lr64
Well-Known Member
I seem to remember reading about some propellant using bismuth that didn't have the highest Isp, but provided a lot of oomph relative to its volume. Perhaps that would be good for a powered upper stage.
Seems to me that, however achieved, one could get the highest altitude for the smallest amount of propellant with just high enough thrust to jump off the pad and get a subsonic cruise, followed by modest thrust to maintain it, followed by high thrust once the air was thin. I'm imagining a booster with a single grain shaped like the one in Estes motors, i.e. a core that extends only partly into the grain, so it starts more normally and then becomes an end-burner. There could be some high powered propellant on top of that, or a second stage. Alternatively, a small, nozzleless booster, then an end burning second stage, then a high powered sustainer.
Seems to me that, however achieved, one could get the highest altitude for the smallest amount of propellant with just high enough thrust to jump off the pad and get a subsonic cruise, followed by modest thrust to maintain it, followed by high thrust once the air was thin. I'm imagining a booster with a single grain shaped like the one in Estes motors, i.e. a core that extends only partly into the grain, so it starts more normally and then becomes an end-burner. There could be some high powered propellant on top of that, or a second stage. Alternatively, a small, nozzleless booster, then an end burning second stage, then a high powered sustainer.