Does artificial gravity improve the reliability of life-support systems?

[ScallopPotato]

I don't think that gravity inherently makes any of the systems more reliable, but there probably are more tried and true systems that rely on gravity than ones that were built around micro-g.

On the thread about the proposed 2021 Venus-Mars flyby a la Apollo 8, one of the better arguments against the mission was life support reliability issues. AFAIR, the ISS is going to test a self-sustaining life support system (ECLSS) later this decade, and it's not certain that the system will be ready to use on a different spacecraft by 2021.

Apparently one of the possible designs in NASA's latest design proposal for a manned mars mission would use artificial gravity in the crew transfer vehicle during transit. Having a space toilet that stays up for the entire 2-3 year mission or at least is easily repairable would be very important, along with all the other life support systems. And of course the astronauts will have gravity when they're on the surface of mars.

While having artificial gravity would likely mean fluids would have to be pushed "up" and "down" to work right, the health benefits and possibly reliability benefits greatly outweigh the costs.

[Roastduck]

I think the benefits of artificial gravity are as much physical as psychological. Having to hook a vacuum to your nether parts would probably get tiring after about 6 months, let alone 2-3 years, so making the spacecraft feel as much like home as possible is definitely worth looking into.

[Nibb31]

"I think" is meaningless. We don't know what the benefits of partial or full artificial gravity are because it has never been studied.

We need years of research on the subject before we ever reach a TRL that is compatible with manned interplanetary travel, which means that either we wait a few more decades to do the proper research and development, or that the first manned expeditions will have to go without artificial gravity.

[Roastduck]

"I think," for us, is not meaningless, since none of us are going into space any time soon, and most, if not all of us aren't aerospace engineers. Reading reports and and reaching our own conclusions about the options is pretty much all we can do. And I know I, personally, would prefer not having to attach a vacuum hose to my butt every morning for 2-3 years, so I can't imagine astronauts feel any different. They might tolerate it, but they would most definitely take an alternative if one was available.

[vger]

For me, physical health is a crucial aspect of life-support. I don't just mean being able to breathe for instance, but also the health of the lungs that are doing the breathing. Just having gravity present when you're not doing ANYTHING, gives your body more exercise than it would have in the absence of gravity. This helps keep everything in the body running smoothly. From that standpoint, gravity already improves life support. As for whether or not the devices that generate life support would fare better with gravity? I don't see why really.

With the example of toilets, a pump system will be needed whether there is gravity or not, so the toilet stands just as much of a chance at breaking. But it would indeed be more comfortable.

[architeuthis]

For me, physical health is a crucial aspect of life-support. I don't just mean being able to breathe for instance, but also the health of the lungs that are doing the breathing. Just having gravity present when you're not doing ANYTHING, gives your body more exercise than it would have in the absence of gravity. This helps keep everything in the body running smoothly. From that standpoint, gravity already improves life support.

I agree, but artificial gravity is not the same as real gravity. There are some pretty substantial physical differences that play directly into the psychological heath of astronauts who might use such a system.

[SargeRho]

You can't tell the difference between real and artificial gravity, unless it's generated by a small centrifuge.

[architeuthis]

Practically speaking most hypothetical space station artificial gravity systems are effectively small centrifuges.

Unless the angular velocity is low or the radius is very large Coriolis acceleration will make balance feel odd, especially for rapid movements that aren't parallel to the spin axis. The otoliths and semicircular canals in our ears basically measure linear and angular acceleration, our eyes give us a measure of attitude and orientation. If our brain get conflicting information from these different sensors it can be extremely disorienting. For instance moving your head around in a centrifuge can make your eyes hunt or spin (like after spinning yourself as a kid). It can also cause stationary objects to appear to be in motion. Also unless floors are machined to be curved to the radius of rotation then there will be an optical illusion of the floors appearing to be slanted or inclined haunted house style. We don't really know about long term psychological effects of these kinds of things, so artificial g systems will have to be carefully designed to mitigate this stuff.

Edited March 17, 2014 by architeuthis

[vger]

Unless the angular velocity is low or the radius is very large Coriolis acceleration will make balance feel odd, especially for rapid movements that aren't parallel to the spin axis. The otoliths and semicircular canals in our ears basically measure linear and angular acceleration, our eyes give us a measure of attitude and orientation. If our brain get conflicting information from these different sensors it can be extremely disorienting. For instance moving your head around in a centrifuge can make your eyes hunt or spin (like after spinning yourself as a kid). It can also cause stationary objects to appear to be in motion. Also unless floors are machined to be curved to the radius of rotation then there will be an optical illusion of height of inclination. We don't really know about long term psychological effects of these kinds of things, so artificial g systems will have to be carefully designed to mitigate this stuff.

I doubt it's anything the brain can't adjust itself to. Though you'd need some time to readjust when leaving the centrifuge.

You can get a similar phenomenon from running on a treadmill. Technically you're not even going anywhere. There's no actual acceleration for your body to experience. And yet after stepping off of it, you'll experience the illusion of moving forward. It's the after-effects of your mind compensating for the bizarre environment of the moving treadmill.

There are perhaps better examples of this though. One is in our own eyes. We actually see everything upside down. We're born this way, but our brains learn to adapt and artificially invert the image for us. Experiments have been done wearing glasses that invert the image an additional time. After a certain amount of time, the brain would again adapt and flip the image for the wearer. Then removing the glasses would require another waiting period for the brain to adjust.

The mind is HIGHLY adaptive. I don't think it's a question of "could we handle it?." The bigger question is how much time is needed to adjust between the two extremes.

[SargeRho]

No, they are centrifuges. Not neccesarily small centrifuges. I think 20ish meters was the diameter of a centrifuge producing 1g without dethroning the vomit comet.

If you have a ring station that's 1.5km in diameter, you only have to spin it once a minute or so, and the inhabitants wouldn't feel weird at all.

Building such a ring is not too hard since building tensile spokes is easier than building a 1.5km tower. Would require asteroid mining ofc.

[architeuthis]

The mind is HIGHLY adaptive. I don't think it's a question of "could we handle it?." The bigger question is how much time is needed to adjust between the two extremes.

Some things we can adjust to, other things perhaps not. Without actual long term study it is difficult to know.

Building such a ring is not too hard since building tensile spokes is easier than building a 1.5km tower.

Sure that would be fine, but building 1.5km-radius torus stations doesn't seem to be in humanity's near term forecast. Unfortunately:(

No, they are centrifuges. Not neccesarily small centrifuges. I think 20ish meters was the diameter of a centrifuge producing 1g without dethroning the vomit comet

IRC 2 RPM is optimal for human comfort and 6 RPM is the lower limit of what most people can tolerate. For 1G of acceleration and optimal comfort you would need to have a radius of 245 m. If you settled for the lower limit you would need about a 27 m radius. Since even 27 meters is pretty damn big as far as any human space structures go, I call anything smaller than than this "a small centrifuge".

Edited March 17, 2014 by architeuthis

[Aghanim]

Without actual long-term study...

We doesn't have the TRL yet...

Its unproven...

Because of this, why no one go up there, and attach a centrifuge module so we could prove that this is possible? If we doesn't prove it, it won't magically prove itself

[ScallopPotato]

Well it turns out the image link doesn't work. It's under William Black.

Space donuts really won't be an issue because the entire spacecraft will be a centrifuge, spinning in a way that produces the artificial gravity. The habitation module would probably be two or more "floors" with a ladder connecting them. The command area and storm cellar would be located closer to center of the ship.

Here's a video of the constellation program mars mission, where the crew vehicle is the artificial gravity ship I mentioned.

[Xenotheos]

Simulating 1g may be ideal, but it doesn't seem entirely necessary for anything but the most long term of missions. I would think 0.5g would be a much more cost effective goal and would be enough artificial gravity to significantly improve sustained space travel.

As for spinning the entire ship, what is the solution for solar panels and communications?

[SargeRho]

For communications you can mount the dish at the center of the ship, point it at Earth, and then start the spinning. If you have a bimodal NTR you don't need solar pannels.

[Camacha]

It occurred to me some time ago that a wheel is actually not necessary to produce artificial gravity. You could build a crew compartment on one end of a long tether, and an equipment compartment on another. Spin those two against eachother in a dumbbell configuration and you can build a 1 g environment with relative ease.

I do realise that this will pose some problems when it comes to balancing things out, propulsion and a couple of other subjects, but that should not be impossibly complicated - especially as it means that you can build a full on gravity environment with just a couple of easily launched segments. I feel the positive effects that the gravity environment will have on the health of the cosmonauts is well worth the trouble, as they are expected to function in such an environment at Mars and will have little time or opportunity to recover.

Edited March 18, 2014 by Camacha

[SargeRho]

Then you'd basically have two space stations hanging from one another. Mars Direct would use something like that, by using the spent upper stage of the booster rocket as counterweight, on the crewed flight.

[KerbMav]

We don't know what the benefits of partial or full artificial gravity are because it has never been studied.

What do you think the guys in the MIR, ISS and all other adventures were doint up there all the time?

The effects of zero/micro-gravity are very well known today and we have every reason to find remedies/a way to create artificial gravity to keep our spacers healthy - they wont do nothing even in Du... Mars' low gravity environment after their bones are half gone and their muscles atrophied.

Some gravity is always better than none at all and as others already wrote, the brain can adept to a lot of input - some people will stay seasick for an entire voyage, but most will adept - not everyone is cut out for every adventure (equally well).

Having to hook a vacuum to your nether parts would probably get tiring after about 6 months, let alone 2-3 years

Well, as soon as you leave the US youtube will spam you with "not available in your region" messages and hulu will also quit on you - so, after a few months that vacuum thing might be the only entertainment ...

(For real: The space toilet is not to make skin contact, it is not like you imagine it right now - I will never find that link now, but just trust me here. )

[Winter Man]

Simulating 1g may be ideal, but it doesn't seem entirely necessary for anything but the most long term of missions. I would think 0.5g would be a much more cost effective goal and would be enough artificial gravity to significantly improve sustained space travel.

This right here. You don't need a full g, because when you get to Mars you're only going to have 0.36g to play with anyway. I mean, you could go the Ares 1 route and start at 1g and slowing down along the trip, but there's little point.

edit: While I'm thinking about the Ares 1, those gravity rings were made of 8 spent Shuttle fuel tanks each. Those things have about 25T dry mass, so we could realistically make a 100m ring with only 4 Falcon Heavy launches.

Edited March 18, 2014 by Winter Man

[FREEFALL1984]

It occurred to me some time ago that a wheel is actually not necessary to produce artificial gravity. You could build a crew compartment on one end of a long tether, and an equipment compartment on another. Spin those two against eachother in a dumbbell configuration and you can build a 1 g environment with relative ease.

I do realise that this will pose some problems when it comes to balancing things out, propulsion and a couple of other subjects, but that should not be impossibly complicated - especially as it means that you can build a full on gravity environment with just a couple of easily launched segments. I feel the positive effects that the gravity environment will have on the health of the cosmonauts is well worth the trouble, as they are expected to function in such an environment at Mars and will have little time or opportunity to recover.

The system could be docked in orbit, have its cable attached, to its counterpart, one section could consist of all the none critical hardware such as the lander, communications array, solar array, battery backup and enough fuel/water for the journey, the other segment could contain the living quarters, the command module and lab. Once the vessels have performed the transfer burn, they are undocked and using RCS the cable is loaded and the rotation begins. and mid course corrections could be performed by RCS over several hours by the computer. All the fuel lines (for the RCS) water lines and communication lines could be incorporated into the cable. The cable itself would only be carrying about 1000Kn of force max, which is well within the realms of current industrial hardware. Alternatively the fuel and water supplies as well as the battery backup could be store midway along the cable, in order to remove load from the cable itself, and the mission payload and living quarters could then balance each other out

[FREEFALL1984]

No, they are centrifuges. Not neccesarily small centrifuges. I think 20ish meters was the diameter of a centrifuge producing 1g without dethroning the vomit comet.

If you have a ring station that's 1.5km in diameter, you only have to spin it once a minute or so, and the inhabitants wouldn't feel weird at all.

Building such a ring is not too hard since building tensile spokes is easier than building a 1.5km tower. Would require asteroid mining ofc.

It wouldn't need spokes, the tensile strength could be allowed in the actual ring itself, providing the weight was evenly distributed, it would holed its own structure in the same way a compressed air cylinder does.

[Seret]

AFAIR, the ISS is going to test a self-sustaining life support system (ECLSS) later this decade, and it's not certain that the system will be ready to use on a different spacecraft by 2021.

Not self-sustaining I'm afraid. All the systems looking to be flown in the next few years are open loop, like what you currently have on the ISS.

[SargeRho]

It wouldn't need spokes, the tensile strength could be allowed in the actual ring itself, providing the weight was evenly distributed, it would holed its own structure in the same way a compressed air cylinder does.

You want to have a part of the station that doesn't rotate however, so that spacecraft can dock to it. The best place to put it is in the center of the wheel, so the ring station will have to be a wheel station.

[magnemoe]

The system could be docked in orbit, have its cable attached, to its counterpart, one section could consist of all the none critical hardware such as the lander, communications array, solar array, battery backup and enough fuel/water for the journey, the other segment could contain the living quarters, the command module and lab. Once the vessels have performed the transfer burn, they are undocked and using RCS the cable is loaded and the rotation begins. and mid course corrections could be performed by RCS over several hours by the computer. All the fuel lines (for the RCS) water lines and communication lines could be incorporated into the cable. The cable itself would only be carrying about 1000Kn of force max, which is well within the realms of current industrial hardware. Alternatively the fuel and water supplies as well as the battery backup could be store midway along the cable, in order to remove load from the cable itself, and the mission payload and living quarters could then balance each other out

My thought too, however I don't think you would transfer anything other than data over it, if you have to transfer stuff wind in and dock.

This would be pretty easy to test in orbit, using an small space station with a Soyuz or dragon pod as counterweight.

[ScallopPotato]

Speaking of life support systems, does anyone know what's the world's most reliable toliet that uses little to no water? I know the first space toliet on the ISS lasted 7 years (which is long enough for one mars mission lol). I imagine toilets on naval ships are very reliable, but a mars craft or base isn't going to have an ocean to do the flushing.