Explosion in space

[Bionic Modeler]

I was watching the Science channel of all places where they were discussing various theories about how to defend against a comet or asteroid impact. One theory was to explode a nuclear bomb near the object to deflect it's path away from earth. I googled this and got no clearly definitive answer but it would seem that this would have no effect since there would be no shock wave to do the job. No air no shock wave. Most answers seemed to agree but what say you who have far greater knowledge than me on the subject.

[thorst]

Interesting question! As the mass of the bomb is insignificant against the mass of the asteroid, I'd say that a momentum change caused by mechanical forces is neglectable. The energy of the explosion would, so I assume, be mostly transferred in radiative form (X-Rays, Gamma-Rays, UV and optical light). So if the bomb explodes close to the object, nearly 1/2 of the radiation energy would hit a more or less small spot on the surface and heaten it up. The farer the bomb explodes, the bigger is the spot, but the less energy is concentrated there.
So the big question would be then how asteroid material behaves when it is heated by high-energy photons... The assumtion, that not too much happens, seems logical to me. But perhaps it could lead to material leaving the asteroid, which would then change its orbit a bit. If there are projects to explore the bomb method, I'd guess it's
this mechanism.

Best regards,
Thorsten

[Don Boose]

If the bomb were on the surface or, better, in a crater, would not the ejection of material provide enough reaction to change the course of the asteroid in the same way that steering rockets were used on the space shuttles (How does a space shuttle in outer space manages to steer and turn, when in space there is no mass to push? - Yahoo! Answers)?

Don

[Paper Kosmonaut]

Shockwaves actually *do* occur when something explodes in space. It has nothing to do with air. Also in space, action = reaction, one of Newtons basic laws of movement.

Those fantastic lightyear-long pillars of cration in the Eagle Nebula, we all got to know so well from Hubble's pictures? well, they might not exist anymore. Some 7000 years ago a supernova exploded nearby and blew the gas pillars apart. The fact we still see them is that it still will take 1000 years for the light to reach us. Some say this is not the case but I won't be around to see the proof. Fact is, scientists here suggest shockwaves of supernovas can destroy gas clouds 1000s of light years away from the actual explosion.

In the fifties the U.S looked into this as a means of propulsion for spacecraft. See this Wiki article.

[airdave]

I thought they did this already?
Crashed something into an asteroid to study the amount of ejection force
and how much deflection they could cause to the asteroid's path?
Obviously if the deflection occurs at a manageable distance from the earth,
then the amount of deflection needed would be very minimal to cause
the asteroid to miss the earth.

I think Don is correct...we already have evidence of how manouevering thrusters
work in space...ejected material from a blast should have a similar effect?

I remember another discussion about running a craft up against an
asteroid, firing rockets, and gently pushing the asteroid off course.
Once again, you only need the smallest of course deviation while the object
is still a long way off, to cause it to miss its original target.

My idea involves firing a "harpoon" at an incoming asteroid.
The harpoon is of course at the end of a very long cable.
Then firing another harpoon, attached to the other end of the cable,
at another asteroid.
Preferably one going in the opposite direction.
ta daaa!

Whatever the solution, we need to work out another plan soon
...Bruce Willis will not be with us forever.

[KCStephens]

Originally Posted by airdave

Whatever the solution, we need to work out another plan soon
...Bruce Willis will not be with us forever.

I think a spaceship full of butterflys and monkeys would somehow do the trick

[codex34]

They did 'crash land' a probe on one, but it was going slowly, more of an uncontrolled landing.
There isn't a total conversion of mass to engery in a nuclear explosion, so you would get alot of material with mass travelling at high velcoity, though with such an idea you'd have to be fairly close to the asteroid to have an effect, but not as close as to break it up, but how would you know what the correct distance is?
We can't always see them in time and you'd need to be extremely accurate.
Declassified U.S. Nuclear Test Film #66 - YouTube

If an ion cannon can launch objects into space........

[maurice]

Any explosion is a violent expansion in the volume of a quantity of matter.
In an atmosphere that expansion happens to cause a shockwave. In a vacuum the expansion still occurs and in a controlled form it gives us rocket propusion and steering thrusters. Hopefully it also gives us the ability to give a course altering nudge to an asteroid.

[Bionic Modeler]

I understand most of the theories presented. it makes sense that exploding the bomb from the asteroid would create propulsion away from the blast just as a large rocket engine would, but in this program they were exploding it in proximity to the object not directly from it. So just how much of an effect would this have?

[spaceagent-9]

I would imagine that the effect on the gravity well of the asteroid would be the most disturbed by the explosion,
it would also broil it into slag, and that alone might change its orbit.
the last thing we would want would be a huge spray of meteorites hitting the earth from it shattering from a direct hit from the nuclear bomb.
a nuclear rocket spearing into it and pushing it behind the earth as it tracks in its orbit might work.