Hard sci-fi question: rotational artificial gravity space station

Quickleaf · Apr 18, 2016

freyar said:
There's a lot of good stuff here already, so I'm not sure exactly what to add. As people have already said, if you're not already rotating with the station, you won't feel any "gravity." Also, the Coriolis effect will be a lot more pronounced. So, if you throw a ball "straight up," it will come back down but will not come back to you. From your perspective (standing at one spot on the inner surface of the station), the ball will curve off as it flies up and down.

I found one Coriolis effect calculator online, but it was asking for Latitude and wind speed and didn't make sense.

I also found something interesting written by Larry Bogan about the seeming increase/decrease in astronaut weight (and therefor their speed) depending on whether running in the direction or rotation or against it. Just like a people mover at the airport.

Eltab · Apr 18, 2016

Somebody (forget my original source) figured out that a 2001-like spinning station is too small: people get dizzy and disoriented from the rotation. If you want to use a huge (km+ between 1G "ground" level and rotational axis) structure, that problem should fade away.

Larry Niven introduced a location called _Farmer's Asteroid_ in his Known Space series, which more-or-less is what you are looking at here. He does not develop it extensively (characters visit, they don't stay) but you might be able to use the fragments for inspiration or to fill in parts you don't want to craft yourself.

Eltab · Apr 18, 2016

Umbran said:
I'd just say... I'd not want to play baseball in it.

Oh, I don't know about that. (I'm horrible at baseball anyway; can't throw straight, never caught a fly ball in my life but have had some bounce off, slow-to-average run speed.)
Several astronauts on the Moon did 'basic science' experiments - drop a feather and a rock; gravity pulls all things equally - that were pretty cool, and watching the differences between 'centrifugal baseball' and 'gravity baseball' could be a learning opportunity.

Quickleaf · Apr 18, 2016

Eltab said:
Somebody (forget my original source) figured out that a 2001-like spinning station is too small: people get dizzy and disoriented from the rotation. If you want to use a huge (km+ between 1G "ground" level and rotational axis) structure, that problem should fade away.

That's exactly why I went with a larger sized station, to avoid the "gravity disorientation/nausea" effect.

It would be interesting if there was a zero-G tram running the central axis of the sphere, which then connected to various elevators leading to the "ground." The view out that tram window would be of a 2.36 km circumference spinning at roughly 1.5 RPM. That's a pretty fast spin!

Even if the numbers were smaller for a more efficient cylinder design, you'd still see the ENTIRE interior spin around the tram a couple times en route to your elevator.

Eltab said:
Oh, I don't know about that. (I'm horrible at baseball anyway; can't throw straight, never caught a fly ball in my life but have had some bounce off, slow-to-average run speed.)
Several astronauts on the Moon did 'basic science' experiments - drop a feather and a rock; gravity pulls all things equally - that were pretty cool, and watching the differences between 'centrifugal baseball' and 'gravity baseball' could be a learning opportunity.

I was thinking that — if you had a reflective surface you could see another person in — you could, with practice throw a baseball so that it curved around an intervening obstacle to reach their catcher's mitt.

freyar · Apr 18, 2016

Quickleaf said:
I found one Coriolis effect calculator online, but it was asking for Latitude and wind speed and didn't make sense.

That calculator is set up for the Coriolis effect on earth and apparently for the effects on winds (hence the wind speed entry). In case you're not familiar with the Coriolis effect, imagine you're sitting on a (fairly rapid) merry-go-round. If you toss a tennis ball, it will not only appear to move outward but also curve away from you in a direction that depends on the direction you initially threw it.

Morrus · Apr 18, 2016

Is there a reason for the empty space in the middle? It seems it would be a bit disorienting seeing ground above you, plus pretty wasteful. Would there not be a second wall, maybe a couple of hundred feet in from the exterior one, so that folks looking up just saw a ceiling? You could even use that second wall as a second floor; maybe "layer 1" is normal gravity, and "layer 2" is low gravity. Industrial stuff. Some low-G sports fields. That sort of thing.

Umbran · Apr 18, 2016

Morrus said:
Is there a reason for the empty space in the middle? It seems it would be a bit disorienting seeing ground above you, plus pretty wasteful.

It wastes space. But, dude, you're in *space*. It isn't like you're strapped for room. The only space limitations is in how much it costs to get the building materials up there. And, on that score, the second layer costs only marginally less than the outer one. So, if you are going to spend that money, why not make the living area just that much bigger?

tomBitonti · Apr 18, 2016

Hi,

As above. There are references for a maximum RPM: 1-3 RPM is taken as probably necessary:

See: https://www.quora.com/What-is-the-minimum-size-for-a-ring-shaped-rotating-space-station

About 2 rpm is considered safe for an astronaut. So, if we use our equation: (Omitted)
and we put in 2 for Omega and 9.8 for g, we end up with an r of 223.49 meters.

Now, that is the safe number, it would still be a distraction.

For comparison, in the movie 2001: A Space Odyssey, the rotating ring had a radius of 280 meters.

Also:

In brief, at 1.0 rpm even highly susceptible subjects were symptom-free, or nearly so. At 3.0 rpm subjects experienced symptoms but were not significantly handicapped. At 5.4 rpm, only subjects with low susceptibility performed well and by the second day were almost free from symptoms. At 10 rpm, however, adaptation presented a challenging but interesting problem. Even pilots without a history of air sickness did not fully adapt in a period of twelve days.

A very definite problem in low-G environments (or at least in zero-G / micogravity environments) is the loss of bone strength.
See, for example http://www.space.com/6354-space-station-astronauts-lose-bone-strength-fast.html.

Astronauts that spend long months aboard the International Space Station lose bone strength faster than previously thought and have a higher risk of breaking their hips later in life, a new study reports.

A survey of 13 space station astronauts found that their bone strength dipped by at least 14 percent on the average during their half-year stays aboard the orbiting laboratory.

Three of the astronauts lost up to 30 percent of their bone strength during their long-duration spaceflights, putting them on par with the bone strength of older women with osteoporosis on Earth, the study reported.

Thx!
TomB

Quickleaf · Apr 20, 2016

Morrus said:
Is there a reason for the empty space in the middle? It seems it would be a bit disorienting seeing ground above you, plus pretty wasteful. Would there not be a second wall, maybe a couple of hundred feet in from the exterior one, so that folks looking up just saw a ceiling? You could even use that second wall as a second floor; maybe "layer 1" is normal gravity, and "layer 2" is low gravity. Industrial stuff. Some low-G sports fields. That sort of thing.

I've been thinking the same thing. A lot of the NASA designs are based on these open floor plan idyllic space colonies. I think the scale of these things is hard to imagine, since they're basically arcologies with their own weather systems and agricultural fields.

I agree that a more realistic take of the rotating sections is to have at least 2 layers set up with a ceiling/wall separating the strictly residential from the other uses that take advantage of low-gravity. Can't see any practical reasons not to do that, and it's how the Babylon 5 and Deep Space Nine stations were set up IIRC.

Umbran · Apr 20, 2016

Quickleaf said:
I agree that a more realistic take of the rotating sections is to have at least 2 layers set up with a ceiling/wall separating the strictly residential from the other uses that take advantage of low-gravity. Can't see any practical reasons not to do that, and it's how the Babylon 5 and Deep Space Nine stations were set up IIRC.

Again - you are thinking like someone who has to use compact architecture for reasons of limitations of real estate area, and the structural strength of materials that have to support their own weight under compression. Neither of these hold for a structure Out There. The stresses on the structure resemble those on a suspension bridge more than those on a skyscraper - specifically, most of a terrestrial building's forces are "compression", while this spinning sphere or cylinder instead has lots of tension. And you don't have to worry about restricting your building to fit in a small ground footprint.

The structures we are considering were intended to maximize "normal" living area and psychological impact. The idea is to have high open spaces, because humans are designed psychologically to walk under the open sky on a regular basis. If you put in a ceiling, you negate that.

By the way, DS9 didn't have any major open areas - it was built like a starship that didn't move, and the biggest open areas we saw were large concourse hallways ("The Promenade"), at best a couple stories high. But DS9 assumed artificial gravity generation, not using spin to generate gravity.

Hard sci-fi question: rotational artificial gravity space station

Quickleaf

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Eltab

Lord of the Hidden Layer

Eltab

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Quickleaf

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freyar

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Morrus

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Umbran

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tomBitonti

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Quickleaf

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Umbran

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