Cost to build Gerard K. O'Neill's "Island Three"

Pat Flannery wrote:
On 9/30/2010 3:53 PM, Hop wrote:

To send it to an atmosphere grazing orbit at periaerion, you'd need
about .6 km/sec. It's 1.07e16 kg. Not plausible.

We stick a huge Orion-style pusher plate onto it, and start slowing it
down via nuclear blasts.

Simply ablating the surface with nuclear blasts should do it, without
needing pusher plates, but you'd need a lot of them.

This is 10 times the mass of the KT-killer asteroid, and I had previous
done a BOTE calculation suggesting something like 60 100 Mt bombs would
give it a 1 m/sec deflection. If this holds, then 60*10*600 or 360,000
bombs would do the trick.

The total energy that needs to be transferred to the moon is 430
gigatons, so if a more efficient energy transfer scheme could be devised
then only some multiple of 4,300 100 Mt bombs would be needed. Blowing
off more material at a lower velocity would do that, so perhaps a grand
quarrying project might be called for.

On 9/30/2010 3:53 PM, Hop wrote:

To send it to an atmosphere grazing orbit at periaerion, you'd need
about .6 km/sec. It's 1.07e16 kg. Not plausible.

We stick a huge Orion-style pusher plate onto it, and start slowing it
down via nuclear blasts.

Pat

On Sat, 02 Oct 2010 15:18:04 -0700, Carey wrote:

Pat Flannery wrote:
On 9/30/2010 3:53 PM, Hop wrote:

To send it to an atmosphere grazing orbit at periaerion, you'd need
about .6 km/sec. It's 1.07e16 kg. Not plausible.

We stick a huge Orion-style pusher plate onto it, and start slowing it
down via nuclear blasts.

Simply ablating the surface with nuclear blasts should do it, without
needing pusher plates, but you'd need a lot of them.

This is 10 times the mass of the KT-killer asteroid, and I had previous
done a BOTE calculation suggesting something like 60 100 Mt bombs would
give it a 1 m/sec deflection. If this holds, then 60*10*600 or 360,000
bombs would do the trick.

The total energy that needs to be transferred to the moon is 430
gigatons, so if a more efficient energy transfer scheme could be devised
then only some multiple of 4,300 100 Mt bombs would be needed. Blowing
off more material at a lower velocity would do that, so perhaps a grand
quarrying project might be called for.

Install solar panels, and run cables across the
surface. When it's in sunlight, run current in a loop so
you can decelerate against the solar wind. It'll take
a while, but will be cheaper than 360k nuclear bombs.
--
Duke Basketball: We Crush Dreams

George W. Harris For actual email address, replace each 'u' with an 'i'

Pat Flannery wrote:
On 10/2/2010 2:18 PM, Carey wrote:

Simply ablating the surface with nuclear blasts should do it, without
needing pusher plates, but you'd need a lot of them.

Two problems would be both related to the structure of Phobos; it may
not be solid, but rather a pile of boulders and gravel held together by
only weak gravity attraction.

This does strongly influence the slowing down operation. The escape
velocity of Phobos is 11.3 m/sec so, except for the material you want to
eject for reaction mass, you want to keep any imparted velocity to
significantly below this value. It is okay to stir the rubble pile a
bit, if it settles down quickly enough.

The ablation idea is nice since the surface heats and blows off at high
speed, creating a shock wave propagating normal to the surface - into
the moon. A rubble mass actually damps and absorbs the shock very
rapidly and so it should not cause much spalling material to escape.

If that's the case it may start coming apart as you try to slow it down.
The other problem is that as it gets closer and closer to Mars, the
tidal forces on its inside and outside may be different enough to make
it start coming apart anyway.
Though that may be all to the good if all the parts start coming down
all over the planet, as a lot of good-sized impacts may generate more
heating and melting total than one very large one.

This is 10 times the mass of the KT-killer asteroid, and I had previous
done a BOTE calculation suggesting something like 60 100 Mt bombs would
give it a 1 m/sec deflection. If this holds, then 60*10*600 or 360,000
bombs would do the trick.

Okay, I'm working on it.
The thing is, if this actually did let you start colonizing a planet,
then it actually would be worthwhile to use that vast number of bombs.
BTW, I was re-reading my copy of "Teller's War" and 100 Mt bombs aren't
the upper limit by any means. The guys down at Lawrence Livermore were
looking into _gigaton_ yield bombs as part of the Palisades Of Fire SDI
concept.

A gigaton bomb may work for the ablation scheme since it does not
explode in contact, in which case - if the energy transfer efficiency is
the same - we would need only 36,000 and a lighter overall mass (the POF
scheme - if it works - should have a much higher ytw ratio).


Note, Stickney, the very large crater on Phobos, is 2 km across (about
equal to a 100 Mt crater) on a body with a minimum radius of 9 km. This
indicates that explosions adequate to excavate craters of this size do
not endanger the physical existence of Phobos as an intact body.

George W Harris wrote:
On Sat, 02 Oct 2010 15:18:04 -0700, Carey wrote:

Pat Flannery wrote:
On 9/30/2010 3:53 PM, Hop wrote:
To send it to an atmosphere grazing orbit at periaerion, you'd need
about .6 km/sec. It's 1.07e16 kg. Not plausible.
We stick a huge Orion-style pusher plate onto it, and start slowing it
down via nuclear blasts.
Simply ablating the surface with nuclear blasts should do it, without
needing pusher plates, but you'd need a lot of them.

This is 10 times the mass of the KT-killer asteroid, and I had previous
done a BOTE calculation suggesting something like 60 100 Mt bombs would
give it a 1 m/sec deflection. If this holds, then 60*10*600 or 360,000
bombs would do the trick.

The total energy that needs to be transferred to the moon is 430
gigatons, so if a more efficient energy transfer scheme could be devised
then only some multiple of 4,300 100 Mt bombs would be needed. Blowing
off more material at a lower velocity would do that, so perhaps a grand
quarrying project might be called for.

Install solar panels, and run cables across the
surface. When it's in sunlight, run current in a loop so
you can decelerate against the solar wind. It'll take
a while, but will be cheaper than 360k nuclear bombs.
--

Yeah, I thought that some sort of drag inducing scheme might be good -
but do you have any numbers on this? How fast can we slow it down with this?

On 10/2/2010 2:18 PM, Carey wrote:

Simply ablating the surface with nuclear blasts should do it, without
needing pusher plates, but you'd need a lot of them.

Two problems would be both related to the structure of Phobos; it may
not be solid, but rather a pile of boulders and gravel held together by
only weak gravity attraction.
If that's the case it may start coming apart as you try to slow it down.
The other problem is that as it gets closer and closer to Mars, the
tidal forces on its inside and outside may be different enough to make
it start coming apart anyway.
Though that may be all to the good if all the parts start coming down
all over the planet, as a lot of good-sized impacts may generate more
heating and melting total than one very large one.

This is 10 times the mass of the KT-killer asteroid, and I had previous
done a BOTE calculation suggesting something like 60 100 Mt bombs would
give it a 1 m/sec deflection. If this holds, then 60*10*600 or 360,000
bombs would do the trick.

Okay, I'm working on it.
The thing is, if this actually did let you start colonizing a planet,
then it actually would be worthwhile to use that vast number of bombs.
BTW, I was re-reading my copy of "Teller's War" and 100 Mt bombs aren't
the upper limit by any means. The guys down at Lawrence Livermore were
looking into _gigaton_ yield bombs as part of the Palisades Of Fire SDI
concept.

The total energy that needs to be transferred to the moon is 430
gigatons, so if a more efficient energy transfer scheme could be devised
then only some multiple of 4,300 100 Mt bombs would be needed. Blowing
off more material at a lower velocity would do that, so perhaps a grand
quarrying project might be called for.

Okay, here's what we do; we turn Phobos into a giant recoilless gun; we
drill a hole down to the core on the middle of the long axis, and plant
the mother of all bombs there.
When detonated this blows the whole moon in half, with half decelerating
and hitting Mars; the other half gets blown into a higher orbit and runs
into Deimos, breaking both moons into debris.
This gives Mars a thin ring of material that we mine.
Now about those slave apes that we need to genetically modify to breath
low pressure CO2 and help build the actual Mars colony...now no one said
that part was going to be easy, but who says you can't replace
chimpanzee blood with green algae solution with enough work? ;-)

Pat

On Oct 2, 6:53*pm, Carey wrote:
George W Harris wrote:

* *Install solar panels, and run cables across the
surface. *When it's in sunlight, run current in a loop so
you can decelerate against the solar wind. *It'll take
a while, but will be cheaper than 360k nuclear bombs.
--

Yeah, I thought that some sort of drag inducing scheme might be good -
but do you have any numbers on this? How fast can we slow it down with this?

Insolation at 1.52 A.U. is less than half than what earth receives, so
the panels would need to be larger.

Seems to me the solar wind is a rather tenuous medium to decelerate
against, even more so at 1.52 A.U.

Another scheme: extend a tether to the upper atmosphere of Mars:

http://clowder.net/hop/TMI/PhobosTether.jpg

The tether foot would be moving about .6 km/sec with regards to Mars'
surface. The atmospheric friction would exert a constant drag, slowing
Phobos. Even so I believe this would take a long time to exert a
significant influence.

Hop wrote:
On Oct 2, 6:53 pm, Carey wrote:
George W Harris wrote:

Install solar panels, and run cables across the
surface. When it's in sunlight, run current in a loop so
you can decelerate against the solar wind. It'll take
a while, but will be cheaper than 360k nuclear bombs.
--
Yeah, I thought that some sort of drag inducing scheme might be good -
but do you have any numbers on this? How fast can we slow it down with this?

Insolation at 1.52 A.U. is less than half than what earth receives, so
the panels would need to be larger.

Seems to me the solar wind is a rather tenuous medium to decelerate
against, even more so at 1.52 A.U.

Another scheme: extend a tether to the upper atmosphere of Mars:

http://clowder.net/hop/TMI/PhobosTether.jpg

The tether foot would be moving about .6 km/sec with regards to Mars'
surface. The atmospheric friction would exert a constant drag, slowing
Phobos. Even so I believe this would take a long time to exert a
significant influence.

To get a 600 m/sec velocity change in 100 years a drag of 2 billion
Newtons is needed. NASA has tested a Mars lander supersonic ring-sail
parachute at over 500 N/m^2, so a ribbon chute drag system with an area
of 4 km^2 should do the job. If your nanotube cable has a 100 GPa
tensile strength it need only be 200 cm^2 in cross section (apply your
favored multiplier for the reduced strength of bulk nanotube cable and
for safety margins).

This seems like the way to go if deorbiting Phobos is in fact a
desirable event.

On 10/2/2010 7:37 PM, Hop wrote:


The tether foot would be moving about .6 km/sec with regards to Mars'
surface. The atmospheric friction would exert a constant drag, slowing
Phobos. Even so I believe this would take a long time to exert a
significant influence.

That does sound like the cheapest way by far to do it though.
I imagine you could run a whole series of tethers down into the
atmosphere, each with something like a parachute at the end.

Pat

On 10/2/2010 9:27 PM, Carey wrote:
Hop wrote:
On Oct 2, 6:53 pm, Carey wrote:
George W Harris wrote:

Install solar panels, and run cables across the
surface. When it's in sunlight, run current in a loop so
you can decelerate against the solar wind. It'll take
a while, but will be cheaper than 360k nuclear bombs.
--
Yeah, I thought that some sort of drag inducing scheme might be good -
but do you have any numbers on this? How fast can we slow it down
with this?

Insolation at 1.52 A.U. is less than half than what earth receives, so
the panels would need to be larger.

Seems to me the solar wind is a rather tenuous medium to decelerate
against, even more so at 1.52 A.U.

Another scheme: extend a tether to the upper atmosphere of Mars:

http://clowder.net/hop/TMI/PhobosTether.jpg

The tether foot would be moving about .6 km/sec with regards to Mars'
surface. The atmospheric friction would exert a constant drag, slowing
Phobos. Even so I believe this would take a long time to exert a
significant influence.

To get a 600 m/sec velocity change in 100 years a drag of 2 billion
Newtons is needed. NASA has tested a Mars lander supersonic ring-sail
parachute at over 500 N/m^2, so a ribbon chute drag system with an area
of 4 km^2 should do the job. If your nanotube cable has a 100 GPa
tensile strength it need only be 200 cm^2 in cross section (apply your
favored multiplier for the reduced strength of bulk nanotube cable and
for safety margins).

This seems like the way to go if deorbiting Phobos is in fact a
desirable event.

You will have to reel the cables in as the altitude lessens.
I still like the idea of running a whole series of drag chutes on
individual cables down into the atmosphere to speed things up.
The nice thing about this approach is that compared to other ways of
doing this it's both very simple and dirt cheap.
Hop and I don't agree on much (obviously), but this is a top-notch idea
on his part.

Pat