Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: moccacake on 10/05/2007 12:19:13

Title: nuclear explosion as a way of space travel
Post by: moccacake on 10/05/2007 12:19:13

is it possible to propel a spacecraft by setting off a nuclear explosion in space? how fast can an object be pushed by a nuclear explosion in the vacuum of space? can it get close to the speed of light?

Title: nuclear explosion as a way of space travel
Post by: another_someone on 10/05/2007 13:21:54

A nuclear explosion is a very short pulse of energy, so you have two choices - you receive enough energy to vaporise you, or you stand far enough back to only receive a very small fraction of the energy, and it will only give you a moderate kick.

In any case, it is a very wasteful means of propulsion.  In space, with little gravity to contend with, you don't need massive amounts of force to cause a gentle acceleration, and a long slow acceleration is often more efficient (and certainly less dangerous) that a short big kick.  For this reason, you will get more speed from an ion drive (that only gives minute amounts of acceleration, but it does so very efficiently), and maybe drive that ion drive from a nuclear reactor, than get a dramatic kick from a single big explosion.

The other question is how the energy would be transmitted from the nuclear explosion to the space craft.  In the atmosphere, a big explosion will send shock waves through the air, but in space, without any air, there are not quite the same kind of shock waves.  You would only receive energy by either being bombarded by the fission products themselves, or, if you are further back, simply by being bombarded by the radiation.  Neither are particularly comfortable things to be bombarded by, and the protection systems (even if they were technically possible) would probably weight so much as to make it that much more difficult to accelerate the craft to a substantial speed.

But, lets assume that in the fraction of a second that the explosion happened, you could accelerate yourself to (as a totally fanciful notion) half the speed of light - you would be subjecting yourself such massive acceleration that you would ends up being little more than a pancake embedded in the rear wall of the spacecraft.

Title: nuclear explosion as a way of space travel
Post by: RD on 10/05/2007 16:31:35

Quote from: moccacake on 10/05/2007 12:19:13

is it possible to propel a spacecraft by setting off a nuclear explosion in space?

http://en.wikipedia.org/wiki/Project_Orion_%28nuclear_propulsion%29