posted
I had a quick question I wished to pose for those who may know off the top of their heads. I didn't really know which forum this might fall under, so if a mod wants to move this, please do if it might get more attention.
This question came from reading an article in a past Popular Science magazine ["Deep Space Traveller" - July 1998]. In the article it mentions the speed of the Deep Space Probe could reach 3,600 meters per second after a year of acceleration. My question is this: What is the maximum speed a human could travel in space and tolerate safely? And is there anything in the works - short of the magical "intertial dampener" of Star Trek - that could lessen the centripetal forces inside a space-going vehicle?
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Registered: Jan 2001
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posted
Loaded question, in a way. If there is proper radiation shielding and so forth, presumably there isn't anything that would keep a person from attaining 99.999999% the speed of light.
WITHOUT said shielding you've got a roasted hairless ape due to doppler shifts.
And of course, the logistics of getting you going that fast are pretty complex. If you can make those survivable, hey, the stars the limit.
Registered: Jan 2001
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Assuming that we're talking about gradual acceleration, too. Going 0-lightspeed in 12 flat is probably bullshit.
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I believe astronauts and fighter pilots are trained up to about 9 g, which is a lot. I'd weigh about 1,412 pounds under such acceleration. This would be uncomfortable, but not fatal.
G forces are not dependant on velocity, but acceleration. Let's say we have a magic drive, which makes our spacecraft go whatever velocity we choose without accelerating to get there. Our g force will remain zero throughout the flight, even when the ship is traveling at the speed of light. A g force is what you feel when you slam on the brakes at a red light, or go sailing through the curves of a speedy rollercoaster.
Assuming the probe accelerates at a constant rate for an entire year (or 31,536,000 seconds) to reach a speed of 3,600 m/s, its average acceleration was just .000114 m/s^2. That's about 85,000 times less powerful than the pull of gravity on you right now.
(Keep in mind that it is HIGHLY likely my numbers are so totally messed up as to have no connection to your question, or any other question ever asked on this planet.)
Anyway, Air Force experiments established the maximum non-serious-to-fatal tolerance of the human body to be 10,000 pounds for a quarter of a second or less.
There exists really only one way to increase the body's ability to withstand high g forces, and that's the swanky g force suit fighter pilots wear. It's like a wearable balloon that inflates around the legs and torso to force blood back up into the brain, to prevent blacking out.
Some science fiction writers have suggested immersing future astronauts in a breathable liquid, like in The Abyss, which would allow them to withstand greater accelerations. This has the downside of being rather unpleasant. The ability to cancel out inertia would represent a fundamental break with current physics, and would be Very Interesting, to say the least.
Having said that, there's really not much need to worry about high accelerations, unless you absolutely need to get to some relatively nearby location in a hurry. Assuming you had an engine that could constantly accelerate at one g (giving you the happy side effect of perfectly normal artificial gravity aboard), a spacecraft could get up to .9 c in a little less than a year.
Registered: Mar 1999
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...On the other hand, Stephen H. Dole's book "Habitable Planets for Man" -- a product of the Rand Corporation -- discusses at length the effects of gravity on the human body.
It's been a while since I read it, but as I recall, the book indicates that while the human body can tolerate short periods of high G forces, over prolonged periods it would likely be extremely hazardous. The book postulates that 1.5 Gs is about the top toleratable gravity that humans could withstand if they were up and moving about (say on a prolonged space voyage or living on a planet larger than Earth). Above that, the risk of cardiovascular failure shoots way up, as does the chance of accidental and perhaps fatal injury from something as simple as falling down.
This book was also a source used by Okuda and Sternback in creating the internal TNG Writers Technical Guide. In fact, at least one of the tables is copied right out of it! The book's been out of print forever (I had to get it through an interlibrary loan from the Univeristy of Nevada Las Vegas), but it's a good primer on the various criteria for what factors would influence habitability of planets and what stars would and would not be likely candidates for finding them. Some of the calculations make for dry reading, and a few of the suppositions about planetary formation are a tad out of date (thanks, Hubble!) but much of the rest of it is pretty darned interesting.
-------------------- "Well, I mean, it's generally understood that, of all of the people in the world, Mike Nelson is the best." -- ULTRA MAGNUS, steadfast in curmudgeon
Registered: Feb 2001
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posted
Actually, a G-suit only adds about 1g to what a trained person can normally stand. The main way they survive the extra g-loading is by doing the "Anti-G Straining Manuver," or AGSM in pilot-speak. It's basically done by flexing all your musscles from the stomach down and then using short and strong exhales and inhales. It sounds weird, and isn't too fun to do. It forces all the blood back up to your head and keeps you from blacking out. But I can only do it for short periods of time before I get sick of it. That's why I fly the heavies.
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posted
Well, I don't believe I made any claims about the capabilities of said suits, simply that they were the only mechanical inertia-fighter around.
Registered: Mar 1999
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I find it rather amusing that the AGSM is the same technique used in the Kama Sutra and other "aphorisms of love" books to pevent a man from ejaculating prematurly - or even at all. Thus increasing the length of time in a given sexual encounter.
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