In article ,
says...
Musk was asked this by Everyday Astronaut and specifically says "No,
weâ??re building a BFR dev ship to do supersonic through landing tests
in Boca Chica, Texas".

'Through landing' makes it sound like there WILL be powered landings,
so there seems to be some conflict there.


No, you're mixing two different vehicle, Musk says the mini-BFR won't
do that type of testing, it will bne done by the already known "BFR
dev ship" (currently being built)!


The wording and presentation here didn't make it clear to me that two
different ships were being discussed.


Sorry this was confusing. I thought this first paragraph in the
original posting made it clear that this vehicle was something new.

| Elon Musk tweeted yesterday that SpaceX plans to build and fly
| a mini-BFS prototype as a Falcon 9 upper stage. This is to test
| the lightweight thermal protection system as well as the
| aerodynamics of their "belly flop" reentry and flight down to
| subsonic speeds.

Mini-BFS:
The announcement of this new mini-BFS indicates that it will fly as a
Falcon 9 upper stage. It is therefore surely a sub-scale prototype
meant to test the thermal protection systems, hypersonic aerodynamics,
and the flight control systems. As we all know, hypersonic aerodynamics
is still a bit of a black art.

Yes we have CFD today, but I've often heard it said that you fly your
first hypersonic vehicle so that you can then tweak the CFD model so
that it matches the real world. This new mini-BFS allows just that. So
SpaceX won't have to risk a presumably more expensive full scale BFS in
order to do this.

Full scale BFS:
As far as I understand, the prototype BFS that is being built for test
flights (likely out of Boca Chica Texas) is a full scale article built
as close as they can get to a production vehicle (i.e. Musk has said
that the first full sized cylindrical composite fuselage sections being
produced are for this prototype). The full scale BFS test article will
be able to launch and take off under its own power (since all of its
engines were changed to sea level engines some time back). The full
scale BFS is the one that *might* be able to achieve SSTO (with little
to no payload), if all goes well.

Meanwhile when the full scale BFS is complete, it can start doing
"hops" in order to validate their vertical landing strategy. At one
point Musk said the first stage will land back on its launch platform.
I'm not sure if that is still the plan or not, but if it is, I would
think a bit of testing of that would be in order. It certainly sounds
like that landing mode will be like threading a needle. Throw in a good
crosswind and I'm sure landing the BFR first stage will be "sporting".

Jeff
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