The term "Iterative development" has been drilled into me by the
regular posters here.

So I ask this in that context.

SpaceX has by now plenty of experience with Falcon 9 and its 2nd stage,
and with Dragon variants (2 generations, and second generations having
both Cargo and Passenger versions).

I can understand how the "iterative" part moved SpaceX move from
building rockets (where it had experience) to building glorified flying
grain silos. It had to learn how to work with steel, how to weld it so
it doesn't rupture when filled with cryos etc.

However, the experience it already had for "rocket" stuff like landing
gear, thrusters etc should have been able to advance during the time
SpaceX was learning to build grain silos.


So I am quite curious why the teams working on the project don't have
proper landing gear yet, and thrusters still seem like experimental
thinsg mountied outside of fuselage with some discussions still going on
on what sort of fuel will be used.

Seriously, can the current Starship landing gear that is inside the
skirt really be a final design? or shouldn't a passenger carryihg ship
have a much larger footprint to increase odds of survivung landing
intact on a ship with no ejectable passenger capsule?

And how come thrusters would be bolted on the outside at this stage of development? Shouldn't plans already include the space needed for them
inside fuselage for aerodynamic pruposes and ensuring thry don't burn up
on re-entry?

It seems unreal to me that SpaceX would focus on one thing at a time and
only now would start working on thrusters. You can't just tag on stuff
as you progress because eventually, it needs to all integrated into a
neat aerodynamic rocket that doesn't have components stick out. Have
they not planned space inside fuselage for thrusters yet and they will
deal with that later?


Much thinking was put on selection of methane as fuel because of ability
to generate some on Mars. How come the selection of fuel for thrusters
wouldn't have been done at same time?


I can understand early SNs having just a tank of liquid nitrogen and a
valve as a thruster, but by now, shouldn't they have been iteratively be developping real thrusters and placing them in their final position to
test fuselage integrity, and mounting design to allow for their inspection/maintenance) ?



SpaceX worked in parralel to develop software, engines and the steel
grain silos. How come landing gear and thrusters appear to have been
left behind with thrusters only now getting some attention?


As SpaceX has stopped testing the Starship in preparation for n orbital
flight later this year, I would have expected the Starship to have
advanced to a point where it is ready for orbital flight with its
components having been tested. Can it really do orbital flighst and
re-entry with externally mounted naked thrusters?

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JF Mezei wrote on 7/16/2021 :

As SpaceX has stopped testing the Starship in preparation for n orbital flight later this year, I would have expected the Starship to have
advanced to a point where it is ready for orbital flight with its
components having been tested. Can it really do orbital flighst and
re-entry with externally mounted naked thrusters?

Starship does not have externally mounted naked thrusters.

The externally mounted naked thrusters seen in some pictures have been
mounted on booster segments. Those were a new design, and they were
preparing to test them on what are stages still under development, but
then decided they weren't ready to test them in flight. Perhaps
plumbing issues. And the hot gas thrusters were/are, AIUI, to use the
same fuel as the Raptors.

As for the landing legs, it was already known that the Falcon legs
wouldn't scale to the weight of Starship, and external legs might be a
problem for full re-entry, anyway. The legs seen on the SN flights
have been iterated (after SN6, IIRC), but were still considered early
test models.

Perhaps the leg problem has taken more design time than expected, and
with Raptors no longer being the long pole in the tent (in the context
of Gantt charts for the project) and the tanks having iterated so
quickly, the leg design delays are more noticable now.

I've certainly been on projects where the hard problem of the design
was done on time because it got enough resources, but other parts of
the design became the barrier to shipping, because you still need to
have all the screens done (user interface) and you still need to have
the packaging.

I expect that the heat shield tiles are stable design-wise by now, but
the mounting methods are still being checked out. So far, we've only
had "can they survive fueling temperatures? can they survive the
shaking of liftoff and landing?"

/dps

--
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Well hung: curricle-hung in fact. Come sit by me and we'll test the
springs."
(Speculative fiction by H.Lacedaemonian.)

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Snidely pounded on thar keyboard to tell us

JF Mezei wrote on 7/16/2021 :

As SpaceX has stopped testing the Starship in preparation for n orbital
flight later this year, I would have expected the Starship to have
advanced to a point where it is ready for orbital flight with its
components having been tested. Can it really do orbital flighst and
re-entry with externally mounted naked thrusters?

Starship does not have externally mounted naked thrusters.

I believe that Starship has cold gas thrusters using propellants, as
we've seen them tested during cryo tests and before hot fire tests.
We've seen similar thruster tests during the BN3 cryo test.

The externally mounted naked thrusters seen in some pictures have been mounted on booster segments. Those were a new design, and they were preparing to test them on what are stages still under development, but then decided they weren't ready to test them in flight. Perhaps plumbing issues. And the hot gas thrusters were/are, AIUI, to use the same fuel as the Raptors.

As for the landing legs, it was already known that the Falcon legs wouldn't scale to the weight of Starship, and external legs might be a problem for full re-entry, anyway. The legs seen on the SN flights have been iterated (after SN6, IIRC), but were still considered early test models.

Perhaps the leg problem has taken more design time than expected, and with Raptors no longer being the long pole in the tent (in the context of Gantt charts for the project) and the tanks having iterated so quickly, the leg design delays are more noticable now.

I've certainly been on projects where the hard problem of the design was done on time because it got enough resources, but other parts of the design became the barrier to shipping, because you still need to have all the screens done (user interface) and you still need to have the packaging.

I expect that the heat shield tiles are stable design-wise by now, but the mounting methods are still being checked out. So far, we've only had "can they survive fueling temperatures? can they survive the shaking of liftoff and landing?"

/dps

--
Yes, I have had a cucumber soda. Why do you ask?

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On 2021-07-16 19:06, Snidely wrote:

Starship does not have externally mounted naked thrusters.

The externally mounted naked thrusters seen in some pictures have been mounted on booster segments.

Thanks. Was a bit confused. Was under the impression that the bosster
needs thrusters a lot less since it uses tha grid fins for most of work,
and it has a short duration trip. (falcon 9 uses simple N2).

Again, considering SpaceX' experience both woth Falcon 9 and with
Starship (with regards to weight/strength of steel, and hence force
needed for side thrusters), I am surprised that the
architects/engineers didn't work on that aspect all this time and only
now getting around to it.

hot gas thrusters were/are, AIUI, to use the
same fuel as the Raptors.

Things are starung to fall into place now. Back in 2020, Musk stated
they were working on gas trhusters (methane gas, O2 gas) which makes it
much easier to use in 0G. The the hot gas thrusters are (also() destined
for Starship that currently ha prototype stage simple N2 thrusters.

I wonder if the decision to land super heavy in the arms of the launch
tower resulted in need for much mroe powerful thrusters than originally
planned N2 and hence the development of the new hot gas ones was
accelerated?

(But still, since it was known for some time that Starship woyuld have
hot gas thrusters, would have though they would have been in development
and testing so at a more advanced stage now.

problem for full re-entry, anyway. The legs seen on the SN flights
have been iterated (after SN6, IIRC), but were still considered early
test models.

Do we know whether the current "swivel down, lock" mechanism is final
and theyKs just improve it, or is the future fuzzy enough that we might
still get legs that are much more elaborate and perhaps spread out to
wider footprint than Starship fuselage?

Think doors on skirt section of fuselage that swings up or down to let
landing gear come out.

Perhaps the leg problem has taken more design time than expected, and
with Raptors no longer being the long pole in the tent

I have raised this concern in the past: this iterative design process
may end up with a core design that just doesn't allow something whose
design is slated for future. AKA: design the skirk to house the engines
but later, when you finally get around to designing landing gear, you
find out that the skirt's design, now too late to change, makes landing
gear too difficult.

I expect that the heat shield tiles are stable design-wise by now, but
the mounting methods are still being checked out.

Not doing a full deckout on the last flown SN is understandable. But on
the first orbital one, I would expect full decking out of the tiles as
this is truly the first time their performance can be tested for real.

Hopfully it doesn't take too many iterations before they get it right.

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In article <wfnII.4529$Dk6.456@fx20.iad>, jfmezei.spamnot@vaxination.ca
says...

The term "Iterative development" has been drilled into me by the
regular posters here.

So I ask this in that context.

SpaceX has by now plenty of experience with Falcon 9 and its 2nd stage,
and with Dragon variants (2 generations, and second generations having
both Cargo and Passenger versions).

I can understand how the "iterative" part moved SpaceX move from
building rockets (where it had experience) to building glorified flying
grain silos. It had to learn how to work with steel, how to weld it so
it doesn't rupture when filled with cryos etc.

However, the experience it already had for "rocket" stuff like landing
gear, thrusters etc should have been able to advance during the time
SpaceX was learning to build grain silos.

I'm sure they've already tested the thrusters at McGregor Texas. IDK
about landing gear.

So I am quite curious why the teams working on the project don't have
proper landing gear yet, and thrusters still seem like experimental
thinsg mountied outside of fuselage with some discussions still going on
on what sort of fuel will be used.

Iterative development. The current test flights will provide data which
can be used to refine the landing gear design. Besides, the first
orbital attempt won't be landed on land anyway.

I'd bet gaseous methane and LOX for the thruster propellant. SpaceX has
been clear that is needed for the Mars ships.

And how come thrusters would be bolted on the outside at this stage of development? Shouldn't plans already include the space needed for them
inside fuselage for aerodynamic pruposes and ensuring thry don't burn up
on re-entry?

Because inside is LOX or liquid methane. They have to be on the outside
(or inside the interstage). Aerodynamic fairings aren't needed for this
first Super Booster test article. I'm not sure it will even fly.
Static fires are planned though.

It seems unreal to me that SpaceX would focus on one thing at a
time and only now would start working on thrusters.

That's the very definition of iterative development. That's exactly how
Falcon was designed.

You can't just tag on stuff
as you progress because eventually, it needs to all integrated into a
neat aerodynamic rocket that doesn't have components stick out.

Sure you can.

Much thinking was put on selection of methane as fuel because of

ability

to generate some on Mars. How come the selection of fuel for thrusters wouldn't have been done at same time?

It certainly did. They'll use gaseous methane and oxygen for the Mars
ships. That eliminates tanks for inert gas (e.g. helium on Falcon).

As SpaceX has stopped testing the Starship in preparation for n
orbital flight later this year, I would have expected the Starship
to have advanced to a point where it is ready for orbital flight
with its components having been tested. Can it really do orbital
flighst and re-entry with externally mounted naked thrusters?

Starship is ready for an orbital flight attempt. TPS covered
aerodynamic surfaces have been spotted in Boca Chica. Again, the Super
Booster prototype being tested now isn't the one they'll use for the
orbital attempt. They'll likely have fairings over the thrusters for
the orbital attempt.

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,
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In article <70qII.20829$Yv3.4294@fx41.iad>,
jfmezei.spamnot@vaxination.ca says...

On 2021-07-16 19:06, Snidely wrote:

Starship does not have externally mounted naked thrusters.

The externally mounted naked thrusters seen in some pictures have been mounted on booster segments.

Thanks. Was a bit confused. Was under the impression that the bosster
needs thrusters a lot less since it uses tha grid fins for most of work,
and it has a short duration trip. (falcon 9 uses simple N2).

Grid fins don't work as the vertical velocity approaches zero.

Do we know whether the current "swivel down, lock" mechanism is final
and theyKs just improve it, or is the future fuzzy enough that we might
still get legs that are much more elaborate and perhaps spread out to
wider footprint than Starship fuselage?

We don't know if the current swing out legs are the final design for
Starship.


--
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.

--- SoupGate-Win32 v1.05
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On 2021-07-18 0:21, Jeff Findley wrote:

In article <wfnII.4529$Dk6.456@fx20.iad>, jfmezei.spamnot@vaxination.ca says...

...

So I am quite curious why the teams working on the project don't have
proper landing gear yet, and thrusters still seem like experimental
thinsg mountied outside of fuselage with some discussions still going on
on what sort of fuel will be used.

...

And how come thrusters would be bolted on the outside at this stage of
development? Shouldn't plans already include the space needed for them
inside fuselage for aerodynamic pruposes and ensuring thry don't burn up
on re-entry?

Because inside is LOX or liquid methane. They have to be on the outside
(or inside the interstage). Aerodynamic fairings aren't needed for this first Super Booster test article. I'm not sure it will even fly.

Musk has confirmed that the booster currently being stand-tested will
not fly.

...

As SpaceX has stopped testing the Starship in preparation for n
orbital flight later this year, I would have expected the Starship
to have advanced to a point where it is ready for orbital flight
with its components having been tested. Can it really do orbital
flighst and re-entry with externally mounted naked thrusters?

Starship is ready for an orbital flight attempt. TPS covered
aerodynamic surfaces have been spotted in Boca Chica. Again, the Super Booster prototype being tested now isn't the one they'll use for the
orbital attempt. They'll likely have fairings over the thrusters for
the orbital attempt.

Musk has said that the first orbital attempt will use cold-gas
thrusters, with the hot-gas ones to be used at some later point. I
haven't seen anything about how the cold-gas thrusters will be mounted,
though.

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