January 27, 2014
We Aren't Designed For Zero Gravity

A good science article by Kenneth Chang in the Gray Lady is worth a read: Beings Not Made for Space.

HOUSTON — In space, heads swell.

A typical human being is about 60 percent water, and in the free fall of space, the body’s fluids float upward, into the chest and the head. Legs atrophy, faces puff, and pressure inside the skull rises.

Yes, we are not designed for zero-G. We also aren't designed for radiation and lower gravity (let alone the lack of air) on the Moon or Mars.

We aren't biologically ready for space. Humans need to be genetically reengineered to be able to adapt well to living off this Earth. Even on this Earth only a few populations (Tibetans, a subset of Ethiopians, and some Andes Amerinds) are adapted to high altitude and they differ in their degree of adaptation. I'd take the Tibetan genetic adaptations if I had a choice and needed to live in thin air.

We will need to look for genetic adaptions to extreme conditions found in other species to find ways to adapt ourselves to Mars or the Moon. How to handle more radiation? How to be able to store enough oxygen to let us survive a breech of an enclosed habitat for long enough to get into space suits? We need genetic solutions for these and other problems.

Share |      Randall Parker, 2014 January 27 09:36 PM 

David Friedman said at January 28, 2014 12:08 AM:

The solutions don't all have to be genetic. I've seen a description of a nanotech substitute for a red blood cell, in effect a miniature oxygen tank. Replace some of your red blood cells with these and, when you have a heart attack, you call up the doctor and make sure he has an opening sometime in the next few hours--until which you are surviving on stored oxygen.

Might be an easier solution.

Brett Bellmore said at January 28, 2014 3:13 AM:

I agree with the goal, but achieving genuine zero G tolerance might be a real challenge, we've evolved in 1 g from, likely, our abiotic origins. Things start malfunctioning even at the cellular level, which came as a real shock to me. (Who'd have thought something as small as a single cell could even detect a measely 1 g, let alone rely on it?)

The optimistic scenario, I think, is Niven's, where the people could live in zero g, but women had to move to a rotating habitat for the duration of their pregnancies.

Wolf-Dog said at January 28, 2014 6:51 PM:

Space ships can always use centrifugal forces to provide artificial gravity, but the more serious problem is space radiation. The latter problem can be solved by genetic engineering: many insects such as cockroaches are immune to radiation, but this would also change the mental character of humans as well. It is not just the cells, but also the thought process and feelings that will change as a function of genetic engineering. The latter price might be too high. On the other hand, if the space ship is big, it can be protected from space radiation by making the walls very thick and full of water.



But the only restriction is the thickness of the wall of water or rock that will be used as shield on the space ship. If the ship is big, then there is no question that several meters of rock or plastic can be accommodated as shield.

In any case, any serious space exploration will involve powerful new propulsion systems including fusion reactors, and the space ship will be very big if it will contain astronauts. And so far nuclear science is still not fully developed, maybe there will be totally new forms of nuclear energy that extract a lot more energy from mass than the current maximum of 1 % of the mass from the traditional deuterium-tritium combinations.

k.t.kendrick said at January 29, 2014 4:19 AM:

We are not adapted live in water.That's why we invented aqualungs.We are not adapted to live in sub zero evironments.That's why we invented coats and stoves.Incidently,In regard to space colonies,Visualize a cylinder 1000 miles long,1000 miles in diameter.If the outer rim has 10 levels 1 mile in height,the people living there were given 20 acres of living space do you know how many people such a platform would support?1 billion.

Jay Banks said at January 29, 2014 8:15 AM:

I agree with the comment from k.t.kendrick: it is in our most genuine nature to push ourselves into hostile environment and do the stuff we are now supposed to do. Sure we can find a way to adapt to space, maybe even without having to modify our genome (which would, IMO, be politically unbearable and such meaningless obstacles are usually the hardest to deal with). As the owner of the Jurassic Park John Hammond said: Life will find its way!

Marcel Williams said at January 29, 2014 6:45 PM:

If you travel through interplanetary space for three years or less, then your space ship is going to require at least 50 centimeters of water in order to reduce your lifetime exposure to cosmic radiation to about 60 to 70 Rem. Lifetime exposure for young women is about 100 Rem if they want to minimize their increased chances of getting cancer to just 3%.

If you're on a space station located at the Earth Moon Lagrange points or in orbit around Mars then you're probably going to need more effective shielding if you're going to be there for several years. 50 centimeters of iron around a habitat would reduce radiation exposure below 5 Rem annually (the limit for radiation workers on Earth). That's pretty heavy but doable.

Of course, on the surface of the Moon and Mars, you have unlimited access to mass shielding from the surrounding regolith. Just two meters of dirt surrounding your habitat would be enough to reduce your exposure to cosmic radiation below the limit of radiation workers on Earth. But you could easily increase that to levels normally experienced by humans on Earth by simply adding on more dirt.

Marcel F. Williams

Randall Parker said at January 29, 2014 8:23 PM:


We still do not live in water. We just visit it. The inconveniences and risks are too great. Also, go down deep in water. What happens? Your brain slows way down. Our tools for adaptation water are still pretty weak. Why? We weren't designed for it. The fixes we need would have to be done to our metabolism.

Subzero enviromments: really unfun and people usually do not spend much time in Alaska's northern coast unless they are getting paid big bucks by oil companies.

Space colonies: As Wolf-Dog points out we'd still face a problem from radiation. Also, spinning tubes are orders of magnitude more prone to failure than a big planet. Dangerous.

David Friedman,

Any solutions to outer space living that are not genetic engineering that would work would involve nanotech engineering. Either way we are talking about radical methods to change human metabolism.

Randall Parker said at February 1, 2014 8:33 AM:

Hi Marcel,

Thanks for the numbers. 50 centimeters of iron: that is 20 inches. The energy costs of putting that much iron into orbit would be absolutely huge. Radiation-safe orbital habitats seem far more energy expensive than a Moon base in terms of getting radiation levels down.

The big upside of a really big spinning orbital habitat wold be sufficient gravity. But the costs of construction using materials boosted up from Earth seem orders of magnitude too expensive. Given technologies we'll have 20 years hence could we use nuclear-powered robot ships to bring the materials from asteroids? Even if we did the time to get to asteroids and then gradually move them to Earth's orbit would be many years.

The Moon seems like the best first bet for getting people living for a sustained period off of Earth.

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