So how do rockets fly in space?

Oliver · **Tue Mar 09, 2004 9:38 am So how do rockets fly in space?**

Hi,

Can anyone help me on this topic? I know that space is nearly vacuum, which means no air. It's a void. This implies that no sound can travel through space. OK, fair enough.

But! On the Earth's surface, rockets are being pushed forward by the reaction of the motor. Am I right here? The motor exerts an action onto the air and for every action there is an reaction which explanes why the motor is pushed forward.

However, if you take away the air (like in space), then there would be no reaction of the motor's action! So how do rockets accelerate or decelerate in space? Or even change direction?

Any help would be fine thanks!

Oliver

Gladiator · **Tue Mar 09, 2004 10:01 am**

"for every action there is a reaction" is something that Newton said. The thing is that no matter where you are this law thing and others apply so they say if you're drifting in space away from your space ship, then you take your a part of your backpack off and throw it in the opposite direction towards where you are going. The ship stays floating because theres no gravity there and for the turns they have little rocket things on the sides.

EnsignParis · Lieutenant Commander Joined: 07 Sep 2001 Posts: 257

Just because there is no air in space doesn't mean that rockets don't work. In fact, in space, rockets work better BECAUSE there is no air, and therefore no air resistance.

Rockets in space will accelerate until they reach the speed of the thing that is pushing them; nothing can move faster than what is pushing it.

To negatively accelerate (some people call it decelerate, but negative acceleration is the correct term) rockets use forward thrusters, to counteract the effect of their engines. Since there is virtually no air in space, there is no air resistance, so just turning off the engines won't do much, since there will be no friction (air resistance) slowing the rocket down. The rocket will continue to go the same speed as it was going when the rockets were turned off, so we need a force to push the opposite way the rocket is moving, and one of the ways to do this is to use forward thrusters. I'm sure NASA has other methods of slowing a rocket down, but if you really care, I'm sure you can do some research...because frankly, I just don't feel like doing it

.

Hope that helped you understand that a bit more, and if you have any more questions, I'll be more than happy to help you out if I can.

Oliver · **Tue Mar 09, 2004 10:11 am**

Right! That's the preservation of motion law or something like that. So you mean to say that rockets accelerate, deccelerate or change direction by ejecting matter (this may be air at a high speed) in to the other direction of motion?

EnsignParis · Lieutenant Commander Joined: 07 Sep 2001 Posts: 257

It could be air, but conventional rockets use chemical reactions to produce energy.

Liquid oxygen and hydrogen combust in a controlled environment and this combustion produces energy and this energy is harnessed (in other words, sent out the back of the rocket to propel) to make the rocket move.

PrankishSmart · **Tue Mar 09, 2004 5:31 pm**

I think most of the energy to push the rocket into space is during the first couple of minutes. Rockets poduce 160 million horse power!

Anyways, chemical fuel does have all the fuel and oxygen mix in a dry form these days. The thrust is directed behind the rocket, so the rocket moves in the other way.

imzadi76 · **Thu Mar 11, 2004 8:39 am**

webtaz99 · **Thu Mar 11, 2004 5:50 pm How Rockets work**

To answer your original question:

Rockets burn fuel and oxidizer (sometimes a single substance, but most often a combination) in a combustion chamber. This builds up pressure as the cumbustion products expand. The nozzle lets cumbustion products fly out of the chamber in one direction. This creates an unbalanced force in the opposite direction, pushing the combustion chamber (and the rocket) in the intended direction. The presence or absence of air makes only a slight (less than 10%) difference in thrust.

NASA has developed a rocket engine to get every last bit of efficiency. It's called the linear aeropsike. http://www1.msfc.nasa.gov/NEWSROOM/background/facts/aerospike.html

Gladiator · **Fri Mar 12, 2004 12:29 am**

im or Taz as far as I know when a spaceship connects to a base in space it uses thrusters to control side ways as well as forward and back ward movements. But during long flights is the same correct in outer space?

webtaz99 · **Fri Mar 12, 2004 12:54 pm**

Yes. The shuttles have something like 47 separate rocket engines. Smaller engines used for attitude control are often called "thrusters". But the basic priciple is still the same.

Dax Orien · **Tue Mar 23, 2004 8:49 am**

This is kind of a stupid comment/question, but would a propellar do anything in space?

webtaz99 · **Tue Mar 23, 2004 9:06 pm Propeller in space**

It would spin real fast.

Dax Orien · **Wed Mar 24, 2004 10:28 am**

Well that's all good and dandy. So is that all it would do?

Oliver · **Wed Mar 24, 2004 12:20 pm**

A propellar works on its air displacement and since there is no air in space, it wouldn't be much help...