In article ,
says...

Jeff Findley wrote on Fri, 22 Mar 2019
06:24:34 -0400:


There was some whining online about "why didn't they save that tooling
in case the stainless steel didn't work out". Um, because they've done
the analysis and testing on the hexagonal tiles needed for the new
design and they passed the tests.


Personally I'm still concerned about the transpiration heat shield.
Lots of people in the past have wanted to do similar things and none
of them could make it work. It's not a very fault tolerant approach.
I'd be a lot more comfortable if they'd build a subscale article and
loop it around the Moon so it returns at interplanetary reentry
speeds. Even more comfortable if they could somehow expose it to a
bunch of dust and crap (like by a lunar landing) and then bring it
back.

From what I've read, they plan on flying the first (prototype) Starship
without any transpiration cooling. Then they will find out which of the
hexagonal TPS tiles eroded and add transpiration cooling to only those
tiles which have eroded. This seems to imply that if transpiration
cooling did fail on a tile during a flight, it would erode some, but
still protect the Starship during reentry.

The goal is zero TPS maintenance between flights. But, it also sounds
like a failure in transpiration cooling would be more of a maintenance
issue than anything else. So, in the end, this sounds like a more
durable approach than the space shuttle TPS (low bar, I know).

Jeff
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