How does a rocket work in a vacuum

[Nink]

We have all seen it on TV.  Rockets flying past the karman line at approximately 100km high, where we have no atmosphere and traversing the next 60+ km straight up and into space. At 100km gravity is still at around 9.5 m/s^2 but now we have no atmosphere to push against. How does the rocket continue to accelerate until it reaches the 160km + range where it can find low earth orbit. 

Basic physics tell us that according to the Joule-Thomson effect or free expansion theory we just violated newtons third law of motion.  Some people will argue that this is an equal and opposite reaction of the force of the fuel leaving the rocket but free expansion means that without anything to push against you will not move. Others say it is "the recoil affect like when you fire a gun", or  "we have gained sufficient momentum so we reach orbit before we stop", or the "we push against the previous stage of the rocket" or "explosion inside the combustion chamber forces energy out of the chamber" or ...

So I am hoping someone can explain to me how a rocket actually works in space and describe the process or perhaps even show the calculations of  how we get passed the karman line then up to and beyond low earth orbit in a rocket. This is completely beyond my comprehension.

The official NASA response "The rocket pushes on its exhaust. The exhaust pushes the rocket, too. The rocket pushes the exhaust backward. The exhaust makes the rocket move forward."   https://www.nasa.gov/pdf/153415main_Rockets_How_Rockets_Work.pdf 

Sorry what was that again ?

[Paul-R]

... but now we have no atmosphere to push against.

The Third law doesn't require an atmosphere or anything else to push against. This is why astronauts doing repair jobs on he ISS finding themselves rotating as they try to tighten or untighten bolts.

[Nink]

The Third law doesn't require an atmosphere or anything else to push against. This is why astronauts doing repair jobs on he ISS finding themselves rotating as they try to tighten or untighten bolts.

I think we need to park the astronaut gallivanting around the ISS conversation until we work out how they got into space in the first place. Until then  "In space analogies" are probably a waste of time as some people would argue the astronauts working on the space station are actually working in a swimming pool and pushing against water.  I guess only the astronauts and NASA know for sure. Tiny bubbles https://www.youtube.com/watch?v=ErBFJDQOIHg

And yes you do need something to push against. Start swimming while standing on the ground and see how far you move.  You won't go anywhere without a medium that is dense enough to move you in the opposite direction when you push on it.

[massive]

it would be interesting to see how many sites/sources revert to the Gov/nasa explaination

[TinselKoala]

Amazing! Next you'll be telling me that the Earth is flat. After all, maps are flat, aren't they? And the Sun is hollow, since you can see into the black interior through sunspots.


No, you do NOT need "something to push against". 

Look up "conservation of momentum". 

Mass is discharged very rapidly in one direction out the rocket nozzle. Since momentum is conserved, the rocket itself moves in the opposite direction.

You can prove this to yourself with some bricks and a skateboard.