Sleeping/Excercise Centrifuges, and Grasshopper Dinners?

[Vilkata]

An article I read over at New Scientist/Space made the claim humans aren't likely to ever conquer space because of the lack of gravity.

http://www.newscientist.com/article/...-frontier.html
"One of the first things to be affected is the heart, which shrinks by as much as a quarter after just one week in orbit." The article makes many other claims that seem fairly damning of humans ability to live in space.

A common idea is to build a centrifuge for artificial gravity, but people have noted that if this centrifuge was on the smaller scale, ala 2001 A Space Odyssey, then the apparent gravity experienced by your head would differ noticeably from your feet, and much discomfort would ensue. Well, what about not having to deal with walking around, or standing up? What if the only way you were supposed to experience the artificial gravity centrifuge was by laying on your back against the outer wall, limiting the felt difference in gravity?

What if it was only a sleeping/exercise centrifuge? Picture the carnival ride "The Gravitron". You could lay on the outer ring of the centrifuge, flat against the wall, with a weight lifting system equipped around you for your arms, legs, and abdominals. The centrifuge would spin up to an apparent 1G, and then you could work out against gravity and sleep in gravity. The difference between the gravity felt by your nose, and by the back of your head, can't be significant enough to cause discomfort. Because this would be a strictly sleeping/exercise centrifuge, it could be quite small I imagine.

It seems like you might even be able to spin it up to greater than 1G. If a lack of gravity decays bones & muscle, and gravity helps prevent this, perhaps additional gravity would help even more? This centrifuge would only help prevent muscle & bone loss 8 to 10 hours a day. But who knows, that could still be a huge life saver. And it could be built tomorrow, unlike the fancy space tether designs for total artificial gravity we haven't quite figured out yet.

Furthermore, wouldn't grasshoppers make a fantastic food source on a space station? Grass can grow quite fast. And grasshoppers are packed with nutrition. If we're going to have vegetable gardens for oxygen and fresh food on the moon or other outposts, we should think of grasshoppers as an easy and efficient way of getting our protein..

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[Bynaus]

The problem is, that the typical weightlessness problems (muscle & bone loss) are also experienced by people staying in bed all the time - therefore, just sleeping in a centrifuge will not help to counter these problems. It is the use of muscles, bones that prevents their decay - but you are not using them while sleeping.

[Vilkata]

What I meant was, if the only position you were supposed to occupy in the centrifuge was on your back against the far wall, you could do all forms of exercise, and sleep, in a simulated 1G or greater, in relative comfort, and the width of the centrifuge could be kept down to a minimum. Gravity while you exercise, and gravity while you sleep, seem like they are the easiest things to beat in this muscle/bone loss game. Total artificial gravity for the entire work environment does not seem possible with current technology. As stated, to walk around normally, the diameter of the centrifuge would have to be massive in order to have no felt difference between the gravity experience by your head, and the gravity experience by your feet.

[Antice]

That difference is not such a big deal really. People are capable of getting used to far more discomforting situation than that. There will be some individuals that are unable to adapt tho. though luck for them, but many may very well have no problems at all once they get used to it. The only surefire way to find out is to try it out for real.

[Bynaus]

I know what you meant, Vilkata. And for exercise, it might be worthwile to have such a centrifuge. But using it while sleeping will not help at all to counter the effects of weightlessness.

In the long run, I can imagine donut-shaped, inflatable (or expandable) habitats with diameters large enough to allow some artificial gravity without adding too much mass to the structure. I can also imagine that there will be some medical treatments against bone and muscle loss for missions in the near future.

[galacsi]

That difference is not such a big deal really. People are capable of getting used to far more discomforting situation than that. There will be some individuals that are unable to adapt tho. though luck for them, but many may very well have no problems at all once they get used to it. The only surefire way to find out is to try it out for real.

I completely agree , just think about what sea sickness , it did not prevent millions and millions of people to cross the seas and sailors to do their jobs. This argument is overrated and looks like a strawman to me.

[Bynaus]

Bone and muscle loss is a real problem that has repeatedly been confirmed by both American and Sowjet/Russian missions, and it is not just a question of adaptation like space sickness.

[Extravoice]

I've eaten grasshoppers. The legs got caught between my teeth.

Space travelers will need to take plenty of dental floss with them.

[Antice]

Bone and muscle loss is a real problem that has repeatedly been confirmed by both American and Sowjet/Russian missions, and it is not just a question of adaptation like space sickness.

Bone and muscle loss yes. but living in a centrifuge is not as big an issue as it is made up to be. it's not going to be any worse than any other kind of motion sickness. you do get used to it after a few days, just like sea sickness do pass once the body gets used to the motion.
The centrifuge need not have to be as big as a ferris wheel to do the trick. something much smaller will do nicely. as long as the floor area is large enough to allow for some good old fashioned exercise.
I reckon we could maybe get away with as little as a 10m diameter centrifuge. with just enough rotational speed to give approx 1g at knee height. That is approximately the same size as one of those carnival centrifuge rides btw. Smaller may also be feasible, but may not allow for having an actual running track for jogging. To combat bone loss it is good to do exercises that stimulate bone regeneration. This means doing stuff the same way one does them on earth. making a 10m diameter living module should not be too hard. altho it still is large enough to require it to be sent up as unpressurized pieces. that is. some welding required. the pressure hull itself need not rotate tho. it is enough to have a rotating track running on the inside of the pressure hull. this way we avoid some of the complexity issues with air tight rotational joints and stuff.

[newpapyrus]

To produce a 1G simulated gravity without the nausea of the Coriolis effect, requires rotating a crew habitat nearly one kilometer away from the radius, opposite an equally massed counter weight. However, if humans can adjust to lower levels of gravity, then the radius required from the rotating axis would be shorter. So if humans can adjust to the 1/6 gravity of the Moon then a rotating crew module would only have to be 170 meters from the rotating axis.

Instead of building a super titanic microgravity space station (a cheaper and smaller one would have been just fine), NASA should have launched a simple rotating space station to see how well humans adjust to various levels of simulated gravity. Such a station could have told us if the human body could adjust to Lunar or Martian levels of gravity or even lower or told us how much below Earth levels of gravity are required to maintain human health.

Marcel F. Williams

[IsaacKuo]

An article I read over at New Scientist/Space made the claim humans aren't likely to ever conquer space because of the lack of gravity.

http://www.newscientist.com/article/...-frontier.html

As the comments note, this is ridiculous bunk. Artificial gravity is the obvious solution; one efficient and simple configuration is a "barbell" rotating end-over-end with a living space on one end and a countermass on the other end. (The countermass may be anything from supplies to trash.)

Furthermore, wouldn't grasshoppers make a fantastic food source on a space station? Grass can grow quite fast. And grasshoppers are packed with nutrition. If we're going to have vegetable gardens for oxygen and fresh food on the moon or other outposts, we should think of grasshoppers as an easy and efficient way of getting our protein.

While grasshoppers may be more efficient than cows, they are LESS efficient than soybeans and other legumes. Unlike grasshoppers, legumes can be prepared into all sorts of popular tasty foods ranging from peanut butter to hummus to tofu.

Now, I know that not everyone likes tofu. But if the choice is between tofu and grasshoppers?

[Antice]

If the choice is between tofu and grasshoppers then grasshoppers are going to enter the menu easy if i'm on board.
Soy as protein replacement is just plain evil if you go by my taste buds. Besides. a mono-diet of soy means that you also get an overdose of phytoestrogens. That is not good in the long run. No matter how much you wish to eliminate meat from the human diet, you cannot do so without any morale repercussions amongst the crew. Soy is not an adequate replacement for meat on that level.
If you have enough space to grow enough green stuff to feed the crew then you do have enough space to have a couple of chickens or rabbits as well. never underestimate the morale boosting power of eggs and bunny stew. Besides these critters would eat surplus produce and parts of the product that is simply not human digestible without heavy processing. a bunny or a grasshopper for that matter is a decently efficient plant to protein conversion machine. and they take very little room to keep. for a spaceship in transit a farm does not make any sense however. since freeze dried foods are infinitely store-able.

And I'l state again. Coriolis forces is not an important factor when sizing a spinning hab. humans can get used to it. just like we get used to the floor constantly moving underneath us at sea. a 10m diameter centrifuge spinning fast enough to give 1 g would not be any worse than standing on the wall of the carnival ride mentioned up-thread. and very few people actually get sick from that ride despite the down vector shifting constantly due to the operator varying the rotation speed to make the ride more exciting.

[joema]

...Coriolis forces is not an important factor when sizing a spinning hab. humans can get used to it...

I wouldn't say it's NOT important, but there's evidence certain humans can adapt to high levels of Coriolis effect. The crew of a Mars mission would be very small and highly selected for various criteria, so adding one more selection criteria doesn't seem impossible. E.g, the Mercury astronauts couldn't be over 5 ft 11 inches tall. There were (and will be) adequate candidates to fill the needed pool.

Re building a short radius centrifuge within a vehicle for short-term daily conditioning, a rotating section for ISS was initially planned. However it was expensive and would have cause vibrations interfering with other microgravity research. During that period ISS itself was in peril of being cancelled. That module was scrapped in the interest of getting ISS flying: http://en.wikipedia.org/wiki/Centrif...dations_Module

However nobody knows exactly how much conditioning at what rotation rate and G force would be required for a mission of x duration.

Human sensitivity to Coriolis dizziness varies widely. Some studies indicate selected humans could permanently adapt to to 7.5 or even 10 rpm. For short-term conditioning, even 20 rpm might be tolerable for selected humans.

http://www.ncbi.nlm.nih.gov/sites/en...t=AbstractPlus
http://articles.adsabs.harvard.edu/c...IF&classic=YES

Initially there were plans to launch a Skylab B, and experimentally spin the whole thing at 4 rpm to produce roughly lunar gravity, about 0.18 g. Skylab B was never launched, so this wasn't done. Skylab wasn't designed to spin, but structural and control analysis indicated it might sustain 4 rpm for a limited period for experimental purposes.
http://en.wikipedia.org/wiki/Skylab_B
http://ntrs.nasa.gov/archive/nasa/ca...1979072679.pdf

We obviously have the technology to design a spinnable habitat or vehicle for artificial gravity. But it's more costly and complex than a non-spinning vehicle. If humans can adapt to zero G for long-duration missions, you don't need that cost and complexity. A key mission of ISS is figuring out whether humans can tolerate long duration zero G.

If the accumulating evidence indicates that's impossible, then artificial gravity (of some type) seems the most likely solution.

However there's a good argument it didn't take the immense investment of ISS to determine this, and the time and money would have been better spent *directly* engineering artificial gravity and other long-term spaceflight solutions.