Space/Science — HabitableZone

Space/Science » in reply to Thermal protection is a problem

re: Thermal protection is a problem
Larry J — (archived)

Starting back in the late 1950s, there were several fighters that could exceed Mach 2, some going as fast as Mach 2.5. They couldn't maintain these speeds for more than a few minutes due to limited fuel capacity (a typical fighter running in full afterburner will consume all of its internal fuel in about 15 minutes*). To the best of my knowledge, they didn't have too many thermal problems**. If that's the case, then perhaps the same will be true for the RASCAL mothership. It'll only spend a few minutes at top speed before doing the zoom climb, so the amount of heat soaking may well be manageable without exotic heat shielding.

*Afterburners suck fuel like crazy. According to this table, it isn't uncommon for the specific fuel consumption of a modern jet engine in afterburner to be 3 time or more than the non-afterburner rating. For example, the F100 engine used in the F-15 & F-16 has a SFC of 2.05 (lb/hr) / lbf and 29,000 pounds of thrust. This means it would burn over 59,000 pounds of fuel per hour per engine at max power. It doesn't take long to suck the tanks dry at that consumption rate.

**I read a recent article in Aviation Week about how difficult it is to test highly complex integrated aircraft like the F-22. That plane features supersonic cruise (supercruise) without needing to run the afterburners and it has a massive avionics load, so there's a lot of heat management that has to take place. The F-22 circulates fuel around the hot spots to cool them off and to reduce the IR signature. The need to handle supercruise heat loads and to maintain IR stealth complicate the F-22 considerably.

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