Expert: Mars Astronauts Would Lose Teeth 323
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.
Real Url (Score:2, Informative)
http://dsc.discovery.com/news/briefs/20010827/m
Do people read the bit which says "Check URLS" anymore?
Talez
Re:Real Url - Still broken, Try this - no space (Score:4, Informative)
Re:Gravity == Acceleration? (Score:2, Informative)
There are two good alternatives, though, which have been tossed around, and have the same effect, though with very little fuel use. One is to send a cylindrical ship, and spin it about it's axis, so that there is a force pushing the astronauts to the outside walls. Like in 2001.
That works, but it creates some weird design problems, as far as headroom and living on the walls.
The other option is to let out a tether with a countermass on the end of it, and then spin around a central point on the tether. With a big enough countermass, or a long enough tether, this works really well, and it's comfortable for the astronauts, as they can stay oriented to the 'floor' of their ship.
There was originally a plan to put something necessary at the other end of the tether, like fuel for the return trip or something, but it turns out to be much more efficient if you can just put something disposable on it (like one of those big boosters you used to leave Earth). That way you can just pop a bolt when you get to Mars, and don't have to worry about the tether snagging when you try to reel it back in.
A book that talks a lot about this is Robert Zubrin's "The Case for Mars". He's the president of the Mars Society, and is pretty knowledgeable about this stuff. I highly recommend the book to anyone interested in some of the design challenges, and why we can beat them.
30 Hertz vibrations (Score:5, Informative)
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. (Score:5, Informative)
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:Artificial Gravity? (Score:3, Informative)
A possible solution would be to have a nuclear reactor and use superheated water or a gass of some sort as fuel. In this way we get very high acceleration with relatively little "reactive mass".
If we had enough delta-v to do this, we could get to Mars in less than a week, and the problem wouldn't exist.
It turns out that nuclear power doesn't help us do this.
If we're using a nuclear core to heat fuel directly (as with the NERVA project), we get efficiency comparable to a chemical rocket, because our core (and thus exhaust) temperature can't be greater than the core materials can handle without degrading.
If we're using a nuclear core to generate electricity to power an ion drive or a plasma drive or another class of electromagnetic drive, we have nice delta-v, but very low acceleration, which doesn't help either the bone problem or our total travel time (if we're just going to mars; it would help for destinations farther away).
Other styles of nuclear drive have similar problems. They're great for long-haul trips, but won't give high acceleration and high delta-v at the same time.
Fusion drives won't exist for a while, so they're not a solution candidate yet.
Re:ways to combat body atrophy (Score:1, Informative)
Regarding your question, bones respond to the demands placed upon them, much like muscle tissue. Repeated stress causes growth and increased strength in both tissues. The article is complete wrong -- the mechanism most certainly does NOT "shut down," it's just not utilized by the typical sedentary 70 year old woman. Same goes for astronauts -- the bones are called upon to support weight, therefore they atrophy. There are countless studies which show that bone density can be increased at any age through moderate exercise and weight training. In, or out of a gravitational field.
The author must have slept through HS Biology class.
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Spaz!