[Interview+] Can Sweating Heat Shields Solve Re-Entry Problems for Reusable Rockets?
Heat shields are one of the trickiest problems left to solve before we can have truly reusable spacecraft. So far we've seen different solutions, like ablative materials or ceramic tiles. But can a sweating heat shield be a solution? Finding out in this interview.
🟣 Guest: Dr. Hassan Saad Ifti https://nal.tamu.edu/
Watch the video here (with no ads) or on YouTube: https://youtu.be/04rSPGwMLlM
Comments (11)
I would think that liquid CO2 would be relatively easy to store. I wonder how well it works as a cold-gas thruster.
Wouldn't a more accurate example be a diesel piston at 7500 m/s? Compression rather than friction?
Dr.
Dr. Hassan Saad,
I know that the image of the reentry vehicle puffing liquids or gas is interesting. The name huff and puff comes to mind.
Dr. Saad said that turbulence in the surrounding air heats up a spacecraft more than surrounding air that has laminar flow (and that since thinner atmospheres are less turbulent, trajectories are designed to bleed off as much heat as possible in those regions, etc.) Is there a theoretical reason why turbulent air should heat a spacecraft traveling through it more than laminar-ly flowing air, or is this an experimental result?
One thought I had was about the interaction between the sacrificial gas/liquid and hull/TPS material in the reentry environment. My understanding was that carbon fiber can dissolve in some reentry scenarios. If starship used oxygen or methane, that might react with metal tiles. Where ceramics tend to be less reactive.
That was a great interview, the enthusiasm of Dr. Ifti for his subject was infectious.
If you dont have any context clues, the (sub-?) title of this episode can sound a bit like a "private problem" lol
Probably a dumb idea but this just popped in my head... What if we could capture all that velocity energy by slowing down slower and converting the heat into electricity and store it... Into what, hmm we need a way to create matter from energy like creating hydrogen or other propellant from electricity. Oh boy, I'm probably making up crazy things at this point.
You're not crazy since conservation of energy definitely applies here but engineering tradeoffs also apply. So energy of motion (velocity) is getting turned into energy of heat via friction. Now the problem is how to handle that heat so the reentry vehicle doesn't turn into an oven. Some materials can convert heat into a voltage differential (thermoelectric) or heat a medium like water/salt and use a turbine to convert to current. The challenges I see would be: 1.) Capacity of material/system to absorb as much heat as generated w/o breakdown 2.) Mass required (a perennial challenge with current space flight technology) 3.) Electricity is a 'use it now' type thing unless stored in chemical (batteries), mechanical (pressure vessel) or similar storage so too much energy needs to be used or stored at the time of generation (more mass) 4.) Use of electricity tends to generate more heat through resistance. (so back to where you started)