Rotating Space Wheels Q & A

[Chip]

Hi,
So why is the old idea of the classic science fiction space station that resembles a wagon wheel, and rotates while orbiting Earth, not an engineering consideration today?



Is there something inherently illogical about inducing artificial gravity inside a rotating wheel or drum-like structure?



It seems like an interesting idea to me. What about counter-rotating wheels for long space voyages? (i.e. Mars.) Micro-gravity would be near the hub, and artificial gravity induced in the rims. Counter-rotation would eliminate the possibility of drifting off course due to momentum. (Or is such a thing not physically correct in space?)

In terms of maintaining a gravitational environment that is more natural and comfortable to the human body, it seems like this would be a step toward healthier space travel. (If human space travel were the goal.) Any thoughts? [img]/phpBB/images/smiles/icon_wink.gif[/img]

(*If you post a reply - please edit out the picture links to avoid repeating them.)

[Tom]

The rotating wheel design is still a good one. However, to be effective, it has to be very big. And thus, very expensive. So far, we lack the aerospace infrastructure that requires and would support such a station.

Also, Hilton has backed out and PanAm is out of business. [img]/phpBB/images/smiles/icon_smile.gif[/img]

[g99]

Would not the central hub have to be gigantic to hold all fo the fuel, support systems, and thrusters?

[Nanoda]

You don't need the counter-rotation. You do need quite a bit of spin, even with large structures. We don't have the technology yet to build such large ships.

Besides all that, I don't believe the absence of gravity is considered a serious problem on a Mars flight. There are plenty of easier ways to condition the body for the (6, 8 months?) it would take.

For orbit, it would be nice to have one, but it would have to be much larger than the IIS, and maintainance would be a nightmare once it was spinning. Here's some trivial info about that kindof thing.

[Colt]

You would not necessarily need to have it be shaped as a ring. You could have a solid disk with different levels of gravity with the inner levels composed of the machinery to run the station (think of trying to walk on a floor that constantly sloped, tiring). -Colt

[informant]

Or a cylinder rotating about its axis.

[informant]

One cheap design for a station was the Annulus Erectable Model (AEM) -- an inflatable doughnut 24 ft in diameter, compartmentalized for safety in the event of punctures by micrometeors. Structure deemed too risky and not sufficiently protective from radiation. Astronauts would have had to wear a form of pressure suit constantly.

[img]/phpBB/images/smiles/icon_lol.gif[/img]

Is it just me...?

[Colt]

Yeah, there are quite a few designs for a rotating cylinder (Rama) which would stay in Earth orbit. One of the most interesting designs to me is the long cylinder with strips of glass set in the [i]bottom[/b] and angled mirrors reflecting sunlight inward. An extreme example of the ring type is a ringworld (Larry Niven, The Ringworld). -Colt

[Chip]

On 2003-03-19 15:36, Colt wrote:"One of the most interesting designs to me is the long cylinder with strips of glass set in the [i]bottom[/b] and angled mirrors reflecting sunlight inward. An extreme example of the ring type is a ringworld (Larry Niven, The Ringworld)."

Fiction or actual design? Who's working on it? [img]/phpBB/images/smiles/icon_wink.gif[/img]

[Chip]

Thanks for interesting ideas. There are occasional articles and websites devoted to rotating artificial gravity space stations and ships. All in the hypothetical - idea phase. I might be wrong, but nobody at NASA or in private industry seems to be taking the idea realistically, even to the "back burner" - (as a "feasibility study.")

I think the engineering principle however is sound but as was pointed out above, expensive. I'm not so sure if it is enormously expensive - as in the realm of science fiction - future society expensive. Perhaps it could be as relatively "cheap" as several modern large oil tankers would cost to build and operate.

[patrioticamerican]

NASA and the aerospace industry definitely take the idea of a large, rotating space "city" seriously, and I'm certain there's plenty of existing designs. The problems are the logistics and expense involved in building such a large structure in orbit. However, as you say, if/when the world gets back in order, hopefully manned spaceflight can again be a high priority, and this will be doable.



<font size=-1>[ This Message was edited by: patrioticamerican on 2003-03-19 19:53 ]</font>

[roidspop]

Fiction or actual design? Who's working on it?

The idea for the particular design you described came from Gerard K. O'Neil. His book, The High Frontier, is definitely worth reading if you want to get a sense of the projects we once considered undertaking. Now it's more than we can manage to keep the ISS going. Progress.

[Colt]

Just stopping by, it took me three and a half hours to clean up two images; going to try to write the paper portion real fast.

That design I was talking about is fictional, one of the ideas that is feasible but would need alot of work and money. -Colt

[tvelocity]

I think a cheaper and easier way to generate artificial gravity is with an orbital tether system. Just have two habitat modules, or just one, tethered about a kilometer apart. Have one end of the tethered system pointed toward earth, while the other points toward space. The tidal force creates microgravity, not much, but maybe enough to hold off the effects of zero gravity on human physiology. NASA did an experiment with such a system a couple of years ago and the principle is sound. Any scientist types out there know the exact correlation between tether length, orbital altitude, and the apparent tidal force? If you orbited a long enough tether system around, say, Jupiter, you might be able to get one G.

[Simon]

No, a tether like that wouldn't generate gravity on a human scale. I believe the idea is that you have two satellites stretched on opposite sides of a tether, and the difference in orbital velocity keeps the tether taut and lets you, for instance, lower a satellite into the upper atmosphere, lower than you could go and maintain a stable orbit alone. There would be some tidal effects stretching the satellites apart around the whole thing's center of gravity, but they would probably be on the order of a few cm/s accelleration over however tens of km long your tether is.

(Someone better at explaining physics than I, please turn this into something meaningful. [img]/phpBB/images/smiles/icon_biggrin.gif[/img])

Now, if you had a tether and wanted artificial gravity, you'd just tie a craft to each end and spin them. It would have the same effect as the big ring-stations, but without having to actually build a big ring. However, trying to de-spin it so you can, say, dock with the ship, may be an excersize in both engineering and nausea.

For more fun with tidal effects, read a short story by Larry Niven called "Neutron Star".

[patrioticamerican]

Besides all that, I don't believe the absence of gravity is considered a serious problem on a Mars flight. There are plenty of
easier ways to condition the body for the (6, 8 months?) it would take.

That's not true. Zero-G results in serious losses in bone and muscle mass, and other physical deterioration, despite prolonged exercise and other means of prevention. By the time the astronauts reached Mars, they possibly wouldn't even be able to stand up on it's surface. Here's a good article about it:

http://web.mit.edu/newsoffice/tt/1995/nov29/41238.html

The tether idea to simulate gravity seems like a good one, but also imagine the hell that would break loose if the tether should snap!

[Gsquare]

On 2003-03-20 21:01, patrioticamerican wrote:

That's not true. Zero-G results in serious losses in bone and muscle mass, and other physical deterioration, despite prolonged exercise and other means of prevention. By the time the astronauts reached Mars, they possibly wouldn't even be able to stand up

Hmmm. Well, OK; Crank it up to 2 G and they'll be muscle-bound supermen on Mars.
Just an idea. [img]/phpBB/images/smiles/icon_biggrin.gif[/img]

[DaveOlden]

On 2003-03-20 21:19, Gsquare wrote:
Hmmm. Well, OK; Crank it up to 2 G and they'll be muscle-bound supermen on Mars.
Just an idea. [img]/phpBB/images/smiles/icon_biggrin.gif[/img]

If that's 2 Earth-G's, then that would be 5 Mars-G's.

Supermen is right! [img]/phpBB/images/smiles/icon_eek.gif[/img]

[AstroCreep]

so what your saying is that Superman's powers aren't because of the yellow sun, that his planet just had a lot more gravity than Earth, and that is why he can fly...he's just jumping REAL high? makes sense now. [img]/phpBB/images/smiles/icon_smile.gif[/img]

[ToSeek]

On 2003-03-21 12:21, AstroCreep wrote:
so what your saying is that Superman's powers aren't because of the yellow sun, that his planet just had a lot more gravity than Earth, and that is why he can fly...he's just jumping REAL high? makes sense now. [img]/phpBB/images/smiles/icon_smile.gif[/img]

Note that originally Superman couldn't fly. He could just "leap tall buildings with a single bound."

There are very fundamental physics issues with being able to fly non-aerodynamically.

[SAMU]

In a cetrifuge the semicircular canals in the inner ear cause vertigo due to their changing orientation caused by the rotation. Staying in one position in the centrifuge doesn't cause it but turning your head or otherwise moving around will cause you to be incapacitated.

[informant]

Astronomy/physics-ignorant question:

Is that due to the Coriolis effect?

[Wunderhund]

You guys might be interested in checking out the Space Islands Group, which is trying to convince NASA to leave the shuttle's external fuel tanks in orbit so that they can be used to create commercial space stations, such as a rotating wheel space hotel:

http://www.spaceislandgroup.com/home.html

[Chip]

In a centrifuge the semicircular canals in the inner ear cause vertigo due to their changing orientation caused by the rotation. Staying in one position in the centrifuge doesn't cause it but turning your head or otherwise moving around will cause you to be incapacitated.

That might be true on a fast spinning carnival ride, where one is spun around in a relatively small area, but I'm not so sure the effect would be as incapacitating if in a huge (one or two kilometer in diameter) rotating wheel.

[Senor Molinero]

Shakespeare in a centrifuge.....
....the Coriolanus effect?

[logicboy]

I just had an idea, some one probably already thought of it.

What about making a station out of two cylinders. One is inside the other, the outer cylinder spins the inner with magnets. Then you can use solar power to make artificial gravity.

[Chip]

I just had an idea, some one probably already thought of it.

What about making a station out of two cylinders. One is inside the other, the outer cylinder spins the inner with magnets. Then you can use solar power to make artificial gravity.

And the crew could access the inner and outer cylinder structures while they were both rotating, by way of passageways and tunnels at the axis points on the ends of either cylinder. Intuitively, I'd like the two cylinders to counter rotate, with the inner cylinder rotating proportionally faster than the outer. Docking and observation areas could be at the ends - in micro gravity (i.e. weightlessness.)

[sideways]

When you're referring to the double-cylinder space station spun up with magnets, are you taking about a setup similar to that of a maglev train? Whatever the case, it sounds like a great concept for science fiction. I think I might want to use that for my own SF stories.

[Madcat]

It bears mentioning that you don't actually need a full ring for centripetal force. I would have figured that someone would have built at least a very small enclosure with simulated gravity by now. Ah well, as roidspop said, progress.