2006-08-03 09:42:18 · 13 answers · asked by Anonymous in Science & Mathematics ➔ Astronomy & Space
Thrusters on spacecraft are rockets. There surely is nothing for rockets to thrust against in space as you stated. However, they do thrust against something. What though? Well, they thrust against the spaceship itself! Within the rocket motor is an almost sealed compartment that holds the chemical reaction. There is only one way for the expanding gasses to expand through, and that is the nozzle of the rocket. What allows the rocket to propel the spacecraft is the gasses expanding and pushing against the side opposite to the nozzle while being expelled through the nozzle.
Furthermore, it is this expansion against the side opposite the nozzle, and this expansion ALONE, that propels the rocket. In no way is a rocket more efficient when it has anything to push against on the outside such as atmosphere! Thus space being a vacuum in no way affects the thrusters.
2006-08-03 11:40:56 · answer #1 · answered by A Guy 3 · 4⤊ 1⤋
Firstly, just to be pedantic, space is not a perfect vaccuum; it does have a few particles and molecules knocking about, but it doesn't matter for the purpose of this question.
This question concerns Newtons Third Law of motion, namely: Every action has an equal and opposite reaction.
When a rocket engine is working, a large amount of gas is being pushed out of the engine, this is an action and it takes energy to cause this action. As Newton's Third Law states, there must be an equal and opposite reaction. The reaction is the spacecraft being moved along in the opposite direction to the gas being pushed out of the thruster.
You can see from this the reason why you need so much fuel. A spacecraft is quite a massive thing and you need a lot of gas to be pushed out of the thruster to cause a significant reaction (make the spacecraft go!)
Because there is near enough a vaccuum in space, rockets are actually more efficient out of the atmosphere as the energy of the gas escaping isn't wasted by having to push any of the atmosphere out of the way.
There are many good websites, but at the end of the day it boils down to good old mathematics :-)
2006-08-04 03:28:41 · answer #2 · answered by Dive, dive, dive 2 · 0⤊ 0⤋
There's a simple way to demonstrate how thrust works.
Buy a small inflatable dinghy and take it to a duck pond.
Get into the dinghy with a large paving slab.
Row to the middle of the duck pond.
Stand up with your feet close together facing the side of the dinghy with the paving slab and then with all your strength hurl the slab as far away as you can.
You should find that you end up going in the opposite direction to the slab.
Likewise a spaceship uses fuel in place of the slab of concrete.
2006-08-03 23:43:28 · answer #3 · answered by skiparoouk 3 · 0⤊ 0⤋
Nothing.. the spaceship technically.
By the conservation of momentum lots of light gas moving away incredible fast gives a opposite force to (and is acted upon smilarly) the heavy accelerating space ship.
Here's something you can try, get a friend and get on skates or skate-boards and push away from each other.
Or even get two people on a skateboard to be the spaceship and one to be the thrust.
Have fun!
2006-08-05 12:13:55 · answer #4 · answered by Anonymous · 0⤊ 0⤋
They don't thrust 'against' anything.
They rely on Newtons 3rd. The directional venting of a gas causing an acceleration in the opposite direction.
2006-08-03 09:48:27 · answer #5 · answered by 'Dr Greene' 7 · 0⤊ 0⤋
They are actually "thrusting" against themselves, via the reaction produced by the release of gas. An "equal and opposite reaction" propels the thrust-er away from where it thrust-ed.
2006-08-03 09:58:09 · answer #6 · answered by MakeMusicNotWar 3 · 0⤊ 0⤋
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2016-09-28 21:13:48 · answer #7 · answered by Anonymous · 0⤊ 0⤋
Newtons third law of motion, Every action has an equal and opposite reaction.
2006-08-04 02:08:29 · answer #8 · answered by greebo 3 · 0⤊ 0⤋
Sir Issac Newton's third law of motion.
2006-08-03 11:41:59 · answer #9 · answered by Tim C 4 · 0⤊ 0⤋
A rocket motor basically just moves alot of mass really fast. Move mass in one direction, and you move in the other. No air needed.
2006-08-03 11:16:10 · answer #10 · answered by berger 1 · 0⤊ 0⤋