Designing an orbiter that is able to endure the brutal -250 F in the outer stretches of space, as well as the bewildering 3000 F during the reentry is a ridiculously challenging task.
Space shuttle is the name for the entire setup, whereas the orbiter is the ‘plane’ attached
The Thermal Armor
Ergo, after churning the minds of the elite scientists and engineers, we now have the TPS (thermal protection system) that protects the orbiter from this harsh temperature difference.
The thermal protection system is like an armor that maintains the outer skin of the orbiter within acceptable temperatures. This is achieved by employing various materials on the outer structural skin.
Wait, what kind of materials?
The tile’s material is an insulator. These materials do not exchange heat easily.
Cardboard, being an insulator protects your hand from the hot coffee. (PC: Nirzar)
Conductors on the other hand are the exact opposite. They love to give away their heat.
This is the reason why touching a hot aluminum / stainless steel ( Conductors ) pan at a moderate 100 C would cause burns, but touching the Space shuttle tile (An amazing insulator) at 2200 C is probably not a bad idea!
Let’s cut to the chase: What are they?
Those small white cubes are LI-900. It is a type of low-density insulating material which is composed almost entirely of silica glass fibers.
Purest quartz sand with 94% air by volume constitutes the LI-900.
It’s sort of like foam/ a sponge, if you think about the huge amount of air that it contains.
And also, Air and silica are both extremely poor conductors of heat and thus great insulators.
As is evident from the animation provided above, they can be heated to 2200°F, and even after being subjected to that temperature can be picked up almost immediately.
White tiles (known as LRSI) were used mainly on the upper surface and have higher thermal reflectivity. These are therefore pointed towards the sun in order to minimize solar gain.
Black tiles (known as HRSI) are optimized for maximum emissivity, which means they lose heat faster than white tiles. This property is required in order to maximise heat rejection during re-entry.
Screwing up the TPS is a recipe for disaster
Due to a damaged heat shield, the space shuttle Columbia disintegrated upon reentry in 2003, killing all crew members. Designing such an integral component of the space shuttle requires utmost meticulousness.
When something feels hot to you, it’s really because there is a large amount of heat transferred between the object and your skin.
And when there is very less heat transfer, we perceive it as cold!
In the case of the space tile, since it’s a good insulator it is conducting (transferring) energy at a remarkably low rate.
Ergo, if we were to touch it, it will fell the same as a quotidian household object.
Cool eh ?