Realistic, near-term, rotating Space Station

[Roy_H]

I think a space station with artificial gravity should be a priority. The main argument I have received against this concept is that it would be too costly, so I want this thread to focus on cost.

There are major health benefits to having artificial gravity, and also comfort and convenience.

The most significant adverse effects of long-term weightlessness are muscle atrophy and deterioration of the skeleton (spaceflight osteopenia). Other significant effects include a slowing of cardiovascular system functions, decreased production of red blood cells, balance disorders, a weakening of the immune system, and vision (focus) issues.

Going to the bathroom, showering, cooking, and even washing clothes are all more difficult in a weightless environment. Another benefit of artificial gravity is growing food, required to make the station more self-sufficient.

It is pretty obvious it will cost more, but I think less than double for a given occupancy. Potential areas to save are regular shipments of food and clothes if some food can be grown and clothes washed. Other savings can be had by having standard bathrooms and cooking equipment, instead of expensive custom designs.

Currently, astronauts to the ISS must maintain a rigorous exercise program, are all future astronauts going to be up to this? Artificial gravity greatly reduces the need.

My proposal is based on using Bigelow BA330 modules, two outfitted for weightless uses such as scientific research, manufacturing, and entertainment. Shown, in my rather crude sketch, are 4 modules attached in two pairs rotating about the central hub at 2 rpm (if using 223 meter cables) or 1 rpm (if using 890 meter cables). I should add that my sketch shows the paired rotating modules in a straight line, but in fact they would be slightly canted to align along the arc. The initial design could have just 2 rotating modules, and capacity could be added over time by extending the modules along the arc in balanced pairs until a complete ring is created. Small maneuvering rockets on the rotating modules would be required to create the initial spin-up and to keep the modules properly oriented to the hub. These should not be be required to operate frequently, and ideally only during construction phase.

The central hub would not rotate, and would include power source, docking facilities and ports for the elevator system. The rotating modules would be attached to a large ring around a specialized node near the center of the hub. This ring would not be rigidly attached to the hub, but would be sandwiched between two rings that are attached to the hub. These outer rings would have small clearance in the axis direction but allow large radial movement of the inner ring. The spacing would be maintained by magnetic fields, and coils within all rings would be used to transfer electric power. The large radial movement would allow small imbalances between the rotating module pairs with no force being transferred to the central hub. This design has no physical connection between the hub and rotating parts.

Two elevators would be used to transfer people and equipment to/from the hub and rotating modules. To maintain balance both elevators would operate together even if only one is required. A system of weights would also be used that travel up and down the cables to fine tune the balance and keep the rotating system centered on the hub.

A pair of robotic arms would be used to pluck the elevators off the moving cables and attach the elevator to the central hub. The slow rotation of the outer assembly should make this easy. The elevators would travel down the cables and mate with a port on the rim, no robot arms are required at this end. The elevator entrance should be at least as large as conventional elevators on earth, and on the rim end, the connection would have a smooth floor to ease movement of heavy loads that could be on a conventional hand pallet truck. The elevators could be based on the Bigelow Sundance modules (actually they may be too large, and somewhat smaller versions might be more optimal).

In my version, I suggest that the two modules on one set of cables would be used as a farm, while people would eat, sleep, have office space etc. on the other pair. Workers would use the elevator to go to work in the weightless environment, but spend at least half their time in the rotating portion.

There are a lot of engineering details to be worked out, but no show stoppers I can think of. Probably would want to have a spare elevator module mounted on a third port on the central hub in case there is a problem with one of the operating ones. The VASIMR engine in this version would be small and intended for orbital boost only. I think the rotation in orbit would have to have the axis parallel to the surface of earth and 90 degrees to direction of travel to avoid problems with gyroscopic procession. That is if the station was orbiting above the equator, the axis would be north-south.

The point I am trying to make here is that a rotating space station is doable in the near term and should be pursued. I believe that this design will be viewed by many as more attractive for manufacturing, research, tourism, and dare I say it, Hollywood films.

Edit: Modified drawing after reading some comments, thanks.

I have now shown small station keeping thrusters. Although I have shown groups, it would probably be better to have one or two articulated to point in almost any direction. I would expect these to be used sparingly like 1 minute per week or less.

New edit: after a long hiatus I decided to revive this thread. There are many changes in my new version and I also feel that some of the criticism were based on my poor simplified drawing and so now have attempted to make much more detail drawing to make the concept clearer. New version has two parts to the central hub like a bicycle wheel so that the cables are crossed like spokes on a bicycle wheel to give it more stiffness. These attachment rings are all so much more rigidity attached to the main central hub assembly and no longer allow any radial play. Please see my new post starting at 06/23/2018.

[Roy_H]

A variation of this space station could have a nuclear (LFTR) powered VASIMR rocket, and used as a transit vehicle for deep space such as travel to Mars. This version would be designed to go from LEO to LMO and back again. The VASIMR design would allow braking into orbit, no aero-braking required. The low acceleration of the ion drive would not greatly distort the spinning modules. Turning the station around for braking would require the use of the small rockets on the rotating modules to keep the modules properly oriented to the hub as the hub was turned around.

[Roy_H]

The farm modules would supply food, and oxygen. CO2 would be collected from the other modules and delivered to the farm modules, and oxygen returned.

Would the farm modules come anywhere near paying for themselves? How much is spent on delivering food and oxygen?

Added later version. Can download complete pdf (after pictures):

[guckyfan]

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.

[Roy_H]

I really don't get it.

You really don't.

None of the above.

Just to make living and working up there easier and healthier.

[cro-magnon gramps]

This is a transition; not an end in of itself. People will do on this, as people do. Work, experiment, visit, and enjoy the scenery. What it's main purpose is, will be to proof the ability to generate and utilized a space station with artificial gravity.
 While the International Space Station is wonderful, it was not meant to be the pattern for all space stations. Humans need gravity, and we will want to generate it where and how we use space. Certainly for some applications we will go without gravity for a time, but for general purpose of living, we will want to have it where we live most of our lives.
 
That is why Ron H, has asked the question in regards to a FIRST attempt at a gravity generating station: Quote; The main argument I have received against this concept is that it would be too costly, so I want this thread to focus on cost. end quote

edit, btw I am in no way qualified to post regarding costs! Just interested in the answers

[IRobot]

I've already asked you on another thread: without fixed structures, how to you avoid wobbling ( in 3 axis) due to mass distribution variations?

[blasphemer]

Make the central hub rotate, too, so there is no need for any complex rotating joints. Docking ships will match rotation.

[cro-magnon gramps]

Make the central hub rotate, too, so there is no need for any complex rotating joints. Docking ships will match rotation.

Kinda like this??

[guckyfan]

I really don't get it.

You really don't.

None of the above.

Just to make living and working up there easier and healthier.

I thought my question was clear. What are you proposing to do in that rotating station? What could be its function? Making people a little more comfortable is not a function in itself.

[rklaehn]

I really don't get it.

You really don't.

None of the above.

Just to make living and working up there easier and healthier.

I thought my question was clear. What are you proposing to do in that rotating station? What could be its function? Making people a little more comfortable is not a function in itself.

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

[Andrew_W]

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.

[cuddihy]

I believe NASA looked into sonething very similar about 8 yrs ago, will try to find the briefs. Involved the hub using a canfield joint to connect rotating and stationary parts.

[nacnud]

Counterweight the habitation with the fuel tanks (or any other two lumps of mass, one habited the other uninhabited), engines between the two. Adjust the length of the tethers to suit, spin up and send on its way.

Not my idea, just seen it on the interwebs somewhere

Here is a place to start looking for more information http://selenianboondocks.com/2010/06/agnep1/

[Roy_H]

I've already asked you on another thread: without fixed structures, how to you avoid wobbling ( in 3 axis) due to mass distribution variations?

Small amounts of wobbling are tolerable. This is a function of the length of the cables, so the longer 890 meter cables would be less susceptible to mass motion. I think you are concerned with a person walking from one side of the module to the other. I don't have the ability to analyze and give exact figures, but I think moving a few hundred pounds over 10 ft in an overall mass of 20,000 lbs would produce a very small movement and angular displacement with a radius of hundreds of meters would be vanishing small. My gut feeling is that it would not present any problem. Large masses, that get moved once during construction/installation would have to be countered by the small positioning rockets.   

[Roy_H]

Make the central hub rotate, too, so there is no need for any complex rotating joints. Docking ships will match rotation.

Bad idea. The concept shown in 2001 would in fact be very difficult to do, and serves no purpose. The primary reason for the non-rotating hub is to provide a microgravity work place for experiments and manufacturing. As soon as you spin it this becomes useless for these applications.

[Roy_H]

Counterweight the habitation with the fuel tanks (or any other two lumps of mass, one habited the other uninhabited), engines between the two. Adjust the length of the tethers to suit, spin up and send on its way.

Not my idea, just seen it on the interwebs somewhere

Here is a place to start looking for more information http://selenianboondocks.com/2010/06/agnep1/

In this design, the counterweight is the farm modules.

[gbaikie]

"I think a space station with artificial gravity should be a priority. The main argument I have received against this concept is that it would be too costly, so I want this thread to focus on cost."

Main cost of ISS is yearly operational costs.

So a space station with 1/2 billion dollar yearly cost, would fit definition of a focus on costs.
And operational cost of 1/2 billion dollar or less per year, probably means space station can't be
in LEO.
If in LEO a station needs to be re-boosted:
http://en.wikipedia.org/wiki/List_of_unmanned_spaceflights_to_the_International_Space_Station
So starting November 1998, ISS has had 68 spacecraft go to it- building it, bring crew and bringing supplies and re-boosting it.
So say 6 flights a year and say they are about 200 million each gets over 1 billion per year. And billion dollars is fraction of the yearly cost.

Now if station had artificial gravity then crew could stay longer, but sending and returning isn't a large cost
and do really want crew to spend a lot of time at the space station- years.
What is higher costs than sending crew and the supplies they need and rocket fuel needed to boost the station.

So low costs would be something like 5 billion to make and 1/2 billion per year to operate it.
And I think we already have this space station. Spend couple billion to move ISS out of LEO and put in an orbit that require little station keeping or yearly re-boost.
Or we need to spend probably about billion dollar year to keep ISS in orbit- even no crew were aboard.
So put ISS somewhere so it can have no crew in it and costs say 50 million per year just to maintain it.
And if sending crew to it, it costs 1/2 billion to say 4 billion per year, depending what is done.

An attraction of ISS is it has weightless. All science being done is largely because it has microgravity.

Now if ISS is moved to high earth orbit which doesn't require re-boosting, one could other things around it- one could have separate living spaces which have artificial gravity- say .5 km from it.
Plus if in LEO re-boosting something spinning is complicated.
So good place for artificial gravity space station is say Earth/Moon L-1. And one could spend 5 billion to make it, and 1/2 billion per year to run it. Your main cost would resupplying for crew living there. But 2 crew
at L-1 could be as cheap as 4 crew at LEO. Supposing you wanted crew to be in space more than one year, so resupply per crew is higher, but 1/2 many crew and 1/2 as many trip there and back would make as much or less costs.
Or say the station was rented. So 100 million per crew per year was rent. Such station at L-1 could be
close to profitable. Whereas at ISS 100 million per year per crew is not profitable- you can't run ISS for 200 million or 700 million per year. But if ISS was in high earth, 100 million per year could more profitable.
So the 100 million is just rent, not getting there or leaving and not food and water, etc.
The cost getting crew to L-1 or high earth would twice as much as LEO- same goes for the supplies. But if staying longer, than per year cost of getting there and back is reduced.
Or saying different way LEO, is more economical if people only went there for month or less.
So station at LEO charging 30 million per week could more attractive than L-1 charging 100 million per year.

So one could trip cost to LEO being 20 million, hotel week charge of 30 million and misc 10 million.
So trip to space for week: 60 million. So station at L-1 would far more, but if wanted to stay longer than 1 year it becomes more affordable compared to LEO- 1.5 billion for "hotel room" for a year vs 100 million.

So for brief stays LEO wins. But if want station so people can stay longer, it shouldn't be in LEO.

[Aussie_Space_Nut]

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.

First is fuel, air, water and food. IMO we need a system as close to self sustaining as possible. I imagine the initial goal could be that a crew wishing to spend a year at a space station be able to carry with them on the craft that delivers them all the fuel, air, water and food required for that year. Some of the food could be seeds and fertilizer. The idea being to use as much as is possible natural processes to produce the air, process the water & grow the food. Using water as the station keeping fuel just seems to make sense in that it is very safe to transport. The hope is that over time we will become ever better at self sustaining systems such that the number of inputs from ground significantly decrease. For fuel use reasons given how heavy the water jacket will be for radiation shielding, see next point, the space station needs to be at a Lagrange point such that only minor station keeping burns are required, no orbit boosts.

Second is the radiation risk. IMO we need a set and forget radiation protection system such that crew need not drop everything and scurry into a safe hold somewhere on the station. Water appears to be the simplest form of protection for a space station at this time.

Third is Gravity. Spending long periods of time without gravity is simply not healthy. However one of the reasons for going to space is being able to conduct research without gravity. IMO plants and animals grow best in 1G. Therefore the space station must have both 0G and up to 1G sections. Having some wobble due to movement of people and items within the gravity section would be no problem for the people, think of people living on boats at sea, however that movement may not do the 0G experiments much good.

Obviously it would be tedious to have to don a space suit or ride some sort of small shuttle to get between the 0G and 1G sections. Not to mention the safety dramas involved.

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

The general design rationale,
1) Human friendly environment.
2) As much as is possible self sustainable.
3) Keep inputs from the ground to a bare minimum by designing as many components as possible to exceed the design life of the station.

So is it possible to build a human friendly space station for a reasonable cost?

[KelvinZero]

I was never that interested in the Inspiration Mars mission itself, but I would like to see something like that 500 day lifesupport + manned dragon attached to the ISS and under continual trials so we could begin accumulating the huge confidence in existing hardware we should aim for if we wish to travel months from earth or any possible support.

Adding a cable and some sort of counterweight to the above could let you conduct a 500 day spin gravity experiment, which would also be a valuable test that the same lifesupport functions without surprises for 500 days in mars gravity environments, in addition to all the zero gravity testing it would get.

If anything goes horribly wrong, it will not endanger the ISS (it will be well away before being spun up) and the crew can return directly to earth in the Dragon.