wrote:
wrote:
wrote:

I was recommending looking into Transhab not because it gave you the
space structure you wanted, but because it answered your material
questions and would give you working mass estimates.

multi layered sandwich and insulation and such. Ok. Point taken.

First problem: Shell strength and mass.

You want an environment with enough pressure that construction
workers
can promptly ditch their space suits, or at least reduce them. That's
going to require ~3psi of air pressure (pure oxygen).

why pure oxygen? The eventual goal is to be able to breathe in it, but
for the moment, an air tank doesn't weigh anything.

If you cut the
first shell down to a bare minimum with little margin of safety for
restraining just 3psi, it's still going to need to be 0.5mm thick and
made out of an ultra-strong fiber like Zylon.

Sure, reinforced with some sort of ultra strong fiber and adhesive
matrix. What about Zylon degrading in UV light?
My hope was that sending a really bare minimum shell, hardly able to
constrain 1 or 2 psi would allow workers to then work in a much less
bulky pressure suit over the next several years while they pasted on a
couple more of the fabric and insulation layers for the main
shell.(Sent up in much smaller, easier and less expensive shipments)
Of course the main shell wouldn't be able to be fully pressurized for
years, but with it up, you could easily set up smaller interior rooms
that COULD be fully pressurized. And which you could lease out for
income while you worked on augmenting the entire shell.

At a minimum, the shell
will be 24 tons (assuming a fully dense Zylon shell; more likely it'd
be about 36-40 tons). That shell will be inadequate for a 14.7psi
atmosphere.
Yes. I was SO disappointed when informed that the current launchers
only can carry 20 tons or so. Even if the workers have to use full
space suits for a while, working INSIDE, they don't have to worry about
falling, or dropping things, or drifting away, so I think it would
still be much easier.


Aluminized Kapton does not have anywhere near the yield strength to
handle 3psi at 0.5mm thickness. With a 30000psi yield strength (at
room
temperature), a Kapton sphere would need to be 3.5-4mm thick, which
would result in a 160-ton shell (just to handle 3psi).

What about a multilayer sandwich - aluminized Kapton outer shell to
help shield from UV,(oh, 2 mil thick. Check me on this, wouldn't that
be 1.46 grams for 200 square centimeters? Then, with Zylon fabric inner
shell bonded to it? Perhaps with another layer of Kapton inside it?
The separate layers could even be launched separately and inflated
inside each other before the bonding agent sets up, not necessarily
with anything near 3 psi, just enough to push them together under
tension.

Second problem: air mass.

The 3psi oxygen atmosphere will be about 250 tons. That's a lot of
tonnage to lift with current launchers. Which brings up problem
three...

We don't need to start out with anything near 3 psi, or 1 psi or 1/2
psi. The outside of the space station is vacuum. The inflatable will
inflate with practically nothing. What was the inside pressure of ECHO
I?

Third problem: existing rocket payload capacity.

If you want existing, in-production launchers to get the job done,
you're going to need 11-12 uprated Delta IV heavy launches (22 metric
tons to LEO) or 11 shuttle launches just to get to the stage where
you
have a bare minimum, air-filled sphere.

We don't need to start with an air filled sphere. We just need the
sphere. Once we have the sphere up - everything else is easier.

However, you'll probably want a
couple more launchers to deliver some climate control equipment (to
keep all that air from overheating), power systems, etc. So you're up
to about 13 launches before the workers get to climb out of their
space
suits during construction. Note that the Delta IV heavy, as currently
flown, is not really up to snuff for launching the initial, bare
minimum shell.

Alternately, if you don't want to wait on internal construction
activities for 11 big launches to fill the sphere with air, then you
can deliver the sphere shell (1 launch) and support equipment,
probably
including that bunkhouse you mentioned (2 more launches) and get to
work after 3 launches.

3 launches is what I've been figuring lately. 4 when I consider an
inner shell. At $250 million per.


But then the astronauts will be spending all their construction time
in
suits, at least until 11 more launches have delivered enough oxygen
to
give the sphere minimal pressure.

NO! you inflate a much smaller tent inside the sphere, and fully
pressurize that to do most of the construction in, a couple of rooms at
a time. In your shirt sleeves. The main sphere NEVER gets fully
pressurized for years. You just don't worry about it until some
contractor is willing to pay to do it.
Meanwhile, the folks pasting the extra layers on the inside of the
exterior shell will probably have to wear almost a full space suit,(per
Henry) and the folks constructing interior walls and rooms will be
inside a much smaller (oh, 20 meter diameter) inflated tent, working in
their shirt sleeves.

Fourth problem: existing launch capacity

This goal... "There will need to be weekly shipments of all sorts of
materials and equipment. In inexpensive 5, ten and twenty ton
launches." ...requires greater commerical rocket production than is
(I
think) currently available.

Boeing would LOVE to expand its factories to help you launch 20-ton
payloads every week.

And I'd LOVE to pay them to do so!

The idea of firing off 12-13 Delta IV Heavies (33
total common core boosters! wee! profits!) just to get the station
started would make Boeing very happy. And you'll eventually need 30
such launches just to bring the sphere up to 14.7psi, not to mention
another 30 launches to get the shell up to full strength, plus an
unknown number of launches to fill the station with that water,
machinery, etc...

Eventually. Sure.. It could take years. What a boring thought. :-)
Meanwhile, we'll be developing an internal ecosystem, plumbing, going
from one or two paying guests per week to 10 or 20, and from one
lessee, paying to use one 10 meter by 10 meter by 10 meter cube to 25
paying contractors, and giving the passenger space flight industry time
to develop. But meanwhile, THEY would have a destination to take
customers too - and would be able to charge the $5 million dollars per
round trip flight that they will have to, in order to make a profit.
Good development all the way around.


Yes, you could be looking at 100 launches of some rocket in the class
of the Delta IV heavy (or a lot more launches of smaller rockets). If
you want that to happen on a weekly basis, using existing rockets,
the
rocket maker(s) you contract will need to expand their factories.

Which leads me back to my prior suggestion of taking the time to
modify
the rockets. You're already going to have to pay for changes in the
rocket industry, so why not simplify the construction process with
bigger launchers?

I think simple is what I can do now. More complicated is something
that will take maybe a couple years to develop the concept.
I think I can do this now.

Once the launch market starts heating up (I really think I can use two
launches per week -- Yes, I'll pay what you are wanting to charge...)
Somebody out there will develop bigger capacity. I don't have to worry
about that.
And when we start turning a profit, we can think about bigger projects.
Once this is up and operating, outfitting a Mars expedition will be
much simpler. And we will once again need bigger launchers.

The bare minimum shell you want is probably going to be 36-40 tons
even
with super strong materials. Just sticking with the Delta IV example
so
I don't have to google up alternatives, you can get about 30-35 tons
to
LEO with the Delta IV heavy if you strap some solid boosters to it.
Boeing hasn't flown that yet, but it looks like an easy stretch.

Boeing also claims its Delta IV common core booster can be scaled up
to
Saturn V payloads. It'll take modifications to the launch pad and
some
engineering work, but its mostly just strapping 7 common core
boosters
together. It recently flew 3 of them strapped together. With such an
(almost off-the-shelf) rocket, you could launch a full-strength shell
in one leap. You could give a minimum working atmosphere in the shell
in 2 launches, not 11-12.

Alternately, if you're really insistent on launching weekly, perhaps
you should take the time to develop a reusable launcher like the
VentureStar. It'll probably save you headaches in the long run.

Summary of problems:

Getting the station built in exactly the manner you want is somewhere
on the edge of possible/impossible with existing rockets. You need a
shell launched in one piece that's probably going to be 35-40 tons.
Your bare minimum air pressurization ("Once the shell is up and only
slightly pressurized, the facility is open for business") is going to
need 250 tons of oxygen.
No it won't! It will only take a couple of tons of air to make a couple
of rooms fully operational and able to be leased out. A big skyscraper
doesn't wait to start leasing and opening stores and rooms until all
the floors are finished - as soon as a couple of floors are finished,
they move in paying clients and open for business.


You want flight rates that are beyond the
immediate abilities of rocketmakers, but could be achieved with a
little development.

If I start paying for regular launches, the launch market will develop
on its own.

This is good, Mike. You want to go into business?
Harmon