[AR] Re: SpaceX Single Stage to Orbit
- From: Craig Fink <webegood@xxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Wed, 22 May 2019 14:08:55 -0700
On Wed, May 22, 2019 at 12:42 PM Henry Spencer <hspencer@xxxxxxxxxxxxx>
wrote:
On Wed, 22 May 2019, Craig Fink wrote:
paradigm shift in what a "heat shield" is. Moving away from disposable
ablatives and dedicated (extra mass) heat shields to an integrated
system
where the physical tank is the heat shield. Active Cooling of the heat
shield will be the new normal at some point in the future, using a little
propellant mass as the ablative so to speak.
Disposable mass is extra mass, whether it's fixed on the outer surface or
carried in an internal tank. And don't forget that if it's carried in a
tank, it has to get to where it's needed, and the hardware for that is
extra mass too.
Personally, I'm not sure that it needs to be disposable mass with or
without transpiration cooling of the tank. There are plenty of ways to
connect a heatsink to offset the heat source of Entry that doesn't involve
disposing of the mass during Entry. Depends on what they are doing and how
they approach the problem. An example might be that the Auxiliary Power
Unit. If they choose to generate electricity/hydraulic pressure with using
GOX and GCH4 instead of LOX/LCH4, the APU now is a heat pump that can
super-cool landing propellant while in LEO. Possibly even freeze the
landing propellant prior to Entry, a nice heat sink. Don't worry Henry,
it'll probably be melted by the time it's need to land.
A sprinkler head in the tank to water the hot stainless tank wall to keep
it from melting can't be that complicated or massive to build.
--
Craig Fink
WeBeGood@xxxxxxxxx
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