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.

Comments

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

[hillct]

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

30 Hertz vibrations

[Ratface]

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.

Acceleration or Spinning, both are hard.

[dragons_flight]

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.