I have removed the parts of the question regarding landing and the conic nozzle. Adding in those issues makes the question too broad.
No, it makes the question meaningful. It's an essential part of the question, without it the question feels appart.
What you see as different unrelated (or loosely related) questions are the elements of my inability to even understand what is being described.
If the question is too broad than it essentially means that the idea of asking about a "complete rocket" that is the constant mass rocket with its exhaust (closed system) and its interactions (with the outside) is impossible.
And with an open system it isn't even clear what "rocket" and "external world" is at any instant which is the crux of the matter.
In that case, rewording the question and splitting it means missing the whole point.
And please assume good faith!
Revised question: Please address all answers and votes to this revised version of the question.
A rocket taking off on a launch pad sends a dense plume that pushes on the launch pad and is being redirected sideways.
- What (if anything) does the rocket push on?
- What (if anything) pushes back on the rocket?
- Does the exhaust plume pushing on the pad also push on the rocket? If so, at what distance is this effective?
- Does the air which is hit by the exhaust plume also push on the rocket?
I have removed the parts of the question regarding landing and the conic nozzle. Adding in those issues makes the question too broad. If this revised version is well-received, then the landing and the conic nozzle issues may be asked as their own new questions.
Original question: This was the original wording of the question, retained so you can compare to the revised version above. It was revised to the version above because the version below was severely downvoted.
It is usually said that rockets don't push back on anything, ever. They don't push back on air and so they work the same in deep space as at sea level.
I find the claim utterly ridiculous: rockets at least in some cases do push back. A rocket on a launch pad is seen sending a dense plume that's being redirected side way; the plume pushes back on the launch pad; the rocket must be pushing back on the pad through it. There is no way this isn't the case at all in any situation, or you could start a rocket as close to the ground as you want, even fully on the ground, an obvious absurdity.
So the questions are:
- During take off and landing of a rocket engine, at what altitude does the rocket "feel" the land underneath? Notably during LEM landing, at what distance would the land slow down the decent?
- Is atmosphere "felt" by rocket engines?
Maybe the answers is almost never; I still can't understand why people wave away the issue and say there is no pushing back.
The questions are really just one question: is the plume from the rocket a support on which the rocket stands, and at some distance from the ground? How does the fluid transfer forces? (So that's two linked questions actually.)
This is a theoretical question so I want to know whether a physical effects not just whether a practically significant effect exists that needs to be taken care of by engineers.
The claim of "no push back, we are only sending tiny objects downward" seems to directly imply that the conic nozzle plays exactly no role and is dead weight.