The space community is wary of mega-structures that would be required for
rotating space habs. Alglobus suggests that we could reduce the size of
these structures by constructing them within the natural radiation shield
of planet Earth - which would reduce the size of these mega-structures
substantially.

Realizing the first prototype could also be aided by realizing the space
hab in stages and opening them to tourists at each stage:

1. The hull - Tourists can entertain themselves inside the hull in vacuum,
wearing pressure suits. Tourists could base themselves in nearby Bigelow
constructed space habs.
2. The hull pressurized with air - Tourists can spend time in a large zero
g enclosure without pressure suits.
3. The hull pressurized and spun.
4. Fully constructed space hab.

Evidently the first step is crucial, If this barrier is passed the
remaining activities can be taken up with confidence. Are there ideas on
how the hull can be constructed - at minimum cost? Would some kind of
winding process work out cheaper?

Going with Kalpana 1 , with no
shielding, rotating at 3 rpm, having radius of 100m, accomodating 1550
people the mass of the hull is *3000 Tonne*.

(If we can construct a small hull we can with confidence construct larger
ones)

Regards,
Selvaraj

Realizing the first prototype could also be aided by realizing the space hab in stages and opening them to tourists at each stage:
1. The hull - Tourists can entertain themselves inside the hull in vacuum, wearing pressure suits. Tourists could base themselves in nearby Bigelow constructed space habs.
2. The hull pressurized with air - Tourists can spend time in a large zero g enclosure without pressure suits.
3. The hull pressurized and spun.
4. Fully constructed space hab.
Evidently the first step is crucial, If this barrier is passed the remaining activities can be taken up with confidence. Are there ideas on how the hull can be constructed - at minimum cost? Would some kind of winding process work out cheaper?
Going with
Kalpana 1
, with no shielding, rotating at 3 rpm, having radius of 100m, accomodating 1550 people the mass of the hull is
3000 Tonne
.
(If we can construct a small hull we can with confidence construct larger ones)
Regards,
Selvaraj

'Combs, Mike' mikecombs@... [spacesettlers] wrote:

> > 1. The hull - Tourists can entertain themselves inside the hull in
> vacuum, wearing pressure suits.
> > Tourists could base themselves in nearby Bigelow constructed space habs.
>
> Interesting. And the radiation shield would be one of the easier things
> to construct (and it would benefit the construction crew if it was
> completed at an early point). So such tourists would benefit from the
> shielding. Temperature management would become easier too, I would think.

If it's in ELEO, then radiation is really not an issue. Even if it's in
some other LEO, radiation is not a serious concern for short-term
visitors (ISS astronauts handle much longer stays).

> One interesting aspect of this proposal is that you could let tourists
> space-walk to their hearts content without worrying about them drifting
> off to another orbit. On the other hand, I think one of the prime draws
> of space-walks will be the view of the universe.

Right. I'm skeptical about the entertainment value of weightlessness in
a vacuum in an enclosed space. The risk and discomfort of vacuum are
quite high, and your view is no better than it was inside the ship.

*Maybe* for construction (e.g. a shipyard or maintenance bay) there
would be some value at this level, i.e., having a large tent enclosing
an unpressurized workspace. As you say, it keeps people, tools, bolts,
etc. from drifting away. But it still requires you to work in a space suit.

> > 2. The hull pressurized with air - Tourists can spend time in a large
> zero g enclosure without
> > pressure suits.
>
> 2 sounds like lots of fun.

Indeed. This one has HUGE entertainment value. You miss out on the
great views (unless you can contrive to have large windows), but you get
all the fun of zero-G, in a big enough space to enjoy it, and without
those uncomfortable/dangerous space suits to worry about. I think we
would quickly invent zero-G sports, dance, etc.

Beyond pure tourism, such a space would have use in many other
industries: film, construction (shirtsleeve on-orbit assembly of
spacecraft and satellites), etc.

A large pressurized space is so much more useful than a large
unpressurized space, that I wouldn't even bother with the latter. Seal
that thing, crack open a can of air, and have at it.

Note that there is an in-between option:

1.5. Pressurized with an inert gas, but with no effort made at keeping
it breathable. It could be pure nitrogen, plus whatever trace gases
(probably mostly CO2) people spill into it. In this case you'd have to
wear a mask, but no space suit. It's a huge step up from 1, but
obviously not as nice as 2. I'm not sure this is so much easier than 2
that it'd be worth doing, but it might in some circumstances (e.g. a
construction shack).

> > 3. The hull pressurized and spun.
>
> 3 raises the interesting point that a space habitat might be able to
> start generating revenue even before the interior landscaping is
> significantly far along. Almost anyone on Earth would want to vacation
> in a habitat with interior landscaping like the Hawaiian islands. But
> some people would be happy to visit a bare metal hull, just to say that
> they visited a space habitat.

For sure. Or a hull where dirt has been laid, but the grass/landscaping
hasn't grown yet. I certainly would not wait for the greenery to start
booking tickets.

> A part of me thinks: build the structure first, spin it up second, and
> then pressurize (from the outer rim) third. My reasoning is that if you
> pressurize second, and then spin up third, the atmosphere wont be all
> that tightly-coupled with the hull. You might initially find yourself
> facing hurricane-force winds, at least a few feet above the hull.

I really doubt that. It's a massive structure, and not mostly because
of the air. You will necessarily spin it up slowly, and the air will
come along with it. You could certainly erect baffles to increase the
coupling to the hull if needed, but I doubt it would be needed at all --
plain old friction with the ground will do just fine.

> But maybe hurricane-force is overstating it a little. And maybe the
> advantages of having a pressurized hull (we can start working in
> shirt-sleeve) even prior to having much gravity might outweigh the
> problems of stiff winds for a temporary period.

I'd think so.

> > Are there ideas on how the hull can be constructed - at minimum cost?
> > Would some kind of winding process work out cheaper?
>
> I think the least-expensive-sounding idea Ive heard is vacuum vapor
> deposition of metal on a rotating balloon form. But that was visualized
> for ONeill-type structures (a few miles across). Might not scale to the
> smaller structures we presently envision starting out with (with the
> assumption of modular components brought up from Earth). Im unsure
> about this.

This is a great question for a mechanical engineer or architect (and I'm
neither). But I would guess that our best bet, especially early in
development, would be to have the hull composed of identical sections
which are fabricated on Earth, and then welded together on orbit.
Perhaps they would be triangles, like a geodesic dome. A large number
of repeated simple task (like welding triangles together) is well-suited
to being done by ROVs; we might need people on site every few weeks,
while the remotes toil away for months.

Best,
- Joe

sailorbarsoom@... [spacesettlers] wrote:

> That should work: bring up complex stuff (gas exchangers, computers) and
> when it's all in place, wrap the whole thing in plastic (sent up from
> Earth in big old rolls). Then deposit the hull over that. Even if the
> aluminum is sent up from Earth, it might be worthwhile to have a
> seamless structure too large in size, even if not in mass, to send up.

Seems a bit dicey to me. Welding is an extremely mature technology, and
probably even easier in space without that pesky atmosphere causing
things like oxidation of the metals you're trying to weld. Properly
welded seams are as strong (or stronger) than a solid piece of metal.
And my guess (though we're getting into "less mature" technology now) is
that you could do most of that welding remotely, with robots operated
from Earth. A few dozen such assembly robots could probably have your
hull put together in a matter of months.

But I'm no expert, so take my guesses with a grain of salt.

Best,
- Joe

It will be worth qualifying vapor deposition techniques on 1 M dia
spherical models on ground and in space. Depositing thin layers may be
routine. Search in Google does not appear to turn up vacuum deposition to
produce structures.
Regards,
Selvaraj

On Thu, 21 Feb 2019 at 18:20, sailorbarsoom@....com [spacesettlers] <
spacesettlers@yahoogroups.com> wrote:

>
> Whatever works. I'm perhaps a bit impatient to develop space-based
> techniques, when sometimes building it on Earth and good old fashioned
> welding might be best. Well, not that old-fashioned, what with vacuum and
> micro-G and all.
>

Regards,
Selvaraj
On Thu, 21 Feb 2019 at 18:20,
sailorbarsoom@...
[spacesettlers] <
spacesettlers@...m
> wrote:

Whatever works. I'm perhaps a bit impatient to develop space-based techniques, when sometimes building it on Earth and good old fashioned welding might be best. Well, not that old-fashioned, what with vacuum and micro-G and all.

Three D printing will be ideal?
https://www.architectmagazine.com/technology/3d-printing-metal-for-structural-strength-space-and-beyond_o
Regards,
Selvaraj

On Sat, 23 Feb 2019 at 10:13, sraj wrote:

> It will be worth qualifying vapor deposition techniques on 1 M dia
> spherical models on ground and in space. Depositing thin layers may be
> routine. Search in Google does not appear to turn up vacuum deposition to
> produce structures.
> Regards,
> Selvaraj
>
> On Thu, 21 Feb 2019 at 18:20, sailorbarsoom@... [spacesettlers] <
> spacesettlers@yahoogroups.com> wrote:
>
>>
>>
>> Whatever works. I'm perhaps a bit impatient to develop space-based
>> techniques, when sometimes building it on Earth and good old fashioned
>> welding might be best. Well, not that old-fashioned, what with vacuum and
>> micro-G and all.
>>
>>
>

https://www.architectmagazine.com/technology/3d-printing-metal-for-structural-strength-space-and-beyond_o
Regards,
Selvaraj
On Sat, 23 Feb 2019 at 10:13, sraj <
sraj99@...
> wrote:
It will be worth qualifying vapor deposition techniques on 1 M dia spherical models on ground and in space. Depositing thin layers may be routine. Search in Google does not appear to turn up vacuum deposition to produce structures.
Regards,
Selvaraj
On Thu, 21 Feb 2019 at 18:20,
sailorbarsoom@...
[spacesettlers] <
spacesettlers@yahoogroups.com
> wrote:

Whatever works. I'm perhaps a bit impatient to develop space-based techniques, when sometimes building it on Earth and good old fashioned welding might be best. Well, not that old-fashioned, what with vacuum and micro-G and all.