First one says "NO", 2nd says "YES"... alongside spouting some stuff that is general "true/sourced" -- but this Yes/No answer/conclusion --- totally unreliable.
Neither one is correct.
So do not EVER rely on Google AI for "conclusions" -- but only "clues" about what to google next in order to find the true sources it's using.
Agreed, but you still don't understand the sources you've cited, no matter how you came by them. And instead of paying attention to the correction, you just doubled down on it. This one is not correct either :—
Typically when "exhaust is blocked" causing the chamber to build up "pressure" it constricts the outflow of exhaust - and thus decreases "Momentum Thrust" -- which is the "good thrust" from which [most] of the thrust is typically derived.
This is so full of errors it's difficult to know where to start. Literally the only thing that even comes close to being correct is the last half of the last sentence.
Blocking the exit plane does not cause a rise in chamber pressure. Chamber pressure exists literally only between the injector and the throat. After the exhaust is "choked" there, a different regime takes place. Chamber pressure results in exhaust velocity between the throat and the exit plane.
A rising
chamber pressure does not impede exhaust flow. Rather, it accelerates it.
Pressure thrust is purely a function of the ambient pressure at the exit plane, the static exhaust pressure at the exit plane, and the exit plane area. The static exhaust pressure is largely a function of the expansion ratio. None of this has anything to do with chamber pressure.
There is nothing magical about momentum thrust. The different modes of thrust simply have their jobs to do. Exhaust velocity is unimpeded in a vacuum, but it is impossible for the plume to be as coherent in a vacuum as it is in the ambient. In the high-priesthood form of the rocket thrust equation, v
e is not a scalar quantity.
Now to examine your AI misdirections...
Answer: "In a vacuum, pressure thrust does not contribute to a rocket's thrust at all, as there is no ambient pressure to create a pressure differential; therefore, the thrust of a rocket in a vacuum is entirely due to the momentum of the expelled exhaust gases which is achieved through the high velocity of the ejected gas, not pressure differences."
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This didn't sound right to me...
It isn't. The pressure differential is highest when the ambient pressure is zero. And the only way to achieve a zero static pressure in vacuum is to have an infinitely long exhaust nozzle.
Answer: "Yes, for rockets, the pressure thrust is significantly greater in a vacuum compared to an atmosphere because there is no ambient pressure to oppose the expanding exhaust gases, allowing for more efficient expulsion and therefore greater thrust; essentially, a rocket works better in space due to the lack of air resistance."
No, pressure thrust has absolutely nothing to do with the "efficient expulsion" of the exhaust.