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jhwegener
2009-Jan-30, 09:45 AM
Why do so many unfounded speculations of space colonisations?
There is nothing that should make us believe it is a real way to solve our problems on earth!
1: The probabillity there will be self-supporting "colonies" (or giving a "surpluss")seem small.
2: Any significant emigration from earth (or any substantial contribution from "space" to its inhabitants) seems to be pure imagination.

marsbug
2009-Jan-30, 10:36 AM
I think you'll find this thread (http://www.bautforum.com/space-exploration/79158-what-self-sufficent-colony-really-means.html)interesting.

My own opinion is that it would be very difficult for any single colony to be self sufficient. Neither is it likely there will be a mass emigration to space any time in our lifetimes.

However space/planetary habitats could contribute to earth through scientific research, specialist (micro-gravity) manufacturing, adventure tourism, and at some distant point asteroid mining. The total population of space is likely to remain small for the foreseable future but it can grow many times and still remain small next to earths population, so there is a need for habitats to be as self sufficient as we can make them to keep costs down.

Personaly I don't see space colonisation as a means to solve our problems on earth. Space research may provide a few hard to come by answers, space tourism may give us some new commercial opportunities, and space manufacturing may provide some unique materials for very specialist applications. I don't think i've ever heard someone seriously suggest we can solve the worlds problems by going into space though.

Ronald Brak
2009-Jan-30, 11:45 AM
I think that in the future, barring disaster, people will be so rich and have so much advanced technology they will be able to do weird things like build a house on Titan, just for the fun of it.

Whether people, or what passes for people at that point, will do stuff like this is of course impossible to predict.

IsaacKuo
2009-Jan-30, 01:00 PM
Why do so many unfounded speculations of space colonisations?
There is nothing that should make us believe it is a real way to solve our problems on earth!
It's not supposed to solve our problems on Earth. The only significant "practical" application proposed for space colonization is to ESCAPE potential problems on Earth (i.e. survival of humanity in the case of global catastrophe).

1: The probabillity there will be self-supporting "colonies" (or giving a "surpluss")seem small.
Why, exactly?

Certainly space colonies won't be completely independent for a long time, but they don't need to start off completely independent. Earth is around to supply high value low mass hardware like computer chips and such.

It should be pretty obvious that an ultimate goal of complete independence is a difficult long term goal at the end of a long road. To reach the far-away end of that long road, it's still necessary to take the first step. That first step won't get you to the end, but that doesn't mean it isn't worth taking.

We can argue about what the appropriate "first steps" should be. Certainly, this includes CELSS research, which is ongoing. I'd argue that developing emergency underground "bunkers" are a better use of our current resources than trying to establish a space colony immediately--but only until we have a better space transport infrastructure.

2: Any significant emigration from earth (or any substantial contribution from "space" to its inhabitants) seems to be pure imagination.
That depends on your definition of "significant".

Even if you don't understand the allure of space travel, there is a practically unlimited number of us humans who do. There will NEVER be a shortage of volunteers for space travel, no matter how hazardous. NEVER. The limit will ALWAYS be the technological/economic capacity of how many humans we can/will lift into space.

mugaliens
2009-Jan-30, 09:34 PM
My own opinion is that it would be very difficult for any single colony to be self sufficient.

On Earth single colonies of populations all the way down to one individual can be self-sufficient. However, the risk of failure increases as the numbers decrease. For a single person, a simple skeletal break or virus can be enough to doom the colony.

Thus, colonies with larger numbers tend to be more successful, although for societies with simple levels of technology, the point of diminishing returns is reached in the dozens to a couple hundred. The more complex the society, the larger the numbers required to reach that point.

Similarly, the more dangerous the climate, the greater the risk for any given number of people in the colony, and the success rate increases with increasing numbers.

For extraterrestrial colonies, the dangers are as steep, if not steeper, than deep-sea diving, or climbing Everest. It's not that it takes extreme physical capabilities. Rather, it takes extreme planning to account for, and prepare for, to counter, all contingencies, and for environments such as Mars and the Moon, those are extreme.

Let me illustrate:

You're in a lunar colony composed of 40 people in a series of 9 interconnected, pressurized domes made of tough fabric impregnated with an atmospheric sealant. For additional protection, particularly against micrometeorites, the domes are covered with a layer of lunar soil. Primary, secondary, and tertiary atmospheric generators are available, each of which is capable of recreating the entire atmosphere in a period of 24 hours. For additional protection, each of the domes is automatically sealed off in case of a leak.

So, while five people are in one of the domes, one of the workers drops a piece of lab equipment and reaches for it abruptly. In so doing, he overreaches and winds up flipping a large, sharp object upwards towards the ceiling, instantly tearing a 3-1/2 inch tear in the dome. The air begins to rush out, the pressure drops, and they're sealed inside.

The generators kick in, but while they're very capable, they're not that capable, and cannot keep up with the pressure drop in the dome.

The experts gather and run through various ideas on how to fix the tear, which is out of reach.

About ten minutes into this scenario, lots of things have been tried, including attempts to stuff the slit with material, all of which is too porous. It looks as if those five people will soon die. But there's one individual there who has this funny knack for coming up with bizarre, but workable solutions to problems.

He breaks out two packs of gum, distributes it and they all begin chewing. Meanwhile, he grabs a piece of paper from a printer. They twist the gum together into a long strand, and lay it on the paper in the form of an ellipse.

Once the gum is thoroughly stuck to the paper, he takes a bit of olive oil and wets the center of the paper before sticking it to the ceiling, slowing the leak to almost nothing, allowing the generators to catch up, the airlocks to be disengaged, and the people to be evacuated until a better patch can be made.

Improvisation. The problem is, only one of those forty people was able to come up with that innovative solution, and just happened to be in the room. That's just human nature.

Double the people and while you do improve the odds, they're not quite double, and there's a point of diminishing returns on that, as well.

So, is space colonization possible? Certainly! But the odds of long-term survival without routine and regular resupply are not very good, even with meticulous planning.

marsbug
2009-Jan-30, 10:29 PM
On Earth single colonies of populations all the way down to one individual can be self-sufficient. However, the risk of failure increases as the numbers decrease. For a single person, a simple skeletal break or virus can be enough to doom the colony.

Thus, colonies with larger numbers tend to be more successful, although for societies with simple levels of technology, the point of diminishing returns is reached in the dozens to a couple hundred.

Ok fair point. The phrase I'm looking for isn't self sufficient, it's disaster proof. As there's no such thing as totally disaster proof the key is still to be part of a larger network that can support you. On the moon, or on any orbit between LEO and there, that could be easy in terms of ideas and creative thinking, you're only 1.5 seconds of radio time away, all of earth can be there to offer creative advice. If you are part of an archipelago of stations and colonies stretching out to the moon emergency resupply and repair are easier to.

Mars presents a much less forgiving arena when viewed from that perspective, and it gets harder the further out you get. Experiance could mitigate the effect: if the first martians are lunar veterans things are a bit better. I think expansion into space would need to be in stages, and we need to be patient when it comes to learning all we can before moving onto the next challenge.

mugaliens
2009-Jan-31, 06:26 PM
Ok fair point.

Thanks.


If you are part of an archipelago of stations and colonies stretching out to the moon emergency resupply and repair are easier to.

While it might take a bit longer to have a "hot spare" ready to be refueled and launched, it's certainly many orders of magnitude cheaper, and still less than a week away. Certainly, emergency shelters could be made available which would support the loonies for a week.


Experiance could mitigate the effect: if the first martians are lunar veterans things are a bit better. I think expansion into space would need to be in stages, and we need to be patient when it comes to learning all we can before moving onto the next challenge.

I wholeheartedly agree on both points! And a successful Loonie would be primed to make a pretty fair Martian.

You would, however, need to salt them into the mix carefully, however, and in minority numbers, lest they take control of the Mars mission. There will be a lot of similarities, but there will be some significant differences, as well, and there is such a thing known as "negative learning." Put simply, this means that some of the lessons learned in a similar, but different environment will not only not transfer well to the new environment, they can be downright deadly if followed.

At one point I was current and qualified on three different aircraft, and while it was a boon in that I could fly any of them, I took pains to ensure I never entrusted critical numbers to memory, lest a number inadvertantly be the one from one of the other airframes. Whether it was V-speeds, weight and balance, capacities, or various comm/nav equipment and capabilities, I always used a checklist in which I'd written the specific numbers for that aircraft, and referenced it any time I used those numbers.

When you're talking about manning a Lunar outpost vs manning a Martian outpost, some of the differences, such as equalizing pressures, or atmospheric mix, can be deadly if a member of the outpost misremembers the number from his or her previous assignment.

marsbug
2009-Jan-31, 10:48 PM
If you plan to do adventure tourism, or even extended science operations away from the main base, emergency shelters would make a lot of sense. If maintaining a system of full shelters is too much of a stretch then a supply of consumables, basic tools, and a life support system that can be hooked into a damaged rover/ pressure suit would do. And a fairly deep hole to hide from radiation storms in.

It would make sense to have a main manned base servicing satellite unmanned bases (there are probably lots of experiments you'd want to do well away from the main hub of activity). If you include an emergency depot with each unmanned base it's not going to be much extra effort to have the personel check and resupply the depot if need be.

Having a rocket sitting on the launch pad, ready to launch 24-7 seems like a big cost in itself, one thats unlikely to get paid for. If something happens to the base that won't wait until the next scheduled run they may have to accept moving to a an unmanned base and living off an emergency depot in a rover until then!

Having a system thats fairly disaster proof might be a must as soon as you get out of LEO. I think that will mean some sort of distributed network.

Ara Pacis
2009-Feb-01, 10:43 AM
Are you guys going camping or planning space colonization? Inflatable and tearable membranes for habitats? That makes sense only for a short term scout mission but not for a long-term or even intermediate-term colony. Some basic metal cladding of plate or expanded-metal would do wonders to prevent punctures and shouldn't be that massy if you're managing such a large tent city.

Also:
- You should have emergency sealing patches on hand in every room with a pressure bulkhead/membrane.
- You should have an emergency compartment in each hab-tent that can itself be sealed. It might be a good idea to store p-suits and O2 bottles here.
- You should have airlocks between each major hab-tent with will be able to cycle even if one side of the airlock loses pressure. Depending on how large each hab-dome-tent is, you may have one or more between internal partitions.

marsbug
2009-Feb-01, 12:22 PM
I'm planning a small but sturdy moon base with nice puncture proof walls and enough dirt over the top to be fairly solar-storm resistant. But there's still lots that could go wrong inside those walls, and I'm sure some people will want or need to go out into the lunar wilds and camp in a tent, so I'm going to want a plan in place for every foreseeable f***k up, and some generall measures for ones I can't foresee.

And I'm hesitant to use the word colony. The moon would be an amazing place to work in and explore but I think it will be a long time before anyone calls it home. It's going to be a long wait before we see bases there, although I'm keeping my fingers crossed that the plans that have been started are followed through!

IsaacKuo
2009-Feb-01, 05:12 PM
I'm sure some people will want or need to go out into the lunar wilds and camp in a tent,
Need? Why? I can think of no possible need. If you need to do some work outside of the pressurized habitat, you do it while wearing a space suit. Period. What possible NEED can there be for getting out of that space suit and into a pressurized "tent"?

Anyway, I don't really see a manned moon base as something necessary or desirable, except perhaps as a tourist destination. Orbital stations have superior sunlight and artificial gravity, and they can be supplied in bulk from unmanned facilities on the Moon/Phobos/Deimos/Jovian outer moons. If you want a "practice" station for Mars, then that can be arranged at far lesser expense/risk here on Earth.

Still...the Moon is possibly an interesting resource to exploit, and you might want a station to orbit the Moon rather than Earth. Such a station can remotely operate unmanned facilities with practically no lightspeed delay.

These unmanned facilities might not necessarily be "on" the Moon, exactly. One weird idea I have is a "Moon Runner". It's essentially a skyhook that circles the moon at a barely suborbital speed. There's a main central body with solar panels and a tether tipped with a foot; the tether may be reeled in/out to telescope the foot.

This foot has a ~1.6km/s tip speed equal to Moon Runner's running speed. Moon Runner can maintain speed/altitude by periodically "pushing" downward onto the lunar surface with the foot. The foot also includes a "scoop" to pick up loose regolith. Moon Runner circles the moon until it has picked up enough loose ore; it can then use rocket thrusters to deliver this ore to orbital refining stations (these stations would enjoy 24/7 solar power, unlike Moon Runner which spends half of the time in darkness).

[edit added:]I just realized, Moon Runner can enjoy 24/7 solar power by running along the Moon's terminator.

cjameshuff
2009-Feb-01, 05:32 PM
Are you guys going camping or planning space colonization? Inflatable and tearable membranes for habitats? That makes sense only for a short term scout mission but not for a long-term or even intermediate-term colony. Some basic metal cladding of plate or expanded-metal would do wonders to prevent punctures and shouldn't be that massy if you're managing such a large tent city.

We're not talking about vinyl pool floats, here. The structures I've seen would be significantly more robust and easier to patch than a rigid metal structure. Multiple layers of extremely tough ripstop Vectran cloth for the Bigelow craft.

A badly torn aluminum panel would be permanently deformed, impossible to quickly patch, and very difficult to repair. The same event might not even puncture an inflatable structure, punctures that do happen would be very limited in size due to the ripstop and flexible nature of the material, and the hull would revert back to a nearly-normal shape afterward. Self-sealing structures are relatively simple to create, concerns with thermal expansion or fatigue are almost eliminated. You've got up to 100 kPa of internal pressure from air that'll never get mechanically fatigued or worn out, you might as well take advantage of it for supporting the structure.

cjameshuff
2009-Feb-01, 06:07 PM
[edit added:]I just realized, Moon Runner can enjoy 24/7 solar power by running along the Moon's terminator.

There's an idea. You'd need to accelerate by a couple m/s every orbit to keep the orbit aligned.

The moon has some benefits for a manned presence. Early on, cheap radiation shielding and thermal mass, and a lab for developing low gravity/vacuum environment machinery, mining, and industrial processes for use on the moon and elsewhere...human hands on-site will make for a much faster development cycle, allowing diagnoses and repair of problems and reconfiguration for different ways of attacking a problem. It may also turn out that lunar gravity is sufficient to maintain reasonable health, allowing simpler habitats on the ground.

marsbug
2009-Feb-01, 06:26 PM
Need? Why? I can think of no possible need. If you need to do some work outside of the pressurized habitat, you do it while wearing a space suit. Period. What possible NEED can there be for getting out of that space suit and into a pressurized "tent"?

Anyway, I don't really see a manned moon base as something necessary or desirable, except perhaps as a tourist destination. Orbital stations have superior sunlight and artificial gravity, and they can be supplied in bulk from unmanned facilities on the Moon/Phobos/Deimos/Jovian outer moons.

If you want to be the first person to hike across mare imbrium you are going to want a pressurized tent to sleep in, a suit can only be worn for so long, and a moon base cannot be carried on your back.

You seem to have much more faith in automation to run and maintain experiments and equipment then I do. I feel that a manned presence, that can take a rover out and fix a malfunctioning piece of equipment, would be irreplaceable for the foreseeable future. At the very least I'd want facilities on the base to support humans if their presence was needed. It would also provide a first destination for tourists to acclimatize to lunar gravity. I'm just not convinced robots, even ones operated by a relatively near by human, can do as good a job as an on site human. Time will tell which of us is right!




Still...the Moon is possibly an interesting resource to exploit, and you might want a station to orbit the Moon rather than Earth. Such a station can remotely operate unmanned facilities with practically no lightspeed delay.
A surface base could be shielded from solar storms by regolith, and would have the benefit of some gravity for the astronauts health. Artificial gravity has not been demonstrated on any manned habitat, and until it is I wouldn't count on it for future plans. Maintaining an orbit around the moon means constant course corrections as the moons gravity is uneven, so a station big enough to be comfortable would need a lot of extra fuel to stay up.

It would be much more efficient to have a few relay satellites keeping a fixed moon base in touch with automated bases, or even relaying instructions from earth.
If you're going to trust automation to run a moon base you might as well trust it and operate the base from earth. If it's smart enough to do the job it's smart enough that 1.5 seconds signal delay won't matter that much.

IsaacKuo
2009-Feb-01, 07:08 PM
If you want to be the first person to hike across mare imbrium you are going to want a pressurized tent to sleep in, a suit can only be worn for so long, and a moon base cannot be carried on your back.
That's a "want", not a "need". And it would still be a much better idea to stay in the space suit. Are you really going to lug around the extra air to fill a pressurized "tent" for each night of sleep? Or a compressor to recover that air?

You seem to have much more faith in automation to run and maintain experiments and equipment then I do.
Perhaps I just have a different idea of when we'll seriously start industrializing the Moon. The refinery hardware is going to involve such a massive investment that I don't see it happening within the next several decades. Maybe half a century to a few centuries from now. Either way, our robotic technology will be all the better by then.

At the very least I'd want facilities on the base to support humans if their presence was needed.
You could have a small pressurized station with basic life support and communications equipment.

It would also provide a first destination for tourists to acclimatize to lunar gravity.
Tourists can acclimate to lunar gravity while in transit. The shuttlecraft taking tourists to the Moon can have artificial gravity which matches lunar gravity.

A surface base could be shielded from solar storms by regolith,
So can a lunar orbital base. If you have any sort of lunar industry, you have some sort of economical launch method of hauling stuff off of the Moon's surface.

and would have the benefit of some gravity for the astronauts health. Artificial gravity has not been demonstrated on any manned habitat, and until it is I wouldn't count on it for future plans.
I would count on artificial gravity for future plans. It's really basic physics. If, for some bizarre reason, artificial gravity is deadly to humans, then we're just going to have to learn to live in zero gee (we already have significant experience with it).

Maintaining an orbit around the moon means constant course corrections as the moons gravity is uneven, so a station big enough to be comfortable would need a lot of extra fuel to stay up.
Nonsense. An orbit is an orbit. It doesn't matter how big or small the station is. (Assuming it's not stupidly large, like bigger than the Moon itself.)

It would be much more efficient to have a few relay satellites keeping a fixed moon base in touch with automated bases, or even relaying instructions from earth. If you're going to trust automation to run a moon base you might as well trust it and operate the base from earth. If it's smart enough to do the job it's smart enough that 1.5 seconds signal delay won't matter that much.
I actually don't think manned orbital stations in orbit around the Moon are necessary, for this basic reason. If there's some maintenance that requires realtime remote operation, it can typically wait until you send a spacecraft from an Earth orbit station.

Also, one good type of Earth orbit to use is a ten day highly elliptical orbit with very low perigee and apogee at the Moon's altitude. This orbit has very nearly Earth escape velocity, while also dipping near Earth to maximize the Oberth effect. It's the perfect place to get to/from the Earth system to/from elsewhere in the Solar System. Since you'll have stations in these elliptical orbits, it will only be a matter of days before one naturally comes near your lunar facilities.

mugaliens
2009-Feb-01, 08:04 PM
If you plan to do adventure tourism, or even extended science operations away from the main base, emergency shelters would make a lot of sense. If maintaining a system of full shelters is too much of a stretch then a supply of consumables, basic tools, and a life support system that can be hooked into a damaged rover/ pressure suit would do. And a fairly deep hole to hide from radiation storms in.

I was thinking more along the lines of a lferaft. An inflatable shelter that can be powered by up to three weeks with a fuel cell (to cover Luna's 2 weeks of darkness), with minimal food, but the fuel cell and reclaimed humidity (from all sources, yech) would provide the water, with a small supply for leakage. Once the sun rolls around, the entire top surface, coated with solar cells (both for shade as well as power) recharge the fuel cells. Naturally, it would have a built-in airlock, radio, and perhaps even a couple of books, board games, maybe even a laptop.

This shelter would be self-contained in something the size of a footlocker. It would be easily activated with an easy three-step actuator, such as a push, turn, and pull. Upon activation, a distress beacon is activated, and that also serves as a homing beacon and position indicator.

It would be designed so that it could be activated either on the surface, or inside one of the primary domes - the latter, in case a leak requires the use of an emergency shelter.

It might cost a lot more than a 20-man life raft, but its size would be comparable, perhaps two to three times the volume to account for the additional requirements.

Regardless, it would be the cat's meow until a rescue craft from Earth could resupply the unit, deliver any necessary tools and equipment, etc.

Even if you did have an emergency depot, you'd still need emergency shelters co-located with the outpost.


Having a rocket sitting on the launch pad, ready to launch 24-7 seems like a big cost in itself...

No need. One can be kept in ready reserve status, requiring only final assembley and attachment of the boosters (couple of days).

[qutoe]If something happens to the base that won't wait until the next scheduled run they may have to accept moving to a an unmanned base and living off an emergency depot in a rover until then!

Having a system thats fairly disaster proof might be a must as soon as you get out of LEO. I think that will mean some sort of distributed network.[/quote]

Now we're thinking along the same lines. Again, for the Moon, we're close enough here that an emergency lunar shelter and a rocket that can launch in three days to a couple of weeks may be all that's required. If it's designed properly, however, the shelter may very well last its inhabitants for three months.

marsbug
2009-Feb-01, 10:23 PM
That's a "want", not a "need". And it would still be a much better idea to stay in the space suit. Are you really going to lug around the extra air to fill a pressurized "tent" for each night of sleep? Or a compressor to recover that air?

Ok, allow me to clarify: the astronauts wants to cross mare imbrium. They need to be able to sleep properly in order to do that. Thats hard in a suit. Then one of them gets ill, and the team needs to diagnose the problem to decide what action to take. Thats impossible in a suit. I don't know much about the required hardware but I'd be surprised if you couldn't carry it on a sledge, or wheeled cart under lunar gravity, the way antarctic adventurers do with their gear.


Perhaps I just have a different idea of when we'll seriously start industrializing the Moon. The refinery hardware is going to involve such a massive investment that I don't see it happening within the next several decades. Maybe half a century to a few centuries from now. Either way, our robotic technology will be all the better by then.

I was thinking of science bases set up in the next half a century, not mass industrialization at some point beyond that- crossed wires



You could have a small pressurized station with basic life support and communications equipment.



Tourists can acclimate to lunar gravity while in transit. The shuttlecraft taking tourists to the Moon can have artificial gravity which matches lunar gravity.


So can a lunar orbital base. If you have any sort of lunar industry, you have some sort of economical launch method of hauling stuff off of the Moon's surface.



I would count on artificial gravity for future plans. It's really basic physics. If, for some bizarre reason, artificial gravity is deadly to humans, then we're just going to have to learn to live in zero gee (we already have significant experience with it).

No lunar industry, no mass transport to lunar orbit, and while the physics behind artificial gravity is simple the engineering and practicalities are not, else the ISS and Mir would've used it.


Nonsense. An orbit is an orbit. It doesn't matter how big or small the station is. (Assuming it's not stupidly large, like bigger than the Moon itself.)
Mascons. (http://en.wikipedia.org/wiki/Mascon)

To quote the article:

The lunar mascons alter the local gravity in certain regions sufficiently that low and uncorrected satellite orbits around the Moon are unstable on a timescale of months or years. This acts to distort successive orbits, causing the satellite to ultimately impact the surface

I concede the article leaves room for a satellite/station in a high orbit, but as you say, the argument is academic since it would be simpler to run the show from earth.

Also, one good type of Earth orbit to use is a ten day highly elliptical orbit with very low perigee and apogee at the Moon's altitude. This orbit has very nearly Earth escape velocity, while also dipping near Earth to maximize the Oberth effect. It's the perfect place to get to/from the Earth system to/from elsewhere in the Solar System. Since you'll have stations in these elliptical orbits, it will only be a matter of days before one naturally comes near your lunar facilities.

We're thinking in different time Issac, you seem to be in the early 22nd, I'm looking at the mid 21st!

cjameshuff
2009-Feb-01, 10:52 PM
No lunar industry, no mass transport to lunar orbit, and while the physics behind artificial gravity is simple the engineering and practicalities are not, else the ISS and Mir would've used it.

That would have made conducting microgravity experiments, one of the primary purposes for the existence of the stations, difficult to impossible. They don't have centrifugal "gravity" because it was unnecessary and something they were going into orbit to avoid.

marsbug
2009-Feb-02, 07:37 AM
They couldn't have had one small section rotated for gravity? Having a rotating station makes docking harder, and the station heavier as it must be built to take its own 'weight' for the duration of its working life. Having rotating and still sections means designing an interface between them that will last.
If someone can dig up an example of a manned space vehicle with artificial gravity that either has been built, is seriously planned to be built in the next twenty to thirty years, or was planned and was canceled for something other than engineering problems related to it spinning, then I'll admit that lunar tourists could acclimatize in their ship on the way.

In fact that sounds like an interesting thread to start: Why no artificial gravity?

Mugs: the only thing I'd add to your life raft is that in be set up in a small sized cave for radiation protection.

Ara Pacis
2009-Feb-02, 09:16 AM
We're not talking about vinyl pool floats, here. The structures I've seen would be significantly more robust and easier to patch than a rigid metal structure. Multiple layers of extremely tough ripstop Vectran cloth for the Bigelow craft.

A badly torn aluminum panel would be permanently deformed, impossible to quickly patch, and very difficult to repair. The same event might not even puncture an inflatable structure, punctures that do happen would be very limited in size due to the ripstop and flexible nature of the material, and the hull would revert back to a nearly-normal shape afterward. Self-sealing structures are relatively simple to create, concerns with thermal expansion or fatigue are almost eliminated. You've got up to 100 kPa of internal pressure from air that'll never get mechanically fatigued or worn out, you might as well take advantage of it for supporting the structure.

You wouldn't patch the metal cladding, you'd patch the membrane. The metal cladding would merely exist to prevent sharps from reaching the membrane.

IsaacKuo
2009-Feb-02, 12:56 PM
They couldn't have had one small section rotated for gravity?
No, because you need a somewhat large radius for artificial gravity. A "small" section won't cut it.

Having a rotating station makes docking harder, and the station heavier as it must be built to take its own 'weight' for the duration of its working life.
The station does NOT need to be significantly heavier. The outward force due to artificial gravity is far less than the outward force due to air pressure.

Docking is not significantly harder. You would either dock to a non-rotating airlock or onto an auxiliary shuttlecraft.

Having rotating and still sections means designing an interface between them that will last.
The most robust interface is a cylindrical airlock chamber. In practice, this chamber is works like an "elevator", but instead of changing altitude it changes rotational speed. It has two doors (or sets of doors). The "outer" door opens to the non-rotating docking hub. The "inner" door opens to the rotating station.

If someone can dig up an example of a manned space vehicle with artificial gravity that either has been built, is seriously planned to be built in the next twenty to thirty years, or was planned and was canceled for something other than engineering problems related to it spinning, then I'll admit that lunar tourists could acclimatize in their ship on the way.
Zubrin's Mars mission designs use artificial gravity for the space travelers in transit between Earth and Mars.

In fact that sounds like an interesting thread to start: Why no artificial gravity?
You would only need artificial gravity for a long duration mission--like a mission to Mars. So far, we have not sent a manned mission to Mars.

And the science of our space station missions are infinitely more interested in learning about the long term physiological effects of microgravity than the long term physiological effects of normal gravity. We're still learning about the physiological effects of microgravity. If you're going to spend billions of dollars on a space station, wouldn't you like to use it to do science which can't be done here on Earth?

marsbug
2009-Feb-02, 02:35 PM
Ok I know when I'm beat, and we're wandering far off topic. I'm suspicious of such a simple idea that seemingly hasn't been tried yet though, I'm sure it must be a lot harder to pull off than it's made out to be.