Space Habitats

[magnemoe]

Wow, this thread has gotten some where dark. First of all Godwin's Law once again remains true...

Ok, anyways, please remember population growth in industrialized nations is a negative number. More and more people are waiting later and later to have children, having fewer children, or not having any children.

Right now the US's population growth has been supported be immigration, and if you look at the numbers more immigrants left last year than arrived, so that's a negative number too.

This isn't cultural, this is true of any culture that industrializes due to children going from being a resource can use to work the fields into an expense you have to pay for while they go to school to learn how to do the modern jobs. It will happen to every nation at differing paces.

So yeah we'll probably hit 9 Billion in the next 50 years, but if we can get past that it will start dropping.

If you do low tech farming, many kids are useful as they can help you farm. In an city or with an middle class living style kids become an major expense.

Was pretty surprised then this was true in Sims 2 too with the dlc who added farming, and yes you wanted to keep the kids home from school so they could work more. No they removed the option to use kids as farmhands in Sims3.

[lajoswinkler]

*bubbles bubbles bubbles*

Osteporosis and muscle atrophy is awesome.

[ThirdHorseman]

Osteporosis and muscle atrophy is awesome.

Disuse osteoporosis and muscle atrophy are only an issue if you plan on returning to a gravity well. If you plan to live your entire life in space then these are not a concern.

However, there are already plenty of ways to reduce and/or eliminate these issues. Electrical muscle stimulation is used all the time in physical therapy to prevent disuse muscle atrophy, and there have been several studies which have shown EMS can also prevent bone loss.

http://www.medwirenews.com/news/article.aspx?k=39&id=77470

Rather than trying to spin a massive metal structure, or wrap yourself in bungee cords and trying to run on a treadmill, you just lay back in a chair for a little while every day and have yourself worked over. There is no reason why the system couldn't be tweaked to the point where it happens at night while you sleep.

People are so caught up in trying to force the environment to conform to human needs. Why not force humans to conform to the environment? Come on, you really want to go all the way into space just to lug around your 80-90 kilos on your aching knees and spine, your heart straining to pump blood under the oppressive force of 1G? Wouldn't you rather drift around effortlessly, free from the fears of falling and breaking a hip? You can keep your 1G on the ground where it belongs...

[SargeRho]

Exept zero g has other negative health effects. Specailly on the digestive and circulatory systems.

[ThirdHorseman]

Exept zero g has other negative health effects. Specailly on the digestive and circulatory systems.

Never heard about digestive issues. Any links? And the only circulatory system issues are fluid redistributions that cause your upper body to swell up a bit (only cosmetic) and can cause feelings of sinus congestion. Nothing serious at all.

The only other big issue is the reports of visual impairment, again most likely due to changes in fluid distribution which causes pressure on the optic nerve and can lead to vision issues, similar to an existing condition called intracranial hypertension. This only seems to happen in a percentage of those who spent long amounts of time in space, so I wonder if there are underlying medical issues that exacerbate the problem (perhaps only in older people who are already starting to suffer macular degeneration?). There are ways to treat intracranial hypertension such as draining of the cerebrospinal fluid (CSF) by doing a lumbar puncture, as well as certain medications that can reduce production of CSF.

More study on how microgravity affects human health are required, that is for sure. But I would rather concentrate our efforts on adapting our biology to fit the environment, using medications and new forms of treatment, rather than just lugging our old environment around with us...

[SargeRho]

Your heart muscle also atrophies in zero-g. It has much less blood to pump, and no gravity to fight against. If you return to Earth, this can cause serious health issues.

[lajoswinkler]

Disuse osteoporosis and muscle atrophy are only an issue if you plan on returning to a gravity well. If you plan to live your entire life in space then these are not a concern.

However, there are already plenty of ways to reduce and/or eliminate these issues. Electrical muscle stimulation is used all the time in physical therapy to prevent disuse muscle atrophy, and there have been several studies which have shown EMS can also prevent bone loss.

http://www.medwirenews.com/news/article.aspx?k=39&id=77470

Rather than trying to spin a massive metal structure, or wrap yourself in bungee cords and trying to run on a treadmill, you just lay back in a chair for a little while every day and have yourself worked over. There is no reason why the system couldn't be tweaked to the point where it happens at night while you sleep.

People are so caught up in trying to force the environment to conform to human needs. Why not force humans to conform to the environment? Come on, you really want to go all the way into space just to lug around your 80-90 kilos on your aching knees and spine, your heart straining to pump blood under the oppressive force of 1G? Wouldn't you rather drift around effortlessly, free from the fears of falling and breaking a hip? You can keep your 1G on the ground where it belongs...

So, bumping your head into something and fracturing your skull like an egg is worth it?

The extent of the effects of gravity are enormous. Immune system, for some reason, really likes gravity.

Human body could not grow up normally. Development of inner ear that's a sensory system for spatial orientation would fail.

It would take a complete genetic reengineering of a human being to comply with a lifetime worth of living in microgravity. That's a bigger pipedream than establishing a colony on Mars.

[m1xte]

Or just launch raw materials into orbit, which have higher tolerances and thus can be launched cheaper and easier than delicate instruments and organics.

I wonder how much safety and success rate adds to a cost of launch.

Ginormous SRB-launcher controlled by smartphone could bring cheap stuctures and fuel to LEO and only explode every second launch, but who cares when its not a billion dollar satellite that explodes.

[drakesdoom]

Ideally you don't ever launch material. You would mine in space, process in space, and build in space to stay in space.

[Apature rocket science]

The reality of living in space and having the whole thing rotate to make gravity is the dumbest idea ever if you jump you will just float and keep gonig till you touch something else, it only works if you are torching the rotating object

[andrewas]

Um. No. When you jump, you still have the velocity you had when you were on the floor, plus the velocity you had when you jumped, which puts you on a straight line trajectory (when viewed from a non-rotating reference) which brings you back into contact with the ground, and when viewed from inside the habitat looks very much like a jump and landing performed under normal gravity.

[Kimberly]

The reality of living in space and having the whole thing rotate to make gravity is the dumbest idea ever if you jump you will just float and keep gonig till you touch something else, it only works if you are torching the rotating object

Have you ever jumped in an airplane? Did it hurt when you slammed into the back of the plane at 570 miles an hour?

[Thaniel]

There is also the issue of aerodynamic drag inside the habitat, wich will work against weightlessnesness. You will allways be pulled along with the rotation.

On a slightly related note, while wheel-constructions of metal and glass would be prefered for rigidity, there is a possible lighter sollution for the much nearer future when it comes to such devices. Inflatable structure supported by an expanding strut construction. There's been done some work on this by Nasa back in the days. But that stopped due to limiting in size.

The benefits by using something akin to Bigelow's system would be imense. It would still require "a few" launches, but if the spin was limited to give only half a g instead a full one g, then it's absolutely within feasability.

[ThirdHorseman]

So, bumping your head into something and fracturing your skull like an egg is worth it?

It will never get that bad. Most of the bone loss is in the lower part of the body, and in addition you don't see total bone loss...you see a slow progression of bone loss until it eventually plateaus and the both reaches a new equilibrium. So you will never lose enough bone density to become as fragile as an egg shell, and if you intend to spend the rest of your life in microgravity you won't have any problems. If you intend to get back under gravity at some point then you will want to maintain some bone density, or at least start to rebuild it as your time for return approaches using either electrical muscle stimulation, additional dietary calcium, or drugs that are being tested to allow calcium retension. All these options are much easier than artificial gravity.

The extent of the effects of gravity are enormous. Immune system, for some reason, really likes gravity.

While there have been some studies that show immune system deficiencies in microgravity:

http://www.esa.int/Our_Activities/Human_Spaceflight/Research/Goldfinger

http://www.sciencedaily.com/releases/2013/04/130422132504.htm

http://www.space.com/4302-stresses-immune-organs.html

But there is evidence that it is not actually microgravity that causes the immune issue. Tests of U.S. Army Rangers during intensive training exercises showed the same kind of response. So it's more likely that it is the fact that the endothelial cells are being stressed and were attempting to adapt to the new environment, and therefore couldn't respond as well to infection:

"We saw what maybe one could guess in retrospect that you would see, which was that the immune system was involved in the stress of being a Ranger, and when we added these pathogens -- the virus, bacteria and toxin -- in separate experiments, they didn't respond to them. And we saw something very similar to that in space. The cells were probably preoccupied with the response to microgravity, and, therefore, when exposed to LPS, yes, there was a response, but it certainly wasn't comparable to what we were seeing on the ground."

So these issues can be handled medically or simply allowing the body to adapt to microgravity. There have been no studies to show that this reduced immune response continues over long periods, and most likely the immune system would revert to normal function once the body adapted to the new environment.

Human body could not grow up normally. Development of inner ear that's a sensory system for spatial orientation would fail.

There have been many studies which show that organisms, including mammals, can develop normally in microgravity (http://www.plosone.org/article/info%3adoi/10.1371/journal.pone.0006753 is a good one):

There are issues, or course. Attachment of the embryo to the uterine wall can be problematic. It's highly likely that permanent habitation in microgravity will require a shift from normal fetal incubation to ectogenesis, where IVF is performed and the resulting embryo is incubated in an external device where development can be more easily monitored. I'm a proponent of this method regardless of the environment, but it will be especially valuable in a microgravity habitat.

But there is nothing stopping humans from procreating in microgravity. And I've never seen any study that shows the inner ear doesn't develop properly in microgravity. While 40% or so of people who go into space experience visuo-vestibular mismatch...space sickness...the issues go away after anywhere from a few days to a week. The body adapts to the new environment.

It would take a complete genetic reengineering of a human being to comply with a lifetime worth of living in microgravity.

This is completely false. We have the medical knowledge, and the available materials, to allow permanent habitation in microgravity right now. It will be a lot different than living on Earth, but the human body is remarkably well suited to adaptation. We can't keep bringing our Earth environment with us everywhere we go, it's too difficult and just burdens us with physical and psychological baggage. So while you suffer under the weight of 1G, I'll take my calcium supplements, zap my muscles, and float like a bird in my bubble habitat...

Here is another good link that has lots of information on the physical issues with microgravity, and methods to counter them:

http://chapters.marssociety.org/usa/oh/aero4.htm

Edited August 29, 2013 by ThirdHorseman
added link

[ThirdHorseman]

Ideally you don't ever launch material. You would mine in space, process in space, and build in space to stay in space.

Yes, ideally you would have material already in space that you could use. But in the short term we'll have to send large quantities of raw materials (water, O2, metal, etc) into space. But these can be launched far cheaper than things like complex electronics or people, and we can settle for a higher failure rate when launching raw materials.

But hopefully we would quickly be mining from asteroids and the moon and rely less on materials from Earth.

I wonder how much safety and success rate adds to a cost of launch.

A lot. Which is why we establish a permanent habitation in orbit so we don't have to keep shuttling people and expensive machines into space. If the vast majority of launches are just raw materials then we can accept a lower safety threshold and lower success rates, which can bring down costs.

[ThirdHorseman]

The benefits by using something akin to Bigelow's system would be imense. It would still require "a few" launches, but if the spin was limited to give only half a g instead a full one g, then it's absolutely within feasability.

Again, the big problem of using centripetal force as artificial gravity is that it isn't real gravity. Unless you are spinning really slowly and at a very large diameter then you have all kinds of issues. And unlike the issues involved with living in microgravity, these cannot be adapted to or alleviated with drugs or medical procedures.

The best option would be inflatable habitats attached to the ends of long struts, which rotate like spokes on a wheel. But the lengths required are so long that the stresses on the structure become unmanageable without some new super light and super strong miracle material.

Much better to just adapt human physiology to live in the new environment...

[Moon Goddess]

The reality of living in space and having the whole thing rotate to make gravity is the dumbest idea ever if you jump you will just float and keep gonig till you touch something else, it only works if you are torching the rotating object

An object in motion tends to remain in motion unless acted upon by an outside force

It's one of the most basic ideas in physics, in fact, it's the only reason the whole spinning to make artificial gravity work in the first place. We move you this way... and you continue moving in that way but we've not moved the floor and so that way becomes down and we move you the next way. It's this same law that lets us orbit in the first place, gravity pulls you down, inertia moves you forward, the net result is a circle.

Lex I: Corpus omne perseverare in statu suo quiescendi vel movendi uniformiter in directum, nisi quatenus a viribus impressis cogitur statum illum mutare.

[magnemoe]

Again, the big problem of using centripetal force as artificial gravity is that it isn't real gravity. Unless you are spinning really slowly and at a very large diameter then you have all kinds of issues. And unlike the issues involved with living in microgravity, these cannot be adapted to or alleviated with drugs or medical procedures.

The best option would be inflatable habitats attached to the ends of long struts, which rotate like spokes on a wheel. But the lengths required are so long that the stresses on the structure become unmanageable without some new super light and super strong miracle material.

Much better to just adapt human physiology to live in the new environment...

Some hundred meters in diameter should be enough. Perhaps 5-700 for 1g. you would build this as an wheel, an rigid ring and spokes to the center. Inflatable would work well but you would want to inflate them on the top of the ring. Quite possible to make with steel and aluminium, far simpler than an suspension bridge as you just connect the spokes to an small strong ring in the center and we can make them kilometer long.

[Mr Shifty]

EDIT: Too much snark. Mods please delete.

Edited August 29, 2013 by Mr Shifty

[Thaniel]

Again, the big problem of using centripetal force as artificial gravity is that it isn't real gravity. Unless you are spinning really slowly and at a very large diameter then you have all kinds of issues. And unlike the issues involved with living in microgravity, these cannot be adapted to or alleviated with drugs or medical procedures.The best option would be inflatable habitats attached to the ends of long struts, which rotate like spokes on a wheel. But the lengths required are so long that the stresses on the structure become unmanageable without some new super light and super strong miracle material.

• Oh, you mean something like the suggestion you just snipped away from my post there? And rewrote yourself? That asside, there realy isn´t need for anything super light and super strong and magical. We allready have materials able to do this job fairly light and easy. Kevlar and titanium to mention some. In this case, aluminium will also get to play a part without trouble.
  

• As for size, Why so large? Ofcourse, the larger the ring, the slower it can rotate, but a diameter of around a 100 meter as I proposed means a circumference of a little more than 300 meter, (you could place the ISS in the hub of the wheel, the outer tips of the solar panels would be around the wheel´s rim), is a decent and viable small size to aim for. But double that then, to a 200 meter in diameter. The wheel itself launched in 30-32 launches, using todays tech and variations over modules being developed today. Add in wire support to a hub, a couple of inflatable shafts to the center, a hub-module or two, giving 0.5 g at 2 rpm. That´s significant.
  

• Now here comes a few sad numbers, if about 50% of the space shuttle´s ET´s could have been salvaged for a station, out of the 135 launches, say we could utilize some 67 of them. That could give a wheel-station either 46 meter wide, ca 90 meter radius (560 meter circumference). Used side by side like that, it would give the benefit of each piece of straight floor to have very little deviation from the wheel´s normal, hence, the percieved gravity would be nice and uniform. Spinning this up to 2.2 rpm would give a nice and toasty 0.5 g at the rather large floorspace. Easily several decks actualy.
  

• Now, if placed end to end, the wheel would be considerably larger. The problem with this setup is that atleast for smaller wheels, the vector of the gravity in each module will be significantly different depending on where in the module you would be. But, 67 tanks, each some 47 meters long, gives a wheel with a circumference of roughly 3.14 km. That means a diameter of around 1 km. Giving a radius of say, 500 meter. Spinning this up to 0.3 rpm is all it´d take. That is less than a third of a revolution per minute, to produce 0.5 g. The problem with using the ET´s for this is that they would need some external support, and they would have had been redesigned a little from the begining. But something along those lines where actualy proposed. In wich case, we would already have launched a lot of the hardware for a pretty large station with artificial gravity. These numbers are sad, because the Orbiter is now retired, and atleast for the foreseeable future, no such large tanks will be launched into orbit is such an abundance.
  

• At this point, I´m guessing you still yell on about needing superstrong materials and such. If that´s the case, then please, read up on what materials we have available today. Because this is ONLY a question of engineering with what we have now (politics and economy asside).
  

• I´d still prefer the first wheel station to be made up of inflatable modules like I first suggested though, as that would be simpler, cheaper, and be a nice proof of concept. And if it for some reason failed as a concept, atleast the modules could be salvaged into a more traditional configuration. And we didn´t have to build a time machine first
  

• Edit: Thanks Mr. Shifty
  

Edited August 30, 2013 by Thaniel

[Mr Shifty]

Edit: For some silly reason, it seems I´m not allowed to divide this wall of text into smaller potions.

Yeah, for many of us, the forums are having issues after the update yesterday. Carriage returns appear to be one of the casualties. I've had to workaround by using

• BB codes to separate out paragraphs.
  
  • Here is one paragraph.
    
  • Here is the next one.
    

Looks crappy with the bullets, but it's better than a wall of text:)

[ThirdHorseman]

Oh, you mean something like the suggestion you just snipped away from my post there? And rewrote yourself?

I misread your post. I assumed you were referring to an O'Neill cylinder that was an inflatable structure. Yes, something like your suggestion would be the best option for a spinning habitat.

That asside, there realy isn´t need for anything super light and super strong and magical. We allready have materials able to do this job fairly light and easy. Kevlar and titanium to mention some. In this case, aluminium will also get to play a part without trouble.

That depends on the size of the structure. For the structures you detail in your post, yes those could be assembled using existing materials without much problem. But the amount of research that has been done on human comfort in artificial gravity situations is spotty at best. If you choose one study, then your numbers are fine. But choose another study and you are now looking at radii in the range of tens of kilometers. Such a structure would not be so easily manufactured using existing materials.

At this point, I´m guessing you still yell on about needing superstrong materials and such. If that´s the case, then please, read up on what materials we have available today. Because this is ONLY a question of engineering with what we have now (politics and economy asside).

No, what I'm still yelling on about is why you want gravity at all.

Could you build an orbital habitat right now, given existing materials and technologies, that spins in such a way to give the inhabitants 1G with a decent level of comfort (i.e. no vestibular illusions or nausea)? Maybe, depending on who you listen to. If you go by one study you would need a radius of almost 100km, which is probably not do-able with existing materials and technologies. If you go by another study you could build the same system with a radius of 22m, which is definately do-able. So without having accurate research on human comfort in artificial gravity then you can't really say how possible such a habitat is.

And this issue goes beyond orbital habitats. There is every reason to believe that permanent inhabitants of lunar (and even Mars) bases will have the same type of physiological issues associated with living in microgravity. Someone on the Moon will only experience .16G...not much more than what they would have in microgravity. What are you going to do, spin your lunar base around to simulate gravity? Mars, only .39G, might offer the same complication.

So again, why live in 1G? It has been shown beyond a doubt that humans can survive and live quite comfortably in low gravity environments, and they will have to if they ever plan on living in any habitat on any body other than Earth (asteroid, moon, etc). They can do so utilizing current medical technology, and further advances will only make it even easier. Low gravity offers many benefits, so why not take advantage of it?

[magnemoe]

Note the easiest way to test this would be an inflatable habitat or another light and cheap one in one end, in the other end put the wire and winch, rcs for spinning up and down and the return capsule.

Astronauts enter the habitat who is separated and winded out while the thing is rotated. At various distances you perform tests, spin up and test more, then wind out and continue. At the end you slow down and return the habitat.

[Thaniel]

Note the easiest way to test this would be an inflatable habitat or another light and cheap one in one end, in the other end put the wire and winch, rcs for spinning up and down and the return capsule. Astronauts enter the habitat who is separated and winded out while the thing is rotated. At various distances you perform tests, spin up and test more, then wind out and continue. At the end you slow down and return the habitat.

Agreed. Such an experimental "station" for a few years would be able to give a lot of new information on the topic. I assume one or possibly two launches of a SLS heavy would be able to place a large enough habitat module with a built in bunker of sorts, and a counter weight. Should get several decks in such a place. Spin it up, get different gravities, monitor crew at something like moon gravity, mars gravity, and 0.5 g over atleast a year at a time. With only short stops for resuply, if needed. Could possibly be made with a rotating docking port at it's mass center and an inflatable tube to get there. Only used for visits and suplys.

[NGTOne]

Well, there was actually a module like this proposed for the ISS, for exactly this very purpose. Not TransHab, but by Bigelow. Never got off the ground (the funding was cut).