connection between rotating and nonrotating sections

(Henry Spencer) writes:

In article ,
Richard Lamb wrote:
A C Clarke described a nover air lock in RAMA.
A rotating cylinder within a stationary cylinder.
The stationary cylinder has openings 180 apart.
The rotating cylinder only has one opening.

Unfortunately, that huge area of sliding contact (which has to have very
tight clearances to avoid significant leakage) is just asking for the
thing to seize up one day. It would take some very fancy materials
engineering to make something like that reliable.

There was a lot of effort put into intake and exhaust valves for auto
engines that worked on that principle in the early part of the last
century (no valve float, higher max RPM, more power) with exactly the
results Henry points to.
--
Joseph J. Pfeiffer, Jr., Ph.D. Phone -- (505) 646-1605
Department of Computer Science FAX -- (505) 646-1002
New Mexico State University http://www.cs.nmsu.edu/~pfeiffer
Southwestern NM Regional Science and Engr Fair: http://www.nmsu.edu/~scifair

Harmon Everett wrote:

Its going to be unrealistic for a long long time. The "plentiful and
cheap" materials in orbit is not going to happen for decades if not
centuries.

Oh, say two or three decades, if we decided to make it a priority.

O'Neill's argument was that the moon's low gravity and lack of atmosphere made
horizontal electro-magnetic launch of raw material off the surface possible.
And that such EM launch would be many orders of magnitude cheaper than launch
via rockets.


--


Regards,
Mike Combs
----------------------------------------------------------------------
We should ask, critically and with appeal to the numbers, whether the
best site for a growing advancing industrial society is Earth, the
Moon, Mars, some other planet, or somewhere else entirely.
Surprisingly, the answer will be inescapable - the best site is
"somewhere else entirely."

Gerard O'Neill - "The High Frontier"

"Henry Spencer" wrote:
In article ,
Harmon Everett wrote:
I've been wondering about an airlock plus large plastic ziploc baggy
arrangement for minimizing air loss.

As Chris has already noted, it's hard to make this work when you look
at the details.

What you can do is to have close-fitting airlocks for things which come
in reasonably standard sizes -- notably people -- to minimize empty volume
in the airlock.

Something like an iron maiden, that out to work reasonable
well. The problem with the membranes is that they're either
horribly complicated or only solve some of the problems.
Plus, the vacuum sealed bag idea doesn't solve the problem
at all, as the whole purpose is to save the air and if you
can pump the air out of a flexible bag you can certainly
pump it out of a similarly sized rigid container. With the
added benefit that the rigid container of the same volume
won't act as a remarkably effective restraint device. In
other words, you really need a much "smarter" and more
sophisticated membrane than just a flexible bag, or even a
baloon. Now that I think about it, you'd really need
something approximating an animal gut (able to close tightly
around an object but also release it).

The way I look at it, I think there are a variety of
different techniques that can be layered together to
minimize air loss. Each technique will have its own degree
of cost/benefit so I'd expect that at some point you end up
with enough stuff together that works reasonable well at a
given cost.

The biggest problems I see with the docking spacesuit is that
it makes routine maintenance harder, since the suit is
outside most of the time, and it decreases flexibility a
lot. In other words, it creates more of a firm disconnect
between inside and outside, and that can have a lot of
disadvantages.

I really like the sorption pump concept because it's
relatively simple, should work well in space (where cold is
always available fairly easily), and should recover most
of the air in the airlock.


Another thing to think about would be separate airlocks for
crew and for equipment, such that the equipment airlock could
use more "uncomfortable" and perhaps less timely methods of
air recovery. For example, with an equipment airlock it
doesn't much matter if it takes hours for it to operate.

(Harmon Everett) wrote in message . com...
(Alex Terrell) wrote in message . com...
I've proposed non rotating outer shells simply because of the mass
needed to stop radiation, and the fact that a non rotating, radiation
/ meteor shield can be made of cheap slag / by products.

OR cheap almost anything - or storage for bulk commodities, or waste
water treatment, or junkyard, all very good shielding for a
non-rotating outer shell. Easy to make, easy to maintain and very
useful!

I think it more economical to bring back entire NEOs. Then you have a
lot of waste sulphur and other fairly useless materials, as well as
all the Oxygen and Water storage.

Plus simle mass (solid or liquid) is effective as a meteor shield.


For a Cylinder structu

For transfer of people (and small cargos), I suggested a ring around
the axis, the interior of which would be a bit like a train. People
would enter from the gravity section, the ring would decelerate, and
people would exit on the other side. This has the advantage that
people don't have to travel to the axis, where there would be a lot of
congestion (especially as I propose one end of the axis as a light
pipe).

But the light pipe doesn't have to travel through the middle once it's
inside. Once inside, it can be directed anywhere without taking up
congested real estate, right?

Exactly: in the centre you have a complex mirror shape to direct the
light everywhere. This somewhat limits the max length of the colony,
but not too much.


For transfer of electricity, brush contacts could be used, or
potentially induction transfer, or motors and dynamos operating on the
circumference.

For transfer of data, I'd use wireless links running in small channels
(physical grooves, that are protected from interferenced with the next
groove). Each one would handle several Gbps of data packets.

For transfer of bulk cargos, a central airlock that would match spin
with the rotating section. This is a fail safe method of linking the
two. For a 500,000 person, 4km diameter cylinder this could be 25m
diameter, 100m long airlock.

Liquids and gases present the biggest problem, because the inner
section is pressurised and the outer section isn't (for the most
part). On the whole, water would be recycled within the rotating
section. However, for heat dissipation reasons, agriculture and CO2
breakdown would be done outside the main hab. Oxygen could be
reintroduced in a packaged liquid through the central airlock, which
would help with cooling.

CO2 would be solidified in giant radiators attached to the rotating
part (technical problem of shifting the CO2 and not blocking up the
radiators) and exported as dry ice to the farm areas, via the cetral
airlock.

A 500,000 people cylinder would need about 1,500 tons of 02, 750 tons
of food to come in per day, and 2,250 tons of CO2 to exit per day.

I'm working on a much smaller scale, about 125 persons, and a LEO
station 100 meters across. So you are thinking to export the CO2 to
the farms, and import O2 and food from the farms each day? I'm
thinking the agriculture will need to be integral to the living area.
Instead of hallways lined with filing cabinets, the hallways will be
lined with planter racks hooked up to the drip irrigation or
hydroponics tubes and fiber optic lights, and the harvesting and
maintenance would go on amidst the daily traffic. That still leaves
lots of agriculture that has to be done in its own area, but that
won't be open space particularly, either, as it will be done in
stacked racks allowing only as much vertical room as the
plants/aquaculture tanks/small animal pens need. I was counting on
growing algae as part of the sewage remediation, which would produce
O2 and animal feed. Would you export the sewage to the farms too?
Harmon

I'm beginning to think that two clylinders along the same axis might
be better. One for habitation, the other for agriculture. Then you
avoid all the rotation matching problems for you largest (by far)
import (food and Oxygen) and export (CO2 and waste). The second
(greenhouse) cylinder could actually be connected toruses - ligher
construction, and seperate, optimum climate in each.

I think for smaller scale there is less need to have linked living and
agricutural areas.

I think we're in agreement. I see many generations of space colony
before we get to large cylinders, and I've outlined some in he

http://www.geocities.com/alexterrell.../Routemap4.doc
(this is not my most up to date thinking)

However, I don't really see the merit of your next design. A 100m
inflatable hull would either be very thin, and hence no meteor /
radiation protection, or very heavy. My HEO2 station has habs rotating
in free space, and then covered in NEO material for protection. Given
a low gravity environment, and enough tension cables, this should be
quite feasible. [It has been pointed out that a three hab structure
would be more stable than a 2 hab structure]

I've also realised that if Rotovators work, LEO will serve virtually
no purpose. High Earth Orit will become easier to reach than Low Earth
Orbit.

Alex

(Alex Terrell) wrote in message . com...
snip
However, I don't really see the merit of your next design. A 100m
inflatable hull would either be very thin, and hence no meteor /
radiation protection, or very heavy.

Yeah, it starts out very very thin, which is how it can be lofted with
current launch vehicles. Then over next years more fiberglass/epoxy
or kevlar/epoxy layers, or whatever fabric/epoxy layers get applied in
several layers to make it more substantial. It also gets augmented
with whatever else comes our way, and there probably will be a layer
something like a waterbed with fibers and water in it to provide some
measure of self sealing in case of punctures. But at first it would
be just a very thin membrane like aluminized mylar that gets inflated
and then hardened. It would be very delicate until several more
layers get applied. The thing is, we wouldn't have to wait until
the skin was fully augmented before we started developing and using
(and leasing) the internal space. The internal space would be
functional within a year or two of getting in orbit. Or, parts of it
would be anyway. The skin would just be very delicate for a while.
There would probably be a construction crew whose whole job would be
to do nothing but develop the double hull. fabric and spray foam?
carpeting and spray foam? The double hull works out great this way,
because the crew could be putting extra layers on the inside of the
outside skin, and the outside of the inside skin, and they'd be
working between the two skins the whole time and never have to go
outside the structure to patch the hull.

Harmon