Spinning In Space

International Space Station

When a classmate sent me a link showing how the International Space Station (ISS) was constructed module by module it dislodged a question that has been lurking in the back of my mind for a long time.  (Please note, when you click on the link, the page may take a few seconds to load.  The start arrow is small, in the lower left corner.) Whatever happened to the idea that a proper space station should rotate to provide artificial gravity? That was the design pictured in the 1968 (my, has it been that long?) science fiction movie, “2001, A Space Odyssey”. The space shuttle from Earth approached the spinning station at its center, matching its rotation in the process. That scenario has some credibility because it was conceived by author and scientist Arthur C. Clarke, the same guy who first conceived the practical notion of the communications satellite.

A Rotating Space Station Design

The manned space program is probably the most glamorous and expensive single project ever undertaken by man, so most people pay attention and they probably also know that living in zero gravity is bad for your health. The ISS has been up there in one phase or another for almost 14 years now, so I know that some astronauts have stayed up there so long in zero G that they were too weak to stand up when they came back to Earth. I looked up the record and it’s held by a Russian Cosmonaut – 438 days, or more than a year plus 2 months! But anyway, zero G causes calcium to leech out of your bones, the cartilage in your joints to swell, and your muscles to weaken. The Wikipedia page for Astronauts says,

Astronauts are susceptible to a variety of health risks including decompression sickness, barotrauma, immunodeficiencies, loss of bone and muscle, orthostatic intolerance due to volume loss, sleep disturbances, and radiation injury.

Seems clear to me that a good deal of that could be alleviated by artificial gravity, so why hasn’t it been included in the design? As you can see from the construction link at the top of this post the ISS is basically a long series of cylinders of modest diameter, kind of like a man-sized version of one of those hamster habitat things and the only things they have provided to alleviate the effects of weightlessness is exercise regimes and treadmills.  Why does the ISS design depend on using small cylinders?  It’s a matter of well-understood engineering:  pressure vessels, whether they be spacecraft or airplane fuselages, need to be small to be light in weight.  Weight for a circular  pressure vessel increases exponentially with diameter.

It turns out that the problem of zero G has been studied  since the early twentieth century. The biological problem is laid out in a good Wikipedia page of its own under the heading, “Artificial Gravity”. The introduction says,

Without g-force, space adaptation syndrome occurs in some humans and animals. Many adaptations occur over a few days, but over a long period of time bone density decreases, and some of this decrease may be permanent. The minimum g-force required to avoid bone loss is not known—nearly all current experience is with g-forces of 1 g (on the surface of the Earth) or 0 g in orbit. There has been insufficient time spent on the Moon to determine whether lunar gravity is sufficient.

The rest of the article is thorough and interesting to anyone who likes technical detail, but the bottom line here is that while providing artificial gravity by centrifugal force is altogether practical and sensible with present-day technology, it is not economically practical. The cost of lifting weight to orbit is somewhere between $2,000 and $18,000 per pound, depending on the lifter, and just constructing the ISS the modest way it has been has run up at least $35 Billion dollars so far! Or at least until we develop and build Arthur Clarke’s space elevator. 

Glamorous adventure that it is, manned space flight is wonderful stuff  but when we read about NASA’s budget and follow the politics of it, I submit we need to keep in mind the impracticality of putting people up there for long periods of time, and

RNC Study Group?

especially for sending them to Mars to collect rock samples. Without artificial gravity, they might be too weak to swing a rock hammer and to provide gravity would be so expensive that, well, let’s say the Tea Party would have a budgetary fit and fall in it. Or maybe not, come to think of it. They want to shrink Medicare, virtually eliminate Medicaid, and increase a Defense budget that is already half the size of the all the defense budgets of all the rest of the world put together.   They might be ready to go where nobody has gone before.

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About Jim Wheeler

U. S. Naval Academy, BS, Engineering, 1959; Naval line officer and submariner, 1959 -1981, Commander, USN; The George Washington U., MSA, Management Eng.; Aerospace Engineer, 1981-1999; Resident Gadfly, 1999 - present. Political affiliation: Independent, tending progressive as the GOP recedes from its Eisenhower roots.
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19 Responses to Spinning In Space

  1. You might want to check out a site called http://www.orionsarm.com. It’s what we sci-fi types call a “hard” sci-fi site, with a group-written “future history” of mankind out about 10,000 years. The far future stuff is pretty far out there (all puns included), but the near-term “history” is full of very accurate science, including artificial space habs and ships. Some of the ideas they’ve floated would include a small ship going to Mars, with a long tether holding the two parts together. The ship would launch with the two halves joined, then (in interplanetary space) the two halves would stretch to the end of the tether and rotate around a common center. Alternatives have small habitation pods rotating around a central engine core, also on tethers. Then there’s the variation as seen in the movie “2010” (the Russian ship, “Leonov” – I think) and later used for EarthForce ships in the TV series Babylon 5 – a wide central section rotating around a central core, again with command at the front and engines at the back.
    And now you know how I fill my idle time! (Well, that’s not totally true – I’m currently re-familiarising myself with British aircraft of WW2. I like to keep one foot in the past, and one in the future.) 😀

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    • Jim Wheeler says:

      I agree, John, SF is great fun. In my youth I was a big fan of John W. Campbell Jr. and his magazine, Astounding SF.

      I too thought of the rotating tether configuration – seems to me that would be a necessity for a Mars trip by humans, but I still think there’s no good reason to send them – unless Curiosity finds LGM’s. 😀

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  2. PiedType says:

    Not mentioned in your quote are eye problems. When researching eye problems earlier this year, I came across at least one article that mentioned eye problems as a side effect of life in zero G. (http://news.discovery.com/space/eye-problems-astronauts-120313.html) We tend to think of astronauts as being at risk only during their missions, but apparently long-term or permanent aftereffects are a real consideration. I suppose if test pilots and astronauts are willing to risk death for their professions, compromised vision or blindness must seem a small price to pay. As the article points out, however, it could be a real problem on long space flights. It wouldn’t do much good to send a man to Mars, for example, if he’s going to go blind before he gets there.

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    • Jim Wheeler says:

      Very interesting, PT. My first reaction to this was that it could be either weightlessness or prolonged exposure to low air pressure, but I searched online and found the ISS keeps their air pressure near normal seal level (760 mm of Hg). So to me, that leaves zero G.

      Thanks for the insight. For the Mars mission, how about a really long hose with the life support capsule at one end and the water supply at the other, rotating on the way? No, wait, that won’t work – they use the water up and become unbalanced. Dang. Back to the wheel.

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      • The water goes to the front of the non-rotating part as a radiation shield made of ice, and is held between multiple layers of polyethylene in the habs. That assumes the “pods on a string” rotating section attached to a fixed core with drive, flight, and “mechanicals” (computers, life support, sensors, stores, etc.). If the ship is a two-piece orbiting a central point on the connecting cord, you keep the fresh water with the crew (again, in poly liners) and the waste to be filtered and processed in the other part of the craft. Not to be TOO disgusting, but let’s say that “waste” water can be used as coolant for the computers and other heat-generating devices opposite the crew capsule.
        Or, you just go find a guy named Zephram Cochrane, living in Montana (I believe), and tell him to get that warp drive finished ahead of schedule! 😀

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        • Jim Wheeler says:

          Excellent, John. Seems not fair though – somebody has had more than the two days I’ve devoted to the subject to think about this! 🙄

          Actually, I recall reading in my brief research for the post that the present construct, the ISS, does recycle waste water as drinking water, so the only problem with it is psychological. I wonder if that might intrude on the crew’s subconscious during the three year roundtrip voyage?

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          • Well, since I started investigating ship design back in my teens, I have been at it almost as long as you were in the Navy. So I might be able to build a better spaceship, but I’ll leave building a better sub to you. Deal? 😉
            From what I’ve heard, the recycled water hasn’t been anything worth mentioning – at least officially. Then again, I know the system isn’t 100% efficient, so they do add fresh water from time to time. The real psychological kicker will be recycling … well … number two. That gets sent back to Earth from the ISS (is it any wonder the cargo modules are unmanned? EWWW!!!), but depending on what kind of life-support system they use, a Mars (or other world) voyage would recycle at least part of the solid waste. If it’s used to grow food en route, well, like I said before – EWWW!!! 😀

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          • A sad related story – MSNBC has announced Neil Armstrong is dead, aged 82. As Brian Williams just said, Neil may very well have been the last great American hero. One of my earliest memories, back at the ripe old age of 6, was of those grainy ghostly pictures of a human being on another world.
            Godspeed, Neil. The constellations have a new star among them.

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            • Jim Wheeler says:

              Amen to that, John. I sure hope he’s not the last hero, but you and Brian Williams have a point, real heroes seem to be in short supply these days. I wonder, has culture changed, or is it simply harder to maintain privacy these days?

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        • To be disgusting: wouldn’t the ‘waste’ water have to be reused, after having been reprocessed?

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          • Yep! I believe they are doing at least limited reuse of water onboard the ISS. The trick, of course, is that you need a water source at your destination, or else you have to shlep a WHOLE lot of water (ice) to keep your shield in place. That’s why there’s a lot of research into what lightweight stuff you can use as a radiation shield. Oddly enough, polypropelene stops a LOT of the radiation wavelengths (or, if you prefer, larger particles) that would do a lot of damage to the crew. Keep your eye o a material called graphene – basically a one-molecule thickness of graphite. The scientists working with it are finding new uses literally every week.
            And my apologies if that answer repeated other information, or was less than comprehensible. I’m sick right now, and Pseudophedrine and Vicodin tend to make the mental Victrola skip a few grooves here and there. 😀

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  3. Moe says:

    Jim – I think we could get our Tea Party friends to enthusiastically support space exploration if we could just locate something out there to bomb.

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    • Jim Wheeler says:

      That’s an insightful observation, Moe. Consider these quotes:

      “No triumph of peace is quite so great as the supreme triumph of war. – Theodore Roosevelt (From a speech when he was Assistant Secretary of the Navy at the Naval War College in 1897; Roosevelt fervently and successful advocated a war with Spain; he subsequently became a hero in that war.)

      “It is well that war is so terrible — we should grow too fond of it!” – Robert E. Lee (Comment by famed Confederate general to an aide as they watched the slaughter of over 12,000 Union soldiers in a single day at Fredericksburg.)

      “Kings had always been involving and impoverishing their people in wars, pretending generally, if not always, that the good of the people was the object. This, our Convention understood to be the most oppressive of all Kingly oppressions; and they resolved to so frame the Constitution that no one man should hold the power of bringing this oppression upon us.” – Abraham Lincoln

      There is particular irony in Abe’s words, I submit, relative to the Iraq War. The danger persists because nothing else than war is quite so effective for reviving an economy and bringing cooperation to politics. It is a terrible truth.

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      • Moe says:

        Indeed it is Jim. We all know that it took WWII to end the Depression. It’s interesting to me how thoroughly Europe has left militarism behind since then. Perhaps because it was so personal and they suffered so much . . .they’ve been three or four generations now and perhaps their pacifism is now built into the national DNA?

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        • Jim Wheeler says:

          Yes Moe, I think it is something like that. Edward O. Wilson theorizes that human’s are so mentally complex that their culture evolves in parallel with their physical genes. Makes sense to me, but with this caveat: it happened so quickly that it can also be quickly reversed. Food for thought for sure.

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      • Moe says:

        I just read Wilson for the first time – “The Social Conquest of Earth” in which he made that very point. (the man is a poet – wow)

        And yeah, re Europe, you’re right. Given their bloody history, I guess 70 years is not very long.

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        • Ron says:

          Moe, the Tea Party doesn’t advocate for war, its focus is on controlling federal spending and the national debt. Their financial positions makes them more likely to be conservative than liberal, thus, in general, also more in favor of a strong national defense. An urge to involve the country in bombing campaigns surely isn’t limited to conservatives either – consider president Obama and the democratic leadership taking us to war in Libya.

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          • Moe says:

            Ron, you’re right. I’ve not heard any calls for war from Tea Partiers. But they have found a home in the GOP whose recent enthusiams for war all over the MIddle East are quite disturbing. Whatever we did or didn’t do in Libya (we were involved for a very brief time, just months), it was a GOP prez who took us to Afghanistan and then let htat deteriorate for nearly a decade and took us to Iraq on lies and now Iraq is forming an alliance iiwth Iran. And still I hear from the Republicans a call to get involved in Syria, in Iran and . . . well, not sure what is next.

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  4. Jim Wheeler says:

    I just came across a USA Today article on going to Mars – an interesting follow-up on the subject for your consideration. It is one thing to blithely speculate about daring space adventures but when it comes down to hard science, things can look daunting indeed. Science fact versus science fiction, if you will.

    One thing in the article was brand-new to me, a more-efficient space propulsion system, acronym VASIMR. This sounds promising at first glance, because it potentially cuts the round-trip time to about five months. However, when you read carefully you find that it’s just the hind end of the system and doesn’t encompass the power source itself. What would that be, a nuclear reactor? It doesn’t say. Anyhow, getting those rock samples ain’t gonna be cheap.

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