Artificial Gravity from Rotation

[kkattula]

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I'd be interested in your thoughts and comments, as I am working on fleshing out this concept into a more detailed design over the next days and weeks.

I think it's a very good idea.

Of course I also think J-130 (SLS Lite? whatever...) needs some big but inexpensive payloads for the first few years. So I'd build a big, dumb, 2001-like wheel station out steel segments produced in a shipyard.

[rklaehn]

...
I'd be interested in your thoughts and comments, as I am working on fleshing out this concept into a more detailed design over the next days and weeks.

I think it's a very good idea.

Of course I also think J-130 (SLS Lite? whatever...) needs some big but inexpensive payloads for the first few years. So I'd build a big, dumb, 2001-like wheel station out steel segments produced in a shipyard.

I think it would be premature to build a 2001 style station until we find out how much gravity is required to prevent bone loss etc. and how much coriolis force is tolerable. So the first mission should require no assembly and preferably be launched on an existing launch vehicle.

A bigelow sundancer module connected to a counterweight/propulsion module by a deployable boom/tether could be launched fully outfitted and still fit on a Delta IV heavy or maybe even an Atlas V 551. The counterweight would contain enough propellant to spin/despin the entire assembly multiple times, so docking could happen in zero gravity.

Once you have figured out the optimum parameters (radius, rotation rate) for the station you could build a 2001 style station out of a ring of of bigelow ba330 modules. That would create demand for both the SLS and the bigelow stations.

[Xinvoker]

We need to have solid, experimentally based data on what g-loads are required to mitigate the bone-lose, muscle-loss, and other deterioration that occurs in zero-g. 

100% agree. It's an absolutely critical knowledge.
A mini-station capable of various Gees like the one you propose would be a great way to get this information. Not only we need this for future space stations and manned missions to Mars, but we need to know if the 0.38g of Mars is viable in the long term.

It's interesting that NASA went after AG as early as 1966 with Gemini 11, yet here we are today, AG still being an "Advanced Concept"! 

[IsaacKuo]

I agree that a spin gravity physiological research station is a good idea.  However, I think it should use I.S.S. based hardware and use as much commonality with I.S.S. hardware/procedures as possible to minimize costs.  Also, it should fly in the I.S.S.'s orbit, perhaps a few minutes ahead or behind it, so it's possible to travel from one to the other if necessary to transfer people or supplies.

The station should consist of mainly of ATV based modules--four on one end and two on the other end, to simulate Lunar gravity on the heavy side and Mars gravity on the light side.  Between them is a 120m long truss, so it spins end-over-end at 2rpm.

The reason to use a truss instead of a tether is so that the station can de-spin two or three times a year in order to dock with ATV supply ships.  The procedure is:

1) De-spin (using the ATV thrusters).

2) The two old ATV ships undock and leave (this leaves 3 MSS modules on the lunar side and 1 MSS mdoule on the Mars side)

3) The two new ATV ships dock.

4) Re-spin (using the ATV thrusters).

This means the station doesn't spin for a few hours as the trash-laden old ATV ships undock and the new supply-laden ATV ships dock.  This costs a small amount of fuel, but eliminates any need for a complex system for docking or undocking while spinning.

The old ATV ships can travel to the I.S.S., where suitable waste can be exploited for water using the I.S.S.'s more sophisticated recycling systems.

[Warren Platts]

I recall him saying that at least 1/3 G was needed for significant health benefit.

But why 1/3? There is no experimental basis to say that. We have 2 data points: 1 g and zero g.

A simple way to get a third data point would be to set up a research station on the Moon.

Anyways, there's no crisis. We know that humans can withstand months to a year or more with no permanent ill effects. For the foreseeable future humans will be limited to short duration trips in space. A brand new space station just to test for the effects of weightlessness isn't worth it for NASA right now. It would make a good project for the second-tier space powers, however.

[JohnFornaro]

I think it would be premature to build a 2001 style station...

Well, I think we should start building it.  You don't need to say "money" in your response.  I know. 

Dang.  I worked out the numbers, but I can't remember exactly.  About 900m in diameter, about 1rpm equals dang near 1g.  The station is a clock, deliberately kept accurately rotating.  In fact, you could have a Moon and and Earh window, with a clock superimposed on the stable images.  The rotation speed is slow enough not to impose vertigo.  The two pieces are held with a tether at first, which is slowly expanded into the ring structure.

My argument is three fold.  Completely eliminate a subject from the near term need for study.  Get tourists up there in a comfortable fashion.  It is permanent. 

Don't use the word "money" in your response.

[rklaehn]

But why 1/3? There is no experimental basis to say that. We have 2 data points: 1 g and zero g.

A simple way to get a third data point would be to set up a research station on the Moon.

I wouldn't call building a research station on the moon simple. And even if you do it, you just have one more data point (~0rpm, 0.16g). An artificial gravity research station could be done with a single launch of an EELV, and it would allow you to investigate the complete space between 0g and 1g and between, say, 1rpm and 10rpm.

Anyways, there's no crisis. We know that humans can withstand months to a year or more with no permanent ill effects. For the foreseeable future humans will be limited to short duration trips in space. A brand new space station just to test for the effects of weightlessness isn't worth it for NASA right now. It would make a good project for the second-tier space powers, however.

I disagree. If we want to build more permanent space habitats we need to know how much gravity is enough and what rpm is tolerable.

I think it would be premature to build a 2001 style station...

Well, I think we should start building it.  You don't need to say "money" in your response.  I know. 

If a heavy lifter becomes available, the US should immediately take advantage of it by building a 2001 style space station. That would be a good way to provide payloads for the heavy lifter, and be very impressive (you could call it demonstrating leadership in space to sell it to congress...)

But before building such a huge station, you should first fly a small mission to investigate what the optimum parameters are. Just a small habitable volume (bigelow sundancer), a variable-length deployable truss like this, and a counterweight with a propulsion system and enough propellant to spin the whole structure up and despin it a few dozen times for docking.

Dang.  I worked out the numbers, but I can't remember exactly.  About 900m in diameter, about 1rpm equals dang near 1g.  The station is a clock, deliberately kept accurately rotating.  In fact, you could have a Moon and and Earh window, with a clock superimposed on the stable images.  The rotation speed is slow enough not to impose vertigo.  The two pieces are held with a tether at first, which is slowly expanded into the ring structure.

There is this very nice web-based tool called spincalc to calculate parameters of artificial gravity space stations.

[alexterrell]

I disagree. If we want to build more permanent space habitats we need to know how much gravity is enough and what rpm is tolerable.

The design requirements of spin rate are even more improtant, given a = w^2 r.

GK O'Neil assumed 1g and 1 rpm for the Stanford Torus. This required a radius of 1km. For us now, very big, except with tethers.

However, it appears that most humans can take 4rpm, so that makes the radius about 60m.

Assume further that Mars gravity is acceptable - that makes the radius 24m. That's within the reach of SDHLV inflatables.

[kkattula]

Bigelow modules, ATVs?  Those are all zero-g modules. Absolutely not what you want in a rotating station.

I'm not suggesting a 900m 1g wheel straight up.  The point of a much smaller wheel is to test varying g and rpm to find out both what's tolerable and effective.

All the data we have is for small radii in a 1g field. A say 50m wheel running for months at 0.1, 0.2, 0.4 and maybe even 1 g could answer a lot of questions.

[rklaehn]

However, it appears that most humans can take 4rpm, so that makes the radius about 60m.

A 120m deployable boom should be almost a commercial off the shelf item nowadays: the ISS solar arrays use a 30m inflatable and retractable truss. And the SAR boom from STS-99 had a length of 60m.

The load on the truss would be almost exclusively tensional. The main purpose of the truss would be to keep the structure rigid when it is despun for docking or undocking. When spinning, the tension could be held by a tether inside the truss.

Bigelow modules, ATVs?  Those are all zero-g modules. Absolutely not what you want in a rotating station.

Why not? The ATV goes up on an Ariane V, so it is capable of withstanding significantly more than 1g. And a bigelow module inflated to 1 bar (14.5psi) will be almost as rigid as a car tire, so it will not deform significantly under 1g.

I'm not suggesting a 900m 1g wheel straight up.  The point of a much smaller wheel is to test varying g and rpm to find out both what's tolerable and effective.

All the data we have is for small radii in a 1g field. A say 50m wheel running for months at 0.1, 0.2, 0.4 and maybe even 1 g could answer a lot of questions.

But why a wheel? Even if you insist on using a completely rigid structure, a barbell-shaped station would be much lighter for a large radius.

[Proponent]

But before building such a huge station, you should first fly a small mission to investigate what the optimum parameters are. Just a small habitable volume (bigelow sundancer), a variable-length deployable truss like this, and a counterweight with a propulsion system and enough propellant to spin the whole structure up and despin it a few dozen times for docking.

Here's a discussion of just that concept, complete with proposal from kfsorensen.

[Proponent]

I recall him saying that at least 1/3 G was needed for significant health benefit.

But why 1/3? There is no experimental basis to say that. We have 2 data points: 1 g and zero g.

I don't remember; I suspect he referred to bed-rest studies done at varying tilts.  That would hardly be conclusive of course, and I fully agree more research is needed.

[Warren Platts]

But why 1/3? There is no experimental basis to say that. We have 2 data points: 1 g and zero g.

A simple way to get a third data point would be to set up a research station on the Moon.

I wouldn't call building a research station on the moon simple. And even if you do it, you just have one more data point (~0rpm, 0.16g). An artificial gravity research station could be done with a single launch of an EELV, and it would allow you to investigate the complete space between 0g and 1g and between, say, 1rpm and 10rpm.

We're going to the Moon anyway. The effects of 1/6 g will be studied by default, "for free" as it were. What if it turns out that 1/6 g is acceptable? We already know that 0 g is acceptable for 6 months  to a year a time--there are no permanent side effects.

Also, you can't launch your station and the people on it in one EELV; therefore it can't be done with a single launch of an EELV.

Anyways, there's no crisis. We know that humans can withstand months to a year or more with no permanent ill effects. For the foreseeable future humans will be limited to short duration trips in space. A brand new space station just to test for the effects of weightlessness isn't worth it for NASA right now. It would make a good project for the second-tier space powers, however.

I disagree. If we want to build more permanent space habitats we need to know how much gravity is enough and what rpm is tolerable.

But that's just it. We neather want nor need more space stations nor more permanent space stations. We already have ISS.

[rklaehn]

But before building such a huge station, you should first fly a small mission to investigate what the optimum parameters are. Just a small habitable volume (bigelow sundancer), a variable-length deployable truss like this, and a counterweight with a propulsion system and enough propellant to spin the whole structure up and despin it a few dozen times for docking.

Here's a discussion of just that concept, complete with proposal from kfsorensen.

Thanks for the link. I missed it for some reason.

It's not very detailed, but at least it confirms that a transhab style inflatable hab is fine in a 1g environment.

I think an initial facility could be done much simpler though: For starters:
- use simple thrusters for spinup and spindown.
- use multiple fixed solar arrays instead of tracking solar arrays
- have a boom in addition to the tether to avoid having to deal with tether dynamics when unspun

You could also use an ATV full of trash coming from the ISS as a counterweight. That gives you a nice ~20t counterweight for free. Have a dummy docking cone on one side of the deployable boom that the ATV can automatically dock to prior to the boom extension. The ATV would then vent its remaining propellants, depressurize and "passivize" itself.

[rklaehn]

But why 1/3? There is no experimental basis to say that. We have 2 data points: 1 g and zero g.

A simple way to get a third data point would be to set up a research station on the Moon.

I wouldn't call building a research station on the moon simple. And even if you do it, you just have one more data point (~0rpm, 0.16g). An artificial gravity research station could be done with a single launch of an EELV, and it would allow you to investigate the complete space between 0g and 1g and between, say, 1rpm and 10rpm.

We're going to the Moon anyway. The effects of 1/6 g will be studied by default, "for free" as it were. What if it turns out that 1/6 g is acceptible? We already know that 0 g is acceptible for 6 months  to a year a time--there are no permanent side effects.

There are currently no plans to go to the moon. If "we" go to the moon, it will happen significantly after 2020. A simple rotating space station could be launched before 2015.

Also, we know that 0g is acceptable for one year for highly trained astronauts that follow a time-consuming exercise regime. If you want ordinary people to be able to live in space at some point, that is not enough. And if you want to do a mission to mars, phobos or an asteroid that lasts 2 to 3 years that is also not enough.

Also, you can't launch your station and the people on it in one EELV; therefore it can't be done with a single launch of an EELV.

I said that you could launch the station on a single EELV. The crews would obviously be launched in manned dragons or a boeing CST100.

I disagree. If we want to build more permanent space habitats we need to know how much gravity is enough and what rpm is tolerable.

But that's just it. We neather want nor need more space stations nor more permanent space stations. We already have ISS.

First of all, you don't get to decide what "we" want. I want more permanent space stations. And so does mr. bigelow and the other people posting on this thread.

Second, ISS is a station that is specifically designed to study zero gravity. It is completely unusable to study artificial gravity.

This thread is about "Artificial gravity from rotation". If you think that this is not needed and we should rather wait until 2025 when we might have a moon base, you are on the wrong thread.

[Lampyridae]

I recall him saying that at least 1/3 G was needed for significant health benefit.

But why 1/3? There is no experimental basis to say that. We have 2 data points: 1 g and zero g.

I don't remember; I suspect he referred to bed-rest studies done at varying tilts.  That would hardly be conclusive of course, and I fully agree more research is needed.

We do have a lot of RPM research, and that shows that rotation rates of up to 10RPM are feasible. 5RPM appears well within limits for most people, and that makes a significant difference in rotation radius to 4RPM.

There is also hypergravity research with ~30RPM, and studies of "cosmonauts" who lived in a huge centrifuge for about a month.

Bed rest studies seem to indicate that bone loss is steady and permanent, governed by the equation:

Bone density = genetic baseline - (%gravity X Time) + (%gravity x Original)

So Mars would see a 0.6% bone density loss per year (with exercise)and would probably wind up at a constant 50-60% density, just above the critical threshold for fracture risk. Inertia however remains constant, so it would be higher. You could run on a tilted track on Mars or the moon to get higher g levels.

[alexterrell]

I recall him saying that at least 1/3 G was needed for significant health benefit.

But why 1/3? There is no experimental basis to say that. We have 2 data points: 1 g and zero g.

I don't remember; I suspect he referred to bed-rest studies done at varying tilts.  That would hardly be conclusive of course, and I fully agree more research is needed.

We do have a lot of RPM research, and that shows that rotation rates of up to 10RPM are feasible. 5RPM appears well within limits for most people, and that makes a significant difference in rotation radius to 4RPM.

There is also hypergravity research with ~30RPM, and studies of "cosmonauts" who lived in a huge centrifuge for about a month.

Bed rest studies seem to indicate that bone loss is steady and permanent, governed by the equation:

Bone density = genetic baseline - (%gravity X Time) + (%gravity x Original)

So Mars would see a 0.6% bone density loss per year (with exercise)and would probably wind up at a constant 50-60% density, just above the critical threshold for fracture risk. Inertia however remains constant, so it would be higher. You could run on a tilted track on Mars or the moon to get higher g levels.

That's good info (thanks) but I don't see how you can evaluate the effects of exercise from bed rest studies.

If on Mars an 80kg person goes jogging with a 120kg backpack, won't that be just as good as jogging on Earth?

The other point of note, is that long term, humans will need to reproduce off Earth. Lots of animal experiments need to be done before that can happen.

[Hop_David]

So Mars would see a 0.6% bone density loss per year (with exercise)and would probably wind up at a constant 50-60% density, just above the critical threshold for fracture risk.

At that rate, it'd take about 85 years to reach 60% density.

.994^85 = ~.6

[JohnFornaro]

But why a wheel? Even if you insist on using a completely rigid structure, a barbell-shaped station would be much lighter for a large radius.

It starts out as a barbell, maybe even tether based, spokes and rim added incrementally.  The key thing, as I see it, is to start out at 1g, 1rpm.  Eliminate those other lines of inquiry.

True, we'll get to the Moon eventually.  But I see the hotel rooms also being a part of the space station from the beginning.  Even after we do get to the Moon, some vacations will still be less expensive than others.

See also:

http://forum.nasaspaceflight.com/index.php?topic=17823.msg437451#msg437451

http://forum.nasaspaceflight.com/index.php?topic=20529.msg547349#msg547349

http://forum.nasaspaceflight.com/index.php?topic=17264.msg422774#msg42277

[Warren Platts]

We're going to the Moon anyway. The effects of 1/6 g will be studied by default, "for free" as it were. What if it turns out that 1/6 g is acceptible? We already know that 0 g is acceptible for 6 months  to a year a time--there are no permanent side effects.

There are currently no plans to go to the moon. If "we" go to the moon, it will happen significantly after 2020. A simple rotating space station could be launched before 2015.

You're dreamin' if you think a rotating space station can be launched before 2015. We'll be lucky to get a simple, prototype propellant depot in orbit by 2015: (a) the technology isn't ready; (b) there's no pressing need, and hence no plans for one.

Also, we know that 0g is acceptable for one year for highly trained astronauts that follow a time-consuming exercise regime. If you want ordinary people to be able to live in space at some point, that is not enough. And if you want to do a mission to mars, phobos or an asteroid that lasts 2 to 3 years that is also not enough.

Thank you for making my point: 0g is acceptable for highly trained astronauts: that's who NASA sends up there; it is not NASA's job to enable ordinary people to live in space: it is not in the best interest of the US of A to subsidize colonies that are eventually going to rebel against us. As for Mars/Phobos, how do you know that humans cannot withstand 2 to 3 years of weightlessness with no permanent side effects? It's never been done before. So far, the world record holder isn't walking around with a cane, as far as I know.

I disagree. If we want to build more permanent space habitats we need to know how much gravity is enough and what rpm is tolerable. . . . you don't get to decide what "we" want. I want more permanent space stations. And so does mr. bigelow and the other people posting on this thread.

I'm merely pointing out the obvious: that NO ONE has a pressing need to make artificial gravity: not NASA, and not Bigelow. Therefore, neither NASA nor Bigelow is going to fund an artificial gravity spin station. For an outfit like the European Space Agency, however, a spin gravity research station would be an excellent initial project to cut their teeth on.