Lots of space talk on the boards recently, so I thought I’d ask about L5. The idea is to build a space station at the Lagrangian Point L[sub]5** and populate it with thousands of colonists. IIRC there was some sort of scheme to provide power via solar-collection satellites, and the power would also be ‘beamed’ to Earth.
Other than establishing a large-scale presence in space and the possibility of manufacturing things in zero-g, of what use would L5 be?
And a follow-up question: It has been shown that low gravity is detrimental to the human body. Why have NASA and the Russian Space Federation and others decided to build the zero-g ISS instead of an Arthur C. Clarke-style torus-shaped space station whose rotation could provide one g at its outer edge?
A wise man once said that any question that starts with “Why…” or “How come…” can almost always be answered with “Money!”. Building the ISS is expensive as is, and we’re building it with a minimum of pieces/parts.
Making a gigantic rotating wheel that would be stable, and large enough to get an appreciable gravity would be more expensive by several orders of magnitude, I imagine.
As for an L5 habitat, once again, the only reason to be there at this point would be research. I’m all for it, as I feel the only hope for the future of mankind is to get into space. In time, I can see Branson making/purchasing enough room on an L5 habitat to start chargin people for the “ultimate getaway vacation” and once that starts, money can be made.
Proof-of-concept for closed-loop environments (i.e., recycling food/water/air and growing your own food, treating wastes, etc.) that could be used for any number of future space applications. Presumably, some preliminary research would already have been done.
Also … religious separatists or other utopians who just want to do things their own way without interference (although, granted, the cost would be phenomenal anytime in the near future … but some of those televangelists and cult leaders do pretty well with the money …).
Eventually, given a cheap method of bulk space travel (something equivalent to the steamships at the turn of the 20th century that brought so many poor immigrants to the US), you could see such colonies used as actual places for overflow population from Earth to go.
Side question: How “large” are the lagrange points? How large of a volume of space are within the influence? How many colony stations (with attitude adjustment jets, naturally) could we stick there without them crashing into each other or drifting out of their stable orbit?
There is no advantage to building a space habitat at a Lagrange point, and in fact there are good reasons not to put it there. The concept arises in bad science fiction because an object at, say, an Earth-Moon Lagrange point would stay in the same position relative to the Earth and the Moon indefinitely. But so what? It’s not like it’s going to fall crashing into Earth if you put it somewhere else. Meanwhile, L4 and L5, being stable points, tend to accumulate debris (which you don’t want accumulating around an orbital habitat), and L1, L2, and L3 are valuable real estate for various scientific missions which do have a need to be at those points, so no sense cluttering them up with a habitat that could be put anywhere.
As for the existing Space Station, however: They could have made it spin. But why would they want to? If you want to do research in one gravity, you can already do that much more cheaply and easily right here on the surface. The whole purpose of the Space Station is to do research in freefall, and all that money would be wasted if you then went and gave the place gravity.
Not only is it a bad idea for the reasons that Chronos outlines, but also consider this; the Lagrange points are points of gravitational equilibrium between the Earth and Moon (or any two massive bodies). Stuff tends to collect there because they are low energy points; that is to say, the “stuff” that collects there has to have a low orbital momentum in order to stay there. This means, you have to send your spacecraft out to this point and then…stop. When you want to return, you have to accelerate your craft at up to something like orbital speed before you can go anywhere. It’s not like a run down to the grocery; you’d like to keep and make use of all the momentum you’ve built up on the way out to help you speed along your return. The Lagrange points are actually energy-intensive positions to reach, taking on the order as much energy to get to as going to the Moon, but not providing a massy body to swing around once you get there.
Well, you could have high-G and low-G locations, and even a seperate non-rotating hub; indeed, you’d want to have some rotationally-isolated point at which to dock ships, mount directional antenna, or connect to free-floating aparatus. (I always have to stifle guffaws at the scene in 2001 when the Pan Am Clipper Shuttle has to match the rotation of the station; the rotation is going to play havoc with the pilot’s sense of equilibrium and the Coriolis force is going to screw up their instinctual flight dynamics.) But this introduces major leaps of complexity and size to the station; not only does the station now have to maintain structural integrity against internal centripetal forces but it also has to remain balanced, account or compensate for precession and nutation, have some kind of counterrotating or frictionless central hub (as previously noted), and have a propulsion system to spin up and spin down the station.
On a long term mission, say a 30 month mission to Mars, we’d probably need to generate simulated gravity for the health of the explorers; yet another hurdle in manned exploration. But for a small research station to be assembled with minimum expendature of labor it just doesn’t make sense.
Besides, I’m waiting for those Star Trek gravity-generating floor plates that keep working even when the environment system is two minutes from catastrophic failure. How does that work?
As for proof of concept for closed ecologies, we can do that about 1000 times cheaper here on earth. Remember Biosphere2?
It would many orders of magnitude cheaper to set up colonies on Baffin Island or Antarctica than to create colonies at L5 or L4. At least on Baffin Island you have a redundant backup oxygen system in case your colony’s primary crashes, plus you have access to rocks, water, plankton…
It’s kind of cool to imagine living on a space station. Now imagine building a closed ecology in some buildings on the Greenland icecap, moving there, and never leaving. Doesn’t seem so cool? But it would be much safer, much easier, and much cheaper.
I don’t see why not. Welding doesn’t require air, and in fact some metals are welded in inert gas to avoid oxidation.
Getting back to the L5 question, it seems like a bad idea simply because it’s so far away. If you’re willing to go that far, you might as well land on the moon where there’s plenty of material for construction and radiation shielding.
I don’t see any reason you couldn’t use electrical-arc welding. As scr4 says, you wouldn’t have to worry about gas shieding. Cooling, on the other hand, would be slower and you might need to use chill blocks. Oxyacetylene welding might be a bit of a problem without an atmosphere to compress the streams, but then it doesn’t really generate enough heat to get a proper weld on most steels anyway.
But you’d probably design your construction methods to minimize or eliminate welding. Working in a pressure suit is fatiguing, gloves make fine movements extremely difficult, and one can only imagine what hazards would lie in performing heavy construction tasks in freefall and in a vacuum. Even turning a wrench in freefall can be a tricky task, as the Gemini astronauts discovered. Better to make your assembly in IKEA style and ship it up as prefabricated sections.
The purpose of the L5 colonies wasn’t supposed to be scientific research. The whole purpose of them was to move population off the Earth, to insulate humanity from extinction level events. This was during the cold war, remember, and also the time when the fear of the day was a malthusian population explosion that would lead to mass starvation and a collapse of our economies.
The notion was that we’d build mass drivers on the moon, use them to shoot material into space, then assemble huge rotating cylinders that people would live inside. The thick walls would protect them from radiation, adjustable mirrors would regulate temperature and provide light and energy inside, and everyone would live happily. These things were going to be huge. 20,000 people or more living inside a huge artificial world that would be complete with farms, streams, local weather, you name it. The idea was that these colonies would make money beaming energy to earth, providiing goods manufactured in zero-G, tourism, and even farming. As they became wealthier, they would become self-perpetuating, with one colony using its resources to build another, then those two building two more, etc. Eventually, millions of people would be living in numerous colonies.
It was an interesting idea, and great fodder for science fiction, but the timelines proposed by people like Gerard K. O’Neill were insane. He used to claim that we could build the first colonies within 20 years. I suppose this is an example of the kind of wild optimism that was the hallmark of the Apollo era, but anyone with an ounce of engineering sense should have known this was crazy (and they obviously did, since no one invested any kind of serious money in this idea).
The original economic premise of the space colony idea was space-based solar power. A large solar collector in geosynchronous orbit (either direct solar cell or thermal-electric) could remain in sunlight nearly continuously and beam power via microwave to ground stations. Infinitely renewable, next to zero environmental drawbacks, and expandable to orders of magnitude greater than our current world energy needs.
The only problem was cost. Even with the cheapest conceivable space launch capability, it would be too expensive to fabricate the solar collectors on Earth and then assemble them in geosynch orbit. Manufacturing them at a lunar colony might be a little better, but still too expensive given the huge amount of mass to be moved. So then the idea shifted to doing the manufacturing in high orbit. Build a “mass driver” (electromagnetic catapult) on the moon so you can boost huge amounts of material from the moon without needing expendable rocket propellent. Use the lunar material for metal, glass, oxygen, etc. to build powersats, more colonies, or anything else you want. This would require an extremely large robust manufacturing capability in high orbit. And given the number of people needed to support it, it would be too expensive to supply all their food, water and oxygen from Earth. So they would have to have some sort of self-sufficient environment. A colony, as opposed to a mere “space station”. The completed solar collectors could move themselves by solar-electric thrust into their destination orbit.
So the idea was that if you could make a frakkin’ huge one-time investment, you’d end up with a nearly self-reproducing infrastructure in space that would avoid the expense of lifting stuff off Earth as much as possible. Eventually whatever couldn’t be mined from the moon could be acquired from near-Earth orbit asteroids. Purely as a bonus, you presumably get the ability to do microgravity materials processing, and the ability to do extremely robust science in space.
Looks great on paper, so what happened? Well the first hitch is to build an economical way to get anything off Earth to start the whole process. The original studies presumed that a Shuttle-derived heavy launch system would do it :rolleyes: And as has been pointed out, no one’s demonstrated a reliable closed-cycle system, the ability to build massive structures in zero-G vaccum, or any of a host of other things that would be needed to make it work. If the original point is to secure an energy supply, the investment needed could be spent on Earth-based alternatives. The proponents of the colony-powersat concept never were able to get anyone in power to take them seriously.
Oh, and as a postscript: it turns out that L5 isn’t the most advantageous place to site the colonies anyway. The best minimum-energy path from a lunar escape trajectory is a high elliptical Earth orbit.
I’ve been chewing over this for a while, and I’m not going to let this slide by; not so much because I want to be contentious (though that’s fun, too) but as an illustration of how hindsight, often described as being “20/20”, can be just as restrictive and limited as foresight.
We tend to view the future as merely a linear expansion of the past; faster cars, plumper bread, higher fidelity stereo sound, et cetera. We think of advancement, especially technological advancement, in terms of incremental improvement of existing technology; and this explains our current dampened ardor for space exploration; at the rate that the current space programs have been proceeding it will be decades if not centuries before we’re prepared to deploy any permenant, self-sustaining space habitat.
But therein lies the assumption that progress is linear; the candlemaker thinks in terms of a cheaper paraffin, the gas lamp manufacturer of a cleaner gas. Neither are going to invest in some kind of ridiculous scheme involving passing an electrical current (whatever the hell that is) through a tungsten filliment in an evacuated tube. “Light bulb? What the hell is that? Everybody knows you can’t make a wick burn in a vacuum!” Innovations, like the electric light bulb, offer a new array of possibilities that one couldn’t even conceive of with existing technology.
O’Neill[sup]1[/sup] initially developed his ideas in the Sixties, during the heady days of Gemini and Apollo when mankind had gone from lobbing a highly inaccurate rocket just far enough to (hopefully) reach London from across the Channel to putting men in highly accurate orbits around the Earth and even reaching the Moon. But O’Neill wasn’t counting on Saturn V rockets, or a scaled up version thereof, to fulfill his grandiose schemes. He was counting on the next generation of propulsion technologies to let the space program go from tenatively sending three mean to the moon for a few score of hours to sending dozens or hundreds of persons out in ships that could reach the asteroid belt and beyond. These weren’t technical pipe dreams, either; these were genuine programs, supported by research and testing, such as the NERVA nuclear rocket (which would have powered the proposed third stage Apollo-N and possibly the Apollo Plus vessels) and the Orion nuclear pulse rocket. Each of these programs had potential stumbling blocks, but both NERVA and Orion programs had demonstrated significant proof-of-concept achievements when cancelled (NERVA/Rover in 1972, Orion in 1964) due to political and public relations concerns about using nuclear propulsion. Even then, space advocates held out hope of reviving the technology; a conceptual design for a NERVA-type engine for the Shuttle was developed in 1979 as a swap-out for the SMEs; the nuclear pulse/pusher plate concept lived in on conceptual projects Daedelus/Longshot(USN) and Prometheus. If such a technology (particularly the ultra-heavy lift Orion-type booster) were operational today, manned space habitats and interplanetary exploration would not only be possible but almost inevitable; the cheap cost to orbit and the general inapplicability as an ICBM would relegate it to manned spaceflight, and we’d be hard pressed to fill up an entire 5000+ ton payload with high school science experiments and communication satellites.
Self-sustaining oribital colonies need more than boosters, of course; they need to be able to return their (massive) costs in a reasonable time period. O’Neill suggested a number of schemes, from fairly mundane lunar and asteroid mining to the highly speculative and even conceptually problematic proposal to beam converted solar power to ground stations by microwave. Other requirements are necessary, too; colonies must (eventually) be able to provide their own food, process their own water and air out of space resources, generate simulated gravity, resist radiation and micrometeroid hazards, et cetera. Many of these issues were briefly addressed and lightly passed off as being details that we’d figure out when we came to them; that may seem blase, but in fact, it makes the (correct) assumption that in learning to solve any one of these problems we’d discover methods and techniques which would be more generally applicable to all areas of habitat design and support. Such technical challenge and the innovations required tend to expand our capabilities in a way that is not readily extrapolated from existing experience. O’Neill and his supporters were relying upon innovation, not incremental development, to provide for the requirements of their concepts. That some of these necessary innovations, such as nuclear-based heavy-lift propulsion, have not been developed is actually more of a political issue than a technical one. There are technical arguments against Orion, but the cancellation was due to treaty restrictions and a desire to keep the limelight upon Apollo.
Today, we assume, based upon our experience with an intentionally developmentally-retarded American space program, that O’Neill’s concepts and timeline were “insane”. No doubt 20 years represents an extreme minimum bound for a project of this scale, but given the heavy lift and high specific impulse propulsion that O’Neill was assuming to be available we should certainly expect to be far beyond a small, barely sustainable three-man “space station” in Low Earth Orbit. Given fifty years of leap-frog development and access to cheap resources in space, it is not at all unreasonable to propose large-scale permenant habitats, space-based industries, and interplanetary exploration. Hindsight tells us this is foolish only because we do not wish to acknowledge what could have been had we not been so limited and indecisive.
Regarding the placement of habitats at libration points and in response to arguments (including my own) previously submitted in objection to that notion, I suspect the rationale for placing a habitat at a Lagrange point stems from the concern of vast, many kilometer-long structures under the impulse of tidal forces; such forces, outside the equilibrium points, would tend to make a such a large, rotating body undergo nutation, requiring regular readjustment to avoid destabilization. At the L-points, the influence of tidal forces is minimal even for a large object. The objection regarding the collection of residual junk and the energy required in reaching and stopping at that point remain, though the latter is somewhat mitigated by the presumption of high impulse propulsion that allows your vessel to take a more direct, high energy path rather than a low energy, purely ballistic intercept (as Apollo did with the Moon orbits). This doesn’t apply to more modest structures in Earth orbit (you’d presumably direct the axis of rotation through the Earth’s center of mass to minimize tidal forces and expend whatever small budget of energy required to correct for the influence of the Moon) but might be a serious concern for larger structures. I’ll have to play around with the math to see how much impact it would have.
Anyway, O’Neill and his supporters may have been somewhat overenthusiastic and space-happy, but I think they were hardly insane in their vision or general timeframe; the notion that we have to inch our way up from LEO, minor enhancement by by minor enhancement, is not only limited but wrongheaded. We aren’t going to be using a slightly bigger Shuttle or Saturn rocket to go to Mars or explore the outer planets; indeed, we shouldn’t be using chemical propulsion at all. We aren’t going to advance a spearhead into space by replacing a three-man station in LEO with a six-man station in an intermediate circular orbit (to be followed in three decades by an eight-man platform in high earth orbit). We are currently, in fact, scarcely beyond where we were in pre-Apollo days; a Big Gemini capsule and the Manned Orbiting Laboratory of the mid-Sixties could have provided virtually the same capabilites that we currently have with the Shuttle/Soyuz/ISS. We could be (and should have been) well on our way to, if not O’Neill’s visionary and extravagant colonies, at least a program of continuous exploration, resource exploitation, and technical development. Instead…we keep aerospace contractors fat and happy. That is the epitaph of NASA.
Stranger
[sup]1[/sup]O’Neill was a professor of physics at Princeton University and an scientist-astronaut candidate during the Apollo program. His ideas, which came to be known under the general subject of “O’Neill colonies” (massive rotating orbital colonies located at the libration points of the Earth-Moon system) were formed during the Sixties though he didn’t really express them in any public forum until 1969, when he famously asked a freshman physics class, “Is the surface of a planet really the right place for an expanding technological civilization?” From there he went on to publish his ideas in publications such as Physics Today, Scientific American, et cetera, and found the Space Studies Institute at Princeton, which acts as a clearinghouse and coordinator for various space-related research and projects. (Although the L5 Society was formed to support his ideas, he was not actively involved in its founding.)
A space station, wouldn’t need to worry as much about the glass cutting down on your light, since sunlight isn’t filtered through atmosphere before it gets to the glass (or plastic or whatever they’re using in spacecraft windows these days).
