We Need Bruce Willis

[cp1969]

No, space isn't a true vacuum, but it's darn close--something like 1x10e-15 Torr. I don't know how to calculate how much if any shock wave can be propagated through an atmosphere than thin.

The rocket works using F=ma. It ejects hot gas in one direction, and the rocket is thrust in the other. It makes no difference whether it's in a vacuum or not--just has a lot less aerodynamic drag if it isn't.

I like the idea of planting a thruster on the aseroid to deflect it. That would work. I'm still not convinced that a nuke would have the desired effect, but maybe it would.

 

[RoyJackson]

"I like the idea of planting a thruster on the aseroid to deflect it. That would work. I'm still not convinced that a nuke would have the desired effect, but maybe it would. "


Wasn't my concept. After "Deep Impact" and "Armageddon" came out, there was a flurry of articles and TV shows (watch TLC or the Discovery channels, they repeat these shows frequently) discussing how to detect and prevent an Earth strike. The Nukes or thrusters (and, remember the Orion project (a nuclear powered rocket)?) were one or two scientist's solutions to destroy or deflect the asteroid..

As far as a shock wave traveling through space...I may have used the wrong comparison. We think of a shock wave (perhaps more correctly called a <font color=red>Pressure Wave</font color=red> as a rapid expansion of hot gases and atmospheric pressures resulting from an explosion. Thinking of a Nova (star exploding)..I suppose in this context it would be more of a high energy wave, rather then what we would consider a shock (pressure) wave.

If my memory serves me, the Orion rocket would use a series of nuclear explosions against a "pusher plate" to propel the space craft. For more detailed information, do a web search. Again, this is using Newton's "opposite reaction" noted in my previous post.

Getting back to the "vaccum" in space discussion...read about <font color=blue>interstellar ram jets</font color=blue>. These engines would use the hydrogen atoms in space to fuel the engine. It's a fascinating theory.

 

[MJB]

I have heard of a few other methods to deflect asteroids. One idea is to land a small probe on the surface of the asteroid and then deploy a sail to catch the solar wind. Another method has the probe mine into the asteroid and throw the spoils into space thus pushing the asteroid in the opposite direction. Either of these methods would require alot of advance notice in order to move the asteroid out of a collision course with earth. I also have heard of another method that uses a probe with a large parabolic mirror. The idea is to focus the suns energy onto a small spot on the asteroid and break it up.

 

[Chuck52]

If you could hit the object at a sufficient distance from the earth, the force required to cause it to miss the earth could be trivial. Imagine one of your 50 caliber projectiles encountering a BB while on it's way to a target. Where in it's path the encounter occurs makes all the difference in the world, as far as the target is concerned. I woke up at about 3AM this morning and was lying there thinking about space-based laser weapons and if one of those could cause such an object to alter it's course. Unless it were some kind of particle beam, a laser would only be able to deliver energy which would heat the object. Would heating it change it's orbit? If it contained some ice or other volatile component which could be lost, thus altering the effect of the many gravitational fields influencing the object's orbit, I suppose that might work. If you assume the loss by vaporization would be non-uniform, a safe assumption, then that would also result in a nudge. However, that would be a really small nudge, and would have to be applied at a very great distance.

Anyway, it does seem to me that early detection and accurate orbital calculations are the key. We've proved we can send space vehicles very great distances with considerable accuracy. If we can detect objects coming our way at a sufficient distance, we can put a Daisy airgun in space to deflect them.

I'm not a pysicist, but I did used to read Physics Today. It gave me a headache and I quit.

Chuck

 

[Ozarker]

Absolutely correct. It doesn't require a lot to change the trajectory of an object moving through space. The trajectory of a bullet is affected by cross wind, blades of grass, leaves, twigs, small branches, heat rising from the ground, etc.. Anything it hits in flight affects it's trajectory in some way.