Gee, thanks. Now I’m gonna have The Blue Danube playing in my head for the rest of the day. 
I can also imagine that spinning the space station would put a lot of stress on the supports, which would require the station be stronger and thus heavier, adding even more costs to the project.
Vibration is the enemy of all things microgravity. Large powered rotating machinery tends to have vibration. e.g. the de-spun central docking port.
The 2001 space station would be 2 to 3 orders of magnitude bigger / costlier than ISS. Which pretty much broke NASA’s financial back.
With our current tech & budgets, that kind of space station will not go to space today.
Why go up into space to emulate earth conditions? Until there’s enough people up there to be able to pay for luxury accommodations, both worksites and living areas will share microgravity, the unique condition that makes being up there interesting in the first place.
You can get the same effect on the carnival ride where you stand in a big flat cylinder and it spins you around very fast. While spinning, try turning your head, bouncing it from side to side, etc. (Have fun with coriolis force by trying to lift your forearm and move it around…)
IIRC, in the making of 2001, Clarke mentioned they just fudged the numbers for the spaceship centrifuge. To avoid significant inner ear problems, the rotating part would actually have to be 300 feet in diameter to get 1G; Discovery is obviously nowhere near this.
Another issue nobody has mentioned - a gas-tight seal that constantly rotates. Not trivial. Plus, what are the structural components of the hub? The main structure of the non-rotating piece has to go through the middle of the hub, or you have an opening that opens and closes like a guillotine every rotation on the shafts to the rim (opportunity for interesting ending to a sci-fi thriller…)
if the hub grabs the ship and spins up to wheel speed, then the ship structure has to be strong enough to be spun by the nose so to speak. The entire mass of the spaceship is being rotated by whatever is gripping the airlock door.
At this point, it’s not worth the effort. Plus, as mentioned, most low orbit stuff de-orbits if not boosted. Skylab lasted what, 6 years? Mir lasted 15. The ISS is being continuously boosted. Besides, the rotating wheels of Willy Ley and Stanley Kubrick glossed over the fact that they need a lot of electricity; the reason there’s almost a football field of solar panels is - that’s what it takes to run the basic functions of the “small” ISS.
They also change the orbit slightly from time to time to avoid space debris. A large rotating station would be a beast to nudge around.
The ISS is also meant to be expandable. Adding new modules would be a problem. Even if stuck on the non-rotating part, you have to keep the overall center of balance aligned.
Also think of the difficulties rotation would cause for astronauts on spacewalks. They and any equipment they carry would tend to fly off when working on the rotating parts.
Thanks for all the answers guys, very interesting read on it all.
The rotation would make EVA ( space walks ) dangerous…
Wee … Hey earth, you now have a new man sized satellite !
ALso the space walks are for assembling and repair… the centrifugal force (inertia in a rotational context) introduces complications… SLow it down… slow it down… stop it… stop it now… Bang … ! … . Ooops its broken free… do we have a spare spare one of them ?
It’s quite easy to do. Simply have two space modules joined by a very long carbon fire cable - like a Bolas. Imagine a cable 1-2km long and the two modules spining around each other.
You can keep your tiny space stations as before but enjoy reasonable pseudo-gravity in each one.
However moving from one module to the other is a bit of a bitch! Probably they’d have a central hub that also acted as a docking point and winches to travel to each module (though how they solve the Eotvos effects is another matter)
Indeed.
And if humans need occasionally to experience some G force, as things currently stand it’s more cost-effective to return them to earth than to make this happen in orbit.
Maybe there could be ballast tanks along the circumferance which could automatically distribute a working fluid to balance the load.
No, the point of space exploration, development, exploitation, colonization etc. isn’t to experience the joy of microgravity. You can hitch a ride on one of those parabolic “vomit comet” plane rides, or perhaps soon you’ll be able to spend a few minutes in LEO on a space plane, if you want to bounce around in “zero-g.” There are plenty of known health hazards associated with extended stays in microgravity, and we’re going to need to simulate normal gravity in space if we want to spend significant periods of time there.
It’s like saying, why build off-shore oil platforms when the whole point of the ocean is to swim in it?
True to a point, but the point of space stations like the ISS is to take advantage of microgravity.
Adding pseudo-gravity to the mix is mission creep - it’s adding (expensive, complicated) features that are well beyond the originally designed intent.
Who said it was? Who are you disagreeing with?
I think very few of these experiments could be performed on a parabolic flight.
This, for instance:
Naturally we’re interested in studying the effects of microgravity and its potential usefulness in various experiments, but the ISS is used for other things, too. If we want to someday travel to asteroids or Mars, the point of those things isn’t to experience microgravity; microgravity is just something you have to deal with while you’re out there.
Here’s the wiki article on ISS’ purpose.
Arguing that the International Space Station (ISS) exists “explore how humans are affected by microgravity[sic] in the long term” begs the question for the need to continue to study human physiology in freefall conditions. In fact, there is a large extend body of work from Soviet/Russian experience and the American Skylab program which demonstrates the various detrimental effects freefall has on the human body over a duration of months, to the point that it is essentially assured that any crewed long duration missions or interplanetary transits will almost certainly require centrifugally generated acceleration to simulate gravity (pseudogravity). However, we have essentially no data on the effects of fractional gravity on human physiology, and a habitat that rotated to generate Lunar- or Martian-equivalent pseudogravity would be exceptionally useful in understanding those conditions on humans.
The real reason that the ISS was not designed as a rotating structure is cost, complexity of assembly and operation, and logistics. The cost is obvious; a rotating station would have to be much larger and also built to withstand the stress of operating under a constant radial acceleration load, requiring more structural elements, a non-rotating hub (to mount the power-generating solar array, docking hubs, and any other high gain antenna, telescopes, et cetera which require a stationary platform). Even a minimum size station–say, something 30 meters in radius–would be more expensive by easily half an order of magnitude or greater, so instead of being US$150B (2010 dollars) you could expect somewhere upwards of US$650B to over a trillion dollars.
The complexities of assembling and operating such a station are fairly obvious; the station would likely have to be fully assembled prior to spinning up. (The ISS was constructed by integrating pre-built modules at what are essentially complex docking ports; constructing a space station by manually assembling structural elements by hand as depicted in fiction would be a nearly impossible undertaking.) Spinning up the station would require a substantial amount of propellant or a counterrotating mass; either would require many additional launches to lift the require mass. Rotating the station to correct for precession and nutation errors would require more propellant. A non-rotating hub would have complex bearings with slip rings and seals (the best option is probably an electromagnetic bearing and liquid metallic lip seals to minimize hysteresis losses and maintenance requirements).
The logistics are also complex. The ISS was assembled over a period of 12 years with substantial modifications (modules delayed or eliminated due to budgetary constraints, loss of Columbia and temporary hiatus of STS flights, disagreements between ISS partners) before being declared completely operational. A station designed for rotating operation would need to be assembled much more quickly and completely in order to reach even partial functionality. (Certainly, you could inhabit the non-rotating habitat modules but not making use of any features or functions requiring simulated gravity.) The STS fleet was operating at maximum rate and often with pressure to accept waivers and bypass normal safety inspections and protocols on the aging Orbiter Vehicles in order to maintain schedule. There is just no way a larger and more complex station could have been assembled quicker than the ISS was without developing a new superheavy launch system.
And that gets to the crux of the matter; the ISS was not designed to explore space or research freefall conditions; it was developed as a political fop to enjoin other nations (specifically Russia) in space development while spreading the cost (though the US bore the bulk of the costs even for the Russian-provided modules that make up the core of the station) and, more importantly, to give the STS someplace to go, which ironically helped to prevent development of a replacement system for the Shuttle and extended the operation of the STS beyond both the design life and well past the point that anybody was comfortable with the increased risks being taken to keep the STS fleet flying (the so-called “normalization of devience”) including launching with thousands of outstanding waivers at the time that Columbia destructively reentered in February 2003. Even after a US$1.75B fix, the “Return to Flight” mission displayed the same falling frozen foam that destroyed the wing leading edge of Columbia. As a result, the ISS was hurriedly assembled and the STS fleet required without a replacement launch system in the wings. The current Space Launch System is still a good five years away from being able to carry crew, and will be too expensive for regular crew rotation or resupply missions to the ISS, which will be entering its end-of-life phase at that point anyway.
As for rotating two habitats connected by a tether, this can be done and is probably the easy answer for any future interplanetary transit, but this system is not workable for a long duration space station in Low Earth Orbit owing to loss of rotational momentum through tidal drag. Such a system would have to be periodically spun back up which is not trivial (would require additional propellants). This type of operation would be more feasible for a station in the stable Lagrange points (L4 and L5) but that would make the crew rotation and resupply efforts more costly and complex.
Stranger
Aside: why the [sic] after microgravity? As far as I know, that is the universally accepted term for the conditions in orbit. I’m quite aware that the gravitational acceleration from Earth is barely reduced from surface levels, but this is not a useful quibble given that gravity is a pseudoforce to start with, and freefall simply means that the pseudoforces sum to zero. Microgravity is as good a name as any for these conditions.
That’s all true but it doesn’t invalidate the research they do perform, which includes microgravity effects (and how to ameliorate them) that go beyond what was performed on Skylab/Mir/etc.
I suppose it should be pointed out that one can perform hypogravity (Moon/Mars/etc.) research on mice more easily than humans. I’ve seen some proposals for smallish centrifuges to be put aboard the ISS for small animals; I don’t know if any of them ended up going up, though.
Nitpick: Isn’t it more correct to refer to it as ‘simulated’ rather than ‘artificial’ gravity? Didn’t Einstein prove that acceleration via inertia (a spinning space station) was fundamentally different than gravity by mass-warped space (standing on the Earth)?
Quite the opposite. They’re fundamentally the same thing. In both cases they’re pseudoforces: apparent accelerations that are really a result of a change in coordinate systems.
If you’re inside a rotating space station, there is an apparent centrifugal force holding you to the inside surface. But an external observer has a different view: your body would “prefer” to move in a straight line, but that can’t happen because you’ll intersect the surface. So it bangs into you and accelerates you into a circular path.
The same thing is true of gravity, though the cause is a bit more subtle and you can’t really have an external observer. Nevertheless, the reason why objects are attracted is not because of a force like electromagnetism, but because their paths through spacetime curve towards each other.
I don’t see any reason to get worked up about “simulated”, “artificial”, or any other similar term. The apparent acceleration is just as real as gravity. The name just means that we’ve induced the acceleration via some means besides large masses. Just as “synthetic diamond” is still diamond, and the “synthetic” descriptor just refers to the means of production.
The amount of medical and human physiological research performed on the ISS (at least, based on publication in the Journal of Aerospace Medicine and Human Performance) is paltry compared to the extraordinary investment. In fact, the bulk of papers arising from ISS research are in remote sensing and Earth surveillance, virtually all of which could be done using uncrewed satellites. (There are a handful of applications which have power requirements in excess of what could be supported by a platform capable of being launched by a Delta IV Heavy or Ariane 5, but that doesn’t argue for a crewed presence as much as it does higher capacity heavy launch vehicles and/or a solar power satellite network).
NanoRacks (the company that has a CubeSat deployer on the ISS) hosts a small centrifuge built by Astrium. The planned Centrifuge Accommodations Module was cancelled. While centrifuge research on mice provides some information on mammalian response to fractional gravity conditions, it doesn’t really tell us about the human-specific responses, particularly cardiovascular, vestibular, and musculoskeletal systems. It is likely that human beings can survive with manageable deficiencies in some fraction of simulated Earth-level gravity but we don’t have enough of a body of research to even establish a threshold, and none of the research being done on the ISS is contributing to developing this.
Stranger