If space is a vacuum, what do rockets push against in order to get back to earth?

Question

Why aren't there a load of rockets in space wondering how to get down again?!
In order to go forwards, there's got to be something there to push against. But if space is a vacuum, there would be nothing there to push against..or would there?
Help!

Answer 1

The rocket "pushes" on the exhaust gasses that are coming out of the back. there is the equal and oposite reaction.

For every pound of thrust exerted out of the rocket, and equal and opposite pound of thrust pushes the rocket forwards.

If you were up in space, surrounded by the vacuum and had a supply of tennis balls, you could acheive "thrust" by throwing the ball out into nothingness. The energy propelling the ball backwards will be counterbalanced by an equal and opposite amount of energy propelling you forwards.

This works in a vacuum better than a non-vacuum - as the non vacuum presents friction which is a way of wasting the energy - converting kinetic energy into heat energy.

Mark

Answer 2

Rocket propulsion does not require a medium to push against. For every action there is an equal and opposite reaction. The action, in ths case, is the forcing of rocket exhaust out of the engine by the explosion of combustion, and the reaction is the movement of the rocket in the other direction. The pushing is done by the rocket exhaust on the back of the engine, and the force is provided by the expansion of combustion products in the continuous explosion.

The fact that space is a vacuum but rockets work very well up there should suggest to you that your statement about needing something to push against is flawed.

Answer 3

When a rocket engine is firing the hot exhaust gases come out of the open end of the nozzle and push against nothing in outer space. The high pressure gases within the firing chamber are also pushing forward. Since there is no escape for the gases pushing forward the rocket is pushed forward from the gas pressure. In short, in outer space, the rocket engine high pressure exhaust is pushing the rocket away from itself. It's Newton's law, for every action there is an opposite equal reaction.

Answer 4

there is nothing in a vacume, the rockets push, therefore, against the shuttle itself. newton's law says every action has an opposite equal reaction. The rocket just moves forwards, and will continue at the same speed, even if the rockets are then turned off, until it either hits something, or until it changes speed.


They don't push against anything, but them selves.

Answer 5

The rocket pushes on itself. Newtons third as stated. When the rocket fuel burns the hot gasses are thrown backwards at great speed. Although it may not have great mass the speed and mass combined gives a force. The same amount of force, only directed in the opposite direction, is what moves the spacecraft. The spacecraft doesn´t move as fast as the rocket exhaust becuase the crafts mass is much greater. But the force, as a function of mass and speed, is the same.

Answer 6

newtons laws are the answer. law #3 states that every action has an equal and opposite reaction. well the rocket is using fuel and burns it at a very strong force, the opposite reaction will propel the rocket forward. the rocket will not stop unless it hits somthing which is newton's first law. so a rocket can be propelled at mach 4 and will continue to go the same speed forever unless it hits somthing.

Answer 7

Space, while not being an actual perfect vacuum, outer space contains such sparse matter that it can be effectively thought of as one. But, that isn't important, becuase of Newton's Third Law, for every action there is an equal and opposite reaction, so if the force of the thrusters are backward, it will go forward.

Answer 8

newtons third law of physics, every action has an exact and opposite re-action.... for example if you fire a gun, the explosion from the bullet pushes out with just say 100 N, your hand with the gun will then be pushed 100N in the opposite direction or thereabouts, excluding waste gasses ect... another good example is a baloon, even in a vacuum if an inflated balloon has its gasses released it will fly around, same thing goes for a rocket but on a much larger scale

Answer 9

Their own weight. It has to do with kinetic force. The thrust that those rockets make is still BEHIND the shuttle. So they push it.

It's actually easier, and takes less fuel to get going when you're in space than it is on earth because you aren't fighting gravity as well.

Answer 10

ok lil dude... because i'm going to asume that you are only 8 years old, they dont push realy against any thing, the got it's motion thanx to a newton law i'm sure that is the second one
remember to any action there is a reaction in place when the rocket explodes he recives a push because the explotion but the rocket doesn't pushes anything