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You seem to be ignoring the space shuttle entirely, which handled the heat of re-entry at 17,000 mph and was still reusable. You have to make trade-offs on wei

You seem to be ignoring the space shuttle entirely, which handled the heat of re-entry at 17,000 mph and was still reusable. You have to make trade-offs on weight and materials (like heat tiles), but it's not impossible.

nradov 5y ago
The Space Shuttle wasn't reusable in any meaningful sense. It required a complete overhaul after every mission, including replacement of many damaged ceramic heat shield tiles. And it only flew at hypersonic speeds for a few minutes during re-entry.
baybal2 5y ago
Space Shuttle used expendable ablation, thermal barrier materials, and thermal mass of its structure. All of that was only to last for a few minutes of re-entry, not constant flight in such conditions.
- mdorazio 5y ago
  I'm sorry, but you are either misinformed or we're talking about different things. The HRSI tiles on the shuttle were not ablative, were absolutely reused multiple times, and there's no indication that they couldn't withstand high temperatures for long durations. They were largely inspected and replaced due to impact damage from micrometeorites and ice, not due to thermal ablation. The biggest issues with the shuttle's thermal management approach are that it used an aluminum airframe and the tiles alone wouldn't be suitable for the leading edges of an atmospheric air breathing plane due to the higher dynamic pressures and probably higher heat involved. At mach 4 temps they would be fine. At mach 6+ you'd need something better on the leading edges combined with a temperature-resistant airframe. There's a good paper on the topic here [1]. [1] https://ntrs.nasa.gov/api/citations/20080017096/downloads/20080017096.pdf https://ntrs.nasa.gov/api/citations/20080017096/downloads/20...
  - baybal2 5y ago
    Thermal barriers will slowdown the rate at which heat gets into the aircraft, but it cannot keep it out it forever.
    - mdorazio 5y ago
      Yes... That's exactly what I said in the second paragraph. Not sure what your point is.

nradov 5y ago

The Space Shuttle wasn't reusable in any meaningful sense. It required a complete overhaul after every mission, including replacement of many damaged ceramic heat shield tiles. And it only flew at hypersonic speeds for a few minutes during re-entry.

baybal2 5y ago

Space Shuttle used expendable ablation, thermal barrier materials, and thermal mass of its structure. All of that was only to last for a few minutes of re-entry, not constant flight in such conditions.

mdorazio 5y ago
I'm sorry, but you are either misinformed or we're talking about different things. The HRSI tiles on the shuttle were not ablative, were absolutely reused multiple times, and there's no indication that they couldn't withstand high temperatures for long durations. They were largely inspected and replaced due to impact damage from micrometeorites and ice, not due to thermal ablation. The biggest issues with the shuttle's thermal management approach are that it used an aluminum airframe and the tiles alone wouldn't be suitable for the leading edges of an atmospheric air breathing plane due to the higher dynamic pressures and probably higher heat involved. At mach 4 temps they would be fine. At mach 6+ you'd need something better on the leading edges combined with a temperature-resistant airframe. There's a good paper on the topic here [1]. [1] https://ntrs.nasa.gov/api/citations/20080017096/downloads/20080017096.pdf https://ntrs.nasa.gov/api/citations/20080017096/downloads/20...
- baybal2 5y ago
  Thermal barriers will slowdown the rate at which heat gets into the aircraft, but it cannot keep it out it forever.
  - mdorazio 5y ago
    Yes... That's exactly what I said in the second paragraph. Not sure what your point is.