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Artist, Heather Oliver             

Damp Squibs: Non-News in Space Exploration


Biologists interested in space exploration are consistently delegated to the back of the stellar tour bus, if we’re allowed on at all. We’re Luddites who harsh everyone else’s squee, you see. We keep pointing out that radiation is not kind to living tissue, whether gametes or neurons; that uploading to silicon chassis is not possible as an alternative to carbon bodies; that human babies cannot be hatched and reared by robots at planetfall; that living on extrasolar planets poses huge problems and dilemmas even if they’re quasi-compatible. And that since FTL and warp drive are and will always remain science fiction, we need to at least tackle, if not solve, some of these issues before we launch crewed starships for long exploratory or migratory journeys. This year, there were two non-news items in the domain that brought these matters once again to the fore.

The earlier of the two was the disclosure that “NASA scientists might achieve warp drive” based on Alcubierre’s theoretical concept (by using a Jovian weight’s worth of exotic matter as likely to exist as stable wormholes). Beyond its terminally wobbly foundation, the concept also doesn’t take into account that such folding of space would destroy nearby star systems (and almost certainly also the starship) via distortion of the local spacetime and/or massive amounts of radiation. It’s also unclear how the starship could be steered from within the “negative energy” or “tachyonic matter” bubble. This means that even if fast space travel were possible using this method, it would still take lifetimes to safely reach a planet within a system because local travel would by necessity be at sublight speed.

More recently came the non-news that radiation causes… brain malfunction, as if the term “free radicals” and “radiation damage” were not in the biomedical vocabulary since before I entered the discipline in the mid-seventies (let alone the in-your-face evidence of the Hiroshima and Nagasaki holocausts or the Chernobyl meltdown). Radiation, especially the high-energy portion of the spectrum, breaks atomic bonds directly and indirectly by producing free radicals. Free radicals start chain reactions: lines of descendants, each of which can damage a biomolecule. Radiation causes mutations in the DNA, which is bad enough, but it can also result in other errors: protein misfolding, holes in cell membranes, neuron misfiring. And although cells have several repair mechanisms to counter these insults, they have evolved for the radiation burdens of earth.

All these effects at the molecular/cellular level converge into two large rivers: for dividing cells, cancer; for non-dividing cells (most prominently gametes and brain neurons), death. Kill enough cells, past the brain’s ability to rewire and reroute, and you get neurodegeneration: if the most affected region is the substantia nigra, Parkinson’s; if the cerebellum, ataxia; if the hippocampus and parts of the cortex, Alzheimer’s; if the frontal lobe, frontotemporal dementia; if the Schwann cells of the myelin sheath, multiple sclerosis. Incidentally, radiation also affects electronic devices – something to keep in mind for even short interstellar journeys.


On earth, we are subject to a good deal of radiation from natural causes (radon, solar flares) as well as human-made ones (industrial, occupational, medical, airport X-ray machines). Cosmic radiation constitutes about 5-10% of our total exposure. That will be very different in space, where bombardment by galactic cosmic rays will be both chronic and acute. And whereas cosmic radiation on earth is moderated by the solar wind, the earth’s magnetic field and the layers of atmosphere, none of these protections will be present on a starship. Shielding options are inadequate or, like warp drive, sheer fantasy – which makes this risk one of the major showstoppers to star travel. The best candidate is the most low-tech: water.

Scientific papers that discuss these outcomes, from both inside and outside NASA, have been around since at least the early nineties. So what exactly is new in this study that is making the customary rounds in various space enthusiast sites and blogs? In a word, nothing. In fact it’s a bits-and-pieces study that reaches miniscule, non-surprising conclusions. The adage “labored as if for an elephant and brought forth a mouse” is particularly apt here. As for the originality of its discoveries/conclusions, it’s like hitting someone’s head repeatedly against a cement wall and concluding that such blows eventually cause, um, skull fractures.

At the same time, the authors of the study decided to gild their tinfoil lilies. They used a double transgenic mouse strain engineered to develop amyloid plaques of the Alzheimer’s-associated variety. Despite this loading of the dice, they saw changes in plaque size and numbers and in amyloid processing only in the male irradiated mice. Even the small shifts they saw are far less important than laypeople think: for a while now, the consensus in the field is that plaques may be neutral warehouses. In particular, plaques seem to be a sidebar for sporadic Alzheimer’s which is 90-95% of the disease cases. Many people have heavy amyloid plaque loads with zero cognitive impairment. As is often the case with mice studies, they subjected them to overwhelming amounts of the perturbing parameter (in this case, iron nuclei) that nevertheless represents a simplified subset of what they’d encounter in a real journey. Finally, they saw neither inflammatory microglial activation nor changes in amyloid clearance. They did see changes in a couple of behavioral tests, although in most of them the error bars overlap, which means “not statistically significant”.

The obvious experiment that might give remotely useful results would be to do such studies with a mouse strain that is not merely wild-type but aggressively outbred. However, that would still be superfluous, even if we set aside the limited usefulness of mouse models for human brain function. We already know what would happen during long interstellar journeys, and more or less why. I propose that we use the time and funds spent on irradiating guaranteed-to-develop-disease mice to develop effective, and preferably low-key, shielding. Radical-clearing drugs are also an option, although the favorite defaults bristle with their own host of problems (teratogenicity for retinoids, tumorigenesis for mitochondrial boosting). Like most complex problems, there are no silver bullets to counteract the iron-nuclei ones of galactic radiation. It will have to be done the hard, slow way – or not at all.


Relevant papers:

H White (2012). Warp Field Mechanics 101.

JD Cherry, B Liu, JL Frost, CA Lemere, JP Williams, JA Olschowka, MK O’Banion (2012). Galactic Cosmic Radiation Leads to Cognitive Impairment and Increased A? Plaque Accumulation in a Mouse Model of Alzheimer’s Disease. PLoS One 7(12):e53275

24 Responses to “Damp Squibs: Non-News in Space Exploration”

  1. Zarpaulus says:

    What about antioxidant drugs? From what my radiation biology professor claimed they increased rad tolerance with fairly few side effects. Granted cellular functions require some free radicals and it’s hard to predict beforehand how much radiation you’re going to be exposed to in an unpredictable environment like space.

  2. Athena says:

    You know how respiration works, right? It requires oxygen radicals. The amount of antioxidants needed for space missions would kill us by asphyxiation before radiation did.

  3. Adam says:

    Reminds me a bit of the “GMO foods cause cancer in mice” non-news that came out not too long ago. Sounded scary until bio-science bloggers read the paper and pointed out the mouse-strain was notorious cancer-prone.

    But GCR issues have been known since at least the 1970s and all the current hand-wringing is ludicrous. We know what GCR protection means – mass-shields and/or magnetic-shielding. What’s changed since then is (a) better data on GCRs, (b) high-temperature superconductors, and (c) “mass-aversion” – any spaceship design which includes heavy shielding is dubbed “impossible” because mass-budgets are mentally confined to what can be launched by an ELLV.

  4. Athena says:

    Well, that doesn’t mean that radiation doesn’t cause cancer or neuronal dysfunction. Very different story from the GMO paper, which really fudged its foundational base. But quoting this study as “new and crucial” is emperor’s-new-clothes stuff.

  5. Christopher Phoenix says:

    I have great interest in interstellar flight, and it has become incredibly obvious to me that any discussion of interstellar flight needs to include the areas of research pertaining to the human issues. This includes biology, obviously, because astronauts are biological entities. Anthropology and sociology are important too, since we must plan out a workable ship-board society for all those long years that stretch ahead of those who set out to the stars. Now I feel a bit like I said a car needs wheels.

    It is obvious that space travelers will be exposed to higher quantities of radiation and UV light than people back on Earth, but this has not been discussed much in context of interstellar flight, at least from what I have seen. In particular, galactic cosmic rays seem to be very hard to stop and damaging. The Apollo astronauts saw flashes from passing cosmic rays on their flight to the moon.

    The easiest way to shield the astronauts, as you noted, is to surround them with water. The cube-square law applies here- the thickness of shielding the astronauts require to be safe stays the same no matter how big or small you want to build the ship. The larger the ship is, the easier it will be to shield the astronauts, since the surface area/volume ratio keeps getting smaller, and the thickness of the shielding becomes rather small compared to the size of the entire ship.

    I have a question, Athena. I have heard about the idea of suspended animation, i.e. freezing astronauts so they will last for decades or even longer and then thawing them out at the destination. Hibernation seems to be different, closer to what bears do than to a frozen human popsicle.

    Anyway, I was warned that the corpsicles have a shelf life, since naturally occurring radioactive atoms will cause damage that the suspended body can not repair, since all metabolic processes have ceased. You might need to thaw out the astronauts to allow them to repair the damage periodically. Another suggestion was to raise the astronauts in an environment where no traces of radioactive substances could reach them. I guess they won’t be allowed to eat any bananas. But, in light of the enhanced radiation levels of space, what might the prospects of such frozen astronauts be? It sounds like stray cosmic rays will be doing far more damage than naturally occurring radioactive atoms, and the crew could be riddled with damage before planet-fall…

  6. Zarpaulus says:

    What I didn’t know was how many antioxidants it would require. I’m going to guess that any interplanetary spaceships that are ever built will have more lead plating and water tanks than habitation space.

  7. Adam says:

    Indeed. GCR exposure does do those things, though – contra this paper – there’s no good evidence for the exposure time required for noticeable cumulative effect in humans. The work in the 70s was as much educated guess-work as this latest “finding”.

    We’re continually exposed to the muon secondary debris of the GCRs that smash into our atmosphere, something we’ve adapted to, so we have *some* self-repair ability. The annoying thing is every self-professed expert who poo-poos magnetic shielding. A proper read-up on the subject reveals more than a few studies and generally reasonable power&mass requirements – so long as we’re not imaging launching forth in glorified versions of current rockets.

  8. Athena says:

    That would be my guess as well, Paul, unless we discover radical new ways to achieve shielding.

  9. Athena says:

    Well, the paper made no claims about humans; it restricted itself to mice. Space exploration is a-swim in self-professed experts. Human cells have the same repair capabilities as those of any other mammal. However, some repair systems require replication. This means that non-dividing cells that are permanent (notably, neurons) are even more vulnerable than the rest, which are replaced.

  10. Athena says:

    Christopher, even if it were possible to freeze and thaw a human successfully (still doubtful), the damage you describe would indeed occur. The same goes for frozen embryos, but that might be easier to deal with depending on the cell stage at which they were frozen.

  11. Adam says:

    Natural levels of potassium-40, carbon-14 and uranium/thorium produce about 15,000 decay events per human body per second. Not sure what that cumulates to over long time periods. Most of the radiation back-ground we experience is from muons from cosmic-rays exploding above our heads, and wisps of radon from the ground.

  12. Athena says:

    I listed radon as one of the major natural radiation sources. The conversion/equivalence between decay events and biological effects is not straightforward. Location matters; so does exact outcome. The human body is not a homogeneous block of matter, something often elided in these calculations.

  13. Christopher Phoenix says:

    Ah, I suspected as much. :,D I suspect that even if whole-body freezing and reanimation were possible, that it would be a frightening process- you may emerge from the cryopod with debilitating damage, memory loss, brain damage, or perhaps not at all. But, what if induced hibernation? As I understand it, the difference between cryosleep and induced hibernation is that in hibernation, the body is still running- albeit very slowly, at a much reduced temperature and metabolic rate. If the body is still running, will it repair damage done by background radiation?

    Certainly, a lot of background radiation is caused by secondary radiation from cosmic-rays and radon, not just from naturally occurring radioactive atoms in our bodies. But, it is the debilitating effect of such radiation over decades or centuries of being a corpsicle unable to repair such damage that I am worried about. It is a potentially big problem for cryonic sleep, and limits how grand a voyage we can plan without periodic thawing out the travelers so they can repair the damage. And, what if thawing someone out and refreezing them carries its own risks? If, each time, our astronauts risk loss of cognitive function or even death, then the star-flight may become a terrible waiting game from thaw-out to thaw-out, each time hoping you will remember who you are next time- or at least emerge at all.

    Have you seen this paper, Athena? The technology assumed seems somewhat more SF than reality, especially the assumption that pseudogravity without rotation will be possible, but the paper deals with the difficulties of high-speed subrelativistic space travel rather well. The need to plan out crew size and the shipboard society carefully is noted, as is the fact that the leadership of the expedition will have to be adapted to a multigenerational profile.

    I rather liked the idea of terraforming the surface of an asteroid to provide a varied terrain. It is a bit like the classic asteroid ship turned inside-out. I can’t help but wonder exactly how they plan to push the mass of this asteroid up to 1/6 C, and where the fuel tanks are- perhaps the astroid could be made into a hollow shell containing the necessary reaction mass? It certainly is large enough.

    While the engineering details of this vessel’s propulsion and pseudogravity seem somewhat sketchy, I think any real interstellar flights will have to pay similar attention to human physical and psychological well being. The description of an interstellar ship as a flying micro-planet seems quite apt- the ship must supply EVERYTHING the travelers need during the long flight, from the air and other consumables to basic psychological needs. Just like the Earth does. So does the comparison with the seed pods of terrestrial plants.

  14. Athena says:

    I haven’t read the NASA paper, Christopher. After a while, they all blur into sameness for obvious reasons.

  15. Christopher Phoenix says:

    Well, this was the first paper I have found that discusses the “human” factors of long-duration space flight, such as psychology, planning out crew size so as to keep the crew genetically diverse, leadership, and so on- which I have not seen discussed that often by modern publications. I liked the design of the ship, I might use it for some spacecraft art sometime. Certainly, though, most papers I have run across are not of much interest to me.

    When I was younger, most of my ideas about space travel were formed by reading books on astronomy, rocketry, and space exploration. So, my general concept of the development of space travel went that after we had explored and built bases around the inner solar system, we might utilize space resources to construct something like a generation ship (sub-C, of course, ’cause FTL travel doesn’t exist), and launch it to the stars. I thought about how the travelers would need protection from cosmic rays and micrometeoroids, and that they would need to recycle their own air and grow their own food for a mission that may last centuries. Star travel was likely to be slow and difficult, in my opinion, if it was achieved at all. The Centauri Project ship reminded me of that vision.

    After seeing a lot of the half baked ideas that have been put forward (like uploading and nanny robots), I think I was right the first time around. The other “options” for bridging the time-distance factors, like cryonic suspension, are fraught with difficulties, and it does not appear likely that our first starships will be able to accelerate constantly to relativistic speeds. Unless someone invents something like a warp drive (not too likely), star travel will be slow, and future star travel is most likely to be achieved by ships that approximate small worlds.

  16. A.R.Yngve says:

    I’m fairly certain that space belongs to the robots. They can thrive there, unlike humans. (So let’s be nice to them, eh?)

  17. Athena says:

    Actually, their electronics are as vulnerable as our brains. And if they ever develop true awareness, whether we’re nice to them will be irrelevant — they’ll be true aliens with their own ways of thinking and reacting.

  18. James Davis Nicoll says:

    The now rather old Alpha Centauri (Barton and Capobianco) outfitted its astronauts with internal technology that rendered them both remarkably resistant to radiation and to dehydration; the astronauts comment on how handy this is as they bathe in the Van Allen Belts of an extrasolar gas giant (and the dehydration plays a role in how they do hibernation). Basically, imagine tardigrades IN SPACE!

    There’s the interesting exchange in Usurper of the Sun* about a crewed trip to Mercury orbit:

    “The acute radiation would kill you even if the Builders did not.”

    “Acceptable. Where do I sign up?”

    Although this turns out to be overstated: the protagonist merely has to submit to regular cancer screening for the rest of her life.

    * One rarely sees a disclaimer like this in SF:

    While I tried to keep the science of space travel in the story as realistic as possible, I admit there are a few spots that require the readers to stretch their imaginations. One examples would be the accelerations and speeds achieved by the ships in the story, which are nearly impossible even for a nuclear-powered propulsion system.

    He’s talking about delta-vees in the tens of kilometers per second.

  19. Sue Lange says:

    Thanks for this:

    “Actually, their electronics are as vulnerable as our brains. And if they ever develop true awareness, whether we’re nice to them will be irrelevant — they’ll be true aliens with their own ways of thinking and reacting.”

  20. Athena says:

    Yes, people tend to think electronics are invulnerable — and that robots will be either angels or demons.

  21. Christopher Phoenix says:

    That’s a big misconception that I have noticed a LOT- that electronics are invulnerable to radiation. This faulty belief is often used to back up the idea that “mind uploading” is superior to using normal astronauts- the proponents claim the uploads would need no radiation shielding. This isn’t true- high energy cosmic rays would rip through their “DVD-sized spacecraft”, damaging and destroying components until all its information was lost or at least mangled.

    This is another reason why Charlie Stross’s supposed debunking of The Myth of the Starship fails to support its own conclusions, and in fact undermines them. Stross claims that we should drop the suffix “-ship” from all discussions of interstellar travel. He arrives at this conclusion by denying the feasibility of worldships, assuming that we will never have any greater sources of energy than we have today, believing fervently in the inevitability of mind uploading, and apparently thinking that Starwisp is the ONLY idea we have for sending a payload to another star.

    The “compact disk” sized spacecraft would, even if it worked, be degraded by cosmic rays- which are never once mentioned. They would, however, support the notion of “ship” since ship can have thick hull, CD cannot. This is in addition to the impossibility of mind uploading, at least in the form advocated by Stross- with all the “exporting” and “importing” of minds like a MP3 in Itunes. The final, biggest error I spotted, however, shows the utter lack of attention for detail transhumanists have- Stross neglected to think of how exactly a Starwisp carrying an AGI would SLOW DOWN once it approached another star- Starwisp is only a flyby probe, not a craft capable of rendezvous. Oops.

    All this does is prove to me still further that SF authors shouldn’t write anything about real science and engineering.

  22. Athena says:

    Yes, Stross reatreaded this business about the starship in the first 100 Year Starship Symposium. I left after about ten minutes of the SF author convo, the mutual backpatting was entering sugar coma territory.

  23. rocketsientist says:

    You are the best. I just had to say that. ^_^

  24. Athena says:

    Awww!! Thank you, dear Kathryn!