Realistic, near-term, rotating Space Station

[grondilu]

Artificial gravity would make the design of the habitat much more difficult from an engineering point of view.

It's easy to design an habitation module if it weights nothing, but as soon as you add gravity to the picture, suddenly you need to think completely differently in terms of structural engineering.  You're basically building a house, not a can box.  And this house must be light enough to be sent in space.

Also, artificial gravity puts much higher requirements in the structural integrity.  I mean, imagine you suspend the habitation module on a cable.  If the cable breaks, you'll be lost in interplanetary space or smashed into Earth's atmosphere.  That perspective could make you feel quite uncomfortable.

That's how I explain it hasn't been done yet, anyway.

[guckyfan]

Artificial gravity would make the design of the habitat much more difficult from an engineering point of view.

It's easy to design an habitation module if it weights nothing, but as soon as you add gravity to the picture, suddenly you need to think completely differently in terms of structural engineering.  You're basically building a house, not a can box.  And this house must be light enough to be sent in space.

Also, artificial gravity puts much higher requirements in the structural integrity.  I mean, imagine you suspend the habitation module on a cable.  If the cable breaks, you'll be lost in interplanetary space or smashed into Earth's atmosphere.  That perspective could make you feel quite uncomfortable.

That's how I explain it hasn't been done yet, anyway.

Not that I am convinced we need one. But what about a long cylinder spinning around its short axis? The forces involved should not be too hard to handle. I assume we won't want gravity much higher than Mars at the end of the cylinders. That way there would be space for experiments at any gravity level between max and 0.

I wonder about the design of the docking port. Assuming it needs to be stationary for docking.

[rklaehn]

Artificial gravity would make the design of the habitat much more difficult from an engineering point of view.

It's easy to design an habitation module if it weights nothing, but as soon as you add gravity to the picture, suddenly you need to think completely differently in terms of structural engineering.  You're basically building a house, not a can box.  And this house must be light enough to be sent in space.

Actually, given that a space station module has to be pressurized with a pressure of 100kN/m^2, it has to have a pretty solid structure anyway. For small stations, the additional loads caused by putting the module in 1g would be lost in the noise.

For an ISS module with a diameter of 4.4m, the force trying to pull the module apart along the long axis due to the 1 bar atmosphere is 2.2^2*Pi*100kN/m^2=691150.38379 N or equivalent to about 70 metric tons. An ISS pressure vessel has significant margin for overpressure. So the forces caused by being in a 1g environment are small in comparison.

Also, artificial gravity puts much higher requirements in the structural integrity.  I mean, imagine you suspend the habitation module on a cable.  If the cable breaks, you'll be lost in interplanetary space or smashed into Earth's atmosphere.  That perspective could make you feel quite uncomfortable.

That's how I explain it hasn't been done yet, anyway.

Unless you have a very long cable, a cable break will leave both parts in a very similar orbit. Basically the rotation velocity of the cable will be added/subtracted to the orbital velocity. And since the rotation velocity is very small compared to the orbital velocity, the orbit will remain more or less the same.

[guckyfan]

Actually, I think that making people more comfortable is a function in itself.

For that purpose I recommend staying on earth, much more comfortable. Even space tourists will come for the zero-g experience.

But coming back to the question of what would be the research value of an artificial gravity station:

We obviously have a lot of data for living in 1g, and we have a reasonable amount of data for surviving in 0g. But we have literally zero data for anything in between. Can health problems associated with living in 0g be mitigated when we reach 0.3g, 0.5g, 0.9g? We have no idea. Is mammal reproduction possible at Mars or Lunar gravity? Again, we don't have the slightest idea. That is why such a station would be of huge research value.

There is going to be a small mission by DLR to research intermediate gravity levels: EuCROPIS. Even for this relatively limited mission there is a large interest for participation of research institutions.

OK that's a reason for such a kind of station if it can be made at reasonable cost. Otherwise I think it is better to do those experiments on Mars.

I think a station with gravity for staff and microgravity labs would not be feasible. Rotation will destroy microgravity. Even at the ISS microgravity is already compromised. It would need to have totally disconnected lab and crew quarters. And then how to move between the two? Docking for transfer will also compromise microgravity so can't be done frequently.

[john smith 19]

I really don't get it. What would a station with gravity be good for?

As a colony, with the aim to become self sufficient?

As a service station? Servicing whom? Servicing spacecraft will likely be easier in zero gravity. Servicing people? Again what for?

Washing clothes, taking a shower? That can be done on earth or if you really want in zero gravity, too.

For doing research on plants in Mars gravity? Go to Mars, do it there.

Maybe one thing. You can have different gravities from near zero to ~1g. Then you can do research on plants and animals in varying gravity.

You might like to look up Gary Hudsons 2014 NIAC presentation as head of the Space Studies Institute. (it's on
here as a thread) 

They are currently raising funds for a "g lab" to explore this area.

Here's the thing. There is no knowledge of what (if any) level of g the human body needs to avoid permanent damage.  0g has maybe 6 months at the longest. Longest Moon trip at 1/6 g <75 hours Longest time in 1/3g or Mars. Zero

Getting to Mars (about 186x further than humans have been away from the Earth) is a very bad way to discover humans don't really handle prolonged fractional g very well.     

If humans want to expand into the rest of the solar system these questions (the others are fully closed cycle life support and radiation protection) need to be answered.

It's the difference between becoming a true space faring civilization and doing ego inflating flags and footprints missions. 

BTW cost wise. ISS has cost a shedload of cash to build. But I think the assertion that a rotating space station would cost more is actually pretty shaky.

I think it'll depend on who (and how) it's built.

[IRobot]

Most plants don't grow in zero g environments. A small artificial gravity would increase sustainability of the station by allowing the occupants to grow their own food.

[Roy_H]

List of requirements so far,
A) 0G section is stable and does not rotate. 0G & 1G sections are linked such that crew can easily move between them in their standard clothing without using any system that has to attach or detach from the different sections.

Why do you think that a system that doesn't detach is required? To have a non-spinning and 1g sections there is by necessity a long distance between if you want the rotational speed to be slow and not have any noticeable difference between levels in the 1g area. So an elevator seems to be the logical choice. In order to not transmit vibration and forces between the units, this design keeps them separate. I don't see the drawback of having the elevator attach and detach.
 

1G section capable of less gravity such that the gravity of the Moon and Mars can be simulated. 1G section contains the food production & living areas along with work areas such that as much as is possible the astronauts spend most of their time here.

Yes, this could be done, simply by changing spin rate, but this is not the intention of this design.

B) Use water as the radiation shielding. (Water can be built up over time with each visit.)

Water has been considered ideal, but has much mass and if on the outside it might be difficult to keep from freezing. Would ice work as well? Anyhow, Bigelow claims that their fabric is a much better radiation shield than the ISS, and suitable for BEO operation.

C) Use water as the station keeping fuel.

Well.. let's clarify this. Best arrangement is to use a very efficient rocket engine like VASIMR http://www.adastrarocket.com/aarc/VASIMR . Now let's break the "fuel" issue into two parts, what is ejected to produce force, and the energy source to do so. The Best choices for the energy are solar and nuclear. For the nuclear option, I think the LFTR is best, thorium is cheap, easy to handle, and it would be no problem to carry 100 years supply on the station. The fuel (ejected) for a VASIMR drive can be argon, xenon, or hydrogen. If you wanted to use water, then it would be easy to use the power source to split the water into hydrogen and oxygen. Use the hydrogen for the VASIMR drive and the oxygen to breath. Not sure if this would be better than having tanks of argon or xenon, why do you think water is best?

D) Grow as much food as possible.
E) As much as possible use plants/other natural processes to purify waste including waste water.
F) As much as possible use plants/other natural processes to produce breathable air.

Agreed, that is why this design has two modules for living, and two for farming.

G) The craft that transports the astronauts to the space station is able to carry all of the water & food required for a stay of 1 year along with any of the other consumables they may require.
ossible to build a human friendly space station for a reasonable cost?

Nice to have, but not a requirement for LEO operation.

[Roy_H]

Not that I am convinced we need one. But what about a long cylinder spinning around its short axis? The forces involved should not be too hard to handle.

This design has been proposed before, as a huge colony style. Very expensive and maybe in the (distant) future. I would like to keep this thread focused on near-term, low-cost designs.

[Stormbringer]

eventually the primary use of a space station will not be zero G experimentation. eventually the main reason for a space station will be as a place to shelter humans between excursions into the zero G environment or between shifts at a nearby zero G manufacturing or experimental facility or a way station to long duration space expeditions.

a large facility could be a place to finish up a space ship once the major structures are completed in zero G. It then moves "indoors" so workers can go in and wire and plumb it and add sub-assemblies, and paint it and all the stuff that might be impossible in the zero g.

A spinning station could also of course be a destination for tourists, i hear the Japanese and others are keen on an orbital hotel. you could have that and still have a orbital dry dock and quarters for satellite servicers and miners and scientists from remote orbiting lab facilities and etc and so on...

also a huge spinning gyroscope in space... might that not make an excellent gravity observatory?

and i can almost guarantee that anything that passes through or comes from that facility would sell at a huge mark up. Space carrots! space carrot seeds! Space Bunnies! space dust bunnies! moon dirt! asteroid dirt! a captured bolt that menaced satellites for decades! used space clothing! the cup used by captain queeg for coffee for his entire tour of duty!

[Stormbringer]

in the near future if we have a true permanent presence in space keeping scientists and workers in a gravity environment during off duty hours or at least regularly would extend their health and endurance before having to return to earth. there could be a world class gym and up to a kilometer long jogging corridor complete with 3D scenery on the walls and ceiling. and because there could be multiple levels such a jogging corridor would not be at the expense of other facilities. said corridor could be a well managed green zone with trees plants and aqua culture pools, tanks or streams.

there could be a fully staffed medical/dental facility so that any procedures could be performed in a friendly environment and so routine medical needs could be serviced without an expensive return to planet side and emergencies could be handled in a timely manner.

Dry dock bay capable of handling up to a 300 meter long craft or multiple smaller craft or structures. Tankage for propellants, oxidizers, water and so on. hoppers for raw manufacturing/agricultural materials. Warehouses for finished or partially finished goods.  shops for manufacturing or machine 3D printing. Inventory control for off facility received/shipped goods.

Hotels for tourists including restaurants and clubs and recreation facilities E.G;  a low G zero G Sports court and facilities on the central axis tucked out of the way of the dry dock bay. internet based radio stations, magazine, newspapers, and video network studios (which like on earth could just be ran out of someone's bedroom for very little in  the way of taking up additional space.)

Quarters for space workers and permanent residents. A small security department with temporary confinement facility for handling inevitable breaches of the peace and crimes. 

it may sound ridiculous and ridiculously expensive but with stuff that is happening now and anticipated near term technology it could be feasible. things like 3D metal printing and other enabling technologies may change the economic calculus faster than pessimistic people might think. 

[Roy_H]

C) Use water as the station keeping fuel.

Aaaahhh, forgive me for being slow. Water is an excellent choice! Far simpler than my VASIMR ideal if not as efficient. Use the solar panels to split the water into hydrogen and oxygen, and use in a conventional H2/LOX rocket engine.

I will take this post to address another issue, some have felt that this design cannot be boosted for station keeping in LEO. It requires thrust 90 deg to the axis of the hub, so my diagram is wrong showing the VASIMR engine on the end of the hub (suitable for space travel to Mars, but not orbital housekeeping). In order to keep the exhaust away from cables and spinning modules two small rocket engines would be required on the hub axis near each end and more fired in co-ordination on the spinning modules themselves. All of this points to the fact that the VASIMR design is not suitable for station keeping.

Thanks for pointing this out guys, that is to me the most important function of this thread. That is to identify errors and find solutions.

[Roy_H]

I am beginning to see advantages of alternate gravity simulations. There are basically two approaches, one to spin the system at the appropriate rate, and the other is to add additional modules with shorter cables to achieve the desired lower g. The elevators could be transferred to the various modules as required.

But, this is where the light bulb went off, and I realized that there could be much more interest in funding this style of space station just because of the unique ability to study living at these lower gravity simulations. Now the increased cost can be justified!

[guckyfan]

Not that I am convinced we need one. But what about a long cylinder spinning around its short axis? The forces involved should not be too hard to handle.

This design has been proposed before, as a huge colony style. Very expensive and maybe in the (distant) future. I would like to keep this thread focused on near-term, low-cost designs.

Maybe I used a wrong expression? English is not my first language. I am thinking of a 120m or more long cylinder, maybe 8 or 10m wide or whatever can be built easily. Spin it around its middle - at 60m from each end. The ends of the cylinder have the highest gravity. It would be 20 storeys 3m high from the middle up each with higher gravity until you reach the end of the cylinder. I was not proposing an O'Neill-Cylinder.

I hope I have made myself clear. I don't think this is a complex and expensive design. It does have the advantage of providing lab space for each gravity from near zero to max.

[Jim]

The thread premise is wrong.  There is no need for such a station in the near term

[Jim]

But, this is where the light bulb went off, and I realized that there could be much more interest in funding this style of space station just because of the unique ability to study living at these lower gravity simulations. Now the increased cost can be justified!

No, not the types of stations you have been proposing.  There is no need for a "farm", or space dock or exotic propulsion .  It just needs a few modules like the ISS.

[JohnFornaro]

The thread premise is wrong.  There is no need for such a station in the near term

The thread premise is fine.  It doesn't say "should we?"  It just asks what would be realistic and near term.

Simple answer.   Two capsules on a rope.  Hemp, of course.

[john smith 19]

A facility to test life processes in lower gravity is something we're in desperate need of, but for now it would only require an ISS module.

I think it was called something like the ISS Centrifuge module.

Obviously didn't happen, but there are other ways to do it.

BTW AFAIK the 1st shot at trying this was a Gemini mission, when they unrolled a tether between the capsule and an Agena target vehicle, back in the mid 60's.

Today that would be (hypothetically) a crewed Dragon and an upper stage.

I am fascinated with the idea of generating gravity on a space station. IMO the space facilities created thus far have not been human friendly, with extremely good reason. However if we are to truly step out into space in a big way we need to mitigate to the greatest extent three problems.

True.

<Lots of extraneous detail snipped>
So is it possible to build a human friendly space station for a reasonable cost?

Using water and liquid waste as reaction mass was considered. The device you're looking for is called a "ristojet" because it uses electrical heating to pressurize the reaction mass.

De coupling a rotating from a non rotating system is done by everything from bicycle wheels to the power transfer coupling of the ISS solar arrays.

Currently NASA allocates 5Kg of mass per person per day for human consumables. Most of that is water to rehydrate food. That's 1.85 tonnes for a crew person per year.

Do you see why closed cycle life support is a good idea? Unfortunately if you're also using some of it for reaction mass...

Most plants don't grow in zero g environments. A small artificial gravity would increase sustainability of the station by allowing the occupants to grow their own food.

I did not know this. I thought they grew somewhat distorted but otherwise edible.

I think there was a report that they have grown tomatoes on ISS without AG.

But finding the minimumg for good growth would be an interesting use for this station.

Artificial gravity would make the design of the habitat much more difficult from an engineering point of view.

It's easy to design an habitation module if it weights nothing, but as soon as you add gravity to the picture, suddenly you need to think completely differently in terms of structural engineering.  You're basically building a house, not a can box.  And this house must be light enough to be sent in space.

Also, artificial gravity puts much higher requirements in the structural integrity.  I mean, imagine you suspend the habitation module on a cable.  If the cable breaks, you'll be lost in interplanetary space or smashed into Earth's atmosphere.  That perspective could make you feel quite uncomfortable.

I'm not sure you understand the difference between mass, weight and inertia. While things in space may be "weightless" they are neither "massless" nor inertialess.
All the ISS structures were rigid and free standing on Earth. There is no reason to think they would not also be the same under 1g of AG (or rather less).

I am beginning to see advantages of alternate gravity simulations. There are basically two approaches, one to spin the system at the appropriate rate, and the other is to add additional modules with shorter cables to achieve the desired lower g. The elevators could be transferred to the various modules as required.

But, this is where the light bulb went off, and I realized that there could be much more interest in funding this style of space station just because of the unique ability to study living at these lower gravity simulations. Now the increased cost can be justified!

You need to look at the this year's NAIC presentation and Gary Hudson of the Space Studies Institute  and their proposals for a "g lab."

[IRobot]

Most plants don't grow in zero g environments. A small artificial gravity would increase sustainability of the station by allowing the occupants to grow their own food.

I did not know this. I thought they grew somewhat distorted but otherwise edible.

I think there was a report that they have grown tomatoes on ISS without AG.

But finding the minimumg for good growth would be an interesting use for this station.

Maybe research has progressed in the meantime, but I've read some years ago that the few plants that grew well in zero g had almost zero nutritional value for humans. I'll try to find some info on it.

Edit: VEGGIE was/is supposed to go on the next SpaceX flight.

http://forum.nasaspaceflight.com/index.php?topic=30118.msg968958#msg968958
http://www.nasa.gov/multimedia/imagegallery/image_feature_2454.html#.UwJsg_ldVLE

[Roy_H]

Not that I am convinced we need one. But what about a long cylinder spinning around its short axis? The forces involved should not be too hard to handle.

This design has been proposed before, as a huge colony style. Very expensive and maybe in the (distant) future. I would like to keep this thread focused on near-term, low-cost designs.

Maybe I used a wrong expression? English is not my first language. I am thinking of a 120m or more long cylinder, maybe 8 or 10m wide or whatever can be built easily. Spin it around its middle - at 60m from each end. The ends of the cylinder have the highest gravity. It would be 20 storeys 3m high from the middle up each with higher gravity until you reach the end of the cylinder. I was not proposing an O'Neill-Cylinder.

I hope I have made myself clear. I don't think this is a complex and expensive design. It does have the advantage of providing lab space for each gravity from near zero to max.

Ok, thanks for the clarification. I do not believe this is suitable for my proposed station design, but could be ideal as an addition to the existing ISS. Your focus is on providing experimental work space, whereas mine is providing comfortable accommodation for the workers. Both should be done.

[Roy_H]

The thread premise is wrong.  There is no need for such a station in the near term

I am very glad for your input. You are a true expert and as I understand actually work at NASA. Your opinions and posts are well respected here. I am just an interested party with no space or rocket training. I feel that if I could talk you into accepting this approach, then it would be something that NASA might actually entertain.

I guess the first thing I would like to tackle is the "need" part. Right now the ISS provides everything needed for people to conduct experiments in space. It is filled with highly trained astronauts dedicated to pursuing NASA's objectives. These people willingly suffer cramped living space, awkward hygienics, limited food styles, rigorous exercise routines, and deteriorating body functions. My hat's off for their hard work and dedication. But, as more people are needed to carry out more experiments, run machinery, or just be tourists, are they willing to make the same sacrifices? Do they have to? My argument is that they don't have to, and that providing better accommodation doesn't have to cost an arm and a leg.