Biology is going to put a crimp in the space program

Scott Kelly served on the International Space Station for 340 days, partly as an experiment to see how the human body held up in long term weightlessness. Not well, it turns out. Kelly writes about his experience on finally returning to Earth.

I struggle to get up. Find the edge of the bed. Feet down. Sit up. Stand up. At every stage I feel like I’m fighting through quicksand. When I’m finally vertical, the pain in my legs is awful, and on top of that pain I feel a sensation that’s even more alarming: it feels as though all the blood in my body is rushing to my legs, like the sensation of the blood rushing to your head when you do a handstand, but in reverse.

I can feel the tissue in my legs swelling. I shuffle my way to the bath room, moving my weight from one foot to the other with deliberate effort. Left. Right. Left. Right. I make it to the bathroom, flip on the light, and look down at my legs. They are swollen and alien stumps, not legs at all. “Oh shit,” I say. “Amiko, come look at this.” She kneels down and squeezes one ankle, and it squishes like a water balloon. She looks up at me with worried eyes. “I can’t even feel your ankle bones,” she says.

“My skin is burning, too,” I tell her. Amiko frantically examines me. I have a strange rash all over my back, the backs of my legs, the back of my head and neck – everywhere I was in contact with the bed. I can feel her cool hands moving over my inflamed skin. “It looks like an allergic rash,” she says. “Like hives.”

I’m rather appalled that this experiment was done at all — we’ve known about the deleterious effects of shorter periods of weightlessness for a long time, so it’s bizarre that they pushed for longer and longer exposures. Were they hoping everything would just get better, that the human body would adjust to living in space? Because if they did, they’d have made returning home even more traumatic.

Face it, if we’re going to have people working in space for months or years, the hardware is going to have to provide some kind of substitute for gravity — great big spinning wheels, ala 2001, or built-in central centrifuges. I would hope that our space agencies would stop wrecking human bodies in pointless exercises in endurance.

I can think of more productive experiments. How much gravity is enough? Do we need a full 1G to be healthy, or would, for instance, .38G, as found on Mars, be enough? Of course, to do that kind of experiment they would need to build one of those rotating space stations, so we’re talking big money and a reset of the ISS.

We’re also ignoring the effects of prolonged radiation exposure. It’s not just the weightlessness. I have the feeling that there are a lot of ghoulish doctors working for NASA who are going to be ticking off symptoms and writing papers on the deterioration of human bodies in space,
which will be ignored by the administrators and politicians who will make speeches about the heroic sacrifices our brave astronauts are making.

An alternative strategy: let’s train tardigrades to crew space ships, if we must have biological entities aboard.


  1. davidnangle says

    Doesn’t look good for a Mars trip, without some breakthroughs in engineering and biology that are pretty hard to imagine right now.

    In particular right now, since we’re being led by people that condemn the sorcery of rubbing sticks together… when you can just bash the other tribe and steal their fire.

  2. A. Noyd says

    Part of the justification seems to be that Scott has an identical twin who is also an astronaut but has spent like a tenth of the time in space. What proper ghoul with a medical degree could resist a good old fashioned twin study?

  3. latveriandiplomat says

    An alternative strategy: let’s train tardigrades to crew space ships, if we must have biological entities aboard.

    Has somebody been watching Star Trek Discovery ? :)

    More seriously, I think that they have been trying to improve some of the gravity alternatives (e.g., lots of exercise against springs) vs. what was available to the people who did those original long distance stays. It seems that those alternatives just don’t work. But, I agree, it’s probably time to stop now.

  4. whywhywhy says

    Can we require that folks need to answer the question of how to safely transport humans in space prior to any bloviating about colonizing Mars? And that any discussion about living on Mars needs to be prefaced by a discussion of cosmic rays?

  5. brett says

    We also need to see what level of rotations per minute people can tolerate in the long-run as part of simulating gravity. The rule of thumb used to be 2 RPM was the maximum that people could tolerate, which means you’d need a really big diameter for a ring or tether (hundreds of meters). But I’ve read claims that more recent research shows people can adapt to higher levels of RPM, which would make it much easier to simulate Earth-level gravity.

    @6 whywhywhy

    And that any discussion about living on Mars needs to be prefaced by a discussion of cosmic rays?

    We need to do some longer stays outside of Earth’s magnetosphere first (weeks or months). We know how much radiation they’d get hit with from some of the robotic probes sent over, and have some idea of what the radiation exposure might entail from ISS crews. But IIRC the Earth’s magnetic field deflects most of the heavier ions that could do physical damage along with the higher cancer risk.

  6. John Harshman says

    The simple (possible) solution to the gravity problem would be to try using the moon. The ready availability of lots of rock could solve the radiation problem too.

  7. Mobius says

    Sadly, it seems that there are still a number of hurdles to jump before we make that manned mission to Mars. One way, we are talking six months to a year.

  8. says

    6 months to a year one-way. I really wonder about the ethics of doing experimental testing for that: we’re asking healthy, athletic young-to-middle-aged men and women to knowingly trash their bodies in the name of…science? International competition? Patriotism? Corporate sponsorship? I don’t know.

    What would be the consequences of sending a crew on a two-year voyage through space where some die en route, and the remainder collapse into jellied immobility on return, and we then watch them die of radiation sickness and cancer?

    Meanwhile, robots seem to be thriving in space.

  9. Matt says

    @3 The radiation danger from a Mars trip is Proton Solar Events, which would be fatal to any astronauts outside the Van Allen belts. Apollo was lucky. August 1972 saw an SPE event that would have killed the astronauts on the moon. It occurred between Apollo 16 and 17. Shielding is a possibility, but shielding is heavy, thus very very expensive.

    @10 Seven months travel time for a Hohmann (lowest energy) transfer. But astronauts would have to spend a bunch of time on Mars before returning because they’d have to catch a launch window. For instance, the April 30, 2018 launch window would arrive on January 15, 2019. But the next possible return trip can’t leave until April 13, 2020. With an arrival back on Earth on December 28, 2020. Total time away from Earth is about 32 months, at least 14 of which would be in space. You could speed this up by a few months by expending extra fuel, but can’t do a whole lot better than this without new technology.

    I’m kind of a space nut, but I seriously doubt that humans will walk on Mars in the near future. If we attempt it, they’ll probably die on the way. Robots are far far cheaper, less vulnerable, and can do plenty of things that humans can’t. We should keep using robots for this kind of exploration.

  10. Azkyroth, B*Cos[F(u)]==Y says

    I struggle to get up. Find the edge of the bed. Feet down. Sit up. Stand up. At every stage I feel like I’m fighting through quicksand.

    Funny, I don’t remember going to space. O.o

  11. says

    And that any discussion about living on Mars needs to be prefaced by a discussion of cosmic rays?

    Like how we need to be prepared for people gaining superpowers.

    (Radiation was so much more fun when the worst it could do is turn you into a super-strong rock monster.)

  12. anchor says

    As Scott points out in his article, the equivalent of ten chest x-rays a day is the radiation toll – but that is in close orbit around the Earth while still ‘safely’ ensconced in Earth’s magnetic field which deflects charged particles, although the orbital inclination of the ISS passes perilously into high latitudes close to the magnetic poles where the field dips into the atmosphere – and the station often passes right through the auroral rings.

    Yet that’s nothing compared to what travelers would be exposed to on long-duration missions to and from Mars, where they would be at the mercy of both solar particles and fiendishly energetic cosmic rays. And if the Sun happens to unleash a flare and coronal mass ejection in their direction, the dose could be fatal within days or hours. There is a documented account of how close astronauts aboard an Apollo mission to the Moon came to being exposed to a potentially fatal outburst from the Sun that happened to occur within weeks after their return. (If memory serves, I seem to recall it was Apollo 16, but I could be wrong)

    Its been pretty clear for quite awhile that human spaceflight is not going to resemble romantic fantasies of cheesy space operas. Whether people like Musk and spaceflight enthusiasts like it or not, current and foreseeable technology preclude any large-scale, long-duration human presence in space for a long time to come.

    Centrifuging spacecraft to take care of the weightlessness issue is technically trivial compared to devising some means to protect astronauts from the radiation – whether its brute shielding with a dense material (which is why lead is favored by the nuclear industry) or some artificial magnetosphere is devised (and magnets are fiendishly heavy and demand huge amounts of power to generate a magnetic dipole large and powerful enough to protect a spacecraft) it adds orders of magnitude to the amount of mass that must be heaved.

    Life is a feature of planets like Earth. They’re the natural, potentially safe havens for delicate organic chemistry. If the harsh environment of interplanetary or interstellar space is inhabited in pockets anywhere in the universe, they won’t be occupied by fragile carbon-based organisms, but by self-replicating (von Neumann machine) products of industrial activity by short-lived civilizations.

  13. unclefrogy says

    well until someone invents the artificial gravity that is always used in outer space movies, how is it so directional ( it is a sound stage obviously) it sounds like that the only realistic way we will be traveling to other planets let alone stars will be in very much larger ships. Huge in comparison to anything we have so far built maybe even as large as the habitats that have been envisioned for the Lagrangian points at least for something like really long voyages.
    what we are doing now is really primitive or simple, canoes and rafts when what we need is something more like a double or triple QE-2 in comparison.

    uncle frogy

  14. davidnangle says

    If we had artificial gravity, we wouldn’t have to use it for something as mundane as keeping feet on the floor. We’d use it to accelerate the ship at 1G. There’s your negation of health problems, slow Hohmann orbits and transfer windows keeping you out in the dangerous solar environment, and cargo limitations, all in one go.

  15. busterggi says

    I suspect that biology is the reason that manned space exploration has largely come to a halt. Tom Corbett, Rocky Jones, flash Gordon and Buck Rogers had it wrong.

  16. multitool says

    I am very pro-robot, which is a pariah position among space heads.

    I am also very pro-unmanned terrariums, so we can see if any ecosystem can adapt to space over multiple generations. If they can’t, then humans are a non-starter.

  17. michaelwbusch says

    PZ wrote:

    I can think of more productive experiments. How much gravity is enough? Do we need a full 1G to be healthy, or would, for instance, .38G, as found on Mars, be enough? Of course, to do that kind of experiment they would need to build one of those rotating space stations, so we’re talking big money and a reset of the ISS.

    There was originally a planned module for the ISS called the Centrifuge Accommodations Module (CAM), which was being built by the Japanese space agency (NASDA, now JAXA). The module was canceled along with a couple of other station components following the Columbia disaster, due to the number of subsequent Shuttle launches being strictly limited: .

    CAM’s central piece of equipment was a centrifuge 2.5 m in diameter – there was not enough space to accommodate anything larger inside a module that would fit within the Shuttle cargo bay. That’s obviously not large enough for variable-gravity human studies, but it would have allowed small-mammal animal studies at a variety of spin rates and equivalent effective gravities. Perhaps it would be a good idea to launch an equivalent module to the ISS now.

    Re. discussions of radiation shielding:

    Radiation shielding is indeed necessary for long-term human missions in deep space. As others have written, it takes >6 months to get to Mars. There’s no way around that without a huge expenditure of fuel or a very large power source on the spacecraft.

    Most of the radiation dose outside of Earth’s magnetosphere is from solar wind protons, for which something rich in hydrogen is a better shield than lead. Protons scattering off of lead nuclei keep most of their energy, protons scattering off of other protons – i.e. hydrogen nuclei – transfer most of their energy to the proton they hit. Which is bad when the protons being hit are parts of astronauts’ bodies.

    So shielding designs generally involve something hydrogen-rich: water, hydrocarbons, rocks with a bunch of water chemically bonded within them; in tanks or sandbags around the astronauts’ habitat. Hauling enough shielding mass up from Earth is extremely expensive – it requires hundreds or thousands of kilograms per square meter of spacecraft to be shielded.

    One way to reduce the cost of radiation shielding would be to source shielding material from water-rich near-Earth asteroids with robotic spacecraft, to avoid needing to haul it up a steep gravitational potential well. NASA had planned to demonstrate that, along with several other things, as part of the Asteroid Redirect Mission; which would have launched ~10 tons of robotic spacecraft to bring 20-50 tons of material from asteroid 2008 EV5 back to Earth orbit. Unfortunately, Congress canceled the ARM project earlier this year.

  18. multitool says

    It probably be easier to launch a can on a long tether than to build a wheel.

    You get unlimited diameter and can vary the Gs by pulling in the tether.

  19. Mark Jacobson says

    PZ wrote:

    I can think of more productive experiments. How much gravity is enough? Do we need a full 1G to be healthy, or would, for instance, .38G, as found on Mars, be enough?

    I’d also like to see experiments done on the effect of gravity in doses. If it turns out astronauts can stave off low gee health concerns by exposure to a certain acceleration for periods of time, spaceships and space habitats could benefit from a one-person centrifuge the crew could switch out using a few hours every day, much more viable than a full on gravdeck. Spaceships with a sufficient thrust-to-mass ratio could forgo the centrifuge altogether and just do acceleration burns at regular intervals.

  20. says

    Swollen, painful legs, burning skin, rashes? You don’t need to spend a year in space to get that just give it time. It will all come with age.

  21. Mrdead Inmypocket says

    Yep living in a gravity well is a real drag, man.*Walks away humming Don’t Drag Me Down- Social Distortion.

  22. brett says

    I don’t think the flares are what gets your astronauts. You’d have to turn a small part of your spacecraft into a “storm shelter” with 1-2 feet surrounding water (or water equivalent materials), but that’s doable (you’re going to be carrying a lot of water and food supplies on the ship anyways even with recycling). It’s the cosmic rays you can’t realistically shield against because they’re too energetic – astronauts on a long duration mission will have to take the dose for the foreseeable future. That’s why we need to do gradually increased time length tests in either high earth orbit or lunar orbit, outside of Earth’s magnetic fields, to see if there are other health effects besides the increased cancer risk (which is higher than the career allowed dose that astronauts are currently allowed to have, but not extremely so).

    @24 Ian King

    Tethers are definitely one way to do this, especially if everything your astronauts are using is on one end of the tether (with the counter-weight at the other end being a burned-out upper stage/engine module).

  23. rorschach says

    PZ: “Do we need a full 1G to be healthy, or would, for instance, .38G, as found on Mars, be enough?”

    Weird that gravity on Mars is right at a Fibonacci retracement level of our own! So maybe at the Fibo levels 23/38/50/62 we would be least inconvenienced in space?
    *just kidding*
    *or maybe there’s something too it?*
    *works occasionally in the stock market*

  24. michaelwbusch says

    @brett @27:

    Most of the energy in cosmic rays is also carried by protons (most of the rest after that is alpha particles). Hydrogen-rich materials are effective shields against that. However, cosmic ray energies are generally high enough that the collisions of the primary cosmic rays with the atoms in the shield can produce secondary particle showers that are themselves dangerous.

    It takes a few thousand kilograms per square meter of habitat surface of shielding mass (e.g. sandbags a few meters thick) to block most of the primary cosmic rays & the secondary showers and bring radiation exposure down to levels experienced on Earth’s surface. Which works out to several hundred tons of shield mass for a habitat large enough for a few people for six months at a time.

    Not a small thing. For comparison: The entire ISS is about 420 tons.

  25. says

    How many imes more expensive is it to keep people alive in space and return them home? Ten times? Five times? Even if its only twice as costly, the risk isn’t worth it. And I’m talking only in terms of gun-shy taxpayers opposing further missions, not the lives of astronauts. When machine missions fail (e.g. NASA’s Genesis, ESA’s Sciaparelli) it’s an expensive disappointment, not a national tragedy.

    Machines don’t require life support and are expendible. Human space travel is as much or more about nationalism than about science.

  26. brett says

    @29 michaelwbusch

    I agree, and that’s why we need health research on the effects of them outside of Earth’s magnetic field to fully understand the impact of long-term exposure. There’s no way any relatively near-term spaceship is going to carry enough mass to shield against them, so we really need to know if the health effects are going to be so bad on a trip to Mars that it would be unethical to send them.

  27. Matt says

    @31 The Lunar Reconnaissance Orbiter has an instrument onboard called CRaTER: Cosmis Ray Telescope for the Effects of Radiation, which is meant precisely to study that.

  28. michaelwbusch says

    @brett @31 and @Matt @32:

    The LRO spacecraft (as Matt noted), the Mars Odyssey spacecraft, and the Curiosity Mars rover all have instruments designed to study their local radiation environments – covering variously low lunar orbit, Earth-Mars transit solar orbit & low Mars orbit, and Mars’ surface. Studies of the effects of long-term exposure are currently limited to Earth-based analogues.

    There is a proposed NASA small satellite mission called BioSentinel. It would monitor radiation effects on living samples over an 18-month period in an Earth-leading solar orbit; outside the Earth’s magnetosphere. But its samples are planned to be limited to yeast: .

    Proposed extended human missions in Earth-Moon space but outside of the magnetosphere – e.g. in high lunar orbits – have generally had shorter durations (e.g. 30 to 90 days) than a Mars mission would have to have. And even then there’s been concerns about having enough habitat shielding mass if hauling everything up from Earth.

    The ARM project, which I mentioned above, proposed to try to address that by demonstrating space resource utilization – e.g. bringing asteroid material back with a robotic spacecraft, which could be packed into sandbags. The estimated mission cost for returning 20-50 tons of material, after meeting the mission’s other primary goal (demonstrating asteroid deflection, hence “Asteroid Redirect Robotic Mission”) was estimated at around $2 billion.

    Multiply the mass needed by a factor of ten; decrease the cost some with build-to-print copies of the spacecraft and potentially better target asteroid selection; then add in a large margin for space-based handling. Suggests some tens of billions for the shielding mass for a human Mars mission, along with a decade of robots hauling blocks of asteroid back to Earth orbit. But perhaps not as expensive as shipping all of that mass up from the ground.

    @Intransitive @30:

    The science return from a human Mars mission (or extended human lunar missions, or human asteroid missions) would be orders-of-magnitude greater in terms of raw data than what a robotic in-situ mission would provide. For example: Steve Squyres, who led the Mars Exploration Rover project, estimates that the MER rover teams did field geology on Mars from Earth via the robots between 200 and 400 times slower than a human geologist on Mars would.

    Deciding if that’s worth the cost to do such missions at an acceptable level of risk is up to public opinion.