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Q & A: Blast Off!

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Most recent answer: 10/22/2007
Q:
Why can’t we use a burst of power for example a blast of some sort that would propel a ship into space.The burst would be behind the ship so when it would go off the ship would be propeled at a great speed. This would be used after the ship is in space.
- Leonard (age 29)
S.A,T.X U.S.A
A:
Hi Leonard,

Good idea! That's how rockets work, to have a big blast of some kind at the tail end of the rocket, hurling exhaust gases behind. Newton's third law requires that the rocket must be pushed forwards if the gases are pushed backwards. Rocket fuel is quite explosive, and a rocket engine tries to control the explosion into a steady burn.

It is hard to control a rocket if you only have a one-time, spherically symmetrical explosion behind it -- which way the rocket will go will have a big random component. If you try to control the explosion to force the gases to go backwards, there is a limit to how big the blast can be before tearing the shaping surfaces off the rocket. In the 1950's or so, people speculated about using nuclear explosions to propel rocket ships. This would probably work, but there is an international treaty prohibiting nuclear explosions in space (their electromagnetic bursts would damage our delicate communications satellites and the fallout would potentially poison all the earth, not just near the test site).

Tom J.

(published on 10/22/2007)

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