What does a rocket push against in space?

a reply to: buddha

An propeller, and even a jet, pushes against the air to make thrust, but a rocket doesn't actually push against the air to make its thrust. it's all the same principal whether there's air or not. The rocket is "throwing" a bunch of superheated gas out the back end, and that is producing an equal and opposite reaction in the form of forward thrust. Rockets actually work considerably better in space than in atmosphere simply because of the lack of atmospheric friction.

While atoms of gas might be small, they can still be extremely energetic. Just look at what happens if you seal up a boiler and light a fire under it, it'll explode even though it's only heated water vapor. A rocket is basically just a semi-controlled explosion being direction in a specific direction.

It's simple Newtonian mechanics, every action has an equal and opposite reaction. Oxidizer and propellant are mixed in the rocket's combustion chamber, generating extremely hot expanding gas, moving at high velocity. The rocket nozzle directs the combustion gases out into space, pushing the rocket forward with an equal force to the exhaust velocity.

Or to make an even easier example, take what's called a mass-driver engine, which essentially is a gun used for propulsion. Put your mass driver on an asteroid, hack out a chunk of rock and fire it at extreme velocity opposite the direction you want to move in, the recoil kicks you in that direction. And since there's very little gravity or atmospheric friction in space, you'll have little trouble maintaining that movement.

originally posted by: buddha
"Every action has an equal and opposite reaction."
a rocket in a atmosphere pushes on the atmosphere.
a rocket in the vacuum of space pushes
on the atoms of the gas it fires out the back.
atoms have a very low mass.
that is not enough to move a 5 ton rocket much.

Nothing to do with hoax!
I just find it odd.
some one else will USE it for hoax.

The gas is pushing out of the back of the rocket...so it is pushing out AGAINST the rocket, which has mass. The gas is under tremendous pressure due to the nature of rapid oxidation (combustion.)

a reply to: buddha

This is why they will often slingshot off of objects with gravity so that they are pushing off of the gravity of the object.

Jaden

If you have a 5 ton rocket and you fire out the back 1 ton of mass.
the 1 ton will shoot of about 4 times as fast.
the the rocket will move forward 1/4 of that speed.
fast or slow its the same push.

so the explosion of the gas out the back
of a rocket is not that much in space.
because the Mass of the gas is very very low.

Yes rocket use earth to build up speed to leave earth. sling shot around earth then the moon. but in deep space there is NOTHING Vacuum.

That all backwards.

The rocket is more efficient in space then in the atmosphere. The Earth's gravity also slows the rocket. It has to reach what is call escape velocity.

If you have a 5 ton rocket and you fire out the back 1 ton of mass. the 1 ton will shoot of about 4 times as fast.

Velocity has nothing to due with just the two masses.

I take it this is just a trolling thread because all of this is understood and proven.

Over on this thread somebody asked about nuclear fusion rockets.

What I found about current research at this post here.

Hydrogen gas is lighter than rocket fuel and you get more of an oomph from it. They are shooting for a demo around 2020.

originally posted by: buddha
Has any one calculated how much fuel you would
need to accelerate then decelerate to get to mars?

my point is a rocket in earth atmosphere
has some thing to push against.
But in the vacuum of space you have Nothing to push against.
Only the Gas the rocket pushes out the back!

think about that. when it starts it has nothing at All to push against.
and then as the gas builds up behind it. it will push against that.
So all the weight of the rocket is pushing against a Tiny mass of gas.

Please comment, I would like to know!

Rockets don't push against anything it's called physics. If I use energy to accelerate particles. There is energy that is directed back towards you as well. This is the rule for each reaction there is an opissit but equal reaction. So by accelerating particles causes the craft to move.

If your physics was real we wouldn't have went to the moon because as you point out not a lot on space to push off of.

a reply to: buddha

that is not enough to move a 5 ton rocket much.

The rocket doesn't weigh 5 tons when in space it weighs 0.
Without friction or weight the gas expelling from the rear is more than enough to push the rocket forward.

originally posted by: roadgravel

Yes rocket use earth to build up speed to leave earth. sling shot around earth then the moon. but in deep space there is NOTHING Vacuum.

That all backwards.

The rocket is more efficient in space then in the atmosphere. The Earth's gravity also slows the rocket. It has to reach what is call escape velocity.

Well the atmosphere is minor the main reason is gravity is decreased the further from Earth you go. Lower gravity means less mass to move.

originally posted by: buddha
If you have a 5 ton rocket and you fire out the back 1 ton of mass.
the 1 ton will shoot of about 4 times as fast.
the the rocket will move forward 1/4 of that speed.
fast or slow its the same push.

so the explosion of the gas out the back
of a rocket is not that much in space.
because the Mass of the gas is very very low.

Where are you getting that information? You should really look at the math instead of making up your own.

originally posted by: AugustusMasonicus

originally posted by: roadgravel

Wow. Is this going to be rockets in space are actually a hoax?

You and I both know it is.

It's the no-Mooners at it again.

a reply to: dragonridr

Lower gravity means less mass to move.

The mass is the same - it doesn't decrease.

This is somewhat false it dose still have mass and it still takes energy to accelerate or decelerate just not nearly as much to accelerate ... i dont think the energy needed to decelerate changes

The simplest explanation is its still a small controled exploshion ... imagin a bomb going off in space and ur next to it ... think it would move u at all ... or bye the logic space is void ull be unharmed

The mass may be small but mass x velocity 1 lb moving at 1 mps is 430000 foot pounds of force

1 mps is low also hobbyest liquid rockets do 2.2

a reply to: buddha You don't use a Rocket Engine in space. How can a Rocket Engine work when space is a vacuum no oxygen to burn fuel ? Well you can only use compressed air in a tank. We used Alien Technology a TR3B Craft to reach then Moon. Your Smartphones is the result of Alien Technology

Its like you strap on a pair of roller skates and grab a basket ball, you go out onto a flat parking lot and then push the basket ball away from you. The trust will push you back and cause you to roll. That basket ball doesn't push you because it is pushing against the air, it pushes you because you pushed it. Tons of rocket propellant is pushing against the rocket pushing it forward. Rocket engines are a controlled blast moving at a high speed. It is creating a lot of force.

originally posted by: MissionTruth
a reply to: buddha You don't use a Rocket Engine in space. How can a Rocket Engine work when space is a vacuum no oxygen to burn fuel ? Well you can only use compressed air in a tank. We used Alien Technology a TR3B Craft to reach then Moon. Your Smartphones is the result of Alien Technology

Proof??

You don't use a Rocket Engine in space. How can a Rocket Engine work when space is a vacuum no oxygen to burn fuel ?

How about carrying oxygen to mix with fuel in space.

a reply to: buddha

the rocket pushes angaist nothing, space is almost nothing with space dust,dark matter, and the misterious "dark energy" if it even exists