This is my first post here, and I want to resolve a question that has been bugging me ever since I saw the stats for the YF-19 on Macross Compendium. I have done a search, and there seems to be two trains of thought in this forum, so I just want to clarify which is correct. The issue is the following statement:
Two 42700 kg [x g] class (maximum instantaneous thrust in atmosphere; 67500 [64700] kg [x g] class in space) Shinnakasu Industry/P&W/Roice FF-2500E thermonuclear turbine engines replacing two 56500 kg [x g] class (maximum instantaneous thrust in space) Shinsei Industry/P&W/Roice FF-2200B engines in beginning specifications. In atmosphere, the engines use air as coolant/propellant, but due to problems of cooling efficiency (caused by exceeding output and melting the core) the maximum thrust is limited to 40% to 60% of thrust in space.
--http://macross.anime.net/wiki/YF-19
One train of thought goes: Thrust in atmosphere> thrust in space because in atmosphere you have air as a coolant/propellant, and in space you only have propellant, so that the bold part of the excerpt can be paraphrased: In atmosphere, the engines use air as coolant/propellant. In space, due to problems of cooling efficiency (caused by exceeding output and melting the core) the maximum thrust is limited to 40% to 60% of thrust.
However, to me, that doesn't seem to fit with the entire statement, taking into account that:
1)Instantaneous thrust in atmosphere<Instantaneous thrust in space
2)Space propellant is effectively a coolant since propulsion is achieved by heating and expelling the propellant
Which gives rise to the second train of thought: Thrust in Space>Thrust in atmosphere since the propellant carried by the VF should (logically) be a better heat conductor and have a higher specific heat than air so the engines can work at higher temperatures. Hence the bold part of the excerpt can be paraphrased: In atmosphere, the use of air as a coolant/propellant in the engines result in problems of cooling efficiency (caused by exceeding output and melting the core), so the maximum (atmospheric) thrust is limited to 40% to 60% of (maximum) thrust in space.
The second train of thought then raises a question-- why use air at all? Given the thermonuclear reaction engines(which I assume are closed cycle), the use of air effectively gives the VF unlimited range in atmosphere which could be enough of an advantage that the space propellant is not used in the main engines, but only in the veniers.
So, if you have stayed with me through the explanation, can anyone give the final verdict on whether the 1st line of thought is right, or the 2nd line of thought is right? (Or am I wayyy out of line because this has been flogged like a dead horse?)
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This is my first post here, and I want to resolve a question that has been bugging me ever since I saw the stats for the YF-19 on Macross Compendium. I have done a search, and there seems to be two trains of thought in this forum, so I just want to clarify which is correct. The issue is the following statement:
Two 42700 kg [x g] class (maximum instantaneous thrust in atmosphere; 67500 [64700] kg [x g] class in space) Shinnakasu Industry/P&W/Roice FF-2500E thermonuclear turbine engines replacing two 56500 kg [x g] class (maximum instantaneous thrust in space) Shinsei Industry/P&W/Roice FF-2200B engines in beginning specifications. In atmosphere, the engines use air as coolant/propellant, but due to problems of cooling efficiency (caused by exceeding output and melting the core) the maximum thrust is limited to 40% to 60% of thrust in space.
--http://macross.anime.net/wiki/YF-19
One train of thought goes: Thrust in atmosphere> thrust in space because in atmosphere you have air as a coolant/propellant, and in space you only have propellant, so that the bold part of the excerpt can be paraphrased: In atmosphere, the engines use air as coolant/propellant. In space, due to problems of cooling efficiency (caused by exceeding output and melting the core) the maximum thrust is limited to 40% to 60% of thrust.
However, to me, that doesn't seem to fit with the entire statement, taking into account that:
1)Instantaneous thrust in atmosphere<Instantaneous thrust in space
2)Space propellant is effectively a coolant since propulsion is achieved by heating and expelling the propellant
Which gives rise to the second train of thought: Thrust in Space>Thrust in atmosphere since the propellant carried by the VF should (logically) be a better heat conductor and have a higher specific heat than air so the engines can work at higher temperatures. Hence the bold part of the excerpt can be paraphrased: In atmosphere, the use of air as a coolant/propellant in the engines result in problems of cooling efficiency (caused by exceeding output and melting the core), so the maximum (atmospheric) thrust is limited to 40% to 60% of (maximum) thrust in space.
The second train of thought then raises a question-- why use air at all? Given the thermonuclear reaction engines(which I assume are closed cycle), the use of air effectively gives the VF unlimited range in atmosphere which could be enough of an advantage that the space propellant is not used in the main engines, but only in the veniers.
So, if you have stayed with me through the explanation, can anyone give the final verdict on whether the 1st line of thought is right, or the 2nd line of thought is right? (Or am I wayyy out of line because this has been flogged like a dead horse?)