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Robert M. Blevins

Banned

From: Seattle, Washington State, USA

Registered: 2005-05-04

Posts: 29

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Re: Artificial Gravity

If you have doubts about whether a spinning motion could simulate gravity, you should ask Neil Armstrong about what happened when his thruster controls got stuck open while on the Gemini 8 flight...

Oh, yeah...we have gravity now.

The cool he demonstrated under pressure during this very dangerous incident was a factor in NASA's decision to make him mission commander on Apollo 11.

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Don't give up reaching for the stars...
just build yourself a bigger ladder.

Shaun Barrett

Member

From: Cairns, Queensland, Australia

Registered: 2001-12-28

Posts: 2,843

Re: Artificial Gravity

RMB:-

If you have doubts about whether a spinning motion could simulate gravity ..

    No. I don't think any of us were in doubt.

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The word 'aerobics' came about when the gym instructors got together and said: If we're going to charge $10 an hour, we can't call it Jumping Up and Down.   - Rita Rudner

dicktice

Member

From: Nova Scotia, Canada

Registered: 2002-11-01

Posts: 1,764

Re: Artificial Gravity

It pays, sometimes, to look back at what was possible in an unencumbered spacestation interior, before the gageteers took over. Here is a quote I scrounged while Googling "Skylab."

Weightless recreation is a major feature of space colonies. Skylab was pretty big, big enough for gymnastics. None of the astronauts were particularly good gymnasts, but in 0g that's not really a problem. The Skylab home movies show three men running around the ~20 meter circumference of the station, going upside down, doing flips, hand springs, multiple-twists and all kinds of moves they would never try on Earth. One of the fun things about space colonization is that almost anyone, even those with fairly severe physical disabilities, will be able to do this.

I remember, back then, watching the crew members having fun, endlessly running around the inside circumference of the Skylab in nothing but shorts and shoes, working up a sweat practicing acrobatics-on-the-run. It's all there for the taking, by any of you adept at downloading the many movie clips of their activities.

My point: If a trace of gravity is sufficient to prevent the body from becoming a blob, as claimed a few posts back, that would explain why bedridden persons don't "self destruct," but only "go soft." If, as I believe, you regenerate your cells which have been stressed while you're awake, during slumber, weightless sleep should result in no deterioration.

So, why are't we including in our proposals, to combat muscle-loss and bone-deterioration in weightlessness on the voyage between Earth and Mars, the facilities onboard to enable such easily achieved activities as were possible on the first spacestation? In other words: Forget the experimental centrifuge beds, bungee cords, vacuum confinements and other horrors, as being wrongheaded, and simply provide an unimpeded section of the ship's circumference to allow running around in circles!

RobS

Banned

From: South Bend, IN

Registered: 2002-01-15

Posts: 1,701

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Re: Artificial Gravity

Consider, also, that running round and round an 8 meter diameter cylinder generated a huge difference of gravity between their heads and their feet, and it didn't bother them. This has been an argument on these forums against spinning small spacecraft to make gravity and it did them no harm.

I agree with GCN that there are potential problems, but there may be solutions. If the spin axis is pointed toward the sun, the antennas and solar panels go round and round and are always pointed sunward anyway. We already do that with spin-stabilized spacecraft.

And we can solve the tether problem if we send two vehicles to Mars docked nose to nose. The docking mechanism will have to be fairly strong, but that isn't a problem; after the vehicles dock together normally you bolt or latch them together inside the shirtsleeve environment (no space suits necessary), then you unbolt them before undocking them. The two vehicles could be two interplanetary transit habs, each designed for 3 or 4 persons (giving the mission a total capacity of 6-8) or the hab and a separate Mars descent vehicle. Such an arrangement gives you Apollo 13 style redundancy against accidents in one vehicle (especially if you split the hab into two smaller habs, which will increase mass somewhat, but will also increase safety). If both habs had lengths of 12 to 15 meters, spinning them together would give you Martian gravity at the lower level at about 4 rpm. NASA says astronauts can handle up to 6 rpm. I bet it really isn't a problem; for thousands of years sailors have adopted to rough seas without getting sea sick. But we will have to test something like this to be sure. Creating a gravitied environment has enormous advantages other than health ones; cooking is easier, eating is easier, washing self and clothes are easier, cleaning rooms is easier, making repairs is easier, etc.

Of course, the real issue is when things go wrong, not when they are normal.

As for Martian gravity being enough or not enough, as I have noted in other posts, the human body can accommodate quite a range of "gravities" already. Two years ago I weighed 234; I am now 205; if I get down to 180, where I'd like to be, I'll have lost about thirty percent of my body weight. No one doubts that my bones and heart can handle the changes fairly well. Our bodies have some flexibility in this regard. If 38% gravity is too low, walk around with fifty-pound weights attached to your belt or do jumping exercises (jumping takes as much energy and puts as much strain on muscles and bones on Mars as on the Earth; you just jump higher).

          -- RobS

clark

Member

Registered: 2001-09-20

Posts: 6,374

Re: Artificial Gravity

If there is a choice, choose gravity. We simply don't know enough, and artifical g resolves a whole host of biolgocail issues and questions. It automaticaly creates solutions for show-stopping questions.

Yes, it introduces new technological problems- but we be flexible in solving those problems. We're stuck with what we got in being human. Learn from our nature- if our house is cold, we make it warmer- we don't grow new fur.

Forget cable and go with integrated structures. Instead of living in a artifical-g environment for the entire trip, minimize zero-g time. You don't need much space when you sleep- builf a centrifuge-tomb where astronauts can receive 1+ g while they sleep. Think of it as "training" for free (in addition to their normal physical regime).

Anyway, CEV spiral 5 calls for a 90 day human mars mission. Not 6 months.

dicktice

Member

From: Nova Scotia, Canada

Registered: 2002-11-01

Posts: 1,764

Re: Artificial Gravity

When I rested my case (for running around in circles, as a means of avoiding all that spinning and tethering hoopla) I didn't expect it to just die. Maybe I'm simple minded, but simple is the way to go, first time out. So, an I wrong, or what?

clark

Member

Registered: 2001-09-20

Posts: 6,374

Re: Artificial Gravity

Dicktice, running in circles is not the answer. We want to send people, not lab rats. 6 months of running in circles? Come on...  :laugh:

dicktice

Member

From: Nova Scotia, Canada

Registered: 2002-11-01

Posts: 1,764

Re: Artificial Gravity

Gymnastics, remember? And two or three at a time. It's fun! Take a look at those Skylab film clips, then come back and we'll discuss it.

clark

Member

Registered: 2001-09-20

Posts: 6,374

Re: Artificial Gravity

You mean this:

http://www.firstscience.com/site/video/ … /part3.asp   

Romantic, but not practical. 

dicktice

Member

From: Nova Scotia, Canada

Registered: 2002-11-01

Posts: 1,764

Re: Artificial Gravity

No, that's not the one . . . and I can't locate the list of film clips now, myself. Here's an excerpt from Skylab's history, which gives a hint.

Skylab provided more roomy accomodations for its guests than any space station to date. Even the International Space Station will not have such a large open volume as Skylab's orbital workshop. Skylab was fitted with several decks, and amenities which included an exercise bike and shower. As big as Skylab was, the interior of the shuttle's External Tank is much bigger!
Although in a weightless environment, the crew of Skylab at one point briefly demonstrated the promise of so-called spin gravity (depicted in the movie 2001: A Space Odyssey) when they ran around the inner circumference of the main workshop. Their motions induced artificial "gravity" forces which allowed them to keep traction on the inner wall surface, despite being weightless. Use of spin gravity is often suggested for ET space stations.

Unless someone shoots this idea down, as a first approximation to artificial gravity for maintaining muscle and bone mass, en route, I'll continue to try locating those film clips.
Your conclusion, by the way, that circumferential running is "romantic but impractical," doesn't make any sense to me. Please explain.

clark

Member

Registered: 2001-09-20

Posts: 6,374

Re: Artificial Gravity

How long are they going to run? An hour? Two? Three? Eight?

Will they do all of their duties and chores while running around in circles?

It's a romantic idea to think that having a bit of fun for a couple of minutes will solve this problem. It won't.

They will need sustained exsposure to something that mimics the effects of normal gravity.

dicktice

Member

From: Nova Scotia, Canada

Registered: 2002-11-01

Posts: 1,764

Re: Artificial Gravity

Lying supine in bed, on Earth, is detrimental to muscles and bones. Vertically oriented, on Earth, without excercise, is also detrimental. Running around the inner circumference of a sufficiently large diameter pressure hull will provide both gravity and excercise at the same time, without a lot of specialized, individual gagetry. The ability to run and jump and generally innovate weightless gymastics sounds like fun to me--duration governed by lactic acid accumulation causing pain in the arm as well as the leg muscles, and bone-mass attrition certainly reduced. And then, to relax in weightlessness must provide the best possible sleep, during which the body repairs the muscular damage done to it by the exercise--same as on Earth. A flat centrifuge at one end of the compartment could be spun-up, for experiments during the trip, such as germinating seeds with roots and shoots growing in opposit directions, adjunct to centrifugal running, the possibilities are endless.

Fledi

Member

From: in my own little world (no,

Registered: 2003-09-14

Posts: 325

Re: Artificial Gravity

Sounds like fun. Hohmann even described a way of steering a spaceship by climbing around in circles along various axis of the ship.

SpaceNut

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From: New Hampshire

Registered: 2004-07-22

Posts: 29,433

Re: Artificial Gravity

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