Why artificial gravity?

[savuporo]

The real problem is that we dont know the effects of spin gravity at all.
Effects of prolonged micro-g are well quantified, we have no data on what spin G does to humans over a prolonged period. Trying it out for the first time on a martian sortie with no way to turn back would be a Bad Idea - maybe they will all co crazy from prolonged sea sickness or something.

Engineering related effects on mechanisms etc are much easier to test and quantify, but even that might have some hidden risks.

This is what OCT technology roadmap says on the subject

Artificial-Gravity Systems (TA06, TA07)

Artificial Gravity spacecraft has been researched for years as an option for reducing the detrimental effects of long-duration 0-g on the human physiology. It would also benefit LEO and HEO commercial facilities. Artificial Gravity includes technologies and research of Artificial Gravity spacecraft for long-duration deep space missions.
Examples of technologies required include Coriolis counter-effects technologies; deployable and retracting mechanism for A-G spin-up & down in zero-G; power and/or propulsion for spin-up/spin-down; tethers (momentum exchange); light weight high-strength tension cables; slip-rings for high efficient power transfer on rotating joints; counter rotating docking mechanism; and magnetic force suits (body suits that would experience a downward force due to localized magnetic field).

[JohnFornaro]

What happens if astronauts are kept in some kind of suspended animation? Would that also retard or suspend their skeleto-muscular atrophy?

There is no such a thing at the present time.

[JohnFornaro]

The real problem is that we dont know the effects of spin gravity at all.
Effects of prolonged micro-g are well quantified, we have no data on what spin G does to humans over a prolonged period. Trying it out for the first time on a martian sortie with no way to turn back would be a Bad Idea - maybe they will all co crazy from prolonged sea sickness or something.

I had not considered the idea that spin gravity would be different from gravitational gravity at all just yet.  I would like to see a roughly 900m dia, 1rpm ring station, which would generate one gee at the rim.  There could be lunar and martian rings inside of it.  If the station were at L1, the trip to and fro would be just a few days.

Assuming as always in these speculations, money would not be the main problem, but would have to be considered.

The building of such a station would take at least ten years, assuming greater launch capability than was required for ISS.  It would be started from two habs on a tether, so the spin gravity effects could be studied from the very beginning of construction.  Intuitively, I feel it wouldn't be a problem, thinking that the inner ear, after a day or two, would be well acclimated to that lazy spin.

Smaller, faster rotating components would certainly have deleterious effects.

My approach suggests that the easiest thing on the body be attempted, even though that means more mass to space.   After all, I reason, mass is your friend.

[kkattula]

Apart from toilets, there are a lot of things that are easier and safer in even fractional g, e.g. cooking, cleaning, personal hygiene, sleeping, equipment maintenance & repair, air circulation, water recycling, fire fighting.

Zero g can be designed for as a temporary, transitional state during maneuvering. The crew can be exposed to Mars and Earth gravity levels for weeks before each respective arrival to acclimatise them.

I'm a fan of rotating and non-rotating sections. I'd put the bearing inside the pressure vessel so it can be easily maintained, with several layers of non-load bearing rotating air seals outside that, and scavenging air pumps between some of the seals to reduce air losses to a tiny amount.


Of course it should be tested in cis-lunar space before committing to a Mars trip. It's just a great shame that almost nothing in this field has been tested in space in the last 40 years.

[neviden]

The only good reason why we should have 0g is that it makes design simpler, you can use aerobreaking and you save 5% weight.
1g would keep crew healthy and make many other things simpler. I don't think that it is "ok" for crew not been able to walk after a multi-year mission in space.
 `
Any mission that would take more then few weeks to complete, should be 1g, by default.

[JohnFornaro]

Of course [AG] should be tested in cis-lunar space before committing to a Mars trip. It's just a great shame that almost nothing in this field has been tested in space in the last 40 years.

More supporting evidence regarding the theory of intention regarding HSF that I raise from time to time.

It's more than a "shame". Necessary work is simply not being done, and there's no data whatsoever being offered as to why AG, plant growth, propellant manufacture, etc. are not now, and have not ever, been studied to the extent that they need to be studied.

[RanulfC]

The real problem is that we dont know the effects of spin gravity at all.
Effects of prolonged micro-g are well quantified, we have no data on what spin G does to humans over a prolonged period. Trying it out for the first time on a martian sortie with no way to turn back would be a Bad Idea - maybe they will all co crazy from prolonged sea sickness or something.

Engineering related effects on mechanisms etc are much easier to test and quantify, but even that might have some hidden risks.

There does need to be more research on a LOT of things before we go to Mars, just to retire a large amount of risks that we don't have a lot of practical knowledge base for at the moment.

Of course it should be tested in cis-lunar space before committing to a Mars trip. It's just a great shame that almost nothing in this field has been tested in space in the last 40 years.

Didn't they schedule an experiment during Gemini that had to be called off because of a malfunctioning Agena rocket? Still not much "excuse" for not doing "something" in the last half century, but given the numerous constraints on hardware and finances its not hard to see "why" it hasn't happened but it's frustrating none the less.
(Vibration is a bugaboo for many experiments on the ISS, movement, thruster-kicks and mechanical transients all are bad enough without a rotating section attached )

The only good reason why we should have 0g is that it makes design simpler, you can use aerobreaking and you save 5% weight.

"Simpler" somewhat and you DO save mass but you can "aerobrake" with a ring habitat sized aerosheild if you really want to. Since such a ship would have to be "put-together" building a large areobraking shield is actually easier.

Randy

[neviden]

Those limitations are kind of the worst things about AG that I could find. Some people (big rocket guys mostly) don't like an idea of an assembled shield. I think that it would work just fine.
The same with ekstra complications. 5% isn't that much of a deal either.
`
1 G should be default preference, but that goes against the whole "we must build 0 G laboratory in space, so that we can learn to live in 0 G, that's why we need $100B" idea.. 

[daveklingler]

I would like to see a roughly 900m dia, 1rpm ring station, which would generate one gee at the rim.

Long before that happens, I'd like to see an 893m tether with a hab on one or both ends, spinning at 1 rpm.  It's not a very tall order - the tether would be virtually off-the-shelf and the hab could be a station module modified to hang at 1G.  Berthing could be done either by clamping at the center of the tether, followed by a move down toward the hab, or at the hab itself.

Testing of artificial gravity on human subjects has been done.  Human beings seem to put up with 1 rpm without problems, but 2 rpm was too much.

[JohnFornaro]

It would be started from two habs on a tether, so the spin gravity effects could be studied from the very beginning of construction.

You must have missed that part:

I would like to see a roughly 900m dia, 1rpm ring station, which would generate one gee at the rim.

Long before that happens, I'd like to see an 893m tether with a hab on one or both ends, spinning at 1 rpm.

Hopefully, you see 893m as being "roughly" 900m.  Seems like we agree on the rpm.

[RanulfC]

Those limitations are kind of the worst things about AG that I could find. Some people (big rocket guys mostly) don't like an idea of an assembled shield. I think that it would work just fine.
The same with ekstra complications. 5% isn't that much of a deal either.
`
1 G should be default preference, but that goes against the whole "we must build 0 G laboratory in space, so that we can learn to live in 0 G, that's why we need $100B" idea.. 

There is a lot of resistance to in-space and on-orbit assembly, some based on some not-so-good previous work and some based on a lot of false assumptions

You've got the "zero-g" lab part wrong though, it was and is mostly to learn what we can DO in microgravity rather than if we can "live" there for prolonged periods. We've already proven the former but are still looking for the former

Randy

[JohnFornaro]

You've got the "zero-g" lab part wrong though, it was and is mostly to learn what we can DO in microgravity rather than if we can "live" there for prolonged periods. We've already proven the former but are still looking for the former latter.

Fixed that for ya?

[neviden]

Well, some of that learning involved observing what happens to astronauts living in 0 G.

[nscali]

Without using a tether how big would a rotating hab "ring" have to be to generate comfortable artificial gravity? Are there any concrete studies on this? From what little I've read on the subject you would need a very large diameter ring to create a gravity effect that doesnt make the astronauts want to lose their lunch. Definitely much larger than we could launch in a single piece right?

[neviden]

There are some studies, but nothing definitive. Tens of meters seems to be the minimum.

[nscali]

Even something like this seems far off at around 12-15m, could you imagine the BFR needed to launch it? Not to mention the speed at which it would have to spin...Doesn't seem worth it.....

[JasonAW3]

What happens if astronauts are kept in some kind of suspended animation? Would that also retard or suspend their skeleto-muscular atrophy?

There is no such a thing at the present time.

Not entirely true.

     Over the last few years surgeons have been using a form of deep hibernation for many more complex operations that require the Heart to stop beating.  This usually lasts about 45 minutes.  They have also been able to induce a hibernative state with the use of low quantities of Sulfur dioxide and low temperatures, but have only maintained this for a few hours at best.

Jason

[alexterrell]

Testing of artificial gravity on human subjects has been done.  Human beings seem to put up with 1 rpm without problems, but 2 rpm was too much.

This is not what I've read. I can google for research but I recall that:

- The Stamford Torus chose 1rpm because just about all humans won't notice this (except when playing ball games).
- Most humans are quite happy at 2rpm, but some sensive people may feel the effects.
- Many are quite happy at 4rpm, and may get used to it, but more research is needed.

The difference between 1 and 4 is a 16 fold reduction in radius.

More experimentation is needed - I'd like to see a variable tether experiment. But you can get something into a near term inflatable volume.

[alexterrell]

Even something like this seems far off at around 12-15m, could you imagine the BFR needed to launch it? Not to mention the speed at which it would have to spin...Doesn't seem worth it.....

You could launch an inflatable ring - that would fit in most fairings.

However, to be useful, you need a radius of about 20-25m. The inflatable structure for that could fit into SLS, or even F9 Heavy. But the impact shielding would be very heavy. Plus such a radius is useful for hundreds of passengers. Not the dozen or so who could go on a first mission.

[QuantumG]

All rotation experiments that have been done have been done in Earth gravity.. with the exception of the minor tether experiments done on the Gemini flights.

For all we know humans have no problems with 10 rpm.. if there isn't a gravity field messing with the inner ear.