How does a rocket work in a vacuum

[tinman]

Good to see you started this thread Nink

As you can see, the answers or reasons why a rocket works in the vacuum of space, are the very same ones I gave you in our email conversation before you started this thread.

I am in the process of making my own vacuum chamber.
It will be large enough to test a small rocket powered car in.

Brad

[Nink]

Hi Brad

I still don't have an answer.   I have been told  that F=MA and Carroll and NASA say F=MV in space. NASA do not  say F=MA in a vacuum like everyone else here is saying, NASA says F=MV  https://www.nasa.gov/pdf/153415main_Rockets_How_Rockets_Work.pdf  and then NASA make the bold statement "In real rocket science, many other things also come into play" I have no idea what that statement means and I have no data to model this against.   I think we all fully understand F=MA when we are in the presence of an atmosphere or firing a rocket on the ground with earth to push against but I don't understand how we move from F=MA to F=MV, especially when we have no atmosphere and still have the force of gravity to contend with. 

Until we can mathematically model this with actual flight DATA we have no way to prove this.  With the hundreds of rockets launched we should have the starting mass and fuel consumed at every step of the way. This should include the fuel and total mass, height and velocity at the points that the stages were released and the points approaching and directly after the karman line with the data that continues until we are in orbit.  I appreciate that we all say stuff works.  I could say F=MV when we do not have an atmosphere and it can counteract the negative force of gravity as well but that is not going to make it correct.

Unfortunately building a vacuum chamber is of no value for igniting a rocket for multiple reasons.

1) Your vacuum chamber has an internal surface so when you fire your rocket it will push off that surface (molecules push against the side of the vacuum chamber) 
2) It is not possible to build an infinite sized vacuum chamber, any vacuum chamber you build will not allow for free expansion of gas
3) The instant you ignite your rocket gas will be released and fill up that vacuum chamber so you no longer have a vacuum chamber

We need to get the actual DATA and the formulas and plug everything into a spread sheet. Unless we can at minimum mathematically model these theories all we have is ideas.

I have searched youtube and I am unable to find a video of a rocket that goes straight up for 160km to space. They all start off going up straight but as soon as they get above a certain height they turn and go into an arc.  I am not sure if this is an optical illusion or something else.  https://www.youtube.com/watch?v=zvMlAqC4bm4 

[tinman]

Hi Brad



  https://www.youtube.com/watch?v=zvMlAqC4bm4

I have searched youtube and I am unable to find a video of a rocket that goes straight up for 160km to space. They all start off going up straight but as soon as they get above a certain height they turn and go into an arc.  I am not sure if this is an optical illusion or something else.

Maybe they are going straight up,and only look like they are arcing because the earth is spinning
As your view point is from the spinning earth,the rocket would appear to arc in accordance to that spin. But what if your view point was from a fixed point in space--would the rocket appear to arc then?.

Brad

[Paul-R]

I have searched youtube and I am unable to find a video of a rocket that goes straight up for 160km to space.

Surprisingly enough, that is because that is not where they want to go.

Almost every launched vehicle is on its way into orbit which means travelling to a specific height and to a speed of around 18k mph horizontally. Listen to the RT comms which used to go out live. "Stand by to roll" etc.

[lumen]

I would suggest you simply buy a toy water rocket and you would quickly understand that a rocket works from ejecting mass.
If you pump it up with only air it will not work well, but fill it with water (larger mass) and then some air and it works very well.

http://www.ebay.com/itm/Toysmith-Water-Rocket-also-includes-2-Fuel-Funnels-and-Launcher-New-/331413428205?hash=item4d29c797ed:g:WB4AAOSwpDdU7ASb