Author Topic: Space habitat concept  (Read 31105 times)

Offline pkrahn

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Space habitat concept
« on: 03/12/2015 07:26 PM »
We've come up with a concept for a rotating space station in low-earth orbit, that people will be able to enter using an Oculus Rift or other VR devices eventually.  It'll be used for many activities although the main one is to provide a beautiful vantage point to watch our planet and contemplate possible futures.

So in doing so we'd like to build a habitat that could, in theory, be constructed one day.  We don't expect it to be perfect right off the bat, the main designer and I aren't engineers, however he is an architect and we're both space enthusiasts and are getting some help already.  I'd like to post some pics here along with details and encourage everyone here to pick it apart as best they can, or offer suggestions. 

I'm attaching a main rendering from photoshop, based on Tarik's model, I can add more yet but this will give you the general idea.  It's a torus with a diameter of 960m.  Just over 3 km circumference.  Outside of torus are these complexes, we're not sure what to call these buildings but they'll be individually designed, but their mass will perfectly balance with the building on opposite side of the ring.  There's only a few at the moment but eventually they'll be around twenty in total, evenly spaced.  These can have multiple floors, with rooms holding at most 200 people by my estimate, although nothing you see there now is of this size. 

In order to achieve the equivalent of one Earth gravity on the bottom floor of a complex, we'll be rotating at just under once per minute, although that will need to be worked out exactly yet.  Here's a simple animation...



[EDIT: our math was off, it'll be corrected to a bit over 1 RPM]

We'll update that with a better rendering soon.  In the center is the hub, which is a design we're not a hundred percent sure about but it's what we're trying at the moment.  The "spokes" are for docking.  It seemed tricky to me to dock onto something on a slowly rotating path, however it seems likely to me that computer-controlled thrusters will be able to line it up perfectly.

Because we need perfect balance in order to keep a tight spin, to prevent a docking ship from introducing wobble we imagine that instead of just using thrusters we might have a tube inside the torus, underneath the floor, containing a series of heavy weights that are automatically adjusted to counteract it.  We have some cross-sections from inside the torus attached here but they don't include this yet.  You will see though an example of a private suite, which there will be many of.  The view out the window will be of Earth.

The view from outside the complex, out some windows, will have the sun passing by often.  The lighting inside these rooms might be tricky to work out realistically.  What we have considered is that the internal lights should be able to constantly adjust to keep it at a constant level, although if you look up you should see the lights dimming as the sun passes by.  Although this isn't something we've looked into too closely just yet.

We're utilizing solar energy at the moment, but we're not sure if these panels are enough to power all our operations.  We'd like to find out the likely potential panel efficiency in the coming decades and then decide if we need to add many more to the design, there's plenty of space to include more.

We'll definitely need some sort of radiation shielding.  What we're hoping for is using superconductors in the design, using magnetic shielding, this is something being researched by we'll have to find out how plausible it is to incorporate.  In our concept we want to use technologies that could be in use in fifty years' time.

We were at first planning to attach this atop a space elevator, however the more we looked into it the more it seemed that these elevators will never be built.  Instead, we looked at laser propulsion, and then more specifically to Leik Myrabo's microwave propulsion designs...

http://www.lightcrafttechnologies.com/rpi_www/technical/

These seem to be the best idea for affordable space travel so far.  Because for this concept to work, to be fully immersive, we need a mechanism by which normal everyday people can get to space to attend a talk on dark matter, for instance.  We can't just be using shuttles that cost a quarter million dollars per trip.

Leik's Lightcraft was called by a NASA study potentially "game-changing" but the infrastructure costs are still too high, they require a series of microwave beam stations orbiting Earth, one of which we'll want to model and place near the habitat.  Also we'd like to do beautifully textured models of the craft itself.  At first you'll seen them coming and going from inside the station but eventually we'd like the ability to enter inside and fly around the planet, then return and dock.  BTW the craft themselves would park below the station most likely, and send up smaller landers.

We're definitely open to alternative suggestions though on how to get to this facility, and how to dock.  Along with anything else.  Ours may not be the most likely design but we'd like it to at least be possible. 

I'll add more details if they're requested, or I think of them.
« Last Edit: 03/13/2015 01:23 AM by Chris Bergin »

Offline Burninate

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Re: space habitat concept
« Reply #1 on: 03/12/2015 07:43 PM »
While I appreciate the work, I fear there's not a lot of desire for more of this type of product.  We've been seeing renderings of this sort of thing since the 1940's, Stanley Kubrick illustrated it in explicit detail, it just doesn't add much to the conversation or show us anything about how to get from here to there.

These seem to be the best idea for affordable space travel so far.  Because for this concept to work, to be fully immersive, we need a mechanism by which normal everyday people can get to space to attend a talk on dark matter, for instance.  We can't just be using shuttles that cost a quarter million dollars per trip.
Off by a factor of 4000. The Space Shuttles didn't cost a quarter million dollars per trip, they cost more than a billion dollars per trip.  Reimplemented as passenger vehicles with ~100 people inside, a practical number, you could count that as ~$10M/seat.

Nothing we have on offer could bring us down to a quarter million dollars per seat for human cargo.  Crew Dragon will aim for ~$15M/passenger in the most cramped configuration, and come close to what a Shuttle Passenger Variant would have been if there had been any interest.  You can imagine the larger successor to Crew Dragon, if a market ever develops, and we go through another generation of launch vehicles, making it down to the $3M-$10M range pretty easily, but $1M-$3M is going to be rough, and $300k-$1M is out of the question for now.

Skylon only aims for a 20 ton payload vehicle at present, but is so distant real costs are essentially impossible to predict.

We're utilizing solar energy at the moment, but we're not sure if these panels are enough to power all our operations.  We'd like to find out the likely potential panel efficiency in the coming decades and then decide if we need to add many more to the design, there's plenty of space to include more.

We'll definitely need some sort of radiation shielding.  What we're hoping for is using superconductors in the design, using magnetic shielding, this is something being researched by we'll have to find out how plausible it is to incorporate.  In our concept we want to use technologies that could be in use in fifty years' time.

It's probably best to assume you can never get enough solar panels.  They're in very high demand for propulsion and operations.

You don't strictly need radiation shielding in Low Earth Orbit, where your renderings are sited;  Only in a major solar radiation / geomagnetic event is there much of a threat.  In LEO there is a much greater background radiation dose than on Earth, but not so much to move the cancer risk needle terribly much;  Travelling on airplanes is pretty severe too.
« Last Edit: 03/12/2015 08:00 PM by Burninate »

Offline pkrahn

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Re: space habitat concept
« Reply #2 on: 03/12/2015 07:58 PM »
Quarter million is an estimate of some future technologies, by people who seem like they should know, but it's not meant to be specific. 

Nothing to offer?  I'm not sure if you understand what we're doing, this isn't an attempt by engineers to improve on O'Neill and others, instead it's trying to come up with a slightly original but plausible variation to incorporate into a virtual reality environment.  Have you ever been inside of a space station, and felt it as a real experience?  I assume none of us have.  VR is going to make it possible, and some are already modeling the ISS.  We want something larger, more functional, within which people can think about how to improve on overall design.

I refuse to believe that we as a people can't improve on Space Odyssey.  Mankind has seemingly given up on the idea of space habitation for now, or has been put on pause.  And while the station of 2001 was great, they made their mistakes.  I'm thinking more of their ship, the tight rotation to simulate gravity would have made the occupants sick.  We need more science fiction that attempts to moderately update these ideas.

Offline Jimmy Murdok

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Re: space habitat concept
« Reply #3 on: 03/12/2015 08:21 PM »
Hey nice design!!! Your idea of a VR space station is really cool, I would like to test it when ready.
I like the crossection, is it between 10 to 12m diameter?
As I like short term realistic things, I think the section size fits, but the 960m diameter I feel is too much for this diameter. If we have the technology to setup something that massive, the diameter of the crossection will be much bigger than something the size of an actual station. Skylab was already around this diameter and Bigelow is projecting it's BA2100 for a much nearer future with similar size. So I would reduce the whole station diameter to make it realistic or just go and make something much more massive for the crossection. Just an opinion.

Cheers and good luck!

Offline Burninate

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Re: space habitat concept
« Reply #4 on: 03/12/2015 08:23 PM »
We need more science fiction that attempts to moderately update these ideas.

I think so too, but to connect with present needs it has to update to the conditions;  In the early to mid 20th century we experienced continuous technological revolution, but in the late 20th century it became clear we would not see continuous exponential progress in spaceflight the way we saw exponential progress in, say, semiconductor density.  It has to acknowledge that spaceflight is *hard*, and will remain hard so long as we are recognizable humans with a recognizable economy and recognizable disagreements about priorities.

The possibility/probability I am afraid of is that 50 years on, the ISS will be looked back upon as a quaint memory and the resident population of space will zero, the way people who are not members of this forum look back upon Apollo.  *THAT* is what we need to be fighting.  That is what requires novel solutions that are 10x or 100x as effective as previous ideas.  That is what requires pathways from here to there;  Technological innovation and things getting painlessly easier to do is by no means assured.

There are interesting structural  engineering & architectural questions here, you just have to pose them as such.  Assume a degree of pessimism about the difficulties and you can develop revolutionary concepts, not merely distant renders.

* Mass is extraordinarily hard to get to space from Earth.  Unconsolidated asteroidal regolith, though, is relatively easy to get to a station.  About the only things it's good for from a spaceflight perspective are water and radiation shielding, and you can assume that its structural strength is near-zero.  Earth launch vehicles that cost <$100/kg look more distant to our eyes than they looked to our grandparents' eyes, but there have been very substantial advancements in low-thrust propulsion since the time of these science fiction pioneers.

* Compression structural members are extraordinarily costly from a mass perspective relative to tension structural members.  The lighest-weight trusses and even inflatable membrane structures are much more cost-effective than on Earth.

* Any Earth-architected structure has to be composed of a large number of chunks that each fit in a relatively small tube, and are deployed and connected to each other with relatively fragile, heavy connectors.

* There can be very large density differences in a station: A water tank will have ~1000kg/m3, while a really big inflatable habitat might be closer to 10kg/m3.  Optimizing for low mass and high habitability in future projects will rapidly decrease density of habitats.

* Airflow on a station is an enduring problem: People basically need a light breeze just to continue breathing effectively.  The ductwork and fans alone make the ISS an especially cramped, noisy place to be.

* Any actuated joints are prone to failure, and actuated joints or swivels which have contiguous pressure zones, such that a human could climb through them, are probably impossible for more than a small range of motion.

* Lightweight solar arrays are not very compatible with high-G centrifugal conditions.

The problem is that O'Neill and Kubrick weren't pessimistic enough, and didn't recognize that the gulf between here and there would seem so vast the moment we put our foot in the water, or would require so many hops on the way to their destination.  They weren't making works about the near future, they were making works about the very distant future, and they couldn't know it at the time.  Well - the ideas *remain* about the distant future.  They've been about the distant future longer than I've been alive, and we seem no closer because we've discovered  so much more of the problems in front of us.
« Last Edit: 03/12/2015 09:09 PM by Burninate »

Offline Alf Fass

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Re: space habitat concept
« Reply #5 on: 03/12/2015 08:46 PM »
Why this design over something with a smaller overall diameter and spinning faster with a larger tube diameter, why so few spokes? Why not just go with the more common proposal of docking at the hub? It just looks like a pretty design with no engineering offered as to why that design is an improvement over countless others.
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Offline Burninate

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Re: space habitat concept
« Reply #6 on: 03/12/2015 08:49 PM »
Why this design over something with a smaller overall diameter and spinning faster with a larger tube diameter, why so few spokes? Why not just go with the more common proposal of docking at the hub? It just looks like a pretty design with no engineering offered as to why that design is an improvement over countless others.
Coriolis Nausea afflicts very small diameter designs.  Reasonable rotation rates are up to 2-4rpm;  Above 7rpm there seem to be intractable issues in the short term.

At 480m radius, you can get 1G at 1.365rpm - a guaranteed comfortable experience apparently
At 120m radius, you can get 1G at 2.73rpm - Some side effects, but everyone can acclimate to the condition eventually
At 60m radius, you can get 1G at 5.46rpm - Extremely uncomfortable, some people can eventually acclimate, some can't
« Last Edit: 03/12/2015 09:02 PM by Burninate »

Offline Alf Fass

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Re: space habitat concept
« Reply #7 on: 03/12/2015 08:58 PM »
Why this design over something with a smaller overall diameter and spinning faster with a larger tube diameter, why so few spokes? Why not just go with the more common proposal of docking at the hub? It just looks like a pretty design with no engineering offered as to why that design is an improvement over countless others.
Coriolis Nausea afflicts small diameter designs.  Reasonable rotation rates are 2-4rpm;  Above 7rpm there seem to be intractable issues in the short term.

I know.

1 RPM @ 1g the radius is 894m
2 RPM @ 1g the radius is 223m
4 RPM @ 1g the radius is 55.9m

To get the 1g from the advertised 960m diameter will require spin of 1.36 RPM.
« Last Edit: 03/12/2015 08:59 PM by Alf Fass »
When my information changes, I alter my conclusions. What do you do, sir?
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Offline pkrahn

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Re: space habitat concept
« Reply #8 on: 03/12/2015 09:04 PM »
Why this design over something with a smaller overall diameter and spinning faster with a larger tube diameter, why so few spokes? Why not just go with the more common proposal of docking at the hub? It just looks like a pretty design with no engineering offered as to why that design is an improvement over countless others.

It seems like plenty of parking spots considering the size of the station, although it'll probably need to be adjusted.

You mean docking as in 2001?  This design isn't large and deep enough to do that with many craft, as I understand.  This way we can fit many more craft.  I should mention that the Lightcraft sends smaller landers, the actual ships themselves would have to be parked below or behind the station.

You're right, we don't have much engineering to offer, other than basing some of it on previous designs.  However the variation of having these modules along the outside of the ring is an architectural choice, to create living spaces that are more individual, and offer great views.  We're hoping it's not infeasible to construct.

Offline Nilof

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Re: space habitat concept
« Reply #9 on: 03/12/2015 09:07 PM »
Imho, I think that the best path towards a rotating space station is to use it to test the human reaction to low gravity. That would both allow the space station to be scaled down and make a better business case for it as a laboratory.
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline pkrahn

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Re: space habitat concept
« Reply #10 on: 03/12/2015 09:08 PM »

1 RPM @ 1g the radius is 894m
2 RPM @ 1g the radius is 223m
4 RPM @ 1g the radius is 55.9m

To get the 1g from the advertised 960m diameter will require spin of 1.36 RPM.

Thanks!  Al Globus gave us the 1.93rpm for a 240m radius, which seems dead on, then we doubled the size and just halved the number for now, which we weren't sure about but is now obviously the the correct math.

Offline pkrahn

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Re: space habitat concept
« Reply #11 on: 03/12/2015 09:09 PM »
Coriolis Nausea afflicts very small diameter designs.  Reasonable rotation rates are up to 2-4rpm;  Above 7rpm there seem to be intractable issues in the short term.

At 480m radius, you can get 1G at 1.365rpm - a guaranteed comfortable experience apparently
At 120m radius, you can get 1G at 2.73rpm - Some side effects, but everyone can acclimate to the condition eventually
At 60m radius, you can get 1G at 5.46rpm - Extremely uncomfortable, some people can eventually acclimate, some can't

Thanks for the figures.  The coriolis effect would have to have been very strong on the 2001 ship.

Offline Alf Fass

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Re: space habitat concept
« Reply #12 on: 03/12/2015 09:10 PM »
The usual approach to multiple docking ports in a spinning station is to have a de-spun arm connected through the axis of rotation to the hub with the ports coming off of that.
 There was a thread on here a little while ago suggesting that the despin joints would be some sort of insurmountable engineering challenge, which is nonsense.

http://www.artificial-gravity.com/sw/SpinCalc/SpinCalc.htm
« Last Edit: 03/12/2015 09:19 PM by Alf Fass »
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Offline Burninate

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Re: space habitat concept
« Reply #13 on: 03/12/2015 09:21 PM »
The usual approach to multiple docking ports in a spinning station is to have a de-spun arm connected through the axis of rotation to the hub with the ports coming off of that.
 There was a thread on here a little while ago suggesting that the despin joints would be some sort of insurmountable engineering challenge, which is nonsense.

The problem is more that friction on the despin joint, however large or small, requires a continuous expenditure of fuel to desaturate.  Configurations which balance multiple wheels do not, but they vastly increase the amount of compression structural members and hence mass.  Simultaneously, it is extraordinarily difficult to pass anything through that joint while it's rotating other than maybe power via commutators, due to the problem of vacuum sealing.  Attempts to solve the latter problem make the former problem bigger.

Offline pkrahn

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Re: space habitat concept
« Reply #14 on: 03/12/2015 09:22 PM »
I like the crossection, is it between 10 to 12m diameter?
As I like short term realistic things, I think the section size fits, but the 960m diameter I feel is too much for this diameter. If we have the technology to setup something that massive, the diameter of the crossection will be much bigger than something the size of an actual station.


You make a good point, whether or not the width of the torus should be increased.  It would be nice to have more space, but that also would greatly increase the construction cost I imagine.

Offline Nilof

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Re: space habitat concept
« Reply #15 on: 03/12/2015 09:23 PM »
The usual approach to multiple docking ports in a spinning station is to have a de-spun arm connected through the axis of rotation to the hub with the ports coming off of that.
 There was a thread on here a little while ago suggesting that the despin joints would be some sort of insurmountable engineering challenge, which is nonsense.

The design challenge certainly isn't insurmountable, but it isn't trivial either. There are alternative designs that avoid the use of pressurized joints entirely, such as for example having a small pressurized module along the center that can be spun up for a pressurized connection with the rotating segment, or spun down to dock with a spacecraft or a non-spinning part of the station.
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline pkrahn

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Re: space habitat concept
« Reply #16 on: 03/12/2015 09:36 PM »
We're thinking this station will be built using a reconstituted asteroid.  It would require a 3D printing process that is a bit speculative still. 

What we can't build has to be hauled up, and our best solution to that is the Lightcraft technology, which would be much, much cheaper than what we have now.  If you don't count the microwave satellite infrastructure construction costs and the massive space junk cleanup first needed. 



* Airflow on a station is an enduring problem: People basically need a light breeze just to continue breathing effectively.  The ductwork and fans alone make the ISS an especially cramped, noisy place to be.

* Any actuated joints are prone to failure, and actuated joints or swivels which have contiguous pressure zones, such that a human could climb through them, are probably impossible for more than a small range of motion.

* Lightweight solar arrays are not very compatible with high-G centrifugal conditions.


Interesting about the airflow problem, it's not something I was aware of.  And I know little about joints yet either.  I do know that space stations leak air so an earlier idea of making each "complex" modular... as it in could be replaced with an entire new building... was scrapped, instead we believe it needs to be built, printed, as a single pieces.

It's tough to speculate on solar technologies at the moment, with how rapidly the field is advancing.  Also, I wouldn't have thought that one would consider the center of this station as "high-G", it's rotating quite slowly.  Although if we want to add more panels, extended to near the outer torus, that's something to consider.  I should add the the detailing on the torus at the moment is mostly cosmetic, the final design shouldn't have any details that don't serve a purpose.

Offline Alf Fass

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Re: space habitat concept
« Reply #17 on: 03/12/2015 09:39 PM »
Rotating pressure joints aren't hard or rare, friction in such joints is low, and vacuum stable lubricants are also not hard.

I won't be replying to further comments on this topic as it's derailing the thread.
When my information changes, I alter my conclusions. What do you do, sir?
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Offline pkrahn

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Re: space habitat concept
« Reply #18 on: 03/12/2015 09:41 PM »
The usual approach to multiple docking ports in a spinning station is to have a de-spun arm connected through the axis of rotation to the hub with the ports coming off of that.
 There was a thread on here a little while ago suggesting that the despin joints would be some sort of insurmountable engineering challenge, which is nonsense.

http://www.artificial-gravity.com/sw/SpinCalc/SpinCalc.htm

Very interesting, I hadn't  heard of this before.  I can picture how it would work.

However... with more advanced computer controls, is it still too challenging to control the thrusters to exactly mimic the rotation of the hub?

Offline pkrahn

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Re: space habitat concept
« Reply #19 on: 03/12/2015 09:43 PM »
The usual approach to multiple docking ports in a spinning station is to have a de-spun arm connected through the axis of rotation to the hub with the ports coming off of that.
 There was a thread on here a little while ago suggesting that the despin joints would be some sort of insurmountable engineering challenge, which is nonsense.

The problem is more that friction on the despin joint, however large or small, requires a continuous expenditure of fuel to desaturate.  Configurations which balance multiple wheels do not, but they vastly increase the amount of compression structural members and hence mass.  Simultaneously, it is extraordinarily difficult to pass anything through that joint while it's rotating other than maybe power via commutators, due to the problem of vacuum sealing.  Attempts to solve the latter problem make the former problem bigger.


Thanks.  It seems simpler to build smarter ships, with pinpoint maneuverability.

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