• Michael Vaicaitis

    The prepared and emphasised line that stood out for me, quote:
    “THAT is how a 21st-Century spacecraft SHOULD land”

    Elon was answering questions for 45 mins after and a couple of titbits I noticed from media coverage:
    1) the interior will be padded, not just the silver inside surface of the pressure vessel. Presumably some easy wipe-clean vomit-proof material.
    2) The heatshield is expected to last 10 re-entrys. That’s presumably 9 quick turnarounds of re-fuel and re-fly before overhaul or recycle or scrapyard. Hopefully future enhancements with push that up to 100 re-entrys.

  • Hug Doug

    Pica-X is ablative, meaning that the number of reuses you can get out of it is dependent on how thick it is. i imagine making it 10x thicker to get 100 uses out of it would make it prohibitively heavy.

    unless they’re working on a regeneratively cooled TPS (a very heavy idea) that they haven’t mentioned, the heat shield is one component of the Dragon capsule that will have to be replaced regularly after X number of uses.

  • Michael Vaicaitis

    Well may be, at some later date, Musk will tell us how they intend to reach 100 uses. Or perhaps they will simply announce a gen4 or gen5 or gen6 version. Anyhow, apparently the gen3 is good for 10 and some later gen will hopefully be good for 100.

  • Hug Doug

    A possibility for very high levels of reuse is some form of metallic TPS. Perhaps regeneratively cooled, but that would (as noted earlier) be far heavier than any ablative TPS

  • Douglas Messier

    Musk said they have been incrementally improving the PICA-X material. They’re now on version 3, which apparently ablates far less than the earlier versions.

  • Michael Vaicaitis

    Exactly my point. Gen 1 might be reusable if it weren’t soaked in salt water. The same goes for Gen 2, presumably not yet flown. Gen 3 will ablate less and last 10 re-entrys. Continued data and materials improvements should lead to a higher reuse rate. Can’t be sure the figure of 100 was reported accurately though, but it Musk said it even the sceptic in us has to lend it some plausibility – he’s the man with the research team and the data.

  • therealdmt

    Maybe they could go with something like an improved version of the space shuttle’s tiles. They’ve never mentioned this, but the material is out there.

    The X-37 uses advanced tiles, and the ESA (or actually the German national space agency, I think it was) proposed a non-abalative heat shield material that they have as a possible improvement over the abalative TPS of the Dream Chaser.

    I think with their Mars focus though, they don’t want to get sidetracked into a direction that wouldn’t allow re-entry from Mars, so that is a big part of their choice of abalative, I’d guess.

  • Hug Doug

    i know one of the reasons they like PICA is that it’s much more durable than the Shuttle’s tiles.

    there’s a lot of TPS options out there. what one you need depends on the size and design of your spacecraft, for the most part.

  • The Alchemist

    PICA is heavy stuff. Given the size of that heatshield, adding just 1/16″ to the thickness will be a significant mass hit.

    How would a regeneratively cooled TPS even work? The main function of PICA’s efficacy is it’s ability to ablate and not transfer stored heat. In a sense, the ablating mechanism serves as means to actively cool the heatshield. Removing the ablative properties of the material would seriously degrade its performance.