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. And it wouldn't need to pass a safety inspection until it
was much thicker. In a year or two, after several layers had been laid
down. The first skin would be flexible and fragile, the first fabric
and resin would be much stiffer, but still pretty fragile. The second
layer would be thicker and more capable of being pushed against with
the squeegee, and so on. And each layer would add to the radiation
protection and micrometeorite puncture protection.

Hand lay-up of resin and fibers is prone flaws in ideal factory
conditions. Add in...

*clumsy space suits
Yah. Darn.

*an inability to really squeegee and roll binding resin into the
fabric
without tearing the 5-mil Kapton

I think I can argue this point. I think there are several ways to over
come this problem. Have a moveable curved table to squeegee the resin
into the fabric before the fabric gets moved to its final location. Or
have two part adhesive, one part on the Kapton, one in the fibers. Or
have the first Kapton/fabric/adhesive layer still be somewhat fragile,
but much harder than the Kapton alone. Then the second
Kapton/fabric/adhesive layer you put on can really be rolled on. Then
the third Kapton/fabric/adhesive layer you put on can be practically
applied with a hammer.

*A substrate prone to tearing under the mass of an astronaut

..and you're going to end up with a pressure shell laden with flaws
(resin rich areas, inadequate connection between strips of fibers,
etc). It would also be much more dependent on the strength of the
binding resin rather than the fibers.
Why limited to the strength of the binding resin?

You might be limited to a
fraction of the fiber strength - like 50,000psi instead of
500,000psi.
To make the structure safe, you'd need 2cm or more of thickness in
the
strength shell.
Isn't that what we want anyway? It just doesn't need to happen
immediately.
There's going to be holes and soft spots and attachments. With the
multiple film/fiber blanket/adhesive layers sandwich, you sew in a new
patch of fiber/film/adhesive, epoxy it in and cover it with a patch of
air barrier film, and go on about your business. The only real problem
is a major tear, and you probably criss cross the directions of the
layers of the fabric blankets to minimize that.

Building the shell inside a pressure shell also would make it
difficult
to inspect the layers as you lay them down. It generally helps to
have
access to both sides (such as during ultrasound examinations).
Stitching and other useful means of binding new patches of the high
strength fiber to the shell would be difficult - you'd need to
puncture
the outer hull.
A ultrasound gadget on wheels rolls around the outside of the sphere
attached to cables that run exterior on the surface from pole to pole.
Probably going to need it for exterior human work on the outside
surface anyway.
They have sewing machines that work from just one side of the fabric.
There is going to be a lot of that anyway. Once a couple layers of
fabric get adhered to the outer film, that should be minimal danger.
And besides the several layers of fabric getting laid onto the outer
skin, there will probably be another layer or two of inner film.

Finally, laying down strips of fiber on any surface work best when
you
can really pressure and squeeze down on the surface. For example,
putting a hard mold or plate under two layers of fabric you want to
bond together. That'd be difficult with a 5-mil Kapton outer shell.

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

rather than trying to patch together pieces of a large sphere
while in a small room while weightless.

Instead of a small room, you can use my suggestion of a 30m (100ft)
starting sphere. Further, that sphere would be an excellent place to
locate large weaving machinery suitable for producing a high
strength,
continuously woven shell.
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.
For that matter, unfolding it between the inner and outer shell of the
100 meter spheres sounds even easier. Then we aren't pressing so much
against the outer Kapton film when we squeegee, as against the Zylon
blanket.
It would be easy to inspect the growing
shell, repair any defects, and even strength-test sections. Finally,
by
using this separate sphere as a work space to assemble the full-sized
sphere, your assembly processes no longer worry about stressing the
work space's hull - you can push, prod, and strain the full-sized
sphere's material and not worry about poking a hole in it.
I'm not worried about poking holes - those can be patched, and are
going to be dealt with on a regular basis. I'm worried about not being
able to lease space to paying customers. With the 100 meter fragile
sphere, we can immediately start leasing space for smaller, functional,
internal pressurized rooms within a non pressurized larger hull while
the external shells get their multiple layers applied over the next
several years.
With the 30 meter concept, the whole structure is being used for
constructing the next size structure, with little room left over to
lease to paying customers or vacationing guests.

Note the Transhab, which had a very enviable safety factor, was
assembled from patches in the manner I suggested.
L'Garde says its lobed (pumpkin shaped) design overcomes much of the
tension requirements of a super pressure inflatable. Something about
the determining factor is the local radius of the individual lobe ( or
gore) rather than the overall diameter of the entire balloon.

Harmon Everett
Let's light this candle - Alan Shepard