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I agree with this, I may have said the same thing.. But I was thinking that the tech used for re-entry is what tends to increase the turnaround time (Eg. ablati

I agree with this, I may have said the same thing.. But I was thinking that the tech used for re-entry is what tends to increase the turnaround time (Eg. ablative heat shields, tiles). Making something that's rapidly re-usable which can also withstand re-entry from orbital speeds is probably the greatest challenge in this domain. The shuttle was originally envisaged to be cheap and rapidly re-usable for the time. As built it didnt turn out that way, it would have been overall cheaper and probably faster to launch a fully un-reusable rocket than a shuttle.

inglor_cz 2y ago
Yeah, my guess is that quick turnaround is a function of mainly two variables: a good protection of the ship during re-entry and very reliable engines that require little to none manual checking and can withstand lower thousands of cycles before needing refurbishment. Of those two, I am fairly sure that SpaceX can produce great engines. The Raptors are not quite there yet, but their 4th or 5th iteration will likely be extremely good. Not so sure about the heat shields. Much less aggregated corporate experience there.
- cubefox 2y ago
  It was quickly taken down, but there was a video on YouTube from someone who got hold both of a Space Shuttle and a Starship heat shield tile. He analyzed it with a microscope. He found that the material was nearly identical. I do wonder why SpaceX thinks they can make a ceramic heat shield work when it needed lots of checks and refurbishment for the Space Shuttle. Recently Musk even said they will add an ablative heat shield in certain areas. On the other hand, the at least the reusability of the lower stage shouldn't be a problem.
  - HPsquared 2y ago
    There are quite a large number of parameters other than the material, surely. The whole design is different.
    - cubefox 2y ago
      Not at all. The tiles just consists of two layers. The main body and the dark layer on top. According to the electron microscope analysis, the two tiles were mostly the same.
      - HPsquared 2y ago
        I mean more, the size and shape of the ship, the size/shape/thickness of the tiles, the attachment method, the substrate material, the flight profile...
        cubefox 2y ago
        I'm not seeing where SpaceX could have achieved a major innovation here that solves the problems the Space Shuttle had with the heat shield. I think the latter used glue rather than pins, but probably not because the Space Shuttle people couldn't make pins. If it was that easy...
        HPsquared 2y ago
        Those details could affect the heat flux and temperatures the material is exposed to. The two spacecraft have very different designs.
        cubefox 2y ago
        I guess one advantage of SpaceX compared to NASA is that the former are very trial and error based in their design, so they can iterate much more. NASA tends to design and plan everything in advance and only build it at the end. So when the Space Shuttle reusability didn't quite pan out, they couldn't easily change things up.
  - lupusreal 2y ago
    From what I understand, they are trying to keep their unique type shape count very low relative to the shuttle, which should make tile replacement a lot cheaper. Nonetheless, the tiles seem like the weakest aspect of the whole design. Recall that the early proposals didn't have tiles at all, so the tiles existing now is already and acknowledgement that not everything is going according to the ideal path.
    - cubefox 2y ago
      I wonder whether they considered using a metallic heat shield with heat resistant alloys. The cancelled VentureStar space plane was planned to use this approach: https://ntrs.nasa.gov/api/citations/20040095922/downloads/20040095922.pdf https://ntrs.nasa.gov/api/citations/20040095922/downloads/20...
      - HPsquared 2y ago
        They were originally hoping to use transpiration cooling, the tiles ended up being the fallback.
        cubefox 2y ago
        Yeah, but it isn't clear whether they ever considered a metallic heat shield. At some point in the past it was considered an improvement over ceramic tiles, since the VentureStar was planned as a Space Shuttle successor that fixed its shortcomings.

inglor_cz 2y ago

Yeah, my guess is that quick turnaround is a function of mainly two variables: a good protection of the ship during re-entry and very reliable engines that require little to none manual checking and can withstand lower thousands of cycles before needing refurbishment. Of those two, I am fairly sure that SpaceX can produce great engines. The Raptors are not quite there yet, but their 4th or 5th iteration will likely be extremely good. Not so sure about the heat shields. Much less aggregated corporate experience there.

cubefox 2y ago
It was quickly taken down, but there was a video on YouTube from someone who got hold both of a Space Shuttle and a Starship heat shield tile. He analyzed it with a microscope. He found that the material was nearly identical. I do wonder why SpaceX thinks they can make a ceramic heat shield work when it needed lots of checks and refurbishment for the Space Shuttle. Recently Musk even said they will add an ablative heat shield in certain areas. On the other hand, the at least the reusability of the lower stage shouldn't be a problem.
- HPsquared 2y ago
  There are quite a large number of parameters other than the material, surely. The whole design is different.
  - cubefox 2y ago
    Not at all. The tiles just consists of two layers. The main body and the dark layer on top. According to the electron microscope analysis, the two tiles were mostly the same.
    - HPsquared 2y ago
      I mean more, the size and shape of the ship, the size/shape/thickness of the tiles, the attachment method, the substrate material, the flight profile...
      - cubefox 2y ago
        I'm not seeing where SpaceX could have achieved a major innovation here that solves the problems the Space Shuttle had with the heat shield. I think the latter used glue rather than pins, but probably not because the Space Shuttle people couldn't make pins. If it was that easy...
        HPsquared 2y ago
        Those details could affect the heat flux and temperatures the material is exposed to. The two spacecraft have very different designs.
        cubefox 2y ago
        I guess one advantage of SpaceX compared to NASA is that the former are very trial and error based in their design, so they can iterate much more. NASA tends to design and plan everything in advance and only build it at the end. So when the Space Shuttle reusability didn't quite pan out, they couldn't easily change things up.
- lupusreal 2y ago
  From what I understand, they are trying to keep their unique type shape count very low relative to the shuttle, which should make tile replacement a lot cheaper. Nonetheless, the tiles seem like the weakest aspect of the whole design. Recall that the early proposals didn't have tiles at all, so the tiles existing now is already and acknowledgement that not everything is going according to the ideal path.
  - cubefox 2y ago
    I wonder whether they considered using a metallic heat shield with heat resistant alloys. The cancelled VentureStar space plane was planned to use this approach: https://ntrs.nasa.gov/api/citations/20040095922/downloads/20040095922.pdf https://ntrs.nasa.gov/api/citations/20040095922/downloads/20...
    - HPsquared 2y ago
      They were originally hoping to use transpiration cooling, the tiles ended up being the fallback.
      - cubefox 2y ago
        Yeah, but it isn't clear whether they ever considered a metallic heat shield. At some point in the past it was considered an improvement over ceramic tiles, since the VentureStar was planned as a Space Shuttle successor that fixed its shortcomings.