3
$\begingroup$

All the CMs for Apollo, as well as the space shuttles, basically used "Blunt body" technique for re-entry. While Apollo CMs used "ablative" type of heatshield, the space shuttles used "tiles" for the same. Which of the two is more cost efficient?

$\endgroup$
4
  • 3
    $\begingroup$ Definitely the ablative shield is cheaper, by a couple of magnitudes. But its not appropriate to compare them 1-to-1, they serve different needs. The Shuttle needed the tiles due to its size, complex shape, and reuseability. $\endgroup$ Dec 13, 2021 at 6:55
  • 1
    $\begingroup$ An Apollo or Soyuz type of spacecraft only brings back a small portion of the entire ship back to earth (mostly just the people and equipment that ensures a safe landing), so the amount of ablative material required isn't much, relative to the mass of the ship. But the space shuttle nearly brings back everything. The shuttle probably won't be able to carry any payload had it been covered by ablative material. $\endgroup$ Dec 13, 2021 at 9:19
  • $\begingroup$ @User3528438 do you mean to say that ablative shielding is very heavy? What I read about it makes me feel it should be much lighter than the tiles because it is mainly made up of "Hollow" honeycomb type metal structure, covered with some thin metallic sheet. In fact this is the reason I thought ablative shielding would prove cheaper and lighter (which is also an added advantage) for covering large areas such as that of a space shuttle. YES, It is true that the CMs brought back only a small portion of the entire ship, but the question here is about being cheaper while being equally effective. $\endgroup$
    – Niranjan
    Dec 16, 2021 at 0:43
  • $\begingroup$ @Niranjan The honeycomb is filled with plastic. Ablative heatshield weighs approximately as much as plastic. Shuttle tiles weigh approximately as much as styrofoam with a thin coat of paint, and are about as durable. $\endgroup$
    – ikrase
    Dec 16, 2021 at 6:23

1 Answer 1

2
$\begingroup$

What is most cost effective depends on many things such as how well the technology is understood, how risk adverse the organisation using it is, how open to change they are and how important cost is when compared to other factors.

The Space shuttle tiles were a nightmare and each took multiple man days to fit and test and get right.

SpaceX also use tiles but are more focused on cost. The video link below says it all. It is true that the initial prototypes of Starship have (and will continue to) crash and burn, however I strongly suspect that they will figure out how to build a heat shield without spending man days to attach each tile.

Doing it the SpaceX way shows a great deal of promise for cost reduction and given their track record I would not bet against them. So SpaceX style tiles are probably the way to go for a cost effective solution (to be confirmed).

https://www.reddit.com/r/SpaceXLounge/comments/m4ii51/video_of_spacex_installing_starship_heat_shield/

https://en.wikipedia.org/wiki/Space_Shuttle_thermal_protection_system#Slow_tile_application

$\endgroup$
5
  • $\begingroup$ The major difference is that on the Space Shuttle, almost each tile was unique, whereas the "Starbricks" are almost all the same, with only some differences for the nosecone and the flaps. $\endgroup$ Dec 14, 2021 at 12:28
  • $\begingroup$ Whilst true, the real problem with the shuttle was the complex way that the tiles were stuck on, cured, tested and often reapplied and retested $\endgroup$
    – Slarty
    Dec 15, 2021 at 13:46
  • $\begingroup$ True. Whereas, at the moment, SpaceX has a rather simple system, where the tiles are stuck on, and then they fall off again after a while :-D $\endgroup$ Dec 15, 2021 at 14:02
  • $\begingroup$ @Slarty: I assume that while "tile" in itself would take the brunt of friction with atmosphere, since it was "stuck" to the parent body of the shuttle, the bonding material is actually preventing the heat to be carried to the metallic body of the shuttle. Am I correct in assuming so? $\endgroup$
    – Niranjan
    Dec 16, 2021 at 0:53
  • $\begingroup$ @Niranjan No. The tiles are a very low-density insulating material, they both take the burnt of the heating (which is caused by rapid compression of air, not by friction), and also serve as insulation. They are so insulating that one can touch a tile with bare hands while the inside of it is still glowing red. The bonding material is much thinner and mostly serves to relieve mechanical strain (as the tiles do not match the spaceframe either in rigidity or in coefficient of thermal expansion). $\endgroup$
    – ikrase
    Dec 16, 2021 at 6:26

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.