novel G-Lab concepts (was )

Robert Smith robert@... [spacesettlers] wrote:
> So a Bigelow exterior with centrifuges mounted to spin perhaps along a
> single central beam in the inside (three: 1G, 1/3rdG, 1/6thG and a
> fourth gen-hab letting the critters try to deal with microgravity).

Possibly problematic here is the limited radius. The BA330 has an
internal radius of about 3m. That means, to get 1/3 G we need to spin
at 10 RPM. I think that's reasonable -- most people can adapt to 10 RPM
even on Earth, and it's probably easier in microgravity, and quite
likely that mice are less fussy about it than we are -- but I wouldn't
want to go much faster than that.

To get 1G, you'd have to spin at 17 RPM. That's pretty universally
considered "too fast." Though again, what's too fast for humans might
not be too fast for mice... might be worth a try. Most of the data we
want is at 1/3 G or less anyway.

> Not exactly off the shelf, I think, do they have a few in reserve
> already?

No, but I expect them to become available off the shelf within the next
few years -- roughly the same time scale we could realistically get a
G-Lab off the ground anyway.

> If so, what are their sizes?

BA-330 has an outer diameter of 6.7 m, and a length of 13.7 m. Wall
thickness is a bit under half a meter, so that's an inner radius of 3.12 m.

Bigelow also has conceptual plans for a BA-2100, aka Olympus, with an
outer diameter of 12.6 m (and length of 17.8 m). This gives us an inner
radius of 6.07 m. At six meters, 1/3 G requires 7 RPM, and 1 G requires
12 RPM.

So, a BA-2100 sure would be nice, but I'd suggest planning for the
BA-330, which will always be cheaper both to buy/lease and to launch.

Actually, that raises an interesting possibility. Once there are
several of these BA-330 stations on orbit, you might not need to buy and
launch one at all -- you might be able to just rent one out for some
number of months, do your science, and then yield it to the next
customer. Sure, we could probably dream up enough experiments to keep a
dedicated facility busy for years, even 6 months of data would put us
far ahead of where we are now. (A mouse generation is typically about
10 weeks, so we could expect two generations of native space-mice in 6
months.)

> How to get the centrifuges inside? Deflated already filled with gear
> ala Skylab dry or inflated empty?

I believe the Bigelow modules launch empty, or rather, when deflated,
there's little to no extra room inside. So, the gear would have to fit
through the airlock, and be assembled inside.

My son (an aspiring aerospace engineer) and I kicked around some ideas
today for centrifuge equipment that could be shipped and assembled this
way. These ideas are still quite nebulous, but I'm convinced there's a
good solution there somewhere.

> Two wheels to hold the total craft from tumbling? Or can one alternative
> wheel play against the forces of the spinning centrifuges? When
> centrifuges are spun down to check the critters, how will that affect
> the overall station stability? Is that a dumb noob question?

No, I think it's an excellent question. I'm still somewhat on the fence
between having two counter-rotating centrifuges, and having just one,
plus rapidly spinning flywheel(s) to counter their momentum. I lean
towards the latter, as the centrifuges are going to be a major
obstruction in the interior space, and having two of them makes it that
much worse.

(Note that the BA-330 module has a rigid central shaft that a person can
pass through; the centrifuge core would strap to this, but could be
arranged so that a person can pass from one side of it to the other via
that central shaft. Or so I currently believe.)

> What size do the centrifuges need to be to hold 6 generations of living
> beings without adding stresses to their already stressful testing?

Lab mice are pretty used to small cages. Example:
https://labproductsinc.com/product/10017-mouse/

30x15x15 cm is pretty typical, I think. A wheel 3 m in radius has a
circumference of almost 19 m. So you could easily fit over 100 standard
mouse cages around that wheel. (And an inner wheel at 1.5 m radius
could fit about 60 cages.)

> What is their coriolis limit (has anyone even done that level of testing on
> orbit?... I may be wrong but I still don't think so)

There have been a few very informal, anecdotal experiments done by
astronauts on Skylab and ISS, suggesting that in microgravity we adapt
very quickly (within seconds) to even high rates of rotation. It hasn't
been studied rigorously, though.

Hmm, I wonder what would be required to let our brave grad students do
some experiments on themselves as well as the mice? Could they sit or
lay on top of the cages, and spend some time at 1/3 G 10 RPM? I don't
know if that would be practical or safe. It's an intriguing thought though.

Best,
- Joe