How can spacecraft achieve propulsion in Space?

Question

According to Newton's 3rd law, every action has an opposite and equal reaction, but I do not understand how anything in space can go anywhere if nothing can push back since there is no friction. If a spaceship puts on its boosters they wouldn't have anything to push against which would make propulsion in a frictionless environment impossible. Obviously this is not the case. Please help.

zi_xin: I had considered that but I thought that maybe his law wouldn't work since at the time there wasn't much knowledge about space, etc.

lithiumdeuteride: Thank you for answering the main part of my question. No wonder there are rocket stages, blasts of gas for positioning, etc. Your answer has helped me better understand space travel. Many thanks.

Answer 1

In fact, to maneuver, a spacecraft has to fling pieces of itself away at high speed. Typically, it does this by storing something like compressed gas, then blowing the gas out of nozzles at high speed. The gas goes rushing off in one direction, and the reaction force causes the spacecraft to go in the other. Essentially, the spacecraft is pushing on the gas, and the gas must, by Newton's 3rd law, push back on the spacecraft.

Other methods involve storing separate oxygen and fuel sources (a rocket engine), or vaporizing something like Teflon and blowing the vapor out a nozzle.

Answer 2

if you were on skates in the middle of a hockey rink that had no walls around it, and you threw a ball north, you would move south, yet you never pushed off of anything, but for every action there is a reaction you threw the ball you get pushed backwards.

same thing with a rocket, it throws out gas which then pushes it forward.

even on earth, everyone knows what a bazooka looks like or any kind of rocket launcher, its basically a hollow tube the exhaust from the rocket just goes out the back. it doesn't push against anything.

oh and rockets have stages because it actually takes more fuel mass than the entire space craft weighs, so as the fuel gets used up the spacecraft drops off stages.

with the space shuttle it first loses its solid fuel rocket boosters and then the massive fuel tank. both of which just serve to get it into space, once it is in orbit it doesn't need much fuel or maneuvering

Answer 3

Look at your statement for the 3rd law carefully. Every action has an equal and opposite reaction. This is true regardless of environment. When the rocket propel something out the nozzle, the opposite reaction in this case is the rocket itself being pushed forward. I don't know if you ever shot a gun. If you have, the kick back that you experience is the reaction of the gun to the action of the bullet going forward.

Answer 4

Propulsion jets do not push on space, they push against the forward part of the chamber that they exit.

Answer 5

They have the gas that was expelled to push against.
And since there is no gravity it doesn't take much to get moving.

Answer 6

every action has an equal and opposite reaction.