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Exploration

Wasting The International Space Station On The #JourneyToMars

By Keith Cowing
NASA Watch
November 23, 2016
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Wasting The International Space Station On The #JourneyToMars

After Scott Kelly’s flight, NASA plans five more one-year missions, Ars Technica
“During a subcommittee meeting of NASA’s Advisory Committee earlier this month, former space shuttle program manager Wayne Hale asked Paloski why the space agency wasn’t considering missions longer than a year to truly reflect the time astronauts would have to spend away from Earth were they to go to Mars or other destinations beyond cislunar orbit. “It seems to me that you’re not there yet in determining the health factors for a 30-month voyage,” Hale said. In a follow-up interview, the Human Research Program’s chief scientist, John Charles, explained to Ars that from a logistic and scientific standpoint, the one-year missions offered a reasonable compromise. The station probably has seven years left in its lifetime, and because of advanced planning requirements, there would be the capability to fly, at most, just a single two- or three-year mission during that time. Not only would this adversely affect crew rotations, there’s also the question of statistical significance from just two data points. “Darn it, we biologists like to have statistical validity,” Charles explained. “We have discussed it internally and really think we’re going to be pushing our luck to get five more one-year missions during the station’s lifetime, to get a statistically significant database.”
Keith’s note: I love it when NASA talks about science and statistics. Gee, no one at JSC complained when they flew one, single, elderly person (John Glenn) for “science” – once i.e. N=1 and they have not repeated that experiment in the following 20 years. Has anyone seen the data? As a former NASA space biologist who used to run peer reviews of this sort of research, I totally understand the need for larger research specimen numbers. But when you take all of the informed consent regulations and risk models that NASA uses into account, sending humans to Mars on a multi-year mission, without any actual experience flying humans in space for that long would be unethical – again, according to NASA’s own established procedures.
But if NASA decided to look to other exploration modalities such as mountaineering and polar research – and officially accepted different ways of parsing – and then allowing crew members to personally accept medical risk in exchange for the chance to explore, maybe they could save themselves a lot of time and effort. NASA can’t have it both ways. They ask for the money to build all of this incredibly capable stuff in space then they are afraid to use it for the very purposes that it was supposedly built.
https://media2.spaceref.com/news/2005/risk.book.jpgI spent a month living at 17,600 feet at Everest Base Camp while my friend, astronaut Scott Parazynski (who was also John Glenn’s orbital doctor) risked his life to reach the summit. He trained as much as he could but in the end he was going to do something he had not done before. In the end it was his choice. He signed waivers in order to do this. While I was much safer at Base Camp, I was still at heightened physical risk to due to my age and my prolonged presence at that altitude. But I signed waivers too. I watched two immense avalanches a few thousand feet from my tent. One of them killed a person whose tent was near mine. Years later an avalanche killed people in the precise location where Scott and I pitched our tents for a month.
You can prepare all you want for stuff like this but at some point you just have to sign off on the risk and go for it. NASA cannot seem to decide whether it truly wants to accept the risk inherent in the human exploration of other worlds – or just study it incessantly. Until it does we’ll all be stuck with half-hearted, semi-relevant research on the ISS. And then the ISS will be gone.
Here’s a book from an event John Grunsfeld and I put together back in 2004 on this topic for NASA: “Risk and Exploration“. Its not as if people at NASA have not talked about risk. Rather its whether they really want to make the same tough choices that other explorers do.

NASA Watch founder, Explorers Club Fellow, ex-NASA, Away Teams, Journalist, Space & Astrobiology, Lapsed climber.

64 responses to “Wasting The International Space Station On The #JourneyToMars”

  1. Donald Barker says:
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    I agree totally with your comment Keith – risk aversion has become the norm. And is there not a point of diminishing returns for such experiments especially expensive small n sample sizes, and non-replaceable experimental conditions. Better just to actually start paying from the Mars mission and do it then pretend to prepare for it.

  2. TheBrett says:
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    I guess that would help for an orbital mission, but would a 30-month weightless mission help that much? They’re not going to be in weightlessness for most of that – they’re going to be in low gravity, and NASA doesn’t seem likely to spring for a centrifugal test mission any time soon.

    • Steve Pemberton says:
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      We don’t know yet to what extent Mars gravity will mitigate each of the various health issues. Might help on some but not as much on others. A 30-month mission would help prepare for a worst case scenario.

      And there is always the possibility of lunar missions prior to Mars, possibly long term since we can’t assume that just because the Moon is closer that astronauts will have shorter missions. To keep the costs down, instead of having bi-annual or even annual crew rotations they may prefer to leave one crew there for an extended period. The gravity on the Moon is even less likely to mitigate the health effects of a long term lunar mission.

  3. ThomasLMatula says:
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    It is not surprising they are risk adverse given there are always Congress Critters ready to pounce and hold hearings if anything goes wrong.

    Its basic human nature that folks won’t gamble when the rewards are slim for success while punishment swift and sure for failure. I am sure ISS managers are just hoping the ISS will last until they are finished with it without any major incidents.

  4. Richard Brezinski says:
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    I’d guess it has a lot less to do with risk aversion and more to do with finding volunteers wiling to fly for 1 year, 2 year or 30 month missions. I know I asked one of the first cosmonauts to stay a year, would he do it again-and he responded “no way”-he would fly again for 1 year or longer maybe if it was a mission to Mars, but for a mission in earth orbit, 6 months was long enough.

    One of Charles or Palowski’s explanations about screwing up turnarounds and crew complements makes zero sense. If you fly a crew member for longer, that reduces the requirements for crew turnaround-in fact it could open the opportunity for Russians to fly more tourists and make some cash. It certainly should not be a constraint when we get to 7 crew on the commercial carriers. And there is no reason why crew members on 1 year or longer missions cannot be flying simultaneously. The crews don’t all line up currently so no reason why they need to be lining up in the future.

    I think the real shame is that ISS has been up and operating with permanent crews for the last 15 years, and they did not move beyond the 6 month mission until last year, and only now are beginning to talk about more one year missions. ISS was always supposed to be a test bed for future long term mission including to the planets, and yet NASA has wasted about 3/4 of the station’s lifetime, not doing missions that were required get get statistically significant data.

    Likewise, ISS should have been used to look at other options such as partial G and there is nothing being done. They should not be short of money-ISS is getting as much money as they have ever gotten and with NASA’s widely touted ‘Mission to Mars’ there is certainly rationale to be using the ISS to test for Mars missions.

    NASA is wasting the investment and the opportunities they’ve been given.

    • Steve Pemberton says:
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      I wonder how much a centrifuge would have cost compared to the money that was spent on the robonauts?

      • Michael Spencer says:
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        And I wonder, too, what is the argument against a centrifuge? is this just a fiction writer’s dream, or is it something that really would work if scaled appropriately?

        • fcrary says:
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          Ground-based experiments show there can be problems with balance and inner ear adaptation to centrifugal/centripetal forces, above 1-3 rpm. 3 rpm gives about 0.01 g/meter from the axis. So you’d need a big centrifuge, accept a low “gravity”, or not have astronauts move or turn their heads rapidly.

          • Michael Spencer says:
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            So the bounds of the problem are understood, at least in principle. What do you suppose is meant by ‘big’ in this context?

            We also don’t know (do we?) if the ear can simply adapt to the two forces? Much as, say, tummies do reacting to inner ear confusion.

          • muomega0 says:
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            There are uncertainties in the motion sickness limits; varies by individuals. One approach is to start with a long tether so one could vary rpm and distance as well as the gravity level.
            http://www.nss.org/settleme
            http://www.artificial-gravi

          • fcrary says:
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            Big means spinning on a tether about as long as a football field and able to support 20 tons or so. That’s doable, but not trivial. (By the way, someone else mentioned the Gemini mission tests, and said they worked without problems. That isn’t exactly true. They had tons of problems, which they were mostly able to overcome.)

            As for adaptation to spin, you are stretching my memory. I read that paper about 25 years ago. If memory serves, the duration was of order one day. So long-term adaptation may still be an open issue.

          • Daniel Woodard says:
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            Fiber technology has changed a lot since Gemini. Off the shelf 24mm (~1″) Vectran 12-strand braided line has a mass of only 50.4 kg per 100 meters and a tensile strength of 489kN (110,000 lb).
            http://www.cortlandcompany….
            Steel cable would be 50-100% heavier and more difficult to reel in, but still a minor part of the spacecraft mass.

          • Daniel Woodard says:
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            People can tolerate a lot, but most authorities advise staying under 4 RPM to minimize problems.

          • Bernardo de la Paz says:
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            So, best used when sleeping?

          • fcrary says:
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            Well, most comfortably used while sleeping. But being under spin gravity while horizontal doesn’t put weight on the bones and muscles in the same way as standing and walking. So maybe that isn’t the best use. I’d go for two habitat module connected be a 100 meter tether.

          • Daniel Woodard says:
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            I agree the tether is the most practical strategy, however getting from one end of the bolo to the other would be difficult and the crew would probably want to stay together. The counterweight could be a propulsion and power module or a small nuclear reactor, which would make the distance an advantage.

          • fcrary says:
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            I think we’re getting into designing the spacecraft, rather than convincing ourselves a viable design is possible. It is, and I think we agree on that.

            Personally, an elevator/airlock to go from one end of the tether to the other doesn’t bother me. You’d need that anyway, for maintenance, unless you plan to rely on teleoperation (which you might.) In any case, I wouldn’t use the propellent as a counterbalance. That would cause the center of mass and moment of inertia to shift every time you maneuvered. I also have mixed feelings about plumbing and pumping propellent up a tether. But those are details. Something along these lines could be built, and once it is, trial and error will determine the optimal configuration.

          • Paul451 says:
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            So, best used when sleeping?

            Quite the opposite. Bed-rest is used to simulate low gravity on Earth.

            Sleeping in a centrifuge would be completely pointless.

          • Paul451 says:
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            Ground-based experiments show there can be problems with balance and inner ear adaptation to centrifugal/centripetal forces, above 1-3 rpm.

            More recent work shows that people can adapt up to 10rpm. (It’s hard to test humans in >10rpm on Earth due to the g-load.)

            The early work seems to have been conflating different effects. For example, most of it restricted movement. That was why different experiments got widely varying results, none of which matched the actual experience in space.

            Recent work shows that moving around is how you adapt, allowing adaptation to much high spin-rates, and even to varying g-loads as you squat in a high-rpm/short-radius centrifuge.

            http://www.space.com/images

            Unfortunately, this widespread belief in the need for a low rpm (and hence giant centrifuges) has poisoned spin-gravity as a concept for missions.

          • fcrary says:
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            Thanks for correcting my dacade-old Information, but I’m not sure if the lower spin rate has poisoned the idea of spin gravity. Even at 10 rpm, you’d still have to be about 10 meters from the axis to get one g (or 20 meters apart for two equal mass modules.) That’s still big enough I’d prefer a tether to a rigid structure, and once you go with a tether, making it longer with a slower rotation rate isn’t a huge issue.

            I have some doubts about going up to 10 rpm. That gives enough of a gradient for your feet to be at 100% g and your head at 70%. There could be long-term health issues from that (circulation comes to mind.)

            I may be biased, however. In my field (space plasma physics), spinning spacecraft with 10 to 100 meter deployed antennas are common. So I don’t see two spacecraft connected by a 100 meter tether as all that novel or risky.

          • Paul451 says:
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            Even at 10 rpm, you’d still have to be about 10 meters from the axis to get one g (or 20 meters apart for two equal mass modules.)

            To put that into context, the maximum length of an F9 payload is around 11m. (Without extending the payload fairing.)

            Hence a single module rotating end-over-end (“tumbling pigeon”) at 10rpm would allow you to test Martian gravity for human-tended animal studies. (And simultaneously test lunar gravity at 1.5m from the centre-of-rotation.) That lets you do long-term animal whole-of-life and reproductive-health studies at (for eg) lunar and Martian gravity.

            Of course with a single module, you’d just leave it attached to the upper-stage that launched it. That gives you over 20m length, allowing you go all the way up to 1g within the 10rpm “limit”. (Even allows some wriggle room for different mass balance.)

            Alternatively, for animal studies, at that length you can test Mars gravity at just 6rpm with simultaneous lunar gravity about half way up the module.

            But that system would probably have to de-spin every time you dock a resupply capsule. And even having a crew-return capsule attached changes the centre-of-balance. So scaling up slightly, just two such 11m modules attached to an 11m docking node at the centre-of-spin (which also serves as your power/thermal system), gives you over 30m of length and allows you to dock while rotating.

            For 1g, you’d only need 7 or 8 rpm. And for a research station, Mars gravity would only need 5rpm (with lunar gravity on a higher floor.)

            [Similarly, a pair of BA330’s either side of a 4m wide docking-node would also give you over 30m length.]

            And remember, 10rpm is not actually the known limit, it’s just how high ground research has gotten. Above 10rpm, for a standing human, you are conflating high g-loads. But in space, it turns out that it’s more than enough to not require tethers.

            Using tethers just adds pointless complexity and risk. Even if you wanted to go a little longer, to allow a lower rpm, you’d use a 10 or 20m truss (40m total length, Mars-g at 4rpm). Even an inflatable tunnel with internal cables would be better. (Which gives you tensioned/compression structure, which is very strong and stable. Much more stable, and lower risk than tethers.)

            This is what I meant by “poisoning” the concept.

            There is a widespread belief and self-sabotaging insistence that you need both 1g and 1rpm (or 2rpm depending on the bias of the speaker) to get any benefit from spin-gravity. That would mean a mile-long tether. That instantly kills the concept for NASA, even for a basic LEO research station.

            Once you except that research has moved on since the 1960’s, you realise that merely having a single module with it’s own upper-stage as counterweight allows you to go all the way up to 1g.

            But too often I’ve seen people insist on 1g/1rpm. Even after you convince them that 10rpm is fine, a month later they’ll be back to designing the swivel-seats on the cable-car/elevator that is “needed” to transit between the two ends of the more-than-kilometre-long tethers.

            It’s like inflatable greenhouses on Mars. It doesn’t matter how many times you walk someone through the maths of air-pressure loading (let alone the impossibility of sealing against regolith), a month later they will be back drawing pictures of open-floored greenhouses on bare regolith.

          • fcrary says:
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            I think I prefer tethers for two or three reasons.

            First of all, it is a mechanical solution and therefore something that isn’t too hard to engineer and design. If the “real” limit for human tolerance turns out to 9 rather than 10 rpm, you can redesign the tether and make it 1/0.9^2 or 23.5% longer. That’s a pain, but quite doable. I can’t redesign the astronauts (and I’d prefer not to place additional requirements on crew selection, since it limits the talent pool.)

            Second, something about a strong gravity gradient just feels wrong. I’ll admit that’s not a strong reason, just a gut feeling. But I’m not sure about having someone’s head at 80% of the gravity their feet are at. Also, it limits the ways you can use space, since different parts of the habitat are at different gravities. Although, as you point out, for variable gravity experiments that can be turned into an advantage.

            But, mostly. I don’t see tethers as poisoning anything. Long cables on spinning spacecraft are actually very common and very reliable. Admittedly, they only support a few kilos of instruments at the far end, but the record for reliable deployment is excellent. Let’s see, Magnetospheric Multiscale (four spacecraft launched in 2015) has 16, 60-meter long ones, THEMIS (five spacecraft launched in 2007) has 20, 10 are 25 meters long and 10 are 20 meters long. The Van Allen probes (two spacecraft launched in 2012) has four 40-meter and four 50-meter. IMAGE, a single spacecraft launched in 2000, had four, 250 meters long. And FAST, launched in 1996, had four, 28 meters long. As I said, none of those were load-bearing, but they are long, flexible and deployed from a spinning spacecraft. That’s fifty-two deployed without any failures. So I guess I just can’t see why people get so hung up on tethers.

          • Paul451 says:
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            I think I prefer tethers for two or three reasons.
            First of all, it is a mechanical solution

            They’re all “mechanical”.

            If the “real” limit for human tolerance turns out to 9 rather than 10 rpm, you can redesign the tether and make it 1/0.9^2 or 23.5% longer. That’s a pain, but quite doable.

            Or just slow down to 9rpm. If you started with 1g/10rpm, you’ll still have 0.8g at 9rpm. If we are that touchy about gravity, then we certainly aren’t going to see permanent bases on Mars, let alone colonies.

            However, the idea is to find this out on the first simplest possible “station”. That’s the whole point of a research station. To find the data-points, the shape of the curve, to allow you to design later ships and stations.

            That’s why I’d want to start with something like a Dragon capsule spinning end-over-end with its upper-stage as counter-mass – if the capsule can be made capable without a significant (expensive) redesign. That proves your rpm limits for at least a small sample.

            Then a long-duration animal research station. To allow whole-of-life and multi-generation studies.

            If it can be automated – and the capsule can handle it – this could start with mice/rats on a long-duration DragonLab.

            But assuming animals are too high-maintenance for automated care. I’d suggest:

            A module and a docking node, with the upper-stage that launched the docking node still attached as counter-mass. This can obviously be upgraded by replacing the upper-stage with a second module.

            This set up would also serve for testing Mars-g and lunar-g. And, importantly but often overlooked, finding the minimum g-load that gives the maximum benefit for long-duration space-flight. If you only need 1% of gravity that drastically reduces the complexity of any spin-gravity vehicle/station.

            This station can also do other research like partial gravity fire studies, testing partial gravity plumbing and processing, etc. Or even things like regolith cohesion at asteroid-like gravity loads.

            But, mostly. I don’t see tethers as poisoning anything.

            No, I said: “this widespread belief in the need for a low rpm (and hence giant centrifuges) has poisoned spin-gravity as a concept for missions.”

            Once you start talking about artificial gravity, even educated people start to insist that “studies show” you would need 1g/1rpm and hence O’Neill-scale structures.

            Second, something about a strong gravity gradient just feels wrong. I’ll admit that’s not a strong reason, just a gut feeling. But I’m not sure about having someone’s head at 80% of the gravity their feet are at.

            This is another common believe that poisons the debate. People have this weird intuition that your body cares whether the g-load in your feet matches you head. There is simply zero evidence for that (in centrifuge studies, turn-table experiments, amusement park rides, etc) and a lot of simple experience to suggest otherwise:

            Think about how we use bed-rest to mimic micro-g. That’s because you effectively go from “partial gravity” to 1g every time you get out of bed. Just sitting means that different parts of your body are experiencing different hydraulic loads. You body routinely copes with different parts being under different hydraulic loads.

            The only issue, IMO, is balance and motion sickness. And if recent studies are any guide – and the experience of people doing squats on that “Space Cycle” I showed – that’s not an issue for a large number of people. Not everyone, some people get motion-sick on long car rides, can’t fly, etc. But they’ll already be excluded from astronaut selection.

            Of course, I might be wrong. It would be nice if there was some kind of, oh I don’t know, research station to test these things.

          • Paul451 says:
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            A few more asides (just because I’m a pedantic jerk):

            I’d prefer not to place additional requirements on crew selection, since it limits the talent pool.

            By the time you have thousands of people living on a single station, and hence you need to worry about covering more than 99% of the population, the station must be much, much wider to have enough room for thousands of people, so short-arm high-rpm will no longer be an issue.

            First of all, it is a mechanical solution and therefore something that isn’t too hard to engineer and design. If the “real” limit for human tolerance turns out to 9 rather than 10 rpm, you can redesign the tether and make it 1/0.9^2 or 23.5% longer. That’s a pain, but quite doable.

            Unless you already have the extra 23% tether ready on your spool, I suspect it would be harder to redesign such a system to handle a longer tether than to add one extra section to a modular truss, for example.

            Or in the case of an upper-stage counter-weighted tumbling pigeon, to add dumb mass to the upper-stage (such as pumping a few tonnes of water into the empty “bottom” tank) in order to change the centre of mass by the necessary few metres.

            But, mostly. I don’t see tethers as poisoning anything.

            cont.

            As for tethers, they do add to the poison, from what I’ve seen. You may have had a good run with light, non-loading antenna structures, but when you look at the history of load-bearing tether experiments, it reads like the Mars lander history.

            Indeed, it may even by a solved problem by now. But the troubled legacy seems to remain whenever you bring them up in relation to manned missions.

          • Paul451 says:
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            Aside:

            For automated animal studies (no humans), a DragonLab rotating around its vertical axis would allow you to simulate Mars gravity at 13rpm and lunar gravity below 9rpm. You then freeze and return the samples to Earth in the capsule for study on the ground.

            If the Dragon capsule can work after being inverted for a time, a DragonLab capsule left attached to its upper-stage could generate Mars gravity at just 7rpm, lunar gravity at just over 4rpm.

            In other words, you could do (very) limited human studies in a single Dragon capsule. That would be enough to find the adaptation limits of humans to high-rpm in space. Which then allows you to design a follow-on station with a full module. That allows you to do long-term human-tended animal studies to find the minimum g-load to off-set micro-g damage. Those two data-points allows you to design an ideal long duration space-station.

            Aside 2:

            Spinning around it’s long axis (ie, cylinder-station), Musk’s proposed ITS would allow Mars gravity at 8rpm.

            And it’s 50m long, but since it will carry fuel for landing on Mars, and cargo near the centre-of-mass, it will be tail-heavy and hence the length of the hab end will be more than 25m.

            So if it can spin end-over-end (tumbling pigeon), you can get Mars gravity at just 3.5rpm.

            What need for tethers?

          • fcrary says:
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            I’d rather not spin a spacecraft about its long axis. That’s unstable and it ends up tumbling (and, eventually, spinning end-over-end.) Attitude control systems could compensate, but I hate the idea of needing an active system just maintain control while doing nothing.

          • Paul451 says:
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            Baton-type rotating spacecraft are also unstable due to off-centre loads (asymmetrical around the long axis, not the rotational axis. Asymmetry around the rotational axis doesn’t matter.) Indeed most designs in reality are going to be unstable when containing moving masses, like people.

            You will always need an active system.

            (Double counter-rotating is the most stable design. But even there you have to match the rotational inertia of both sides or instabilities will build up.)

            I suspect the easiest attitude control system will be a combination of moving water between tanks and tilting the solar arrays/radiators to shift the balance in different planes. This would supplement the slower movement of bulk weights to balance more permanent loadings (such as when major items are installed or moved.)

            In later stage systems, you’ll want a large flywheel to allow propellantless spin-down and re-spin during maintenance. That, of course, adds another system that has to be maintained.

        • Moonman says:
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          There are large station sized centrifuges like proposed by vonBraun, 2001 Space Odyssey, etc, and these should pose little risk. On a modular station like ISS you might be able to try something like this by attaching a module to a counterweight (or another module) with a tether or a truss. Such an experiment was tried briefly in Gemini with no serious issues.

          There is also something called a short arm centrifuge that is module sized. This was intended for trial on the ISS and the Japanese were building the module that contained it, when the US deleted it to put some fundng elsewhere-remember the philosophy of some of the more recent ISS management has been that NASA provides a facility but not the experimental equipment-not the same philosophy as prior to year 2000. So the partially completed module sits in Japan. Costs did not go down as a result of the cancellation, they simply put the money into US centered activities.

          Fact is no one knows for sure can humans tolerate the centrifuge for an extended period of time and no one knows for sure just how much of an effects it would have on the zero-G losses -bone demineralization, muscle mass, etc. Until its tried and some data is collected, no one knows how valuable it might be.

          This was one of the original requirements for the ISS. It was one of the points for which the ISS was proposed and on which it was approved. To now miss out on trying it is a waste of ISS potential. There is no rationale that can explain the missed opportunity.

          • Michael Spencer says:
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            I suppose it must be big enough to avoid any sort of ‘gravity’ gradient from head to foot. And it must be large enough again to avoid residents feeling like a grain of sand headed out the Mississippi River towards Texas when the system is under acceleration (Coriolis effect).

      • Bernardo de la Paz says:
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        Pretty sure the centrifuge module that was in work was going to cost far more than the robonaut stuff, but that isn’t justification for not doing the centrifuge.

  5. muomega0 says:
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    “For the benefit of all..mankind”
    The most efficient way to send crew is an ~ 6 month trip, but this places the crew in microg and full GCR. Alternatively, supplies can be sent on the more efficient path and crew sent on a direct path to reduce the time to ~3 months, at more risk. Grumpy old men have more tolerance to radiation, and would be the most likely candidates for initial missions.

    So if the total trip time in microg is 6 or 12 months, is 1 yr on ISS adequate? Should they add x months at 1/3 g or simply extend the entire microg duration to the 30 months? Consider any treatments necessary on their return from ISS based on the stay duration at ISS.

    Is not statistically significant an important consideration as well? Well without a LEO carrier, how does one increase the flight rate?

    What is really required is a lightweight solution to all the crew health issues to improve the efficiency (reduce costs) and to improve the risk factors “for the benefit of all” in *addition* to “old mankind.”

    • Donald Barker says:
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      Bottom line is you will never know all you would “like” to so that you can eliminate all potential risk. Does the average person have a clue as to the risk involved in getting in their little cars and flying down the highway. Not really. So lets stop the hypothesizing, worrying and fear and just get on with it. And yes, there are plenty of people willing to take the risk. My multi-Great Grandfather died on a ship crossing from England to Rhode Island in 1640, “stuff” happens.

  6. Winner says:
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    Why don’t we ever consider a centrifuge? I know tethered experiments have been done before, is it an engineering impossibility that we could build a spacecraft that detaches two halves once on the journey and reels out a tether between them? And then they spin to get some “gravity” for a few months? It seems the hopefully not too complex engineering would be worth it to negate the health issues.

    • TheBrett says:
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      It does add some serious complexity, but of course the other reason is that it would make microgravity health research much less important (after all, if you’re only going to be doing short trips in microgravity from now on . . . ).

      • Steve Pemberton says:
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        I think there are two different concepts, testing centrifuges as a mitigation in and of themselves (i.e during the travel segments of a mission) and using a centrifuge to test the effectiveness of using Mars gravity as a mitigation. From a cost, structural and complexity point of view I think the preference would be to fly to and from Mars weightless, using the time spent in Mars gravity as mitigation. But we don’t know if that will work or not, a centrifuge on ISS simulating Mars gravity could certainly help answer that question.

        Meanwhile ongoing microgravity research will help locate the upper boundaries beyond which you need some amount of artificial (or natural) gravity. If you listen to Scott Kelly’s post-flight interviews, we may already be on the outskirts of that boundary. He said his post mission experience was vastly different after one year compared to six months. More than his slightly increased age would have accounted for.

        • Daniel Woodard says:
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          The effects of gravity on the body are mediated entirely by the loads placed on the muscles, bones and heart. A centrifuge is an exercise device, no more and no less, and tends to be more complex then the alternatives.

          • Steve Pemberton says:
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            All of the effects? Are mediated entirely?

            (from the NASA Office of Inspector General report)

            Human Health and Performance Risks by Space Environment Hazard – Altered Gravity Field

            Vision impairments and intracranial pressure
            Renal stone formation
            Sensorimotor alterations
            Host-microorganism interactions
            Cardiac rhythm problems
            Orthostatic intolerance
            Intervertebral disk damage
            Space adaptation back pain
            Bone fracture
            Reduced muscle mass, strength, and endurance
            Reduced aerobic capacity
            Urinary retention

          • Daniel Woodard says:
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            I was in error in suggesting that all effects of weightlessness are mediated by loading. However the only effects of microgravity that are commonly described as becoming progressively worse with time and thus limiting total safe time in space are muscle and bone loss, which are mediated by loading. Radiation exposure may well limit safe time in space but is not due to microgravity and can be studied more safely with animal experiments on Earth.

            Almost any medical problem can occur in spaceflight, but many of those listed are either rare and sporadic, with limited evidence of a direct relationship to weightlessness (arrythmias, urinary retention), or reach their full effect within a few hours to a few months or less (othostatic intolerance, motion sickness) and do not limit the total time humans can remain in space. In most cases countermeasures, if needed, have already been implemented. Renal stones have been predicted to be a risk of microgravity for many years (due to increased calcium loss) but after 50 years of spaceflight I’m unaware of any epidemiologic evidence that they are actually significantly more common in spaceflight.

            Intracranial hypertension is related to the headward shift of fluids in space and probably begins within days although the ocular effects may increase with time. However fluid-shift-related IH is not unique to microgravity and is a fairly common and well studied medical problem here on earth. It responds very well to acetazolamide, which is carried on the ISS in the event that it should become serious enough to require treatment. So far this has apparently not been the case.

            In some cases adaptation is never going to be instantaneous and some allowance has to be made in mission plans, i.e. to allow recovery from short-term orthostatic intolerance after return to Earth, or for that matter landing on Mars. To require maximal physical performance immediately after landing is unrealistic. But again, this does not limit total time humans can spend in space.

            That said, the opportunity for longer term spaceflights would be useful and one way to facilitate it would be to increase the crew size through improvements in the life support and logistics capabilities of the ISS.

          • fcrary says:
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            Along these lines, are there any statistics on how _relatively_ unhealthy free fall is? There are obviously medical issues, and they shouldn’t be ignored. But many, common activities have negative health implications. Sitting in a cramped seat for ten hours isn’t the healthiest thing to do, but I end up doing that half a dozen times a year on long plane flights. I suppose having a beer with my lunch today isn’t a spectacularly good choice from a purely medical point of view. And, although it’s generally regarded as very stupid, rock climbers have been known to make free solo climbs in bad weather. I don’t think I’ve ever seen the risks of microgravity put in the perspective of day-to-day life. Is this unhealthy in the sense of not exercising regularly, or unhealthy in the sense of chain smoking?

          • Daniel Woodard says:
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            Almost anything you do carries risk. A significant number of people have gotten off long airline flights at Heathrow (the airport that was studied in the best known report) and immediately dropped dead!

            The cause? “Economy class syndrome”, large blood clots which can form in the leg veins due to the cramped seating position and difficulty getting up to move and stretch the legs, cutting off circulation for hours. When the frazzled passenger finally arrives and starts walking around, the clot breaks loose and migrates to the lungs, where it blocks one or more major pulmonary arteries.

          • fcrary says:
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            Yes, I take that into consideration when I am on a long flight. But those medical problems are rare, so if I get stuck in a seat where it is impractical to get up, walk around a bit, and stretch, I don’t think I am putting my life in grave danger. I was wondering if astronauts’ exposure to free fall is at that level, or much more serious. I suspect it is more serious, but I have never seen solid data on how much more serious it might be.

          • Daniel Woodard says:
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            By far the most serious risk is not exposure to microgravity but rather a catastrophic failure of the launch vehicle or spacecraft,

          • Steve Pemberton says:
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            I realize that in comparison to launch failures and other major catastrophes that the health issues are lower on the worry list. But I think it will be an impediment to expanding our human presence in the solar system if being a space explorer means accepting damaging health effects. I don’t think we can compare to explorers in past centuries, because most of today’s type-A personalities in all walks of life tend to be very fitness conscious, and less willing to accept damage to their bodies, except maybe some professional athletes. But I remember Sandy Koufax (LA Dodgers pitcher) ended his career early when he was told that if he continued he risked lifelong damage to his arm. He decided that no amount of money or fame was worth that.

            Another concern is that if two hours of exercise continues to be the minimum requirement to avoid serious damage, what happens if someone becomes sick or injured and is unable to exercise for a lengthy period, that may put them in a potentially dangerous health situation, perhaps suffering permanent damage in some cases.

          • fcrary says:
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            A random note, the blood clots you mentioned could also lodge in the brain or the heart. Strokes and heart attacks are as bad as a pulmonary one.

          • Steve Pemberton says:
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            Hopefully it all works out okay. It’s been sort of a roller coaster or pendulum swing on this topic over the decades. At the dawn of the space age prior to the first human spaceflights there was concern whether humans could even survive in space. Animal launches helped allay fears, and when the first humans went up it confirmed that humans can indeed survive space travel. When missions started extending to multiple days and weeks there was surprise, almost elation to discover how quickly the human body adapts to weightlessness. But then as mission lengths increased to months we found that in some ways the body adapts too well, as we began to see serious issues with returning astronauts who had been in space for a several months. But eventually exercise, diet and medication regimes were developed, and the pendulum began to swing back in the other direction. However although muscle and bone issues seemed to be getting under control, fluid issues and other problems were still not being solved. After several decades of data gathering there have been some troubling signs. Scott Kelly said he experienced some really bizarre and at time alarming symptoms after his return, at one point he even considered going to the emergency room his symptoms were so alarming. Of course that’s anecdotal but it is worrisome nonetheless.

            Hopefully with more research and experimentation we can get the pendulum swinging back the other way and find a way to explore space and still remain healthy.

          • Michael Spencer says:
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            Yes, and no? Centrifuges (edited- I meant to write ‘exercise’) soak up dozens of valuable crew time each week. Focusing on centrifugal devices sufficient to provide artificial gravity, though: complex, sure, but obviating low gravity effects that everyone is so crazy about.

            This appears to be a more straightforward avenue of research.

  7. Daniel Woodard says:
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    It would certainly be interesting to see the results of a longer mission, but for the limited question of whether astronauts could tolerate weightlessness on a trip to Mars the current regime is probably enough. Many years ago I did some of the earliest bone density measurements on humans with chronic spinal cord injury. Our findings were that the bones reach a relatively stable state within about 18 months even without countermeasures, and with even the modest exercise some of the quadraplegic subjects were able to do with tilt tables stability was reached more quickly. With the intensity of exercise the US astronauts maintain, they are unlikely to see any increased risk of fracture during the outbound leg, and probably not even during the return. Once they are back on Earth, even if they have lost enough bone to lead to a slightly increased risk of fracture, they can safely recondition themselves provided they are willing to be patient and take a few months to let their bones and muscles recover.

    Ironically my wife underwent the equivalent of an even longer trip; due to a series of major orthopedic problems she was unable to walk or even bear weight for four years, but finally after multiple surgeries she began to recover. Regaining her muscle and bone strength, cardiovascular reflexes and balance (all severely affected) took almost two more years, though not without discouraging periods and several falls. but she finally regained her ability to walk normally at the age of 67. Seeing the entire process at first hand is convincing in a way laboratory studies cannot match.

    • kcowing says:
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      You know as well as I do that there is no way that NASA can meet its own requirements, such as they are, to certify that humans can safely travel to Mars on a multi-year trip. It has nothing to do with human physiology- rather it has to do with NASA’s self-defeating requirements to never ever take any risk by signing on the dotted line.

      • Daniel Woodard says:
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        In general I agree. In my view the crewmembers themselves are in the best position to judge whether the risk to which they would be exposed is acceptable.

        • kcowing says:
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          Yes indeed. It is called “informed consent” in the real world.

          • Tim Blaxland says:
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            Which would provide more informed consent? 1-year mission + 3-year mission, or 5 x 1-year missions?

            I don’t have an intuitive feel for this one and am genuinely curious as to the answer.

          • fcrary says:
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            Five one-year missions. Biological processes vary from person to person, sometimes dramatically. Repeating the experiment on a larger number of subjects is definitely the way to go.

          • DougSpace says:
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            I’d say 1+3 because things could well happen between years 1 and 3 which we need to know about and which we cannot know about unless we start pushing past 1. Or better yet, 2 pairs of 3 years. There’s no logic to why we cannot have at least two astro/cosmonauts doing a 3-year simultaneously as well as starting another 3-year mission with a couple of other crew starting 6 months later. Follow indicators and return to Earth immediately if concerns develop.

      • Vladislaw says:
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        Keith, is this internal to NASA or Congress telling NASA no one can die if they want funding? Where is it coming from, Congress or NASA?

        • fcrary says:
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          It comes from everyone. Look at the public reaction after Apollo 1, Challenger or Columbia. Or the media coverage. The NASA and congressional attitude is a response to that.

        • muomega0 says:
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          Long duration Crew Health is a Grand Challenge for a reason. In addition, a) 6 day sorties to lunar..long duration data not required b) exercise, medicine not adequate c) ISS centrifuge limitations–small diameter disturbs ug science

      • Gene DiGennaro says:
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        Yes, whatever happened to the swaggering “I’ll strap it on and fly it.” mentality of the legendary test pilots of yore? I bet the astronaut corps is chomping at the bit to venture into the unknown, that’s what they signed up for!

  8. Bernardo de la Paz says:
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    Among the many justifications for building a LEO station was for use as a testing ground and a transportation node for beyond LEO missions. It is very good to see attention being given to that aspect of ISS’s mission. However, there were also many justifications that involved LEO only operations as well. It baffles me that there seems to be an implicit assumption that because we are now paying attention to beyond LEO missions that there is no longer any purpose in continuing LEO operations with ISS or, more importantly, potential successors. (The commercially funded tourist hotel notion is extremely unlikely to reach fruition with the technology on the table today.) The implicit lack of imagination and independent thought at leadership levels is very disappointing.

  9. patb2009 says:
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    why does ISS have a 7 year life? What prevents in orbit repairs,
    to SLEP the bird?

  10. Joe From Houston says:
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    Everyone is still guessing away and competing for control on what path to take based on their admirable credentials. Folks, this clamoring for control is going to fail in the end because it boils down to one person with the most admirable credentials making a decision that is supported by a vast number of colleagues driven by job security. No matter who wins this battle for control with what credentials they have, they can’t make concrete predictions of unknown physiological boundaries without an experiment that accurately mimics the actual gravity and radiation conditions.
    The experiment I suggest is to go to the ISS for 6 months which is the transfer time to Mars, then go to the lunar surface for 18 months at 1/6th gravity of Earth, then come back to the ISS for 6 months which is the transfer time back to Earth from Mars, then come home and measure the results. Ok, so the ISS is so convoluted with operational constraints much less only 7 years left, it is not a good candidate.
    If the ISS isn’t going to be in orbit by that time, we send up a temporary Bigelow inflatable at a tiny fraction of the cost of operating the ISS that is in a desirable orbit inclination for lunar transfers. We all know that the Moon’s gravity is less than the Mar’s gravity, so if they come back and are ok, then by default they are good to go to Mars. If not, then some form of artificial gravity and additional radiation shielding must take place. The Moon-to-Earth return can use aero-braking to get into the orbit of the inflatable habitat in low Earth orbit and a tug can go out and retrieve the capsule back to the inflatable for the 6 month extended stay there before deorbiting and landing on Earth.

    • muomega0 says:
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      The result is crew health issues in the wrong environment, and one still does not have the data to make the correct decisions in the future, not to mention that the moon blocks half the GCR as does earth for LEO, its not just gravity. Better to build a simple tether and place at L2–much cheaper, better data, and the proper environment, or start in LEO.

  11. tutiger87 says:
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    What should be done is fly someone on ISS for 8 months, send them down, zip them to a stay at one of the Earth analogs (Devon Island, etc) for a year, then send them right back to ISS and have them stay for 8 months. No medical attention, no nothing.

  12. DougSpace says:
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    There was a lady from NASA Human Factors on The Space Show. I asked her about the possibility of using a contingency approach where certain factors would be followed and, when one of them was getting too close to a set criteria then that astronaut would depart from the ISS to return home. In this way the crew could remain on the ISS for as long as possible (I suppose up to the length of a full Mars mission). She replied that doing so wouldn’t be compatible with regular crew rotations. I’m not convinced but that’s the answer I got.