Space Tourism … and Much More
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.
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.
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.
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
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.
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.
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.
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.
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.