
order of magnitude here or there.

If they can fit that into a rocket not of sufficient size to be
attention grabbing due to said size, why are they wasting their
time chasing rocks? Why not sell whatever it is they're using
for power? Does it run on the souls of foresaken children? Because
there are zoning work arounds for that.




10e

[Lynn McGuire]

Post by James Nicoll

Post by James Nicoll

Post by Lynn McGuire

Post by James Nicoll

Post by Lynn McGuire
_On to the Asteroid_ by Travis Taylor and Les Johnson
https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/
Book number two of a two book space opera series. I read the
excellently printed and bound MMPB by Baen.
In the middle of the 2020s, there is a space race going on with China,
NASA, and an American private space touring firm. Another firm seeks to
get into the space business by secretly bringing a metals rich asteroid
to Earth using an electric thruster system. The electric thruster
system fails midway to Earth and the asteroid will hit the Earth rather
than going into orbit around it since there is not a backup thruster
system. Since the asteroid is a mile long by a quarter mile in
diameter, the asteroid's path must be changed.
Please note this little series is very hard science fiction. All of
this is possible today using today's technology and materials. And, a
LOT of money.

Oh, yes? How do they explain nobody noticing the geezy huge amount of
waste heat from the propulsion system required?

From the rocket from the Earth to the asteroid ? From the electric
thrusters on the asteroid ?

Both, but esp the second.

Wait, no: even before that: what are they powering the electric thrusters
with and how did they cram it into a rocket nobody seems to have taken
particular notice of, in a competitive environment? Because I get a mass
for the rock roughly 4x10^9 tonnes. They seem to be able to change its
velocity pretty quickly: let's say .01 m/s/s as a handwave. And
lets say the electric drive has an exhaust velocity of 100 km/s because
round number. In the first second, they throw 400 kg, each kg of which
has 5x10^9 J of Ek, for a total of 2x10^12 J. But they do this every
second so that's a power plant that even if it's perfectly efficient
at turning electricity into kinetic energy of reaction mass is significantly
more powerful than the most powerful reactor currently on Earth.
You can reduce the power demands by dialing down the exhaust velocity
but then you have to use more of the asteroid as reaction mass, if using
the asteroid as reaction mass is an option for this drive. At 10 km/s
they have to huck 4000 kg at 10,000 m/s and that only takes 5x10^7 J/kg
for a total of 2x10^11 J. I think. Doing this in my head. If they
do that every second, it's only about 200 GW so merely 20, 25 times
the power output of the largest nuclear reactors? Unless I dropped a
order of magnitude here or there.
If they can fit that into a rocket not of sufficient size to be
attention grabbing due to said size, why are they wasting their
time chasing rocks? Why not sell whatever it is they're using
for power? Does it run on the souls of foresaken children? Because
there are zoning work arounds for that.

Sounds like you need to read the book. And duckduckgo "electric thrusters".

Lynn

[J. Clarke]

Post by James Nicoll

Post by Lynn McGuire
_On to the Asteroid_ by Travis Taylor and Les Johnson
https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/
Book number two of a two book space opera series. I read the
excellently printed and bound MMPB by Baen.
In the middle of the 2020s, there is a space race going on with China,
NASA, and an American private space touring firm. Another firm seeks to
get into the space business by secretly bringing a metals rich asteroid
to Earth using an electric thruster system. The electric thruster
system fails midway to Earth and the asteroid will hit the Earth rather
than going into orbit around it since there is not a backup thruster
system. Since the asteroid is a mile long by a quarter mile in
diameter, the asteroid's path must be changed.
Please note this little series is very hard science fiction. All of
this is possible today using today's technology and materials. And, a
LOT of money.

Oh, yes? How do they explain nobody noticing the geezy huge amount of
waste heat from the propulsion system required?

By what means would someone "notice" this "geezy huge amount of waste
heat"?

[Dan Tilque]

Post by J. Clarke

Post by James Nicoll

Post by Lynn McGuire
_On to the Asteroid_ by Travis Taylor and Les Johnson
https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/
Book number two of a two book space opera series. I read the
excellently printed and bound MMPB by Baen.
In the middle of the 2020s, there is a space race going on with China,
NASA, and an American private space touring firm. Another firm seeks to
get into the space business by secretly bringing a metals rich asteroid
to Earth using an electric thruster system. The electric thruster
system fails midway to Earth and the asteroid will hit the Earth rather
than going into orbit around it since there is not a backup thruster
system. Since the asteroid is a mile long by a quarter mile in
diameter, the asteroid's path must be changed.
Please note this little series is very hard science fiction. All of
this is possible today using today's technology and materials. And, a
LOT of money.

Oh, yes? How do they explain nobody noticing the geezy huge amount of
waste heat from the propulsion system required?

By what means would someone "notice" this "geezy huge amount of waste
heat"?

Infrared telescopes.

There's two different kinds of propulsion methods that go under the name
"electric thruster". One is ion engines. Currently, the ones in use use
Xenon gas as propellant, but it would be impossible to ship enough of
that to bring a large rock like that to Earth orbit. So you'd have to
use some of the rock itself as reaction mass. That would leave a large
cloud of warm ionized rock bits (whatever elements it's made of) behind.
That should show up in IR telescopes (especially orbital ones) as a
large unexplained blob. It also is likely to show up in visible light
scopes, depending on what elements are ionized in that cloud.

The other electric thruster is one that reacts against the Earth's
magnetic field. Currently, I don't think any spacecraft uses it, but
it's been demonstrated to work. It doesn't have ordinary reaction mass;
it expels electrons rather than atoms. I suppose one would work against
the Sun's magnetic field, but you'd need a truly massive amount of power
to change the orbit of a large rock. That means your power plant is
going to need some humongous radiators to keep from overheating. Those
should be big enough and warm enough to show in IR telescopes.

Space is rather noisy in the IR range. An ordinary spaceship at an AU or
so distance might be able to hide in that noise. But this is much larger
than an ordinary spaceship.

[J. Clarke]

Post by Dan Tilque

Post by J. Clarke

Post by James Nicoll

Post by Lynn McGuire
_On to the Asteroid_ by Travis Taylor and Les Johnson
https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/
Book number two of a two book space opera series. I read the
excellently printed and bound MMPB by Baen.
In the middle of the 2020s, there is a space race going on with China,
NASA, and an American private space touring firm. Another firm seeks to
get into the space business by secretly bringing a metals rich asteroid
to Earth using an electric thruster system. The electric thruster
system fails midway to Earth and the asteroid will hit the Earth rather
than going into orbit around it since there is not a backup thruster
system. Since the asteroid is a mile long by a quarter mile in
diameter, the asteroid's path must be changed.
Please note this little series is very hard science fiction. All of
this is possible today using today's technology and materials. And, a
LOT of money.

Oh, yes? How do they explain nobody noticing the geezy huge amount of
waste heat from the propulsion system required?

By what means would someone "notice" this "geezy huge amount of waste
heat"?

Infrared telescopes.

Which are, in your view, constantly pointed at all areas of the sky.

Post by Dan Tilque
There's two different kinds of propulsion methods that go under the name
"electric thruster". One is ion engines. Currently, the ones in use use
Xenon gas as propellant, but it would be impossible to ship enough of
that to bring a large rock like that to Earth orbit. So you'd have to
use some of the rock itself as reaction mass. That would leave a large
cloud of warm ionized rock bits (whatever elements it's made of) behind.
That should show up in IR telescopes (especially orbital ones) as a
large unexplained blob. It also is likely to show up in visible light
scopes, depending on what elements are ionized in that cloud.

Why would they be pointed in that direction? Is there something else
intrinsically interesting about this rock that would lead someone to
be watching it?

Post by Dan Tilque
The other electric thruster is one that reacts against the Earth's
magnetic field. Currently, I don't think any spacecraft uses it, but
it's been demonstrated to work. It doesn't have ordinary reaction mass;
it expels electrons rather than atoms. I suppose one would work against
the Sun's magnetic field, but you'd need a truly massive amount of power
to change the orbit of a large rock. That means your power plant is
going to need some humongous radiators to keep from overheating. Those
should be big enough and warm enough to show in IR telescopes.
Space is rather noisy in the IR range. An ordinary spaceship at an AU or
so distance might be able to hide in that noise. But this is much larger
than an ordinary spaceship.

[Dan Tilque]

Post by J. Clarke

Post by Dan Tilque

Post by J. Clarke
By what means would someone "notice" this "geezy huge amount of waste
heat"?

Infrared telescopes.

Which are, in your view, constantly pointed at all areas of the sky.

Not in all directions at once, but close enough. There are various
programs where automated telescopes constantly scan the sky. Some are
Earth-based and so are limited to what's visible on any particular
night, but others are in orbit and can scan much larger parts of the sky
in a given period. One that comes to mind off-hand is Gaia:

http://sci.esa.int/gaia/

Not all of them are visible light scopes, either. For example, WFIRST
works in the infrared band:

https://en.wikipedia.org/wiki/Wide_Field_Infrared_Survey_Telescope

Others will work in various radio bands. Those will mostly be
Earth-based, but they work in the day as well as the night.

These survey programs are getting more and more common. The main problem
they have is the vast amounts of data they are gathering, which is only
going to get worse. And by worse, I mean by several orders of magnitude.
So they're looking to AI to do the initial triage of the data. The
investigators then will look at what the AI comes up with.

So any writers out there want a realistic scene where astronomers
discover alien spacecraft coming into the system or something like that,
that's what it's most likely to be. After they look at what the AI
found, they'll look at earlier observations from their survey and then
what other survey instruments saw in the same area. All the observations
will be online.

[J. Clarke]

Post by Dan Tilque

Post by J. Clarke

Post by Dan Tilque

Post by J. Clarke
By what means would someone "notice" this "geezy huge amount of waste
heat"?

Infrared telescopes.

Which are, in your view, constantly pointed at all areas of the sky.

Not in all directions at once, but close enough. There are various
programs where automated telescopes constantly scan the sky.
Some are
Earth-based and so are limited to what's visible on any particular
night, but others are in orbit and can scan much larger parts of the sky
http://sci.esa.int/gaia/

Yeah, it takes it over a year to do a full sky scan--it has a sunshade
so it doesn't get pointed anywhere near the sun which blocks out a
good bit of the sky at any given time.

Post by Dan Tilque
Not all of them are visible light scopes, either. For example, WFIRST
https://en.wikipedia.org/wiki/Wide_Field_Infrared_Survey_Telescope

And is it going to pick up this tiny rock while it's doing its wide
field infrared survey?

Post by Dan Tilque
Others will work in various radio bands. Those will mostly be
Earth-based, but they work in the day as well as the night.

That's nice, what of it.

Post by Dan Tilque
These survey programs are getting more and more common. The main problem
they have is the vast amounts of data they are gathering, which is only
going to get worse. And by worse, I mean by several orders of magnitude.
So they're looking to AI to do the initial triage of the data. The
investigators then will look at what the AI comes up with.

They are _surveys_. They don't scan the whole sky every ten minutes
looking for wayward rocks.

Post by Dan Tilque
So any writers out there want a realistic scene where astronomers
discover alien spacecraft coming into the system or something like that,
that's what it's most likely to be. After they look at what the AI
found, they'll look at earlier observations from their survey and then
what other survey instruments saw in the same area. All the observations
will be online.

So how's that working out for finding earth crossing asteroids?

[Dan Tilque]

Post by J. Clarke

Post by Dan Tilque

Post by J. Clarke

Post by Dan Tilque

Post by J. Clarke
By what means would someone "notice" this "geezy huge amount of waste
heat"?

Infrared telescopes.

Which are, in your view, constantly pointed at all areas of the sky.

Not in all directions at once, but close enough. There are various
programs where automated telescopes constantly scan the sky.
Some are
Earth-based and so are limited to what's visible on any particular
night, but others are in orbit and can scan much larger parts of the sky
http://sci.esa.int/gaia/

Yeah, it takes it over a year to do a full sky scan--it has a sunshade
so it doesn't get pointed anywhere near the sun which blocks out a
good bit of the sky at any given time.

Gaia was just the first example of a survey that I thought of. There are
many others and more being started all the time.

Post by J. Clarke

Post by Dan Tilque
Not all of them are visible light scopes, either. For example, WFIRST
https://en.wikipedia.org/wiki/Wide_Field_Infrared_Survey_Telescope

And is it going to pick up this tiny rock while it's doing its wide
field infrared survey?

Not the rock. You may remember in my earlier post I said that it'll
detect the large cloud of ionized material that the rock will expel as
propellant.

But rocks smaller than the one in this book are found by surveys looking
for them.

Post by J. Clarke

Post by Dan Tilque
Others will work in various radio bands. Those will mostly be
Earth-based, but they work in the day as well as the night.

That's nice, what of it.

They could also spot this cloud. It's likely to be giving off some radio
/microwave/submillimeter/terahertz waves as well as IR.

Post by J. Clarke

Post by Dan Tilque
These survey programs are getting more and more common. The main problem
they have is the vast amounts of data they are gathering, which is only
going to get worse. And by worse, I mean by several orders of magnitude.
So they're looking to AI to do the initial triage of the data. The
investigators then will look at what the AI comes up with.

They are _surveys_. They don't scan the whole sky every ten minutes
looking for wayward rocks.

It'll take a long time (months-to-years) to move this rock from its
current orbit to one bringing it to Earth. In that time, it'll show up
as an anomalous object in one of these surveys. My guess it would be
within the first month.

Post by J. Clarke

Post by Dan Tilque
So any writers out there want a realistic scene where astronomers
discover alien spacecraft coming into the system or something like that,
that's what it's most likely to be. After they look at what the AI
found, they'll look at earlier observations from their survey and then
what other survey instruments saw in the same area. All the observations
will be online.

So how's that working out for finding earth crossing asteroids?

Do you think they haven't found any? Earth-crossing asteroids, those
that cross the Earth's orbit, are reasonably common. They find them all
the time. Occasionally, they find one that has a chance to hit the Earth
in the foreseeable future, but those are fairly rare. And then further
refinement of the orbit has always reduced that chance to zero. Well, so
far anyway. I'm sure they'll eventually find one which will hit the
Earth. It may be a century or two before they find one.

[J. Clarke]

Post by Dan Tilque

Post by J. Clarke

Post by Dan Tilque

Post by J. Clarke

Post by Dan Tilque

Post by J. Clarke
By what means would someone "notice" this "geezy huge amount of waste
heat"?

Infrared telescopes.

Which are, in your view, constantly pointed at all areas of the sky.

Not in all directions at once, but close enough. There are various
programs where automated telescopes constantly scan the sky.
Some are
Earth-based and so are limited to what's visible on any particular
night, but others are in orbit and can scan much larger parts of the sky
http://sci.esa.int/gaia/

Yeah, it takes it over a year to do a full sky scan--it has a sunshade
so it doesn't get pointed anywhere near the sun which blocks out a
good bit of the sky at any given time.

Gaia was just the first example of a survey that I thought of. There are
many others and more being started all the time.

Post by J. Clarke

Post by Dan Tilque
Not all of them are visible light scopes, either. For example, WFIRST
https://en.wikipedia.org/wiki/Wide_Field_Infrared_Survey_Telescope

And is it going to pick up this tiny rock while it's doing its wide
field infrared survey?

Not the rock. You may remember in my earlier post I said that it'll
detect the large cloud of ionized material that the rock will expel as
propellant.

Define large in astronomical terms. What is large compared to Earth
is tiny in astronomical terms.

Post by Dan Tilque
But rocks smaller than the one in this book are found by surveys looking
for them.

Sometimes. All of the have not been mapped.

Post by Dan Tilque

Post by J. Clarke

Post by Dan Tilque
Others will work in various radio bands. Those will mostly be
Earth-based, but they work in the day as well as the night.

That's nice, what of it.

They could also spot this cloud. It's likely to be giving off some radio
/microwave/submillimeter/terahertz waves as well as IR.

Why is that likely?

Post by Dan Tilque

Post by J. Clarke

Post by Dan Tilque
These survey programs are getting more and more common. The main problem
they have is the vast amounts of data they are gathering, which is only
going to get worse. And by worse, I mean by several orders of magnitude.
So they're looking to AI to do the initial triage of the data. The
investigators then will look at what the AI comes up with.

They are _surveys_. They don't scan the whole sky every ten minutes
looking for wayward rocks.

It'll take a long time (months-to-years) to move this rock from its
current orbit to one bringing it to Earth. In that time, it'll show up
as an anomalous object in one of these surveys. My guess it would be
within the first month.

If it shows up at all.

Post by Dan Tilque

Post by J. Clarke

Post by Dan Tilque
So any writers out there want a realistic scene where astronomers
discover alien spacecraft coming into the system or something like that,
that's what it's most likely to be. After they look at what the AI
found, they'll look at earlier observations from their survey and then
what other survey instruments saw in the same area. All the observations
will be online.

So how's that working out for finding earth crossing asteroids?

Do you think they haven't found any?

Can you say "whoosh"?

Post by Dan Tilque
Earth-crossing asteroids, those
that cross the Earth's orbit, are reasonably common. They find them all
the time. Occasionally, they find one that has a chance to hit the Earth
in the foreseeable future, but those are fairly rare. And then further
refinement of the orbit has always reduced that chance to zero. Well, so
far anyway. I'm sure they'll eventually find one which will hit the
Earth. It may be a century or two before they find one.

The issue is not finding "some", it is finding one particular one.

[Dan Tilque]

Post by J. Clarke

Post by Dan Tilque
Not the rock. You may remember in my earlier post I said that it'll
detect the large cloud of ionized material that the rock will expel as
propellant.

Define large in astronomical terms. What is large compared to Earth
is tiny in astronomical terms.

You have to remember this cloud is made up of positively charged
particels, so it's going to expand because of mutual repulsion. The
further away the exhaust gets, the larger it'll be. Many times the size
of the asteroid (which is a cylinder 1 mile long and .25 mile in
diameter). Should be easy to spot, since it'll never be more than about
2 AU away from Earth. Not only that, but because of the expansion, it'll
be pointing towards the rock itself.

Post by J. Clarke

Post by Dan Tilque
But rocks smaller than the one in this book are found by surveys looking
for them.

Sometimes. All of the have not been mapped.

Virtually all of them the size of this rock have been.

Post by J. Clarke

Post by Dan Tilque

Post by J. Clarke

Post by Dan Tilque
Others will work in various radio bands. Those will mostly be
Earth-based, but they work in the day as well as the night.

That's nice, what of it.

They could also spot this cloud. It's likely to be giving off some radio
/microwave/submillimeter/terahertz waves as well as IR.

Why is that likely?

When ionized nuclei recombine with electrons, they give off
electromagnetic radiation. The frequency depends on what the nuclei is
and what orbital the electron goes to. After recombination, the electron
will likely be in a high orbital, so it'll drop down to lower orbits,
giving off more e-m radiation. Since the exhaust is probably a mixture
of many kinds of atoms, the wavelengths will be anywhere from UV to
radio waves.

Post by J. Clarke

Post by Dan Tilque

Post by J. Clarke
So how's that working out for finding earth crossing asteroids?

Do you think they haven't found any?

Can you say "whoosh"?

Pull the other one, it's got bells on it.

[J. Clarke]

Post by Dan Tilque

Post by J. Clarke

Post by Dan Tilque
Not the rock. You may remember in my earlier post I said that it'll
detect the large cloud of ionized material that the rock will expel as
propellant.

Define large in astronomical terms. What is large compared to Earth
is tiny in astronomical terms.

You have to remember this cloud is made up of positively charged
particels, so it's going to expand because of mutual repulsion. The
further away the exhaust gets, the larger it'll be. Many times the size
of the asteroid (which is a cylinder 1 mile long and .25 mile in
diameter). Should be easy to spot, since it'll never be more than about
2 AU away from Earth. Not only that, but because of the expansion, it'll
be pointing towards the rock itself.

And the larger it becomes, the more diffuse it becomes. What is the
magnitude of this cloud as seen from Earth?

However what leads you to believe that it is "made up of positively
charged particles? Most ion propulsion provides electron injection in
order to maintain a neutral beam. It doesn't do any wonders for your
Isp if all your "positively charged particles" decide to come back and
cling to your engine.

Post by Dan Tilque

Post by J. Clarke

Post by Dan Tilque
But rocks smaller than the one in this book are found by surveys looking
for them.

Sometimes. All of the have not been mapped.

Virtually all of them the size of this rock have been.

You know that with certainty do you?

Post by Dan Tilque

Post by J. Clarke

Post by Dan Tilque

Post by J. Clarke

Post by Dan Tilque
Others will work in various radio bands. Those will mostly be
Earth-based, but they work in the day as well as the night.

That's nice, what of it.

They could also spot this cloud. It's likely to be giving off some radio
/microwave/submillimeter/terahertz waves as well as IR.

Why is that likely?

When ionized nuclei recombine with electrons, they give off
electromagnetic radiation.

If it's positively charged as you claim then where do all these
electrons come from?

Post by Dan Tilque
The frequency depends on what the nuclei is
and what orbital the electron goes to. After recombination, the electron
will likely be in a high orbital, so it'll drop down to lower orbits,
giving off more e-m radiation. Since the exhaust is probably a mixture
of many kinds of atoms, the wavelengths will be anywhere from UV to
radio waves.

Why would the exhaust be a "mixture of many kinds of atoms"?

Post by Dan Tilque

Post by J. Clarke

Post by Dan Tilque

Post by J. Clarke
So how's that working out for finding earth crossing asteroids?

Do you think they haven't found any?

Can you say "whoosh"?

Pull the other one, it's got bells on it.

In other words you can't say "whoosh".

[Dan Tilque]

Post by J. Clarke
However what leads you to believe that it is "made up of positively
charged particles? Most ion propulsion provides electron injection in
order to maintain a neutral beam. It doesn't do any wonders for your
Isp if all your "positively charged particles" decide to come back and
cling to your engine.

OK, I'll admit that I forgot they released electrons into the exhaust.
Not sure what the recombination time is, so I can't say how big the
exhaust plume will be when that happens.

But it doesn't really matter. The other thing that will be visible from
Earth or Earth orbit is either the giant solar panel array needed to
generate the huge amount of power these thrusters will require or the
huge radiators to get rid of the heat from the nuclear power plant,
depending on which power source they use.

Post by J. Clarke

Post by Dan Tilque

Post by J. Clarke

Post by Dan Tilque
But rocks smaller than the one in this book are found by surveys looking
for them.

Sometimes. All of the have not been mapped.

Virtually all of them the size of this rock have been.

You know that with certainty do you?

Because they don't find many NEAs that are that large any more, but they
do find a fair number that are smaller. That indicates there aren't very
many of that size they haven't found.

Post by J. Clarke
Why would the exhaust be a "mixture of many kinds of atoms"?

Because the material has to come from the asteroid and that's made with
many kinds of atoms. Current ion thrusters use xenon, because it gets
the best results, but it's in short supply. It's going to take a huge
amount of fuel to move a rock like this around and it would be
infeasible to ship all of it from Earth. But it can use other atoms if
those aren't available. There's more corrosion with most other atoms, so
the maintainance costs will be higher.

Post by J. Clarke

Post by Dan Tilque

Post by J. Clarke

Post by Dan Tilque

Post by J. Clarke
So how's that working out for finding earth crossing asteroids?

Do you think they haven't found any?

Can you say "whoosh"?

Pull the other one, it's got bells on it.

In other words you can't say "whoosh".

No. In other words, you don't know how to do a whoosh.

[J. Clarke]

Post by Dan Tilque

Post by J. Clarke
However what leads you to believe that it is "made up of positively
charged particles? Most ion propulsion provides electron injection in
order to maintain a neutral beam. It doesn't do any wonders for your
Isp if all your "positively charged particles" decide to come back and
cling to your engine.

OK, I'll admit that I forgot they released electrons into the exhaust.
Not sure what the recombination time is, so I can't say how big the
exhaust plume will be when that happens.
But it doesn't really matter. The other thing that will be visible from
Earth or Earth orbit is either the giant solar panel array needed to
generate the huge amount of power these thrusters will require or the
huge radiators to get rid of the heat from the nuclear power plant,
depending on which power source they use.

So how large do they have to be? You seem to have an exaggerated idea
of the amount of power needed to apply a tiny thrust to a rock.

Post by Dan Tilque

Post by J. Clarke

Post by Dan Tilque

Post by J. Clarke

Post by Dan Tilque
But rocks smaller than the one in this book are found by surveys looking
for them.

Sometimes. All of the have not been mapped.

Virtually all of them the size of this rock have been.

You know that with certainty do you?

Because they don't find many NEAs that are that large any more, but they
do find a fair number that are smaller. That indicates there aren't very
many of that size they haven't found.

Or that our current technology is systematically missing whole classes
of them.

Post by Dan Tilque

Post by J. Clarke
Why would the exhaust be a "mixture of many kinds of atoms"?

Because the material has to come from the asteroid and that's made with
many kinds of atoms. Current ion thrusters use xenon, because it gets
the best results, but it's in short supply. It's going to take a huge
amount of fuel to move a rock like this around and it would be
infeasible to ship all of it from Earth. But it can use other atoms if
those aren't available. There's more corrosion with most other atoms, so
the maintainance costs will be higher.

Why is it going to "take a huge amount of fuel"? Electric thrusters
have enormously high exhaust velocities. They use tiny amounts of
propellant and the fuel is not part of the propellant.

Post by Dan Tilque

Post by J. Clarke

Post by Dan Tilque

Post by J. Clarke

Post by Dan Tilque

Post by J. Clarke
So how's that working out for finding earth crossing asteroids?

Do you think they haven't found any?

Can you say "whoosh"?

Pull the other one, it's got bells on it.

In other words you can't say "whoosh".

No. In other words, you don't know how to do a whoosh.

[Dan Tilque]

Post by J. Clarke

Post by Dan Tilque
But it doesn't really matter. The other thing that will be visible from
Earth or Earth orbit is either the giant solar panel array needed to
generate the huge amount of power these thrusters will require or the
huge radiators to get rid of the heat from the nuclear power plant,
depending on which power source they use.

So how large do they have to be? You seem to have an exaggerated idea
of the amount of power needed to apply a tiny thrust to a rock.

If they want the rock to get to Earth before they die of old age,
they're going to have to generate a significant amount of thrust.
Currently-used ion thrusters on spaceships only generate about as much
thrust as the gravitation force on a piece of paper. That's probably
less than the amount of light pressure that the sun exerts on the rock
in question.

If they used the same thruster on this rock (which is several orders of
magnitude more massive than a spacecraft) it would take centuries to get
to Earth orbit. So they'll have to either scale one up or use multiple
thrusters or, most likely, both.

Post by J. Clarke

Post by Dan Tilque

Post by J. Clarke

Post by Dan Tilque

Post by J. Clarke

Post by Dan Tilque
But rocks smaller than the one in this book are found by surveys looking
for them.

Sometimes. All of the have not been mapped.

Virtually all of them the size of this rock have been.

You know that with certainty do you?

Because they don't find many NEAs that are that large any more, but they
do find a fair number that are smaller. That indicates there aren't very
many of that size they haven't found.

Or that our current technology is systematically missing whole classes
of them.

You're straining at gnats here. The asteroid in question is a Near Earth
Asteroid, with orbital parameters similar to Earth's. Surveys such as
LINEAR and the Catalina Sky Survey have been finding for these for years
now and, since this is taking place in the future, will have been
looking for many more years. Right now, they're mostly finding rocks
with dimensions in the 10's of meters, rather than the hundreds of
meters of the rock in question. So you'll have to point out what class
of rock they're systematically missing.

Post by J. Clarke

Post by Dan Tilque

Post by J. Clarke
Why would the exhaust be a "mixture of many kinds of atoms"?

Because the material has to come from the asteroid and that's made with
many kinds of atoms. Current ion thrusters use xenon, because it gets
the best results, but it's in short supply. It's going to take a huge
amount of fuel to move a rock like this around and it would be
infeasible to ship all of it from Earth. But it can use other atoms if
those aren't available. There's more corrosion with most other atoms, so
the maintainance costs will be higher.

Why is it going to "take a huge amount of fuel"? Electric thrusters
have enormously high exhaust velocities. They use tiny amounts of
propellant and the fuel is not part of the propellant.

I miss-used the word fuel there. I meant propellant. Yes, they use tiny
amounts for spacecraft, which have a mass less than a metric ton. (Dawn,
which uses an ion thruster, has a mass of only 747 kg.) This rock is
well over a billion metric tons, possibly as much as 2 billion, so the
propellant and power amounts are going to have to scale up.

[Chris Buckley]

Post by Dan Tilque

Post by J. Clarke

Post by Dan Tilque
But it doesn't really matter. The other thing that will be visible from
Earth or Earth orbit is either the giant solar panel array needed to
generate the huge amount of power these thrusters will require or the
huge radiators to get rid of the heat from the nuclear power plant,
depending on which power source they use.

So how large do they have to be? You seem to have an exaggerated idea
of the amount of power needed to apply a tiny thrust to a rock.

If they want the rock to get to Earth before they die of old age,
they're going to have to generate a significant amount of thrust.
Currently-used ion thrusters on spaceships only generate about as much
thrust as the gravitation force on a piece of paper. That's probably
less than the amount of light pressure that the sun exerts on the rock
in question.
If they used the same thruster on this rock (which is several orders of
magnitude more massive than a spacecraft) it would take centuries to get
to Earth orbit. So they'll have to either scale one up or use multiple
thrusters or, most likely, both.

Post by J. Clarke

Post by Dan Tilque

Post by J. Clarke

Post by Dan Tilque

Post by J. Clarke

Post by Dan Tilque
But rocks smaller than the one in this book are found by surveys looking
for them.

Sometimes. All of the have not been mapped.

Virtually all of them the size of this rock have been.

You know that with certainty do you?

Because they don't find many NEAs that are that large any more, but they
do find a fair number that are smaller. That indicates there aren't very
many of that size they haven't found.

Or that our current technology is systematically missing whole classes
of them.

You're straining at gnats here. The asteroid in question is a Near Earth
Asteroid, with orbital parameters similar to Earth's. Surveys such as
LINEAR and the Catalina Sky Survey have been finding for these for years
now and, since this is taking place in the future, will have been
looking for many more years. Right now, they're mostly finding rocks
with dimensions in the 10's of meters, rather than the hundreds of
meters of the rock in question. So you'll have to point out what class
of rock they're systematically missing.

I'm perfectly fine with your argument that we have the capability of
spotting the asteroid if a powerful enough telescope happens to look
at it. But the sky is big, and telescopes of that capability look at
such a small portion. And they are not constantly revisiting portions
they've already looked at (why would they?). So it sounds like pure
chance that that the asteroid would be seen as it became more visible.

"Ground-based telescopes alone have limitations - for instance, they
can only survey the skies at night and in clear skies. Based on
statistical population estimates, about 74 percent of NEOs larger than
460 feet still remain to be discovered."
https://www.nasa.gov/planetarydefense/faq

Chris

[Dan Tilque]

Post by Chris Buckley
I'm perfectly fine with your argument that we have the capability of
spotting the asteroid if a powerful enough telescope happens to look
at it. But the sky is big, and telescopes of that capability look at
such a small portion. And they are not constantly revisiting portions
they've already looked at (why would they?). So it sounds like pure
chance that that the asteroid would be seen as it became more visible.

They do revisit areas of the sky they already looked at.[1] Asteroids
are not fixed; they move around. For example, the wiki-page on
Pan-STARRS says:

| By the end of its initial three-year mission in April 2014, PS1 had
| imaged the sky 12 times in each of 5 filters (g,r,i,z,y).

Depending on where this rock is in relation to Earth, they may not find
it for a month or two, but they definitely will long before the two
years it was going to take to reach Earth would pass. Two Earth-based
surveys that currently find most small asteroids are Catalina Sky Survey
and Pan-STARRS.

https://en.wikipedia.org/wiki/Catalina_Sky_Survey
https://en.wikipedia.org/wiki/Pan-STARRS

Note that Pan-STARRS is expected to find a significant number[2] of
Kuiper Belt objects. Those are way, way dimmer than this NEO.



[1] For that matter, all surveys look at the entire sky (or as much as
they can see) multiple times. It's not that stars and galaxies change
all that much (although that does happen) but there could be problems
with the first observation. Or they could be looking for things that
move or viewing through different filters, or something. At one time,
surveys may have only viewed the sky once (the first Palomar survey from
the 1950s did), but they don't any more.

[2] About 20,000 KBOs, which is much more than are currently known.

[James Nicoll]

Post by Dan Tilque
I miss-used the word fuel there. I meant propellant. Yes, they use tiny
amounts for spacecraft, which have a mass less than a metric ton. (Dawn,
which uses an ion thruster, has a mass of only 747 kg.) This rock is
well over a billion metric tons, possibly as much as 2 billion, so the
propellant and power amounts are going to have to scale up.

For example, say the delta vee to put the rock into an Earth crossing orbit
is 1 km/s and the rocket's exhaust velocity is 30 km/s (which is what ISTR
Dawn's is). The rocket equation says the mass ratio will be 1.03, so about
33 to 66 million tonnes of reaction mass will be needed.

Each tonne has an Ek of 4.5x10^11 Joules so in total the operation takes
between 1.5x10^16 to 3x10^16 J. Dawn generates about 10,000 Joules/second
at one AU so a Dawn-sized solar array would only take 48,000 years to huck
enough reaction mass.

[Lynn McGuire]

Post by James Nicoll

Post by Dan Tilque
I miss-used the word fuel there. I meant propellant. Yes, they use tiny
amounts for spacecraft, which have a mass less than a metric ton. (Dawn,
which uses an ion thruster, has a mass of only 747 kg.) This rock is
well over a billion metric tons, possibly as much as 2 billion, so the
propellant and power amounts are going to have to scale up.

For example, say the delta vee to put the rock into an Earth crossing orbit
is 1 km/s and the rocket's exhaust velocity is 30 km/s (which is what ISTR
Dawn's is). The rocket equation says the mass ratio will be 1.03, so about
33 to 66 million tonnes of reaction mass will be needed.
Each tonne has an Ek of 4.5x10^11 Joules so in total the operation takes
between 1.5x10^16 to 3x10^16 J. Dawn generates about 10,000 Joules/second
at one AU so a Dawn-sized solar array would only take 48,000 years to huck
enough reaction mass.

Don't forget that changing the tumble of the asteroid needs to be taken
into account. This is the "propellant" that the authors are using to
change the path of the asteroid. The path change of the asteroid is
actually quite minor in the book.

Lynn

[James Nicoll]

Post by Lynn McGuire

Post by James Nicoll

Post by Dan Tilque
I miss-used the word fuel there. I meant propellant. Yes, they use tiny
amounts for spacecraft, which have a mass less than a metric ton. (Dawn,
which uses an ion thruster, has a mass of only 747 kg.) This rock is
well over a billion metric tons, possibly as much as 2 billion, so the
propellant and power amounts are going to have to scale up.

For example, say the delta vee to put the rock into an Earth crossing orbit
is 1 km/s and the rocket's exhaust velocity is 30 km/s (which is what ISTR
Dawn's is). The rocket equation says the mass ratio will be 1.03, so about
33 to 66 million tonnes of reaction mass will be needed.
Each tonne has an Ek of 4.5x10^11 Joules so in total the operation takes
between 1.5x10^16 to 3x10^16 J. Dawn generates about 10,000 Joules/second
at one AU so a Dawn-sized solar array would only take 48,000 years to huck
enough reaction mass.

Don't forget that changing the tumble of the asteroid needs to be taken
into account. This is the "propellant" that the authors are using to
change the path of the asteroid. The path change of the asteroid is
actually quite minor in the book.

I am looking at the online free sample and I don't see any propulsive
techniques used on the asteroid aside from two years of electric thrust
and a flyby of Earth. Where do they discuss your method? Which btw
I cannot work out how it's supposed to work.

http://www.baen.com/Chapters/9781476781525/9781476781525.htm

[Lynn McGuire]

Post by James Nicoll

Post by Lynn McGuire

Post by James Nicoll

Post by Dan Tilque
I miss-used the word fuel there. I meant propellant. Yes, they use tiny
amounts for spacecraft, which have a mass less than a metric ton. (Dawn,
which uses an ion thruster, has a mass of only 747 kg.) This rock is
well over a billion metric tons, possibly as much as 2 billion, so the
propellant and power amounts are going to have to scale up.

For example, say the delta vee to put the rock into an Earth crossing orbit
is 1 km/s and the rocket's exhaust velocity is 30 km/s (which is what ISTR
Dawn's is). The rocket equation says the mass ratio will be 1.03, so about
33 to 66 million tonnes of reaction mass will be needed.
Each tonne has an Ek of 4.5x10^11 Joules so in total the operation takes
between 1.5x10^16 to 3x10^16 J. Dawn generates about 10,000 Joules/second
at one AU so a Dawn-sized solar array would only take 48,000 years to huck
enough reaction mass.

Don't forget that changing the tumble of the asteroid needs to be taken
into account. This is the "propellant" that the authors are using to
change the path of the asteroid. The path change of the asteroid is
actually quite minor in the book.

I am looking at the online free sample and I don't see any propulsive
techniques used on the asteroid aside from two years of electric thrust
and a flyby of Earth. Where do they discuss your method? Which btw
I cannot work out how it's supposed to work.
http://www.baen.com/Chapters/9781476781525/9781476781525.htm

Launch of the asteroid rocket:
http://www.baen.com/Chapters/9781476781525/9781476781525.htm

Reuters note on electric thrusters:
http://www.baen.com/Chapters/9781476781525/9781476781525.htm

http://www.baen.com/Chapters/9781476781525/9781476781525.htm

"Electric rockets look futuristic, like an advanced space propulsion
system should. As the xenon gas fuel is stripped of its outer electron
and accelerated toward the rocket’s exhaust by carefully designed
electric and magnetic fields, the entire engine emits a brilliant blue
glow. There is none of the fire and smoke that would be seen from some
conventional chemical rocket engines. Chemical rockets are a brute force
approach to moving things around in space and the only realistic way to
get off the surface of a planet, deep in a gravity well, and into space.
But once you are in space, highly efficient electric rockets are an
excellent alternative.

Chemical rockets produce all the thrust they’re going to produce in
their first few minutes of use by providing spectacular acceleration—the
kind an astronaut can feel as he is pushed back into his seat while the
rocket begins to speed up. Electric rockets produce a continuous, very
small thrust that might not even be felt by a person. But it is a
continuous thrust, and, given enough time, an electric rocket can
accelerate a spacecraft to much higher speeds using only a fraction of
the fuel required by a chemical rocket. Such was the case with the
electric thrusters bound to the surface of the Sutter’s Mill asteroid.

The gentle push began as soon as the thrusters were turned on. Sutter’s
Mill, which would weigh just over two billion tons on Earth, didn’t have
any weight in space. It still had mass, so it still required a
significant total force in order to alter its motion so that it would go
where the mission planners from Asteroid Ores wanted it to go. The
entire operation was similar to a swimmer pushing a barge off its
original course. A single swimmer couldn’t make any abrupt changes to
the course of a multiton ship. But if that swimmer could swim sideways
into the barge for a very long time, then the barge would drift slowly
onto a different path.

The electric thrusters were designed to operate continuously for the
entire two years it would take to nudge the massive rock from its
current course to one that would make it accessible for Earth-based
miners to exploit, including an Earth flyby in just another eleven
months. With each day of operation, the asteroid would be on a slightly
different course on its billion-year journey around the Sun. To bring it
where its operators wanted it to be, two full years of thrusting would
be required."

http://www.baen.com/Chapters/9781476781525/9781476781525.htm

"The electric propulsion system’s small but relentless push on asteroid
Sutter’s Mill was slowly altering its trajectory. Had the high-voltage
power supply that fed the thrusters not shorted out, there is no doubt
they would have placed the rock on a path that would take it safely into
a lunar orbit, making it accessible for Earth’s resource-hungry
population to mine. But the power supply did fail, and the beautiful
blue glow of the thrusters winked out, stopping before the asteroid was
placed in the desired orbit, leaving it on a path that no one had
planned or even yet knew. But soon the smart people back on Earth would
know where it was heading—and they would be terrified."

http://www.baen.com/Chapters/9781476781525/9781476781525.htm

"“Isn’t the rock spinning? All the studies we’ve done show that it’ll be
risky to try and rendezvous with a rotating mountain in space,” asked
the Lockheed-Martin CEO.

“They attached two small spacecraft to the asteroid, one on each side,
each containing a long cable—a tether. Think of an ice skater when she
pulls her arms and a leg in in order to speed up. She’s conserving
angular momentum. As she reduces her rotational inertia by pulling her
arms and leg in, her rotation speed must increase to maintain constant
angular momentum. Now do it in reverse with a spinning rock and extend
five-kilometer-long tethers instead of arms and legs. The rock stops
spinning. Cut the tethers and you’re ready to go.”"

"Electrically powered spacecraft propulsion"
https://en.wikipedia.org/wiki/Electrically_powered_spacecraft_propulsion

"An electrically-powered spacecraft propulsion system uses electrical
energy to change the velocity of a spacecraft. Most of these kinds of
spacecraft propulsion systems work by electrically expelling propellant
(reaction mass) at high speed, but electrodynamic tethers work by
interacting with a planet's magnetic field.[1]"

Lynn

[Dimensional Traveler]

Post by James Nicoll

Post by James Nicoll

Post by Lynn McGuire

Post by James Nicoll

Post by Dan Tilque
I miss-used the word fuel there. I meant propellant. Yes, they use tiny
amounts for spacecraft, which have a mass less than a metric ton. (Dawn,
which uses an ion thruster, has a mass of only 747 kg.) This rock is
well over a billion metric tons, possibly as much as 2 billion, so the
propellant and power amounts are going to have to scale up.

For example, say the delta vee to put the rock into an Earth crossing orbit
is 1 km/s and the rocket's exhaust velocity is 30 km/s (which is what ISTR
Dawn's is). The rocket equation says the mass ratio will be 1.03, so about
33 to 66 million tonnes of reaction mass will be needed.
Each tonne has an Ek of 4.5x10^11 Joules so in total the operation takes
between 1.5x10^16 to 3x10^16 J. Dawn generates about 10,000
Joules/second
at one AU so a Dawn-sized solar array would only take 48,000 years to huck
enough reaction mass.

Don't forget that changing the tumble of the asteroid needs to be taken
into account.  This is the "propellant" that the authors are using to
change the path of the asteroid.  The path change of the asteroid is
actually quite minor in the book.

I am looking at the online free sample and I don't see any propulsive
techniques used on the asteroid aside from two years of electric thrust
and a flyby of Earth. Where do they discuss your method? Which btw
I cannot work out how it's supposed to work.
http://www.baen.com/Chapters/9781476781525/9781476781525.htm

<snip some other stuff>

Post by James Nicoll
http://www.baen.com/Chapters/9781476781525/9781476781525.htm
"“Isn’t the rock spinning? All the studies we’ve done show that it’ll be
risky to try and rendezvous with a rotating mountain in space,” asked
the Lockheed-Martin CEO.
“They attached two small spacecraft to the asteroid, one on each side,
each containing a long cable—a tether. Think of an ice skater when she
pulls her arms and a leg in in order to speed up. She’s conserving
angular momentum. As she reduces her rotational inertia by pulling her
arms and leg in, her rotation speed must increase to maintain constant
angular momentum. Now do it in reverse with a spinning rock and extend
five-kilometer-long tethers instead of arms and legs. The rock stops
spinning. Cut the tethers and you’re ready to go.”"

Uh, no. They could slow the rotation that way but they couldn't
completely stop it. If they want to actually _stop_ the rotation they
will need to apply thrust at some point. They'd also need to get the
tether releases _exactly_ right or they'll induce a wobble that just
might make it impossible for them to control the orbit alteration.

[James Nicoll]

“They attached two small spacecraft to the asteroid, one on each side,
each containing a long cable—a tether. Think of an ice skater when she
pulls her arms and a leg in in order to speed up. She’s conserving
angular momentum. As she reduces her rotational inertia by pulling her
arms and leg in, her rotation speed must increase to maintain constant
angular momentum. Now do it in reverse with a spinning rock and extend
five-kilometer-long tethers instead of arms and legs. The rock stops
spinning. Cut the tethers and you’re ready to go.”"
"Electrically powered spacecraft propulsion"
https://en.wikipedia.org/wiki/Electrically_powered_spacecraft_propulsion
"An electrically-powered spacecraft propulsion system uses electrical
energy to change the velocity of a spacecraft. Most of these kinds of
spacecraft propulsion systems work by electrically expelling propellant
(reaction mass) at high speed, but electrodynamic tethers work by
interacting with a planet's magnetic field.[1]"

Despinning the rock won't have any great effect on the path it takes around
the Sun. And most of the time they won't be near a planet so reacting
against its magnetic field won't be an option.

Same basic tech could be used for a mag sail. But they don't seem to be
doing that.

[Dan Tilque]

Post by James Nicoll
And most of the time they won't be near a planet so reacting
against its magnetic field won't be an option.

There is a solar magnetic field. Off-hand I don't know how it compares
to Earth's for this use. It's much stronger than Earth's, but this rock
is lots futher away from the sun than any Earth satellite. My
expectation is that it would be usable and so they just made an error in
saying "planet's" instead of "solar" or perhaps "interplanetary".

[James Nicoll]

Post by Dan Tilque

Post by James Nicoll
And most of the time they won't be near a planet so reacting
against its magnetic field won't be an option.

There is a solar magnetic field. Off-hand I don't know how it compares
to Earth's for this use. It's much stronger than Earth's, but this rock
is lots futher away from the sun than any Earth satellite. My
expectation is that it would be usable and so they just made an error in
saying "planet's" instead of "solar" or perhaps "interplanetary".

One billionth tesla at 1 AU. Earth's is 25 to 65 microteslas at the
surface. It seems to me intuitively obvious it must drop to about
solar strength just about the spot where the solar wind are deflected
from Earth but my intuition also tells me I have the tiger-like reflexes
of a trained Olympic athlete and the data do not support that model.

There are proposed methods of using the solar wind for propulsion.
Obviously light sails are visible but I don't know how hard it would
to spot a magsail. Although since it's moving something the size of a
small mountain using very small forces, it will be a very large mag-
sail....

Do the authors ever address what happens to the price of a commodity
when someone drops a mountain-sized amount of it on the market?

[D B Davis]

Post by James Nicoll

Post by Dan Tilque

Post by James Nicoll
And most of the time they won't be near a planet so reacting
against its magnetic field won't be an option.

There is a solar magnetic field. Off-hand I don't know how it compares
to Earth's for this use. It's much stronger than Earth's, but this rock
is lots futher away from the sun than any Earth satellite. My
expectation is that it would be usable and so they just made an error in
saying "planet's" instead of "solar" or perhaps "interplanetary".

One billionth tesla at 1 AU. Earth's is 25 to 65 microteslas at the
surface. It seems to me intuitively obvious it must drop to about
solar strength just about the spot where the solar wind are deflected
from Earth but my intuition also tells me I have the tiger-like reflexes
of a trained Olympic athlete and the data do not support that model.
There are proposed methods of using the solar wind for propulsion.
Obviously light sails are visible but I don't know how hard it would
to spot a magsail. Although since it's moving something the size of a
small mountain using very small forces, it will be a very large mag-
sail....
Do the authors ever address what happens to the price of a commodity
when someone drops a mountain-sized amount of it on the market?

A mountain-sized amount of Imperial marks are literally dumped on people
in _An Enemy of the State_ (Wilson). It leads to hyper-inflation and the
eventual collapse of the status quo.
Uncle Sam also likes to drop mountain-sized amounts of one hundred
dollar bills on the Mideast. [1] Is the jury still out as to the social
cost of that particular part of the white man's burden?

Note.

1. https://www.theguardian.com/world/2007/feb/08/usa.iraq1

Thank you,

--
Don

[David DeLaney]

Post by D B Davis

Post by James Nicoll
Do the authors ever address what happens to the price of a commodity
when someone drops a mountain-sized amount of it on the market?

A mountain-sized amount of Imperial marks are literally dumped on people
in _An Enemy of the State_ (Wilson). It leads to hyper-inflation and the
eventual collapse of the status quo.

Do I recall right that Fred Hoyle's story _Element 79_ dealt with this?

Dave, long ago and far away

[Kevrob]

Post by James Nicoll
Do the authors ever address what happens to the price of a commodity
when someone drops a mountain-sized amount of it on the market?

That was a plot point in S M Stirling's 3rd Draka book,
"The Stone Dogs."

If I had access to that, I think I might be tempted to
manipulate teh market in some scarce commodity, as DeBeers
did with jewelry-grade diamonds.

Kevin R

[m***@sky.com]

Post by James Nicoll

Post by Dan Tilque

Post by James Nicoll
And most of the time they won't be near a planet so reacting
against its magnetic field won't be an option.

There is a solar magnetic field. Off-hand I don't know how it compares
to Earth's for this use. It's much stronger than Earth's, but this rock
is lots futher away from the sun than any Earth satellite. My
expectation is that it would be usable and so they just made an error in
saying "planet's" instead of "solar" or perhaps "interplanetary".

One billionth tesla at 1 AU. Earth's is 25 to 65 microteslas at the
surface. It seems to me intuitively obvious it must drop to about
solar strength just about the spot where the solar wind are deflected
from Earth but my intuition also tells me I have the tiger-like reflexes
of a trained Olympic athlete and the data do not support that model.

(trimmed)
The original "Top Gear" TV show had a few shining moments that were almost experiments. In one of them, the host (middle-aged unfit) Jeremy Clarkson played a silly slapping game with Michael Schumacher (then a formula one racing driver and not far from his physical peak). The conclusion seemed to be that Schumacher's no doubt tiger-like reflexes were specific to motor racing. You may have reflexes as good as a trained Olympic athlete - for stimuli outside their sport.

[Lynn McGuire]

On 4/5/2018 8:22 AM, James Nicoll wrote:
...

Post by James Nicoll
Do the authors ever address what happens to the price of a commodity
when someone drops a mountain-sized amount of it on the market?

Yes.

Lynn

[James Nicoll]

Post by Dan Tilque

Post by James Nicoll
And most of the time they won't be near a planet so reacting
against its magnetic field won't be an option.

There is a solar magnetic field. Off-hand I don't know how it compares
to Earth's for this use. It's much stronger than Earth's, but this rock
is lots futher away from the sun than any Earth satellite. My
expectation is that it would be usable and so they just made an error in
saying "planet's" instead of "solar" or perhaps "interplanetary".

It's not the reader's job to provide the editing the authors or their
publisher should have provided.

[Peter Trei]

Post by James Nicoll

Post by James Nicoll

Post by Lynn McGuire

Post by James Nicoll

Post by Dan Tilque
I miss-used the word fuel there. I meant propellant. Yes, they use tiny
amounts for spacecraft, which have a mass less than a metric ton. (Dawn,
which uses an ion thruster, has a mass of only 747 kg.) This rock is
well over a billion metric tons, possibly as much as 2 billion, so the
propellant and power amounts are going to have to scale up.

For example, say the delta vee to put the rock into an Earth crossing orbit
is 1 km/s and the rocket's exhaust velocity is 30 km/s (which is what ISTR
Dawn's is). The rocket equation says the mass ratio will be 1.03, so about
33 to 66 million tonnes of reaction mass will be needed.
Each tonne has an Ek of 4.5x10^11 Joules so in total the operation takes
between 1.5x10^16 to 3x10^16 J. Dawn generates about 10,000 Joules/second
at one AU so a Dawn-sized solar array would only take 48,000 years to huck
enough reaction mass.

Don't forget that changing the tumble of the asteroid needs to be taken
into account. This is the "propellant" that the authors are using to
change the path of the asteroid. The path change of the asteroid is
actually quite minor in the book.

I am looking at the online free sample and I don't see any propulsive
techniques used on the asteroid aside from two years of electric thrust
and a flyby of Earth. Where do they discuss your method? Which btw
I cannot work out how it's supposed to work.
http://www.baen.com/Chapters/9781476781525/9781476781525.htm

http://www.baen.com/Chapters/9781476781525/9781476781525.htm
http://www.baen.com/Chapters/9781476781525/9781476781525.htm
http://www.baen.com/Chapters/9781476781525/9781476781525.htm
"Electric rockets look futuristic, like an advanced space propulsion
system should. As the xenon gas fuel is stripped of its outer electron
and accelerated toward the rocket’s exhaust by carefully designed
electric and magnetic fields, the entire engine emits a brilliant blue
glow. There is none of the fire and smoke that would be seen from some
conventional chemical rocket engines. Chemical rockets are a brute force
approach to moving things around in space and the only realistic way to
get off the surface of a planet, deep in a gravity well, and into space.
But once you are in space, highly efficient electric rockets are an
excellent alternative.
Chemical rockets produce all the thrust they’re going to produce in
their first few minutes of use by providing spectacular acceleration—the
kind an astronaut can feel as he is pushed back into his seat while the
rocket begins to speed up. Electric rockets produce a continuous, very
small thrust that might not even be felt by a person. But it is a
continuous thrust, and, given enough time, an electric rocket can
accelerate a spacecraft to much higher speeds using only a fraction of
the fuel required by a chemical rocket. Such was the case with the
electric thrusters bound to the surface of the Sutter’s Mill asteroid.
The gentle push began as soon as the thrusters were turned on. Sutter’s
Mill, which would weigh just over two billion tons on Earth, didn’t have
any weight in space. It still had mass, so it still required a
significant total force in order to alter its motion so that it would go
where the mission planners from Asteroid Ores wanted it to go. The
entire operation was similar to a swimmer pushing a barge off its
original course. A single swimmer couldn’t make any abrupt changes to
the course of a multiton ship. But if that swimmer could swim sideways
into the barge for a very long time, then the barge would drift slowly
onto a different path.
The electric thrusters were designed to operate continuously for the
entire two years it would take to nudge the massive rock from its
current course to one that would make it accessible for Earth-based
miners to exploit, including an Earth flyby in just another eleven
months. With each day of operation, the asteroid would be on a slightly
different course on its billion-year journey around the Sun. To bring it
where its operators wanted it to be, two full years of thrusting would
be required."
http://www.baen.com/Chapters/9781476781525/9781476781525.htm
"The electric propulsion system’s small but relentless push on asteroid
Sutter’s Mill was slowly altering its trajectory. Had the high-voltage
power supply that fed the thrusters not shorted out, there is no doubt
they would have placed the rock on a path that would take it safely into
a lunar orbit, making it accessible for Earth’s resource-hungry
population to mine. But the power supply did fail, and the beautiful
blue glow of the thrusters winked out, stopping before the asteroid was
placed in the desired orbit, leaving it on a path that no one had
planned or even yet knew. But soon the smart people back on Earth would
know where it was heading—and they would be terrified."
http://www.baen.com/Chapters/9781476781525/9781476781525.htm
"“Isn’t the rock spinning? All the studies we’ve done show that it’ll be
risky to try and rendezvous with a rotating mountain in space,” asked
the Lockheed-Martin CEO.
“They attached two small spacecraft to the asteroid, one on each side,
each containing a long cable—a tether. Think of an ice skater when she
pulls her arms and a leg in in order to speed up. She’s conserving
angular momentum. As she reduces her rotational inertia by pulling her
arms and leg in, her rotation speed must increase to maintain constant
angular momentum. Now do it in reverse with a spinning rock and extend
five-kilometer-long tethers instead of arms and legs. The rock stops
spinning. Cut the tethers and you’re ready to go.”"
"Electrically powered spacecraft propulsion"
https://en.wikipedia.org/wiki/Electrically_powered_spacecraft_propulsion
"An electrically-powered spacecraft propulsion system uses electrical
energy to change the velocity of a spacecraft. Most of these kinds of
spacecraft propulsion systems work by electrically expelling propellant
(reaction mass) at high speed, but electrodynamic tethers work by
interacting with a planet's magnetic field.[1]"
Lynn

Here's the problem. The asteroid is described as being roughly cylindrical ,
a mile long, and a quarter of a mile in diameter. It weighs 1-2 billion tons.

That's big, and a lot of mass.

For the plot to work (I haven't read it, so I could be off here).

* It has to be undiscovered.
* It has to be able to be undetectably rerouted to pass near Earth, and
be captured into Lunar orbit.
* This all has to be done in a reasonable time frame (a few years, max), else
it is not a good investment.

I question whether these constraints can plausibly be met.

It's estimated that over 90% of NEOs (Near Earth Objects) larger than 1 km
have already been found: https://cneos.jpl.nasa.gov/stats/

This rock is not only larger, but we're some distance (about 10 years) into
the future. The chances of an NEO of this size being undiscovered then are
quite low.

The energy requirements for getting this much weight to change orbit
significantly are staggering.

If we pick a rock which is *almost* in the right orbit already, we can greatly
reduce the energy requirement, but that runs into the problem alluded to above;
its an NEO, with a near-Earth encounter in the near future. The chances that it
hasn't been spotted, and no one is checking on it, are very, very low.

A rock that's not an NEO with a soonish near-Earth encounter would require far
more delta-v and energy to shift its orbit. Even ion thrusters are only 65-80%
efficient - where is the power coming from?

The plan is to put it into lunar orbit. We have to get it into just the right
orbit to be captured, which is pretty constraining. This means it has to
approach the Earth-Moon system with a pretty low velocity, since we can't
do any kind of high-acceleration maneuver to put it in orbit. Perhaps something
clever could be done with a 3-body maneuver to reduce the energy needed, but
that would require great finesse.

Finally, as others note, its tumbline, and the use of weights on cables cannot
reduce tumbling to zero. Some space probes us this technique after launch, but
they still need thrusters to remove remnant spin.

All these objections can be handwaved for the sake of a good story, but at some
point you have to stop calling it 'hard' SF.

pt

[Dimensional Traveler]

Post by Peter Trei

Post by James Nicoll

Post by James Nicoll

Post by Lynn McGuire

Post by James Nicoll

Post by Dan Tilque
I miss-used the word fuel there. I meant propellant. Yes, they use tiny
amounts for spacecraft, which have a mass less than a metric ton. (Dawn,
which uses an ion thruster, has a mass of only 747 kg.) This rock is
well over a billion metric tons, possibly as much as 2 billion, so the
propellant and power amounts are going to have to scale up.

For example, say the delta vee to put the rock into an Earth crossing orbit
is 1 km/s and the rocket's exhaust velocity is 30 km/s (which is what ISTR
Dawn's is). The rocket equation says the mass ratio will be 1.03, so about
33 to 66 million tonnes of reaction mass will be needed.
Each tonne has an Ek of 4.5x10^11 Joules so in total the operation takes
between 1.5x10^16 to 3x10^16 J. Dawn generates about 10,000 Joules/second
at one AU so a Dawn-sized solar array would only take 48,000 years to huck
enough reaction mass.

Don't forget that changing the tumble of the asteroid needs to be taken
into account. This is the "propellant" that the authors are using to
change the path of the asteroid. The path change of the asteroid is
actually quite minor in the book.

I am looking at the online free sample and I don't see any propulsive
techniques used on the asteroid aside from two years of electric thrust
and a flyby of Earth. Where do they discuss your method? Which btw
I cannot work out how it's supposed to work.
http://www.baen.com/Chapters/9781476781525/9781476781525.htm

http://www.baen.com/Chapters/9781476781525/9781476781525.htm
http://www.baen.com/Chapters/9781476781525/9781476781525.htm
http://www.baen.com/Chapters/9781476781525/9781476781525.htm
"Electric rockets look futuristic, like an advanced space propulsion
system should. As the xenon gas fuel is stripped of its outer electron
and accelerated toward the rocket’s exhaust by carefully designed
electric and magnetic fields, the entire engine emits a brilliant blue
glow. There is none of the fire and smoke that would be seen from some
conventional chemical rocket engines. Chemical rockets are a brute force
approach to moving things around in space and the only realistic way to
get off the surface of a planet, deep in a gravity well, and into space.
But once you are in space, highly efficient electric rockets are an
excellent alternative.
Chemical rockets produce all the thrust they’re going to produce in
their first few minutes of use by providing spectacular acceleration—the
kind an astronaut can feel as he is pushed back into his seat while the
rocket begins to speed up. Electric rockets produce a continuous, very
small thrust that might not even be felt by a person. But it is a
continuous thrust, and, given enough time, an electric rocket can
accelerate a spacecraft to much higher speeds using only a fraction of
the fuel required by a chemical rocket. Such was the case with the
electric thrusters bound to the surface of the Sutter’s Mill asteroid.
The gentle push began as soon as the thrusters were turned on. Sutter’s
Mill, which would weigh just over two billion tons on Earth, didn’t have
any weight in space. It still had mass, so it still required a
significant total force in order to alter its motion so that it would go
where the mission planners from Asteroid Ores wanted it to go. The
entire operation was similar to a swimmer pushing a barge off its
original course. A single swimmer couldn’t make any abrupt changes to
the course of a multiton ship. But if that swimmer could swim sideways
into the barge for a very long time, then the barge would drift slowly
onto a different path.
The electric thrusters were designed to operate continuously for the
entire two years it would take to nudge the massive rock from its
current course to one that would make it accessible for Earth-based
miners to exploit, including an Earth flyby in just another eleven
months. With each day of operation, the asteroid would be on a slightly
different course on its billion-year journey around the Sun. To bring it
where its operators wanted it to be, two full years of thrusting would
be required."
http://www.baen.com/Chapters/9781476781525/9781476781525.htm
"The electric propulsion system’s small but relentless push on asteroid
Sutter’s Mill was slowly altering its trajectory. Had the high-voltage
power supply that fed the thrusters not shorted out, there is no doubt
they would have placed the rock on a path that would take it safely into
a lunar orbit, making it accessible for Earth’s resource-hungry
population to mine. But the power supply did fail, and the beautiful
blue glow of the thrusters winked out, stopping before the asteroid was
placed in the desired orbit, leaving it on a path that no one had
planned or even yet knew. But soon the smart people back on Earth would
know where it was heading—and they would be terrified."
http://www.baen.com/Chapters/9781476781525/9781476781525.htm
"“Isn’t the rock spinning? All the studies we’ve done show that it’ll be
risky to try and rendezvous with a rotating mountain in space,” asked
the Lockheed-Martin CEO.
“They attached two small spacecraft to the asteroid, one on each side,
each containing a long cable—a tether. Think of an ice skater when she
pulls her arms and a leg in in order to speed up. She’s conserving
angular momentum. As she reduces her rotational inertia by pulling her
arms and leg in, her rotation speed must increase to maintain constant
angular momentum. Now do it in reverse with a spinning rock and extend
five-kilometer-long tethers instead of arms and legs. The rock stops
spinning. Cut the tethers and you’re ready to go.”"
"Electrically powered spacecraft propulsion"
https://en.wikipedia.org/wiki/Electrically_powered_spacecraft_propulsion
"An electrically-powered spacecraft propulsion system uses electrical
energy to change the velocity of a spacecraft. Most of these kinds of
spacecraft propulsion systems work by electrically expelling propellant
(reaction mass) at high speed, but electrodynamic tethers work by
interacting with a planet's magnetic field.[1]"
Lynn

Here's the problem. The asteroid is described as being roughly cylindrical ,
a mile long, and a quarter of a mile in diameter. It weighs 1-2 billion tons.
That's big, and a lot of mass.
For the plot to work (I haven't read it, so I could be off here).
* It has to be undiscovered.
* It has to be able to be undetectably rerouted to pass near Earth, and
be captured into Lunar orbit.
* This all has to be done in a reasonable time frame (a few years, max), else
it is not a good investment.
I question whether these constraints can plausibly be met.
It's estimated that over 90% of NEOs (Near Earth Objects) larger than 1 km
have already been found: https://cneos.jpl.nasa.gov/stats/
This rock is not only larger, but we're some distance (about 10 years) into
the future. The chances of an NEO of this size being undiscovered then are
quite low.
The energy requirements for getting this much weight to change orbit
significantly are staggering.
If we pick a rock which is *almost* in the right orbit already, we can greatly
reduce the energy requirement, but that runs into the problem alluded to above;
its an NEO, with a near-Earth encounter in the near future. The chances that it
hasn't been spotted, and no one is checking on it, are very, very low.
A rock that's not an NEO with a soonish near-Earth encounter would require far
more delta-v and energy to shift its orbit. Even ion thrusters are only 65-80%
efficient - where is the power coming from?
The plan is to put it into lunar orbit. We have to get it into just the right
orbit to be captured, which is pretty constraining. This means it has to
approach the Earth-Moon system with a pretty low velocity, since we can't
do any kind of high-acceleration maneuver to put it in orbit. Perhaps something
clever could be done with a 3-body maneuver to reduce the energy needed, but
that would require great finesse.
Finally, as others note, its tumbline, and the use of weights on cables cannot
reduce tumbling to zero. Some space probes us this technique after launch, but
they still need thrusters to remove remnant spin.
All these objections can be handwaved for the sake of a good story, but at some
point you have to stop calling it 'hard' SF.

Another problem is how to the protagonists know about this asteroid but
no one else does? As I understand it the search for NEOs is a world
wide effort. When astronomers find something they think might be a NEO,
they call upon others to observe and confirm, with the results being
shared very widely. So this one has to somehow be found by the
protagonists _without_ astronomers who are specifically looking for
bodies like it with more observatories and almost certainly better
equipment also finding it.

If it is an already known NEO, then the protagonists would have to reach
it without being observed (all the space powers routinely monitor for
launches, NORAD has a division specifically for tracking anything in
Earth orbit down to the size of an individual bolt so good luck with
that and how are they going to communicate with Earth without everyone
else detecting the ship's radio signals?) and then alter its orbit
quickly enough and greatly enough that the routine followups don't see
it not quite where its supposed to be (which would trigger a lot more
attention) AND without it being rediscovered.

[Robert Woodward]

Post by James Nicoll

Post by Lynn McGuire

Post by James Nicoll

Post by Dan Tilque
I miss-used the word fuel there. I meant propellant. Yes, they use tiny
amounts for spacecraft, which have a mass less than a metric ton. (Dawn,
which uses an ion thruster, has a mass of only 747 kg.) This rock is
well over a billion metric tons, possibly as much as 2 billion, so the
propellant and power amounts are going to have to scale up.

For example, say the delta vee to put the rock into an Earth crossing orbit
is 1 km/s and the rocket's exhaust velocity is 30 km/s (which is what ISTR
Dawn's is). The rocket equation says the mass ratio will be 1.03, so about
33 to 66 million tonnes of reaction mass will be needed.
Each tonne has an Ek of 4.5x10^11 Joules so in total the operation takes
between 1.5x10^16 to 3x10^16 J. Dawn generates about 10,000 Joules/second
at one AU so a Dawn-sized solar array would only take 48,000 years to huck
enough reaction mass.

Don't forget that changing the tumble of the asteroid needs to be taken
into account. This is the "propellant" that the authors are using to
change the path of the asteroid. The path change of the asteroid is
actually quite minor in the book.

I am looking at the online free sample and I don't see any propulsive
techniques used on the asteroid aside from two years of electric thrust
and a flyby of Earth. Where do they discuss your method? Which btw
I cannot work out how it's supposed to work.
http://www.baen.com/Chapters/9781476781525/9781476781525.htm

Later chapters have debris from the asteroid hitting Earth (some of the
rocks were big enough to reach the surface) days before the asteroid
arrives. I consider that to be flatly impossible (I wasn't joking in
earlier posts about violations of Newton's Laws of Motion and also of
Conservation laws).

[Lynn McGuire]

Post by Dan Tilque

Post by J. Clarke

Post by Dan Tilque

Post by J. Clarke

Post by Dan Tilque

Post by J. Clarke
By what means would someone "notice" this "geezy huge amount of waste
heat"?

Infrared telescopes.

Which are, in your view, constantly pointed at all areas of the sky.

Not in all directions at once, but close enough. There are various
programs where automated telescopes constantly scan the sky.
Some are Earth-based and so are limited to what's visible on any
particular night, but others are in orbit and can scan much larger
parts of the sky in a given period. One that comes to mind off-hand
http://sci.esa.int/gaia/

Yeah, it takes it over a year to do a full sky scan--it has a sunshade
so it doesn't get pointed anywhere near the sun which blocks out a
good bit of the sky at any given time.

Gaia was just the first example of a survey that I thought of. There are
many others and more being started all the time.

Post by J. Clarke

Post by Dan Tilque
Not all of them are visible light scopes, either. For example, WFIRST
https://en.wikipedia.org/wiki/Wide_Field_Infrared_Survey_Telescope

And is it going to pick up this tiny rock while it's doing its wide
field infrared survey?

Not the rock. You may remember in my earlier post I said that it'll
detect the large cloud of ionized material that the rock will expel as
propellant.
But rocks smaller than the one in this book are found by surveys looking
for them.

Post by J. Clarke

Post by Dan Tilque
Others will work in various radio bands. Those will mostly be
Earth-based, but they work in the day as well as the night.

That's nice, what of it.

They could also spot this cloud. It's likely to be giving off some radio
/microwave/submillimeter/terahertz waves as well as IR.

Post by J. Clarke

Post by Dan Tilque
These survey programs are getting more and more common. The main
problem they have is the vast amounts of data they are gathering,
which is only going to get worse. And by worse, I mean by several
orders of magnitude. So they're looking to AI to do the initial
triage of the data. The investigators then will look at what the AI
comes up with.

They are _surveys_.  They don't scan the whole sky every ten minutes
looking for wayward rocks.

It'll take a long time (months-to-years) to move this rock from its
current orbit to one bringing it to Earth. In that time, it'll show up
as an anomalous object in one of these surveys. My guess it would be
within the first month.

Post by J. Clarke

Post by Dan Tilque
So any writers out there want a realistic scene where astronomers
discover alien spacecraft coming into the system or something like
that, that's what it's most likely to be. After they look at what the
AI found, they'll look at earlier observations from their survey and
then what other survey instruments saw in the same area. All the
observations will be online.

So how's that working out for finding earth crossing asteroids?

Do you think they haven't found any? Earth-crossing asteroids, those
that cross the Earth's orbit, are reasonably common. They find them all
the time. Occasionally, they find one that has a chance to hit the Earth
in the foreseeable future, but those are fairly rare. And then further
refinement of the orbit has always reduced that chance to zero. Well, so
far anyway. I'm sure they'll eventually find one which will hit the
Earth. It may be a century or two before they find one.

The writers of the book, both certified rocket scientists by NASA, are
taking an Earth orbit crossing asteroid and moving its orbit slightly so
that the asteroid is captured by the Earth. But then something goes wrong.

BTW, it is just a matter of time until some idiot with more money than
brains tries this. The rewards from capturing a metal heavy asteroid
are immense. Pray that the idiot has a backup thruster system if the
primary thruster system fails.

Lynn

[Scott Lurndal]

Post by Lynn McGuire

Post by Dan Tilque
Do you think they haven't found any? Earth-crossing asteroids, those
that cross the Earth's orbit, are reasonably common. They find them all
the time. Occasionally, they find one that has a chance to hit the Earth
in the foreseeable future, but those are fairly rare. And then further
refinement of the orbit has always reduced that chance to zero. Well, so
far anyway. I'm sure they'll eventually find one which will hit the
Earth. It may be a century or two before they find one.

The writers of the book, both certified rocket scientists by NASA,

Appeal to authority noted.

WTF is a "certified rocket scientist"?

[Lynn McGuire]

Post by Scott Lurndal

Post by Lynn McGuire

Post by Dan Tilque
Do you think they haven't found any? Earth-crossing asteroids, those
that cross the Earth's orbit, are reasonably common. They find them all
the time. Occasionally, they find one that has a chance to hit the Earth
in the foreseeable future, but those are fairly rare. And then further
refinement of the orbit has always reduced that chance to zero. Well, so
far anyway. I'm sure they'll eventually find one which will hit the
Earth. It may be a century or two before they find one.

The writers of the book, both certified rocket scientists by NASA,

Appeal to authority noted.
WTF is a "certified rocket scientist"?

From:
https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/

"Travis S. Taylor, Ph.D. is the co-creator and star of the National
Geographic Channel’s hit series, Rocket City Rednecks and can be seen on
the Weather Channel on 3 Scientists Walk into a Bar. Taylor is a
physicist who has worked on various programs for the Department of
Defense and NASA for the past twenty years. His expertise includes
advanced propulsion concepts, very large space telescopes, space-based
beamed energy systems, future combat technologies and next generation
space launch concepts. Taylor is also the author of pulse-pounding,
cutting edge science fiction with the Tau Ceti Agenda series including
One Good Soldier, The Tau Ceti Agenda, One Day on Mars, and Trail of
Evil, as well as his ground-breaking Warp Speed series, with entries
Warp Speed and The Quantum Connection."

"Les Johnson is a NASA physicist and author. By day, he serves as the
Senior Technical Assistant for the Advanced Concepts Office at the NASA
George C. Marshall Space Flight Center in Huntsville, Alabama. In the
early 2000s, he was NASA’s Manager for Interstellar Propulsion Research
and later managed the In-Space Propulsion Technology Project. He was
technical consultant for the movie Lost in Space and has appeared on the
Discovery Channel series, Physics of the Impossible in the “How to Build
a Starship” episode. He has also appeared in three episodes of the
Science Channel series Exodus Earth. He is the author of novel Back to
the Moon, coauthored with Travis S. Taylor, and the coeditor of the
science/science fiction collection Going Interstellar."

Lynn

[Scott Lurndal]

Post by Lynn McGuire

Post by Scott Lurndal

Post by Lynn McGuire

Post by Dan Tilque
Do you think they haven't found any? Earth-crossing asteroids, those
that cross the Earth's orbit, are reasonably common. They find them all
the time. Occasionally, they find one that has a chance to hit the Earth
in the foreseeable future, but those are fairly rare. And then further
refinement of the orbit has always reduced that chance to zero. Well, so
far anyway. I'm sure they'll eventually find one which will hit the
Earth. It may be a century or two before they find one.

The writers of the book, both certified rocket scientists by NASA,

Appeal to authority noted.
WTF is a "certified rocket scientist"?

https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/

That doesn't define the phrase "certified rocket scientist".

Why not just call them physicists who happen to write fiction
in their spare time[*] and are employed by NASA.

Note that fiction, by definition, isn't required to bear any relationship with reality.

[*] Hopefully, I'd hate for them to be writing it on _my_ dime.

[Jibini Kula Tumbili Kujisalimisha]

Post by Scott Lurndal

Post by Lynn McGuire

Post by Scott Lurndal

Post by Lynn McGuire

Post by Dan Tilque
Do you think they haven't found any? Earth-crossing
asteroids, those that cross the Earth's orbit, are
reasonably common. They find them all the time.
Occasionally, they find one that has a chance to hit the
Earth in the foreseeable future, but those are fairly rare.
And then further refinement of the orbit has always reduced
that chance to zero. Well, so far anyway. I'm sure they'll
eventually find one which will hit the Earth. It may be a
century or two before they find one.

The writers of the book, both certified rocket scientists by NASA,

Appeal to authority noted.
WTF is a "certified rocket scientist"?

https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X
/

That doesn't define the phrase "certified rocket scientist".
Why not just call them physicists who happen to write fiction
in their spare time[*] and are employed by NASA.
Note that fiction, by definition, isn't required to bear any
relationship with reality.

Catherine Asaro has a PhD in physics, and writes cience fiction
where psychic abilities are critical infrastructure to an
interstellar empire. Just because an author knows they're breaking
the rules doesn't mean they're not breaking them.
--
Terry Austin

Vacation photos from Iceland:
https://plus.google.com/u/0/collection/QaXQkB

"Terry Austin: like the polio vaccine, only with more asshole."
-- David Bilek

Jesus forgives sinners, not criminals.

[Kevrob]

Post by Lynn McGuire
BTW, it is just a matter of time until some idiot with more money than
brains tries this. The rewards from capturing a metal heavy asteroid
are immense. Pray that the idiot has a backup thruster system if the
primary thruster system fails.
Lynn

Better to park it in the L5 position, or is even that too risky?

Kevin R

[Scott Lurndal]

Post by Kevrob

Post by Lynn McGuire
BTW, it is just a matter of time until some idiot with more money than
brains tries this. The rewards from capturing a metal heavy asteroid
are immense. Pray that the idiot has a backup thruster system if the
primary thruster system fails.
Lynn

Better to park it in the L5 position, or is even that too risky?

Mine it and refine it in-situ and send the results TMiaHM-style.

[Robert Carnegie]

Post by Kevrob

Post by Lynn McGuire
BTW, it is just a matter of time until some idiot with more money than
brains tries this. The rewards from capturing a metal heavy asteroid
are immense. Pray that the idiot has a backup thruster system if the
primary thruster system fails.
Lynn

Better to park it in the L5 position, or is even that too risky?
Kevin R

Conveniently placed for... what? I may be exposing my
ignorance, but if you want to sell raw metal in space,
is L5 the place to sell it from? Or geosynchronous orbit?

And can't you earn more cash by aiming it at for instance
Washington, D.C., then naming your price to redirect it?

At least it mean that if your company goes bust then there
will be considerable interest in assisting it out of its
difficulties with assets intact.

[J. Clarke]

On Sat, 31 Mar 2018 18:31:32 -0700 (PDT), Robert Carnegie

Post by Robert Carnegie

Post by Kevrob

Post by Lynn McGuire
BTW, it is just a matter of time until some idiot with more money than
brains tries this. The rewards from capturing a metal heavy asteroid
are immense. Pray that the idiot has a backup thruster system if the
primary thruster system fails.
Lynn

Better to park it in the L5 position, or is even that too risky?
Kevin R

Conveniently placed for... what? I may be exposing my
ignorance, but if you want to sell raw metal in space,
is L5 the place to sell it from? Or geosynchronous orbit?
And can't you earn more cash by aiming it at for instance
Washington, D.C., then naming your price to redirect it?

How about naming your price to so aim it. I can see it now--a series
of linked kickstarters and the one with the highest total gets the
load dumped on the designated target.

Post by Robert Carnegie
At least it mean that if your company goes bust then there
will be considerable interest in assisting it out of its
difficulties with assets intact.

[Moriarty]

Post by Robert Carnegie

Post by Kevrob

Post by Lynn McGuire
BTW, it is just a matter of time until some idiot with more money than
brains tries this. The rewards from capturing a metal heavy asteroid
are immense. Pray that the idiot has a backup thruster system if the
primary thruster system fails.
Lynn

Better to park it in the L5 position, or is even that too risky?
Kevin R

Conveniently placed for... what? I may be exposing my
ignorance, but if you want to sell raw metal in space,
is L5 the place to sell it from? Or geosynchronous orbit?
And can't you earn more cash by aiming it at for instance
Washington, D.C., then naming your price to redirect it?

I believe the standard asking price is <dramatic pause> One Million Dollars!

-Moriarty

[Gene Wirchenko]

On Sat, 31 Mar 2018 21:03:49 -0700 (PDT), Moriarty
[snip]

Post by Moriarty

Post by Robert Carnegie
And can't you earn more cash by aiming it at for instance
Washington, D.C., then naming your price to redirect it?

I believe the standard asking price is <dramatic pause> One Million Dollars!

It got upped to one hundred billion dollars.

Sincerely,

Gene Wirchenko

[Kevrob]

Post by Gene Wirchenko
On Sat, 31 Mar 2018 21:03:49 -0700 (PDT), Moriarty
[snip]

Post by Moriarty

Post by Robert Carnegie
And can't you earn more cash by aiming it at for instance
Washington, D.C., then naming your price to redirect it?

I believe the standard asking price is <dramatic pause> One Million Dollars!

It got upped to one hundred billion dollars.

Same-same, adjusted for inflation. :)

Kevin R

[Kevrob]

Post by Robert Carnegie

Post by Kevrob

Post by Lynn McGuire
BTW, it is just a matter of time until some idiot with more money than
brains tries this. The rewards from capturing a metal heavy asteroid
are immense. Pray that the idiot has a backup thruster system if the
primary thruster system fails.
Lynn

Better to park it in the L5 position, or is even that too risky?
Kevin R

Conveniently placed for... what? I may be exposing my
ignorance, but if you want to sell raw metal in space,
is L5 the place to sell it from? Or geosynchronous orbit?

Seems like it have more value, near Terra, where you can both
launch finished products manufactured in space into the
gravity well, or elsewhere in the system. You also have feedstock
for building space habitats and vehicles, and fueling them.

Post by Robert Carnegie
And can't you earn more cash by aiming it at for instance
Washington, D.C., then naming your price to redirect it?

I'm staying away from supervillain plots...for now.

{Nyah-ah-ah!}

Post by Robert Carnegie
At least it mean that if your company goes bust then there
will be considerable interest in assisting it out of its
difficulties with assets intact.

Kevin R

[Robert Woodward]

Post by Lynn McGuire
_On to the Asteroid_ by Travis Taylor and Les Johnson
https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/
Book number two of a two book space opera series. I read the
excellently printed and bound MMPB by Baen.
In the middle of the 2020s, there is a space race going on with China,
NASA, and an American private space touring firm. Another firm seeks to
get into the space business by secretly bringing a metals rich asteroid
to Earth using an electric thruster system. The electric thruster
system fails midway to Earth and the asteroid will hit the Earth rather
than going into orbit around it since there is not a backup thruster
system. Since the asteroid is a mile long by a quarter mile in
diameter, the asteroid's path must be changed.
Please note this little series is very hard science fiction. All of
this is possible today using today's technology and materials. And, a
LOT of money.

Nonsense. To begin with, I am certain it is possible to develop a Earth
orbit rendezvous burn that would NEVER intersect Earth itself, no matter
when the drive failed (at least not for several orbits). It shouldn't be
that more energy expensive than the minimum energy rendezvous burn.

Second of all, I glanced through it and there was a good deal of
discussion of debris from that asteroid hitting Earth. Just what was the
cause of that debris? And how did it arrive before the asteroid? I
thought these guys were physicists.

[Lynn McGuire]

Post by Robert Woodward

Post by Lynn McGuire
_On to the Asteroid_ by Travis Taylor and Les Johnson
https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/
Book number two of a two book space opera series. I read the
excellently printed and bound MMPB by Baen.
In the middle of the 2020s, there is a space race going on with China,
NASA, and an American private space touring firm. Another firm seeks to
get into the space business by secretly bringing a metals rich asteroid
to Earth using an electric thruster system. The electric thruster
system fails midway to Earth and the asteroid will hit the Earth rather
than going into orbit around it since there is not a backup thruster
system. Since the asteroid is a mile long by a quarter mile in
diameter, the asteroid's path must be changed.
Please note this little series is very hard science fiction. All of
this is possible today using today's technology and materials. And, a
LOT of money.

Nonsense. To begin with, I am certain it is possible to develop a Earth
orbit rendezvous burn that would NEVER intersect Earth itself, no matter
when the drive failed (at least not for several orbits). It shouldn't be
that more energy expensive than the minimum energy rendezvous burn.
Second of all, I glanced through it and there was a good deal of
discussion of debris from that asteroid hitting Earth. Just what was the
cause of that debris? And how did it arrive before the asteroid? I
thought these guys were physicists.

I would advise reading the book for answers to these questions and more.

One hint: the electric thrusters caused a explosive stress fracture in
the asteroid.

Thanks,
Lynn

[Scott Lurndal]

Post by Lynn McGuire

Post by Robert Woodward

Post by Lynn McGuire
_On to the Asteroid_ by Travis Taylor and Les Johnson
https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/
Book number two of a two book space opera series. I read the
excellently printed and bound MMPB by Baen.
In the middle of the 2020s, there is a space race going on with China,
NASA, and an American private space touring firm. Another firm seeks to
get into the space business by secretly bringing a metals rich asteroid
to Earth using an electric thruster system. The electric thruster
system fails midway to Earth and the asteroid will hit the Earth rather
than going into orbit around it since there is not a backup thruster
system. Since the asteroid is a mile long by a quarter mile in
diameter, the asteroid's path must be changed.
Please note this little series is very hard science fiction. All of
this is possible today using today's technology and materials. And, a
LOT of money.

Nonsense. To begin with, I am certain it is possible to develop a Earth
orbit rendezvous burn that would NEVER intersect Earth itself, no matter
when the drive failed (at least not for several orbits). It shouldn't be
that more energy expensive than the minimum energy rendezvous burn.
Second of all, I glanced through it and there was a good deal of
discussion of debris from that asteroid hitting Earth. Just what was the
cause of that debris? And how did it arrive before the asteroid? I
thought these guys were physicists.

I would advise reading the book for answers to these questions and more.
One hint: the electric thrusters caused a explosive stress fracture in
the asteroid.

While an "electric thruster" has a higher specific impulse (Isp) than
traditional chemical rockets - which means it uses the fuel more
efficiently, the total thrust is still quite low relative to a
chemical rocket.

[Lynn McGuire]

Post by Scott Lurndal

Post by Lynn McGuire

Post by Robert Woodward

Post by Lynn McGuire
_On to the Asteroid_ by Travis Taylor and Les Johnson
https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/
Book number two of a two book space opera series. I read the
excellently printed and bound MMPB by Baen.
In the middle of the 2020s, there is a space race going on with China,
NASA, and an American private space touring firm. Another firm seeks to
get into the space business by secretly bringing a metals rich asteroid
to Earth using an electric thruster system. The electric thruster
system fails midway to Earth and the asteroid will hit the Earth rather
than going into orbit around it since there is not a backup thruster
system. Since the asteroid is a mile long by a quarter mile in
diameter, the asteroid's path must be changed.
Please note this little series is very hard science fiction. All of
this is possible today using today's technology and materials. And, a
LOT of money.

Nonsense. To begin with, I am certain it is possible to develop a Earth
orbit rendezvous burn that would NEVER intersect Earth itself, no matter
when the drive failed (at least not for several orbits). It shouldn't be
that more energy expensive than the minimum energy rendezvous burn.
Second of all, I glanced through it and there was a good deal of
discussion of debris from that asteroid hitting Earth. Just what was the
cause of that debris? And how did it arrive before the asteroid? I
thought these guys were physicists.

I would advise reading the book for answers to these questions and more.
One hint: the electric thrusters caused a explosive stress fracture in
the asteroid.

While an "electric thruster" has a higher specific impulse (Isp) than
traditional chemical rockets - which means it uses the fuel more
efficiently, the total thrust is still quite low relative to a
chemical rocket.

Yes. But since the electric thrusters use electric heat to convert the
liquid mass into high pressure vapor, they are more efficient if you
have solar panels.

Lynn

[Scott Lurndal]

Post by Lynn McGuire

Post by Scott Lurndal

Post by Lynn McGuire

Post by Robert Woodward

Post by Lynn McGuire
_On to the Asteroid_ by Travis Taylor and Les Johnson
https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/
Book number two of a two book space opera series. I read the
excellently printed and bound MMPB by Baen.
In the middle of the 2020s, there is a space race going on with China,
NASA, and an American private space touring firm. Another firm seeks to
get into the space business by secretly bringing a metals rich asteroid
to Earth using an electric thruster system. The electric thruster
system fails midway to Earth and the asteroid will hit the Earth rather
than going into orbit around it since there is not a backup thruster
system. Since the asteroid is a mile long by a quarter mile in
diameter, the asteroid's path must be changed.
Please note this little series is very hard science fiction. All of
this is possible today using today's technology and materials. And, a
LOT of money.

Nonsense. To begin with, I am certain it is possible to develop a Earth
orbit rendezvous burn that would NEVER intersect Earth itself, no matter
when the drive failed (at least not for several orbits). It shouldn't be
that more energy expensive than the minimum energy rendezvous burn.
Second of all, I glanced through it and there was a good deal of
discussion of debris from that asteroid hitting Earth. Just what was the
cause of that debris? And how did it arrive before the asteroid? I
thought these guys were physicists.

I would advise reading the book for answers to these questions and more.
One hint: the electric thrusters caused a explosive stress fracture in
the asteroid.

While an "electric thruster" has a higher specific impulse (Isp) than
traditional chemical rockets - which means it uses the fuel more
efficiently, the total thrust is still quite low relative to a
chemical rocket.

Yes. But since the electric thrusters use electric heat to convert the
liquid mass into high pressure vapor, they are more efficient if you
have solar panels.

My point was that there is unlikely to be enough thrust to "cause explosive
stress fracture" in the asteroid when using hall-effect or ion thrusters.

[Lynn McGuire]

Post by Scott Lurndal

Post by Lynn McGuire

Post by Scott Lurndal

Post by Lynn McGuire

Post by Robert Woodward

Post by Lynn McGuire
_On to the Asteroid_ by Travis Taylor and Les Johnson
https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/
Book number two of a two book space opera series. I read the
excellently printed and bound MMPB by Baen.
In the middle of the 2020s, there is a space race going on with China,
NASA, and an American private space touring firm. Another firm seeks to
get into the space business by secretly bringing a metals rich asteroid
to Earth using an electric thruster system. The electric thruster
system fails midway to Earth and the asteroid will hit the Earth rather
than going into orbit around it since there is not a backup thruster
system. Since the asteroid is a mile long by a quarter mile in
diameter, the asteroid's path must be changed.
Please note this little series is very hard science fiction. All of
this is possible today using today's technology and materials. And, a
LOT of money.

Nonsense. To begin with, I am certain it is possible to develop a Earth
orbit rendezvous burn that would NEVER intersect Earth itself, no matter
when the drive failed (at least not for several orbits). It shouldn't be
that more energy expensive than the minimum energy rendezvous burn.
Second of all, I glanced through it and there was a good deal of
discussion of debris from that asteroid hitting Earth. Just what was the
cause of that debris? And how did it arrive before the asteroid? I
thought these guys were physicists.

I would advise reading the book for answers to these questions and more.
One hint: the electric thrusters caused a explosive stress fracture in
the asteroid.

While an "electric thruster" has a higher specific impulse (Isp) than
traditional chemical rockets - which means it uses the fuel more
efficiently, the total thrust is still quite low relative to a
chemical rocket.

Yes. But since the electric thrusters use electric heat to convert the
liquid mass into high pressure vapor, they are more efficient if you
have solar panels.

My point was that there is unlikely to be enough thrust to "cause explosive
stress fracture" in the asteroid when using hall-effect or ion thrusters.

What if the asteroid was unstable to start with ?

Lynn

[Peter Trei]

Post by Lynn McGuire

Post by Scott Lurndal

Post by Lynn McGuire

Post by Robert Woodward

Post by Lynn McGuire
_On to the Asteroid_ by Travis Taylor and Les Johnson
https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/
Book number two of a two book space opera series. I read the
excellently printed and bound MMPB by Baen.
In the middle of the 2020s, there is a space race going on with China,
NASA, and an American private space touring firm. Another firm seeks to
get into the space business by secretly bringing a metals rich asteroid
to Earth using an electric thruster system. The electric thruster
system fails midway to Earth and the asteroid will hit the Earth rather
than going into orbit around it since there is not a backup thruster
system. Since the asteroid is a mile long by a quarter mile in
diameter, the asteroid's path must be changed.
Please note this little series is very hard science fiction. All of
this is possible today using today's technology and materials. And, a
LOT of money.

Nonsense. To begin with, I am certain it is possible to develop a Earth
orbit rendezvous burn that would NEVER intersect Earth itself, no matter
when the drive failed (at least not for several orbits). It shouldn't be
that more energy expensive than the minimum energy rendezvous burn.
Second of all, I glanced through it and there was a good deal of
discussion of debris from that asteroid hitting Earth. Just what was the
cause of that debris? And how did it arrive before the asteroid? I
thought these guys were physicists.

I would advise reading the book for answers to these questions and more.
One hint: the electric thrusters caused a explosive stress fracture in
the asteroid.

While an "electric thruster" has a higher specific impulse (Isp) than
traditional chemical rockets - which means it uses the fuel more
efficiently, the total thrust is still quite low relative to a
chemical rocket.

Yes. But since the electric thrusters use electric heat to convert the
liquid mass into high pressure vapor, they are more efficient if you
have solar panels.
the

Even at 100% efficiency, 200 GW would require on the order of 100M sq meters of solar panel,
Or about 10 km by 10 km.

Keeping an object that big secret is it feasible.
Pt

[Lynn McGuire]

Post by Peter Trei

Post by Lynn McGuire

Post by Scott Lurndal

Post by Lynn McGuire

Post by Robert Woodward

Post by Lynn McGuire
_On to the Asteroid_ by Travis Taylor and Les Johnson
https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/
Book number two of a two book space opera series. I read the
excellently printed and bound MMPB by Baen.
In the middle of the 2020s, there is a space race going on with China,
NASA, and an American private space touring firm. Another firm seeks to
get into the space business by secretly bringing a metals rich asteroid
to Earth using an electric thruster system. The electric thruster
system fails midway to Earth and the asteroid will hit the Earth rather
than going into orbit around it since there is not a backup thruster
system. Since the asteroid is a mile long by a quarter mile in
diameter, the asteroid's path must be changed.
Please note this little series is very hard science fiction. All of
this is possible today using today's technology and materials. And, a
LOT of money.

Nonsense. To begin with, I am certain it is possible to develop a Earth
orbit rendezvous burn that would NEVER intersect Earth itself, no matter
when the drive failed (at least not for several orbits). It shouldn't be
that more energy expensive than the minimum energy rendezvous burn.
Second of all, I glanced through it and there was a good deal of
discussion of debris from that asteroid hitting Earth. Just what was the
cause of that debris? And how did it arrive before the asteroid? I
thought these guys were physicists.

I would advise reading the book for answers to these questions and more.
One hint: the electric thrusters caused a explosive stress fracture in
the asteroid.

While an "electric thruster" has a higher specific impulse (Isp) than
traditional chemical rockets - which means it uses the fuel more
efficiently, the total thrust is still quite low relative to a
chemical rocket.

Yes. But since the electric thrusters use electric heat to convert the
liquid mass into high pressure vapor, they are more efficient if you
have solar panels.
the

Even at 100% efficiency, 200 GW would require on the order of 100M sq meters of solar panel,
Or about 10 km by 10 km.
Keeping an object that big secret is it feasible.
Pt

Are you a rocket scientist ? I doubt it so I am going to trust that
Taylor and Johnson know what they are talking about here.

Lynn

[Dimensional Traveler]

Post by Peter Trei

Post by Scott Lurndal

Post by Lynn McGuire

Post by Robert Woodward

Post by Lynn McGuire
_On to the Asteroid_ by Travis Taylor and Les Johnson
https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/
Book number two of a two book space opera series.  I read the
excellently printed and bound MMPB by Baen.
In the middle of the 2020s, there is a space race going on with China,
NASA, and an American private space touring firm.  Another firm
seeks to
get into the space business by secretly bringing a metals rich asteroid
to Earth using an electric thruster system.  The electric thruster
system fails midway to Earth and the asteroid will hit the Earth rather
than going into orbit around it since there is not a backup thruster
system.  Since the asteroid is a mile long by a quarter mile in
diameter, the asteroid's path must be changed.
Please note this little series is very hard science fiction.  All of
this is possible today using today's technology and materials.
And, a
LOT of money.

Nonsense. To begin with, I am certain it is possible to develop a Earth
orbit rendezvous burn that would NEVER intersect Earth itself, no matter
when the drive failed (at least not for several orbits). It shouldn't be
that more energy expensive than the minimum energy rendezvous burn.
Second of all, I glanced through it and there was a good deal of
discussion of debris from that asteroid hitting Earth. Just what was the
cause of that debris? And how did it arrive before the asteroid? I
thought these guys were physicists.

I would advise reading the book for answers to these questions and more.
One hint: the electric thrusters caused a explosive stress fracture in
the asteroid.

While an "electric thruster" has a higher specific impulse (Isp) than
traditional chemical rockets - which means it uses the fuel more
efficiently, the total thrust is still quite low relative to a
chemical rocket.

Yes.  But since the electric thrusters use electric heat to convert the
liquid mass into high pressure vapor, they are more efficient if you
have solar panels.
the

Even at 100% efficiency, 200 GW would require on the order of 100M sq
meters of solar panel,
Or about 10 km by 10 km.
Keeping an object that big secret is it feasible.
Pt

Are you a rocket scientist ?  I doubt it so I am going to trust that
Taylor and Johnson know what they are talking about here.

I don't know about Johnson but while Taylor is a rocket scientist his
science fiction is a bit overboard. I've read a lot of Taylor's stuff,
and enjoyed it, but his plot lines are more like the Lensmen stories
with a "hard science" skin and the theories he bases that skin on are
NOT mainstream.

[Peter Trei]

Post by Peter Trei

Post by Lynn McGuire

Post by Scott Lurndal

Post by Lynn McGuire

Post by Robert Woodward

Post by Lynn McGuire
_On to the Asteroid_ by Travis Taylor and Les Johnson
https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/
Book number two of a two book space opera series. I read the
excellently printed and bound MMPB by Baen.
In the middle of the 2020s, there is a space race going on with China,
NASA, and an American private space touring firm. Another firm seeks to
get into the space business by secretly bringing a metals rich asteroid
to Earth using an electric thruster system. The electric thruster
system fails midway to Earth and the asteroid will hit the Earth rather
than going into orbit around it since there is not a backup thruster
system. Since the asteroid is a mile long by a quarter mile in
diameter, the asteroid's path must be changed.
Please note this little series is very hard science fiction. All of
this is possible today using today's technology and materials. And, a
LOT of money.

Nonsense. To begin with, I am certain it is possible to develop a Earth
orbit rendezvous burn that would NEVER intersect Earth itself, no matter
when the drive failed (at least not for several orbits). It shouldn't be
that more energy expensive than the minimum energy rendezvous burn.
Second of all, I glanced through it and there was a good deal of
discussion of debris from that asteroid hitting Earth. Just what was the
cause of that debris? And how did it arrive before the asteroid? I
thought these guys were physicists.

I would advise reading the book for answers to these questions and more.
One hint: the electric thrusters caused a explosive stress fracture in
the asteroid.

While an "electric thruster" has a higher specific impulse (Isp) than
traditional chemical rockets - which means it uses the fuel more
efficiently, the total thrust is still quite low relative to a
chemical rocket.

Yes. But since the electric thrusters use electric heat to convert the
liquid mass into high pressure vapor, they are more efficient if you
have solar panels.
the

Even at 100% efficiency, 200 GW would require on the order of 100M sq meters of solar panel,
Or about 10 km by 10 km.
Keeping an object that big secret is it feasible.
Pt

Perils of posting from an iPad: “infeasible”

Pt

[Lynn McGuire]

Post by Peter Trei

Post by Lynn McGuire

Post by Scott Lurndal

Post by Lynn McGuire

Post by Robert Woodward

Post by Lynn McGuire
_On to the Asteroid_ by Travis Taylor and Les Johnson
https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/
Book number two of a two book space opera series. I read the
excellently printed and bound MMPB by Baen.
In the middle of the 2020s, there is a space race going on with China,
NASA, and an American private space touring firm. Another firm seeks to
get into the space business by secretly bringing a metals rich asteroid
to Earth using an electric thruster system. The electric thruster
system fails midway to Earth and the asteroid will hit the Earth rather
than going into orbit around it since there is not a backup thruster
system. Since the asteroid is a mile long by a quarter mile in
diameter, the asteroid's path must be changed.
Please note this little series is very hard science fiction. All of
this is possible today using today's technology and materials. And, a
LOT of money.

Nonsense. To begin with, I am certain it is possible to develop a Earth
orbit rendezvous burn that would NEVER intersect Earth itself, no matter
when the drive failed (at least not for several orbits). It shouldn't be
that more energy expensive than the minimum energy rendezvous burn.
Second of all, I glanced through it and there was a good deal of
discussion of debris from that asteroid hitting Earth. Just what was the
cause of that debris? And how did it arrive before the asteroid? I
thought these guys were physicists.

I would advise reading the book for answers to these questions and more.
One hint: the electric thrusters caused a explosive stress fracture in
the asteroid.

While an "electric thruster" has a higher specific impulse (Isp) than
traditional chemical rockets - which means it uses the fuel more
efficiently, the total thrust is still quite low relative to a
chemical rocket.

Yes. But since the electric thrusters use electric heat to convert the
liquid mass into high pressure vapor, they are more efficient if you
have solar panels.
the

Even at 100% efficiency, 200 GW would require on the order of 100M sq meters of solar panel,
Or about 10 km by 10 km.
Keeping an object that big secret is it feasible.
Pt

From:
https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/

Travis S. Taylor, Ph.D. is the co-creator and star of the National
Geographic Channel’s hit series, Rocket City Rednecks and can be seen on
the Weather Channel on 3 Scientists Walk into a Bar. Taylor is a
physicist who has worked on various programs for the Department of
Defense and NASA for the past twenty years. His expertise includes
advanced propulsion concepts, very large space telescopes, space-based
beamed energy systems, future combat technologies and next generation
space launch concepts. Taylor is also the author of pulse-pounding,
cutting edge science fiction with the Tau Ceti Agenda series including
One Good Soldier, The Tau Ceti Agenda, One Day on Mars, and Trail of
Evil, as well as his ground-breaking Warp Speed series, with entries
Warp Speed and The Quantum Connection.

Les Johnson is a NASA physicist and author. By day, he serves as the
Senior Technical Assistant for the Advanced Concepts Office at the NASA
George C. Marshall Space Flight Center in Huntsville, Alabama. In the
early 2000s, he was NASA’s Manager for Interstellar Propulsion Research
and later managed the In-Space Propulsion Technology Project. He was
technical consultant for the movie Lost in Space and has appeared on the
Discovery Channel series, Physics of the Impossible in the “How to Build
a Starship” episode. He has also appeared in three episodes of the
Science Channel series Exodus Earth. He is the author of novel Back to
the Moon, coauthored with Travis S. Taylor, and the coeditor of the
science/science fiction collection Going Interstellar.

Lynn

[Cryptoengineer]

Post by Lynn McGuire

Post by Peter Trei

Post by Lynn McGuire

Post by Scott Lurndal

Post by Lynn McGuire

Post by Robert Woodward

Post by Lynn McGuire
_On to the Asteroid_ by Travis Taylor and Les Johnson
https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/
Book number two of a two book space opera series. I read the
excellently printed and bound MMPB by Baen.
In the middle of the 2020s, there is a space race going on with
China, NASA, and an American private space touring firm.
Another firm seeks to get into the space business by secretly
bringing a metals rich asteroid to Earth using an electric
thruster system. The electric thruster system fails midway to
Earth and the asteroid will hit the Earth rather than going into
orbit around it since there is not a backup thruster system.
Since the asteroid is a mile long by a quarter mile in diameter,
the asteroid's path must be changed.
Please note this little series is very hard science fiction.
All of this is possible today using today's technology and
materials. And, a LOT of money.

Nonsense. To begin with, I am certain it is possible to develop a
Earth orbit rendezvous burn that would NEVER intersect Earth
itself, no matter when the drive failed (at least not for several
orbits). It shouldn't be that more energy expensive than the
minimum energy rendezvous burn.
Second of all, I glanced through it and there was a good deal of
discussion of debris from that asteroid hitting Earth. Just what
was the cause of that debris? And how did it arrive before the
asteroid? I thought these guys were physicists.

I would advise reading the book for answers to these questions and more.
One hint: the electric thrusters caused a explosive stress
fracture in the asteroid.

While an "electric thruster" has a higher specific impulse (Isp)
than traditional chemical rockets - which means it uses the fuel
more efficiently, the total thrust is still quite low relative to a
chemical rocket.

Yes. But since the electric thrusters use electric heat to convert
the liquid mass into high pressure vapor, they are more efficient if
you have solar panels. the

Even at 100% efficiency, 200 GW would require on the order of 100M sq
meters of solar panel, Or about 10 km by 10 km.
Keeping an object that big secret is it feasible.
Pt

https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/

[substantial science props of the authors deleted]

I was taking the energy requirements from James Nicoll's post, and
then being generous (in your direction) on the solar power required
to achieve that.

Possibly Jim was wrong. I don't know.

pt

[Lynn McGuire]

Post by Cryptoengineer

Post by Lynn McGuire

Post by Peter Trei

Post by Lynn McGuire

Post by Scott Lurndal

Post by Lynn McGuire

Post by Robert Woodward

Post by Lynn McGuire
_On to the Asteroid_ by Travis Taylor and Les Johnson
https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/
Book number two of a two book space opera series. I read the
excellently printed and bound MMPB by Baen.
In the middle of the 2020s, there is a space race going on with
China, NASA, and an American private space touring firm.
Another firm seeks to get into the space business by secretly
bringing a metals rich asteroid to Earth using an electric
thruster system. The electric thruster system fails midway to
Earth and the asteroid will hit the Earth rather than going into
orbit around it since there is not a backup thruster system.
Since the asteroid is a mile long by a quarter mile in diameter,
the asteroid's path must be changed.
Please note this little series is very hard science fiction.
All of this is possible today using today's technology and
materials. And, a LOT of money.

Nonsense. To begin with, I am certain it is possible to develop a
Earth orbit rendezvous burn that would NEVER intersect Earth
itself, no matter when the drive failed (at least not for several
orbits). It shouldn't be that more energy expensive than the
minimum energy rendezvous burn.
Second of all, I glanced through it and there was a good deal of
discussion of debris from that asteroid hitting Earth. Just what
was the cause of that debris? And how did it arrive before the
asteroid? I thought these guys were physicists.

I would advise reading the book for answers to these questions and more.
One hint: the electric thrusters caused a explosive stress
fracture in the asteroid.

While an "electric thruster" has a higher specific impulse (Isp)
than traditional chemical rockets - which means it uses the fuel
more efficiently, the total thrust is still quite low relative to a
chemical rocket.

Yes. But since the electric thrusters use electric heat to convert
the liquid mass into high pressure vapor, they are more efficient if
you have solar panels. the

Even at 100% efficiency, 200 GW would require on the order of 100M sq
meters of solar panel, Or about 10 km by 10 km.
Keeping an object that big secret is it feasible.
Pt

https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/

[substantial science props of the authors deleted]
I was taking the energy requirements from James Nicoll's post, and
then being generous (in your direction) on the solar power required
to achieve that.
Possibly Jim was wrong. I don't know.
pt

There was some theory of reorienting the asteroid's profile to use the
Sun's gravity as a motive force. I did not quite understand it.

Lynn

[Dimensional Traveler]

Post by Lynn McGuire

Post by Cryptoengineer

Post by Peter Trei

Post by Scott Lurndal

Post by Lynn McGuire

Post by Robert Woodward

Post by Lynn McGuire
_On to the Asteroid_ by Travis Taylor and Les Johnson
https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/
Book number two of a two book space opera series.  I read the
excellently printed and bound MMPB by Baen.
In the middle of the 2020s, there is a space race going on with
China, NASA, and an American private space touring firm.
Another firm seeks to get into the space business by secretly
bringing a metals rich asteroid to Earth using an electric
thruster system.  The electric thruster system fails midway to
Earth and the asteroid will hit the Earth rather than going into
orbit around it since there is not a backup thruster system.
Since the asteroid is a mile long by a quarter mile in diameter,
the asteroid's path must be changed.
Please note this little series is very hard science fiction.
All of this is possible today using today's technology and
materials.  And, a LOT of money.

Nonsense. To begin with, I am certain it is possible to develop a
Earth orbit rendezvous burn that would NEVER intersect Earth
itself, no matter when the drive failed (at least not for several
orbits). It shouldn't be that more energy expensive than the
minimum energy rendezvous burn.
Second of all, I glanced through it and there was a good deal of
discussion of debris from that asteroid hitting Earth. Just what
was the cause of that debris? And how did it arrive before the
asteroid? I thought these guys were physicists.

I would advise reading the book for answers to these questions and more.
One hint: the electric thrusters caused a explosive stress
fracture in the asteroid.

While an "electric thruster" has a higher specific impulse (Isp)
than traditional chemical rockets - which means it uses the fuel
more efficiently, the total thrust is still quite low relative to a
chemical rocket.

Yes.  But since the electric thrusters use electric heat to convert
the liquid mass into high pressure vapor, they are more efficient if
you have solar panels. the

Even at 100% efficiency, 200 GW would require on the order of 100M sq
meters of solar panel, Or about 10 km by 10 km.
Keeping an object that big secret is it feasible.
Pt

      https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/

[substantial science props of the authors deleted]
I was taking the energy requirements from James Nicoll's post, and
then being generous (in your direction) on the solar power required
to achieve that.
Possibly Jim was wrong. I don't know.

There was some theory of reorienting the asteroid's profile to use the
Sun's gravity as a motive force.  I did not quite understand it.

Don't feel bad, most people don't understand gibberish.

[Robert Woodward]

Post by Lynn McGuire

Post by Robert Woodward

Post by Lynn McGuire
_On to the Asteroid_ by Travis Taylor and Les Johnson
https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/
Book number two of a two book space opera series. I read the
excellently printed and bound MMPB by Baen.
In the middle of the 2020s, there is a space race going on with China,
NASA, and an American private space touring firm. Another firm seeks to
get into the space business by secretly bringing a metals rich asteroid
to Earth using an electric thruster system. The electric thruster
system fails midway to Earth and the asteroid will hit the Earth rather
than going into orbit around it since there is not a backup thruster
system. Since the asteroid is a mile long by a quarter mile in
diameter, the asteroid's path must be changed.
Please note this little series is very hard science fiction. All of
this is possible today using today's technology and materials. And, a
LOT of money.

Nonsense. To begin with, I am certain it is possible to develop a Earth
orbit rendezvous burn that would NEVER intersect Earth itself, no matter
when the drive failed (at least not for several orbits). It shouldn't be
that more energy expensive than the minimum energy rendezvous burn.
Second of all, I glanced through it and there was a good deal of
discussion of debris from that asteroid hitting Earth. Just what was the
cause of that debris? And how did it arrive before the asteroid? I
thought these guys were physicists.

I would advise reading the book for answers to these questions and more.

What answers I saw in my glimpse violated Newton's Laws of Motion (and a
conservation law or two).

Post by Lynn McGuire
One hint: the electric thrusters caused a explosive stress fracture in
the asteroid.

Piffle. Assuming a violent failure blows material off the asteroid, it
would be with the asteroid (assuming the thrust ended at the moment). If
the eruption occurred long before the failure, the debris would be
tracking the orbit of the asteroid at that point, which would only
intersect Earth IF AND ONLY IF the asteroid has been on an intersection
orbit at that point. I have trouble trying to visualize how that could
be. Besides, the explanation in the book did not involve an explosive
stress fracture.

[Lynn McGuire]

Post by Robert Woodward

Post by Lynn McGuire

Post by Robert Woodward

Post by Lynn McGuire
_On to the Asteroid_ by Travis Taylor and Les Johnson
https://www.amazon.com/Asteroid-Travis-S-Taylor/dp/148148267X/
Book number two of a two book space opera series. I read the
excellently printed and bound MMPB by Baen.
In the middle of the 2020s, there is a space race going on with China,
NASA, and an American private space touring firm. Another firm seeks to
get into the space business by secretly bringing a metals rich asteroid
to Earth using an electric thruster system. The electric thruster
system fails midway to Earth and the asteroid will hit the Earth rather
than going into orbit around it since there is not a backup thruster
system. Since the asteroid is a mile long by a quarter mile in
diameter, the asteroid's path must be changed.
Please note this little series is very hard science fiction. All of
this is possible today using today's technology and materials. And, a
LOT of money.

Nonsense. To begin with, I am certain it is possible to develop a Earth
orbit rendezvous burn that would NEVER intersect Earth itself, no matter
when the drive failed (at least not for several orbits). It shouldn't be
that more energy expensive than the minimum energy rendezvous burn.
Second of all, I glanced through it and there was a good deal of
discussion of debris from that asteroid hitting Earth. Just what was the
cause of that debris? And how did it arrive before the asteroid? I
thought these guys were physicists.

I would advise reading the book for answers to these questions and more.

What answers I saw in my glimpse violated Newton's Laws of Motion (and a
conservation law or two).

Post by Lynn McGuire
One hint: the electric thrusters caused a explosive stress fracture in
the asteroid.

Piffle. Assuming a violent failure blows material off the asteroid, it
would be with the asteroid (assuming the thrust ended at the moment). If
the eruption occurred long before the failure, the debris would be
tracking the orbit of the asteroid at that point, which would only
intersect Earth IF AND ONLY IF the asteroid has been on an intersection
orbit at that point. I have trouble trying to visualize how that could
be. Besides, the explanation in the book did not involve an explosive
stress fracture.

Uh, you did not read far enough.

Lynn