When the heat flow trough the material reaches equilibrium, the back will radiate exactly as much heat as the front side receives. At that point the heat shield serves no purpose.
right the temperature on the back side would be higher than on current craft, but the backside would be able to radiate heat no?
alternative idea:
the solid aborbs heat (cools the shield) to melt, then absorbs heat to warm up and boil, and the boiling gas is used as retro-firing rockets, any decrease in momentum due to the retro-rockets is less future heat absorbed (since the craft is slowing down faster)
The backing material is also insulation. The R-value is low but the objective is to reduce the heat transfer so it doesn't reach the ignition point, not to actually keep it cool.
Yes, it's extremely low - even a "rear-facing surface" would get hot enough to melt metals such as aluminium during a typical reentry. That's why the space shuttle has all those insulating tiles.
Yes, of course. I was wondering if there are materials that once cooled down would harden but then remain as such also when temperature rises again. Assuming it's doable, it would likely suffer from dilation and contraction anyway.
Hmm, conducting heat well in one direction and not conducting it well in the other.
Isn't it against thermodynamics?
I mean - make two containers connected by that material, if it works as it is described - temperature gradient between these containers will grow with time.
Maybe my physics knowledge is off here. Why would storing a block of material at a constant high temperature be infeasible? Can't we surround the heated material with a forced vacuum to nullify any heat loss, or am I underestimating something like the rate of diffusion through a pinprick in such material?
The fact we don't seem to be able to do this yet suggests I'm missing something, probably several things.
I wonder if this is the wrong way to go about it. You could design a spacecraft so it's heat resistant, and then once it's fully assembled, stick it in an oven and heat it to say 200C and just let it sit for a couple of days, or however long it takes to heat all the way through.
I'm sure this would present some design challenges, but it doesn't seem to me like it would be insurmountable.
The article says that the material is only half the solution. The other half is pipes with water to move the heat to the material so it can be dissipated. I assume that if you stop moving as much water, it doesn't cool as much. (It can't radiant heat that isn't there.)
Heat resistant material will eventually reach equilibrium where the back side is almost as hot as the front side unless it's cooled somehow.
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