Entry/Egress from BFS on Mars

In article ,
says...

On 2019-09-23 07:47, Jeff Findley wrote:

Agree to disagree here. Any solution is going to be constrained by the
structure and tank design. They're not going to make major changes to
the design that would do something like change the tank geometry.

But the designe of the structure above the tanks (the usable space) will
matter and this is where careful planning can make things such as
ladder/doors easy to implement vs extremely big headache that requires
redrawing the upper structure.

And if the structures above the tank might differ betwene the cargo and
manned versions (and I would venture a 3rd model that is used as a fuel
tanker). then you ant to make sure the "baseline" structure around the
Starchip tanks/engines can support/interface with the variable structure
above.

The above is largely nonsense because you keep failing to distinguish
between the areas that have large loads versus areas that are almost
insignificant. Leave these details to the mechanical engineers at
SpaceX. They know their stuff. For nearly three decades I have been
writing CAE software for a living and get to interact with customers at
Beta Test every year that do just this sort analyses every day. I know
what they do with our software because I've seen their models first hand
and talked to them about how they use the software and how we can make
it better. And last I checked, SpaceX using our software to do their
CAE analysis.

Disclaimer: All statements above regarding CAE software do not reflect
those of my employer. They are all my personal opinions and should be
taken as such.

At any rate, you're hand-waving here. We don't yet know the details.
wait for the update.

That's a minor thing compared to, say, the structure needed to support
the winglets/flaps on the spacecraft.

Not so minor if the structural elements needed to support those winglets
blocks the way for a door. As well, if the cargo version with the huge
doors will be in vacuum, that also means planning around lack fo air as
coolant for components. So they would need to likely plan for water or
ammonia loops or whateer is felt is needed. And BTW, how would the
manned version dump excess heat during a 6 months mission? Would it
deploy radiators, solar arrays during the trip and neatly fold them back
for re0-entry in Mars and back on Earth? If they fail to retract and
close doors, that could be a show stopper for re-entry in Earth's
atmosphere.

It is easy to stick an engine below a glorified grain silo. But when you
start to factor in all the various things that "break" a clean smooth
outer skin with doors etc, things become more complex.

You're waving your hands even faster here, but again we don't know the
details. Wait for the update.

I'm pretty sure that the doors used for test facilities at NASA
installations would beg to differ. Especially those in Ohio.

Do these dooors have to maintain perfect seal for perhaps 2 years? (6
month trip each way, plus a year stay on Mars). NASA can paliate for
small leaks by having compressors deal with any leaks in/out of the
pressure chamber.

This is incorrect. Any small leak in a large vacuum chamber ruins the
vacuum that needs to be achieved.

Also, there is the small matter of weight. Those very large opressure
vessels are very heavy, not exactly what they want on a spaceship.

Spaceships have had doors with seals in the past. Again, this is a
simple mechanical engineering problem to solve.

BTW, how did Dragon V1 deal with a CBM hatch at the top during
re-entry?

They shut the door and it reenters. It's on the "cooler" side of things
and made of aluminum which distributes the heat very well.

did crewmembers attach some sort of blanket over it before closing the
station side CBM and releasing Dragon? Ir was the CBM hatch coated with
heat shield material?

No blankets or anything. They just shut the hatch and secured it. Go
watch the undocking videos on YouTube.

Obviously cargo Starship will be the first.

Considering that investor who was promised a ride to the Moon on an
early flight, I wonder if SpaceX can realy delay the manned Starship
till Cargo one is all done. (Unless they really ride the Cargo Starship
with a Dragon V2.0 perched on top instead of the nose)

They're different copies of the vehicle. Why would one have to be done
before starting work on the other? Makes no sense. Large teams of
people can work on more than one thing at a time whether that's design,
test, fabrication, operations, maintenance, and etc.

This idle speculation is largely irrelevant given that Elon Musk is
giving us an update in a matter of days.

And exactly because of that that discussing various issues before that
presentation makes one look at what will and especially will not be
said during his presenation. Avoided subjects just as important as those
that are mentioned.

Meh.

Jeff
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