Harmon Everett wrote:
wrote:
wrote:

Well, it'd be easier, but the resulting structure isn't something
I'd
expect to pass any safety inspection, at least not until it was
much
thicker than a shell made of continuous, woven fibers.

I was thinking the additional layers of fibers would be continuous
woven fabric.

Unless the interior of the sphere is completely empty (of
revenue-generating modules), you're not going to be able to install a
continuous-fiber fabric shell. You're going to have install patches,
which goes right back to the problems of hand lay-ups.

The second layer would be thicker and more capable of
being pushed against with the squeegee, and so on.

Speaking as a materials engineer, I *still* wouldn't trust a composite
shell laid up by hand in that fashion even if you could press and roll
it firmly.

And each layer would add to the radiation
protection and micrometeorite puncture protection.

No, the micrometeorite protection won't increase noticeably with a
slight thickening of the hull. Thick, solid materials are poor means of
stopping micrometeorites.

Why limited to the strength of the binding resin?

Because the fibers would not be interlinked between layers and between
patches. The resin would be the only source of strength in those areas.
The hand lay-up method is also prone to creating resin-rich areas.

You might be limited to a fraction of the fiber strength -
like 50,000psi instead of 500,000psi.

Isn't that what we want anyway?

Why would we want to cripple the strength of the material?

True. But meanwhile, you have enough internal controlled volume to
lease to paying customers.

Correct. And in the years it takes you to slowly hand-assemble your
giant sphere, those customers might as well be operating in a normal
space station, since the enclosing sphere isn't doing much for their
modules.
In fact, they could go to the competitor who doesn't increase rates to
pay for a big, non-profitable sphere.

If you want that sphere to do something useful, you'll want to build it
quickly to the point it can house occupants without separate,
vacuum-rated modules. This painstaking patchwork method does not seem
good for business.

Why weave it on site? Does it not compress or bend well? I would
think making it on earth and unfolding it in space would be easier.

If you have a rocket that can put a 650-ton shell into orbit, sure,
make it on Earth. If you don't, some on-orbit assembly of individual
full-strength segments will probably be necessary. Of those methods,
the hand lay-up method you like is one of the slower and less safe
methods.

So the argument against working in space suits is that they break and

kill people?

There's multiple arguments against them, including their clumsiness.

Is the same argument valid against the stacking multiple
tin cans with space walks concept in developing the ISS?

Spacesuits are much less of a problem for the ISS. The spacewalks
required for the ISS's construction take much less time than assembling
31416 square meters of multi-layered composite in zero-G. It's about
1900 man-hours for the ISS, while it might be over 3000 man-hours per
layer of the sphere with hand lay-up.

If you are working in a space suit inside a volume with
1/2 psi, with the space suit pressurized to 3 psi, and
the space suit develops a leak, are you more likely to
get a slow leak, which you can get back to the fully
pressurized area and patch, or explosive decompression?

Astronauts exploding in a vacuum is a Hollywood invention, and the
difference between 0.5psi and 0psi isn't significant to the leak rate.

Again: this all gets much easier if you're willing to use somewhat
enhanced launchers. You'll strangle the project if you insist on
countless hundreds of little launches and tedious hand-assembly of the
sphere.

It won't take Boeing much to strap some SRBs onto its Delta IV heavy
and give you a 40-ton payload. With that, you can launch entire 0.5mm
shells into orbit in a single bound. If you go larger, up to a 100- or
120-ton launcher, you can put the full pressure shell into orbit in a
single launch. Then its just a matter of spraying on foam insulation,
inside and out, and laying down some non-structural liners and
insulation.

Mike Miller, Materials Engineer