Why are the prominent parts of the space shuttle heat shield black? when white reflects heat best?

Answer 1

The heat that the space shuttle experiences is not received by radiation so its reflectivity is irrelevant.

The heat is caused by physical ablation of the material due to friction with the molecules of the air. The heat created is absorbed by conduction, but is LOST by radiation, however and the best emitter of radiation is a black body.

The most perfect black body is the hole in the surface of a sphere with a seriously black inside, the next best thing is a black, heat resistant shuttle tile.

Sensory bodies, BTW, have nothing to do with the case. Usually I can guess how these aberrant thoughts arise but in this case I have no idea where that even came from, but you have to get used to pseudo-science and non-sequiturs on these boards!

Answer 2

The heat is created on the heat shield by friction with the air, so there is no incoming radiation to reflect.
What we see as white or black is only in the visible spectrum of light and may not be true for infrared radiation (heat radiation).

The heat shield's main mission is to isolate heat really well, so that other parts of the shuttle doesn't get hot and it is not so important if the temperature of the heat shield is a few degrees more or less, since it will only be hot for a few minutes, so I don't think color is much of a consideration when choosing material for the heat shield.

Answer 3

The thermal protection system has many different parts and many different materials. It is too complex to answer here but......

The nose cone encounters the highest temperatures (above 2300F) and is made of reinforced carbon-carbon which is black.

The areas covered in black tiles encounter heating below 2300F. They are black so that they radiate or emit heat during re-entry. About 95% of the heat that they encounter is radiated away by the black surface.

To further explain how this works.......

The heating encountered by the black tiles is not from friction or from radiated heat. The shuttle is a blunt re-entry body and heating occurs in the pressure wave formed in front of the shuttle. The shuttle is then heated by convection within the plasma that is formed. So the tiles are heated by convection and then cooled by radiation.

The white areas of the shuttle are white to reflect the radiation from the sun to prevent overheating on orbit.

Answer 4

Apparently (according to the back of my sunscreen bottle) although black does indeed absorb heat while white reflects it, you should wear darker clothing while out in the sun. The heat is absorbed and somehow this makes the surface temperature is cooler than if it was reflecting the heat off.

I guess the same reasoning is behind the heat resistant plates. Whatever, the bottle really does say wear darker clothes in the sun.

Answer 5

So they can see it against the white clouds when it comes back or maybe to make it look good
By the way narkypoon you are not quite right the air is heated by compression not friction but yes black radiates the heat the best and thats why its black at the points of greatest heating nose belly and wing edges etc

Answer 6

The blackness is to absorb all the heat when re-entering to the earth's atmostphere. It is just like a black body in sensory systems.

Answer 7

While black absorbs heat faster it also radiates it away faster, hence a faster cool down.

Answer 8

It is a different composition: reinforced carbon-carbon. Can stand higher temperature, but it is not as good a thermal insulator, and is more brittle.

Answer 9

actually white is the natural color of the heat shield.
But.
they wanted to make sure they had a token color on the space ship to make it more politically correct.


I'm just sayin.........

Answer 10

because black is the colour of the chemical formulation of the tiles man made not natural