SpaceX to fly mini-BFS prototype as Falcon 9 upper stage

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.

The flight tests will not include vertical landing because Musk says
they already know how to do that (duh). I am speculating it may,
however, test the transition from the "belly flop" attitude to vertical
as that would seem to be a critical part of the BFS flight profile to
prove out.

I'm also speculating recovery might be by parachute. You know, because
you might want to fly the thing more than once. Plus, if they fly a
mini-BFS prototype more than once, they'll be in the record books for
flying the first fully reusable TSTO. You know, because you've actually
got to reuse it to call it reusable.

Elon Musk also tweeted that the first flight of this prototype is
expected by June. But, of course, that's Elon Musk time, so I'd expect
a delay of at least a few months.

Expect articles on space news sites in the coming days since even a
handful of Elon Musk tweets are often turned into articles.

I'm sure SpaceX is doing this mostly for testing, but one could imagine
the utility of a reusable upper stage which integrates the payload
fairing into the design. This is especially true on the Falcon Heavy
since for some missions it's got the extra payload margin to handle the
increased mass of the upper stage.

My cite is the Elon Musk Twitter account. It's easy enough to find and
scroll down to yesterday's tweets.

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.

Jeff Findley wrote:
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.

The flight tests will not include vertical landing because Musk says
they already know how to do that (duh). I am speculating it may,
however, test the transition from the "belly flop" attitude to vertical
as that would seem to be a critical part of the BFS flight profile to
prove out.

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

He earlier say "Ultra light heat shield & high Mach control surfaces
are what we can’t test well without orbital entry" (IE this mini-BFS
conversion).


I'm also speculating recovery might be by parachute. You know, because
you might want to fly the thing more than once. Plus, if they fly a
mini-BFS prototype more than once, they'll be in the record books for
flying the first fully reusable TSTO. You know, because you've actually
got to reuse it to call it reusable.

It doesn't actually say anywhere that it's going to be recovered...

Obviously recovering the stage do have benefits (like inspecting the
TPS) but has to be balanced against the increased development cost and
time.


Elon Musk also tweeted that the first flight of this prototype is
expected by June. But, of course, that's Elon Musk time, so I'd expect
a delay of at least a few months.

The time-frame feels tight even by Musk standard if they do plan to
try recovery but I guess it's possible. It seems likely it would be
faster/easier not add that.

They may think they get that data from various Dragon flights. Or it
could even be done in stages, where the first one just has TPS and
fins while later they add parachutes if they want to down that route.


I'm sure SpaceX is doing this mostly for testing, but one could imagine
the utility of a reusable upper stage which integrates the payload
fairing into the design. This is especially true on the Falcon Heavy
since for some missions it's got the extra payload margin to handle the
increased mass of the upper stage.

Reusing second stages is certainly something that could be useful if
the timeframe for BFR/BFS slips sufficiently. Another possible use
might be that they're considering it to reduce the cost of launching
all those Starlink satellites.


My cite is the Elon Musk Twitter account. It's easy enough to find and
scroll down to yesterday's tweets.

https://twitter.com/elonmusk/status/1060253333116473344

Torbjorn Lindgren wrote on Thu, 8 Nov 2018 15:14:32
-0000 (UTC):

Jeff Findley wrote:

The flight tests will not include vertical landing because Musk says
they already know how to do that (duh). I am speculating it may,
however, test the transition from the "belly flop" attitude to vertical
as that would seem to be a critical part of the BFS flight profile to
prove out.


Musk was asked this by Everyday Astronaut and specifically says "No,
we’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. Their previous plan for
upper stage recovery was inflatable structures. It'll be interesting
to see what they actually do.


--
"The reasonable man adapts himself to the world; the unreasonable
man persists in trying to adapt the world to himself. Therefore,
all progress depends on the unreasonable man."
--George Bernard Shaw

Fred J. McCall wrote:
Torbjorn Lindgren wrote on Thu, 8 Nov 2018 15:14:32
-0000 (UTC):
Jeff Findley wrote:
The flight tests will not include vertical landing because Musk says
they already know how to do that (duh). I am speculating it may,
however, test the transition from the "belly flop" attitude to vertical
as that would seem to be a critical part of the BFS flight profile to
prove out.

Musk was asked this by Everyday Astronaut and specifically says "No,
we’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)!

It was a follow up to an earlier answer when he explicitly says "Won’t
land propulsively for those reasons" (ER mentioned MVac flow
separation and excessive TWR). So there's no conflict, there's two
unambigous statement both saying it won't do powered landings.

Torbjorn Lindgren wrote on Fri, 9 Nov 2018 10:34:51
-0000 (UTC):

Fred J. McCall wrote:
Torbjorn Lindgren wrote on Thu, 8 Nov 2018 15:14:32
-0000 (UTC):
Jeff Findley wrote:
The flight tests will not include vertical landing because Musk says
they already know how to do that (duh). I am speculating it may,
however, test the transition from the "belly flop" attitude to vertical
as that would seem to be a critical part of the BFS flight profile to
prove out.

Musk was asked this by Everyday Astronaut and specifically says "No,
we’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.


--
"The reasonable man adapts himself to the world; the unreasonable
man persists in trying to adapt the world to himself. Therefore,
all progress depends on the unreasonable man."
--George Bernard Shaw

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
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.

In article ,
says...
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".


Ugh, I meant the BFR first stage here, not BFS. What I was getting at
there is that the landing mode for the BFR first stage is "sporting"
since Musk has said it will land on its launch platform.

So far Musk hasn't said much about the BFR first stage so we don't have
any idea when it might start to fly. It's likely considered to be low
risk since it has a flight profile similar to the Falcon 9 first stages
and Falcon Heavy boosters and center core. Still, I would think a few
"Grasshopper" style flights would be in order before stacking a BFS on
top of it for an "all up" test flight.

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.

A wise decision, since building a full-scale BFS and finding out that it
doesn't work as planned will set-back the company a hefty sum.

I agree it will need to be recovered, if only to inspect the heatshield. A
parachute or ballute would be the cheapest method.

"Jeff Findley" wrote in message
...
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.

The flight tests will not include vertical landing because Musk says
they already know how to do that (duh). I am speculating it may,
however, test the transition from the "belly flop" attitude to vertical
as that would seem to be a critical part of the BFS flight profile to
prove out.

I'm also speculating recovery might be by parachute. You know, because
you might want to fly the thing more than once. Plus, if they fly a
mini-BFS prototype more than once, they'll be in the record books for
flying the first fully reusable TSTO. You know, because you've actually
got to reuse it to call it reusable.

Elon Musk also tweeted that the first flight of this prototype is
expected by June. But, of course, that's Elon Musk time, so I'd expect
a delay of at least a few months.

Expect articles on space news sites in the coming days since even a
handful of Elon Musk tweets are often turned into articles.

I'm sure SpaceX is doing this mostly for testing, but one could imagine
the utility of a reusable upper stage which integrates the payload
fairing into the design. This is especially true on the Falcon Heavy
since for some missions it's got the extra payload margin to handle the
increased mass of the upper stage.

My cite is the Elon Musk Twitter account. It's easy enough to find and
scroll down to yesterday's tweets.

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.

In article ,
says...

On 2018-11-08 06:25, Jeff Findley wrote:

The flight tests will not include vertical landing because Musk says
they already know how to do that (duh).

WOuld the Mini-BFS be powered? new methane engines from the BFR/BFS
project, or fitted with Merlin vacuum engines?

No one knows for sure, but my personal guess is Merlin powered to reduce
development time and for compatibility with Falcon 9 launch facilities.

After separating from stage 12, would Mini-BFS accelerate to orbit and
then de-orbit ? Or would just just detach from Falcon 9, float for a
while before re-entry? (can that be well planned/conrolled ?

aka: how much of a working spaceship does this need to be versus an
empty hull to test the outer skin material?

No one knows for sure, but this sounds a lot like a mini-BFS prototype
and not much else. I would expect it to be as close as possible to the
aerodynamics of BFS, so other payloads on the same flight would be
unlikely, IMHO.

It would seem to me that recovering it bcome important to check how the
skin performed. Would they target a landing on ground (no salt water
contamination) or at sea because easier and salt water doesn't matter
much to exa ine how the skin performend?

Recovery is quite likely, IMHO. SpaceX would want to inspect the TPS to
see how it held up.

And in case you can't tell, this is full of speculation. All we have so
far is Elon Musk Tweets to go on. And they were very limited (i.e.
teasers).

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.

JF Mezei wrote on Tue, 13 Nov 2018
05:47:37 -0500:

On 2018-11-08 06:25, Jeff Findley wrote:

The flight tests will not include vertical landing because Musk says
they already know how to do that (duh).


WOuld the Mini-BFS be powered? new methane engines from the BFR/BFS
project, or fitted with Merlin vacuum engines?


I'd assume Raptor for the engine.


After separating from stage 12, would Mini-BFS accelerate to orbit and
then de-orbit ? Or would just just detach from Falcon 9, float for a
while before re-entry? (can that be well planned/conrolled ?


I'd assume it would go to orbit.


aka: how much of a working spaceship does this need to be versus an
empty hull to test the outer skin material?


If the only purpose was to "test the outer skin material", you don't
need to fly it.


It would seem to me that recovering it bcome important to check how the
skin performed. Would they target a landing on ground (no salt water
contamination) or at sea because easier and salt water doesn't matter
much to exa ine how the skin performend?


Why are you fixated on skin?


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn