Space Shuttle: Tiles absorbed the heat but...where did that heat go? (How did the Space Shuttle cool down after landing?)

[Whack-a-Mole]

I assume most of us have seen the demonstration of a Space Shuttle tile coming out of a kiln glowing hot and a person picks one up with their bare hands moments later with no problem (if you haven’t see 1.5 minute video below).

But, it occurred to me, where did that heat go? Did the shuttle just glow for a few weeks after landing from retained heat? I mean, the heat has to go somewhere. So, how did the Space Shuttle cool down after landing?

Space Shuttle Thermal Tile Demonstration

[kenobi_65]

@Whack-a-Mole

So, how did the Space Shuttle cool down after landing?

Slowly; according to this Smithsonian article:

Each shuttle is covered by more than 24,000 of the six- by six-inch blocks. Most of the tiles are made of silica fibers, which are produced from high-grade sand. Silica is an excellent insulator because it transports heat slowly. When the outer portion of a tile gets hot, the heat takes a long time to work its way down through the rest of the tile to the shuttle’s skin. The tiles keep the orbiter’s aluminum skin at 350 degrees or less.

The primary tiles used are given one of two coatings. The tiles exposed to reentry temperatures of up to 2,300 degrees Fahrenheit, such as those on portions of the belly, are given a protective coating of black glass. Black tiles work by reflecting about 90 percent of the heat they’re exposed to back into the atmosphere, while the tiles’ interior absorbs the rest. The tiles’ interiors radiate absorbed heat so slowly that after landing, the tiles take hours to cool.

Shuttle Tiles

[Whack-a-Mole]

Does that mean they mostly had to leave the shuttle be for some hours (or more) before towing it to a hangar? Could the astronauts safely exit the shuttle immediately upon landing or did they have to wait inside a while to let things cool a bit? Or, on the flip side, bail ASAP because the shuttle would slowly heat up?

[Isilder]

The tile is a very low density material… The tile may look to be a gallon of volume, but its far lighter than a gallon of steel or concrete or rock. It has far less heat energy when its at the same temperature… So while they were hot , they didn’t have so much heat energy to give.

But they do ensure the heat absorbed into the skin doesn’t soak through, because a tiny hot spot on a pipe or tank fitting wouldn’t take much energy either.

After the landing, ground crews approached the orbiter to run the cooling systems, and conducted safety checks, checks for damage, leaks from tanks and pipes, hot spots … and ensured it was all cooled down by running ventilation and cooling systems until they were sure that it was all cooled down… Any of the numerous fuel tanks might have been leaking extremely toxic and flammable fuels due to the stress cycles in the mission, so they specifically have to test for leaks near any of those.

[Horatius]

@Whack-a-Mole

Does that mean they mostly had to leave the shuttle be for some hours (or more) before towing it to a hangar? Could the astronauts safely exit the shuttle immediately upon landing or did they have to wait inside a while to let things cool a bit?

Yes, they let it sit for quite a while to cool down before the astronauts could exit. Here’s a video, where they mention it took about an hour before the astronauts could exit:

Space Shuttle Discovery Disembarkation

[LSLGuy]

@Isilder nailed it. Lots of temperature, little heat.

So the temp of the surface of the tiles falls relatively rapidly when exposed to the relative cold of our normal ground temps, be they coastal Florida or the Mojave desert. Now “relatively” isn’t instant. But they’re not like refractory bricks that absorb lots of heat and hold it for a long term, taking metaphorical “forever” to cool.

[Whack-a-Mole]

@Isilder

Any of the numerous fuel tanks might have been leaking extremely toxic and flammable fuels…

I realize this is an aside from the OP but I thought the fuel on the orbiter was hydrazine. I didn’t think that was extremely toxic. I guess I am wondering what “extremely” means in this context. The Wiki page on this makes it seem something to be avoided but not particularly toxic either.

[LSLGuy]

The APUs for hydraulic power used hydrazine. The fuel cells for electricity used liquid hydrogen & liquid oxygen. The OMS engines and the reaction control system thrusters used monomethylhydrazine (MMH) and oxidized with dinitrogen tetroxide.

All sorts of nastiness there.

Straight hydrazine was also used in the F-16. The way they explained it to us is that the fumes in small quantity aren’t promptly fatal, but you will have breathing problems for life if you get a lung full of the stuff.