Expert: Mars Astronauts Would Lose Teeth

Ant wrote to us with a story on Discovery about the long term consequences of manned and "womanned" missions to Mars - lots of research about bone-weakening effects of zero G environments, with tooth loss high on the list.

Re:That's not an insurmountable obstacle

But how are you going to open bottles and tighten bolts on your way home? Teeth are much more mass/fuel effecient than spanners will ever be...

Oh, I'm sorry, I thought this was a Russian mission at first. Teaches me to not read the article...

All I want for christmas is my two front teeth

I say we get all the astronauts to smile for a group picture when they land on mars.

Re:Real Url - Still broken, Try this - no space

http://dsc.discovery.com/news/briefs/20010827/mars teeth.html [discovery.com]

I think the link is broken

It looks like the story link doesn't work. At least it didn't work for me. Here [discovery.com] is the one that worked for me.

Acceleration or Spinning, both are hard.

To give you some idea of how far we are from this. If you could afford the fuel to do 0.5 G to half way and then flip to slow down, the whole trip takes only 2.4 days at Martian closest approach. Ramp it up to 1 G and you get things down to 1.7 days.

Simulated gravity could be made this way but no engine design has fuel sufficiently light to make this even remotely possible with current technology.

As far as spinning. Acceleration = Radius * (angular frequency)^2. To get a good one G in a ship with a 5 meter radius, you'd have to spin it at 1.4 revolutions per second. Okay so make the ship bigger and aim for less gravity? 20 meters for 0.5 G still carries a rate of 0.49 rev. per sec. Spinning isn't generally a simple answer unless you are planning something that is monumentally huge. A station 2 km across can get to 0.5 G with one revolution about every 14 seconds. (If you feel like making the stretch to call that simple.)

Someone might point out that without air resistance or other interactions, getting and keeping a spin isn't the problem it would normally be. This is true, but if the object is small you get all kinds of wierd effects caused by the gradients in force. For instance a 1m tall person standing in that 5 m ship at 1G would have only 80% of the gravity at his feet acting on his head.

I will concede that getting such a ship spinning takes not unreasonable amounts of energy (considerably less than would presumably be spent getting it to Mars at a reasonable speed, and not a problem if you start the spin while in Earth orbit and fuel is plentiful), but then you pretty much have to go in a straight line along the axis, because you've just made the largest gyroscope man's ever seen, and turning the thing would be a bitch.

Some of the other problems would include getting in and out of such a ship (think floating through a hatch on the axis and then somehow matching rotation). Also anything on the outer wall would want horribly much to fly off. Large stresses would be involved in getting it spinning and holding it there. And last but not least on my short list, is that any propulsion system would carry both mass and angular momentum away from the ship affecting the rate of rotation.

Okay, so I've sat down and done the calculations. Sustained acceleration isn't likely to work any time soon. Rotation is technically possible, but certainly not easy given the kind of speed needed and presents serious technical issues to deal with the stresses, manuevering, getting in and out of the ship, etc.

Good luck NASA, I hope you figure something out in my lifetime.

Re:shoot for the moon

Why are we trying to colonize mars when we have the moon soclose? Think about the possibilities.. If raw materials such as iron where to be refined, the cost to transfer the materials would be cheaper because of the short distance.

Because the Moon, in some ways, is actually not closer to us at all, and there are a lot more things worth having on Mars when we get there.

Firstly, Mars has a day almost identical in length to Earth's. Why is this so important? Because it means you might be able to grow plants there by the natural light. Growing plants under artificial light is very inefficient - the only ones that we can afford to do so for are kind of illegal in many places :) You can't grow plants by natural light on the moon because the two-week night would kill most plants (let alone the problems of your greenhouse heating up to boiling point during the two-week day).

Secondly, Mars has almost certainly got a lot more water available than the Moon does. The moon has virtually no water available. You can't have a colony without a water supply :)

Thirdly, just because Mars is further away doesn't mean it's more difficult to get stuff to and from it. The travel time is an important issue for humans, but for cargo it often doesn't matter, and for cargo it takes *less* fuel to land stuff on Mars because you can use the Martian atmosphere to slow down when you get there, unlike the moon where you have to use more fuel slowing down. Going the other way, it's easier to get stuff off the Moon than Mars (because the moon has less gravity), but you can make rocket fuel for your rocket a lot more easily on Mars than you can on the Moon (because if you have water, you can use electrolysis to get hydrogen and oxygen - instant rocket fuel).

Finally, if you're going to run a self-sustaining colony which pays its own way, to pay for imports from Earth you need something you can export back. From what we know about the composition of the moon, we're fairly sure that there's not much there of value (except for Helium-3, which is a fuel that might be used in fusion power plants in the future but is very difficult to extract), but on Mars there's a distinct possibility of finding high-grade deposits of gold, platinum, and other commercially valuable metals. In addition, if we ever mine the asteroids (many of which are virtually pure precious metal and are thus incredibly valuable), it's much easier to supply the miners with food and supplies from Mars than from the Earth or Moon.

In any case, we're not really trying to colonize either yet. As to the interest in exploring Mars, we've been to the Moon and have a fairly good idea of what it's like. Mars is the next step along the line.

Even looking at it from a safety standpoint.. If something were to happen where an evacuation needed to take place, they are that much closer to home. I guess we are just trying to see how far humans can reach into space.

Re:shoot for the moon

if you're going to run a self-sustaining colony which pays its own way, to pay for imports from Earth you need something you can export back.

This is the major hazard of space colonization. You have to get money from it, if you want to pay it with corporate money. And you suggest raw materials!!! I firmly believe transport costs of pure platinum from Mars would be high enough to make extraction from sea water look dirt cheap. Recycling is another thing that will not let the prices go that high. Extraction of gold from used electronics will be cheaper than importing the stuff from Mars.

Information would be cheap to transport, so prodicung it on other planets would be better. For geological/planetological research, every planet will have it's own colony, if robots are not considered better.

However, I think Moon would be the prime place for some sciences: Astronomers would love the continuous two-week data set. Radio interference from Earth would be no problem on the backside of Moon. No atmosphere means all wavelengths (IR to gamma-rays) can be studied from the Moon. Lower gravity means that the telescopes can be made larger. Some deep craters near the Lunar poles are in permanent shadow, so they would be excellent places for far infrared astronomy, where detectors must be at milliKelvin temperatures. To have a 10-K heat sink nearby will make things very easy.

Hazardous biotech research could also be done and safely tested on the Moon. It would be much harder to kill billions of people by stupid accidents.

Another possibility of the Moon is to use coilgun-like launchers that would use solar power to accelerate the cargo. This would eliminate the need for chemical propellant and rockets. Estimated launch price: less than one dollar per kilogram! As launching from Earth will never be able to compete with this, manufacturing satellites etc. could be an interesting option.

Send John Glenn

He probably doesn't have any teeth left anyway.

Artificial Gravity?

What if they just created artificial gravity via centripetal force by simply rotating the craft about its axis on the way to Mars? I don't know the physics involved here, maybe it's just not possible to create enough gravity that way unless you have a spacecraft with a really big radius, such as the space station in 2001.

I'm sure that more-informed minds then mine have already considered this simple idea, I'm just wondering why it's not feasible.

If the manned Mars spacecraft wasn't big enough to create sufficient gravity that way, maybe they could just hire really fat astronauts, in order to make the most of the limited gravity. just kidding...

Re:Artificial Gravity?

It's quite possible. The trouble is that the smaller the "orbit", the faster you have to spin to get decent gravity, and you start getting rather disorienting side effects. However, what you do is get a big heavy piece of stuff (for instance, a spent upper stage of a rocket), a nice big strong (but actually not all that heavy) rope, and attach your Mars vehicle to that, and set the system spinning. If you make your rope reasonably long, the rotation can be nice and slow, and when you get to Mars you just cut the rope and let the useless spent upper stage go.

In Robert Zubrin's book The Case For Mars he proposes just such a system. I haven't checked the physics myself, but it's introductory college physics to do (in fact, I should probably grab my old physics book and do the math just to see if I still can :) )

30 Hertz vibrations

Just this morning I was reading issue 2303 of New Scientist and read an article that states that research has shown that the activity of standing on a vibrating platform moving at 30 hertz for 20 minutes a day has induced sheep to gain 35 % more bone mass within a year.

Trials have been started on elderly female patients with osteporosis and seem to be showing positive results.

Of course, 0G could make it difficult to stand *on* a vibrating platform, but these experiments must be able to teach reserachers something about ways to combat the problems. If tiny, high frequency strains can help improve bone growth then there must be other ways to induce those strains within a 0G environment.