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Old Apr 7th 2019, 04:26 PM   #11
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Just alike a machine gun shooting at a stone nearby on the ground?
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Old Apr 8th 2019, 09:55 AM   #12
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Perhaps more like a pulse detonation motor.

In the early days of nuclear power it was fairly seriously suggested that spacecraft could be powered by a series of nuclear explosions.

This was found to be impractical...

However the obvious impracticalities for spacecraft propulsion should not be show stoppers for comet (or asteroid) propulsion.
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Old Apr 8th 2019, 04:39 PM   #13
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Originally Posted by Woody View Post
Perhaps more like a pulse detonation motor.

In the early days of nuclear power it was fairly seriously suggested that spacecraft could be powered by a series of nuclear explosions.

This was found to be impractical...

However the obvious impracticalities for spacecraft propulsion should not be show stoppers for comet (or asteroid) propulsion.
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If you are referring to the Orion Project, yes. Only in Planetary Defense it is referred to as nuclear ablation. Either in standoff or on or near surface we detonate a nuke to vaporize the surface mass generating thrust and alter the trajectory of the object.

For asteroids (stone/silica) we estimate that we will get a velocity of ~1,000 m/s and vaporize ~25 tons/kt yield (net). The problem in the community is that the boys and girls at LLNL and LANL have not been told to be afraid of Comets (yet?) and consequentially have not done the theoretical or lab work for water ice. So I bring the problem here...

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Old Apr 8th 2019, 05:16 PM   #14
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Since Rosetta's visit to 67P/Churyumov–Gerasimenko we have a much better idea of the composition of comets
(assuming 67P/Churyumov–Gerasimenko is fairly typical).

It might be mainly water ice, but there is an awful lot of other stuff in there as well.
I'm not sure how good a theoretical model based on water ice would be.

We need someone to make a scale model of a comet, with the appropriate composition and consistency,
and attack it with various analogues of nuclear explosions (high explosives, lasers, etc.)
The results of these tests can then be used to inform the theoretical models
which can then be scaled up to make a sensible estimate of the effects of a nuke.
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Old Apr 8th 2019, 07:08 PM   #15
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Cool Vacuum Environment Simulation by Ray

Build a glass shade, put a piece of water ice in it, exhaust the air.
Use an appropriate combination of beams of X ray, Gama ray as well as visible light in proportion to that of nuclear test before to project the ice.
Increase the magnitude of the ray (light) gradually. Probe the velocity and volumn of the vapor.
Make two charts.
Draw a section of curve each other.
Find out the trend.
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Old Apr 8th 2019, 07:22 PM   #16
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Excellent idea. However, I contacted the folks at Sandia and the Z Machine is booked till 2026. And we would need a theoretical model to justify the expense. Problem here is no one in authority has told these folks they should be afraid of Extinction by Comet impact yet... working on that angle every day.

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Old Apr 9th 2019, 06:51 AM   #17
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Woody,

From a perspective of force, strategically deflecting an Asteroid or Centaur or Comet is not a matter of precision but rather one of sufficiency... if not abundance. In other words, there is no such thing as deflecting or exploding or vaporizing them too much. However, almost enough would still be a complete catastrophe.

In that direction, from the work done on nuking asteroids, we already expect that in Space we will see a velocity of ~1,000 m/s and vaporize ~25 tons/kt (net). Since the vaporization point of stone/silica in Space is probably ~1,250 C and the vaporization point of water ice is Zero C and since temperature determines expansion velocity then we should expect water ice to have a far lower velocity than stone.

Therefore, when we design an assault on a Comet, to ensure maximum effectiveness we should assume the whole Comet is water ice. And any stone or iron or carbon that becomes vaporized will considered to be a bonus to generating force.
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Old Apr 9th 2019, 04:48 PM   #18
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This thread is really cool, just as a Holleywood movie...
Theory seems to be a hard nut, while an elegant plan of experiment might be feasible and useful.
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Old Apr 9th 2019, 07:22 PM   #19
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neila9876,

Even less brain sweat would be required to put a B-83 on an Atlas V to heliocentric orbit and Nuke some Comet and see how far it moves. But that would be a billion dollar solution. And Sandia's Z Machine only a couple million. But isn't thinking things through to the theoretical first the reason Dog created academics? And although harder on the brain, that first step shouldn't cost more than a few thousand dollars (academics are relatively cheap). But just in case some bits of this problem have already been solved... I bring it here. Perhaps at least get the hypothetical done for free!
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Old Apr 9th 2019, 07:42 PM   #20
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Talking

Gaiashield:
Yes it's a problem about cost. That's why I suggested a cheap simulation experiment above.
Why so much money spent on singing, dancing?
Theory? Do you think that any discipline would solve your shield plan for mankind?
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