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Galactic Settlement and the Fermi Paradox:
A spacefaring species could easily settle the entire Milky Way given billions of years. Yet the fact is that there is no obvious one in our solar system right now. The supposed inconsistency between these statements is the Fermi Paradox, named for the Nobel Prize-winning physicist who supposedly first formulated it. In a trenchant formulation of the Fermi Paradox, American astrophysicist Michael H. Hart called the lack of extraterrestrial beings or artifacts on Earth today "Fact A." He showed that most objections to his conclusion—that a spacefaring civilization could have crossed the galaxy by now—stem from either a lack of appreciation for the timescales involved (it takes a small extrapolation from present human technology to get interstellar ships, and even slow ships can star-hop across our galaxy in less time than the galaxy's age) or else the dubious assumption that all members of all extraterrestrial species will avoid colonizing behaviors forever (an example of what I've called the monocultural fallacy).
William Newman and Carl Sagan later wrote a major rebuttal to Hart's work, in which they argued that the timescales to populate the entire galaxy could be quite long. In particular, they noted that the colonization fronts Hart described through the Milky Way might move much more slowly than the speed of the colonization ships if their population growth rates were so low that they only needed to spread to nearby stars very rarely. They also argued that being a long-lived civilization is inconsistent with being a rapidly-expanding one, so any species bent on settling the galaxy would not last long enough to succeed. In other words, they reasoned that the galaxy could be filled with both short-lived rapidly expanding civilizations that don't get very far and long-lived slowly expanding civilizations that haven't gotten very far—either way, it's not surprising that we have not been visited.
Being a long-lived civilization is inconsistent with being a rapidly-expanding one.
In a 2014 paper on the topic, my colleagues and I rebutted many of these claims. In particular, we argued that one should not conflate the population growth in a single settlement with that of all settlements. There is no reason to suppose that population growth, resource depletion, or overcrowding drives the creation of new settlements, or that a small, sustainable settlement would never launch a new settlement ship. One can easily imagine a rapidly expanding network of small sustainable settlements (indeed, the first human migrations across the globe likely looked a lot like this).
Another factor affects Newman and Sagan's numbers on timescales and colonization-front speeds. Most of the prior work on this topic exploits percolation models, in which ships move about on a static two-dimensional substrate of stars. In these models, a star launching settlement ships can quickly settle all of the nearby stars, limiting the number of stars it can settle. But real stars move in three dimensions, meaning that they can carry their orbiting settlements throughout the galaxy, and that a settlement will always have fresh new stars to settle if it waits long enough.
Jonathan Carroll-Nellenback, at the University of Rochester with Adam Frank, not long ago finished work, with Caleb Scharf and me, on analytic and numerical models for how a realistic settlement front would behave in a real gas of stars, one characteristic of the galactic disk at our distance from the galactic center. The big advances here are a few:
Carroll-Nellenback validated an analytic formalism for settlement expansion fronts with numerical models for a realistic gas of stars. He accounted for finite settlement lifetimes, the idea that only a small fraction of stars will be settle-able, and explored the limits of very slow and infrequent settlement ships. He also explored a range of settlement behaviors to see how galactic settlement fronts depend on them.
The idea that not all stars are settle-able is important to keep in mind. Adam Frank calls this the Aurora effect, after the Kim Stanley Robinson novel in which a system is "habitable, but not settle-able."
A very interesting read.
(Score: 4, Interesting) by Anonymous Coward on Sunday January 19 2020, @03:52PM (34 children)
Is the assumption that only a minority of star systems are habitable. In fact virtually all star systems are habitable. People who think otherwise are guilty of planet chauvinism.
Any civilization that is capable of interstellar travel is pretty much by definition capable of building space stations, which is where the majority of the population will reside, simply by virtue of available real estate and resources. Most of the valuable resources in a star system are in comets and asteroids, not planets. Sure, by sheer mass, planets have more, but most of it is buried under several trillion tons of inconvenient rock.
To a civilization accustomed to living in space stations - and if for some reason they weren't when they left, they will be by the time they arrive, as a result of hundreds if not thousands of years spent on their ship - the notion of going down to live on a planet will seem as strange as the notion of a modern urbanite going to live as a hunter-gatherer in the jungle. The only reason to go land on a planet is to burn enormous amounts of energy trying to get back off it again.
Since the overwhelming majority of star systems will have asteroids and comets, a star system that is uninhabitable would be truly an oddity. The only realistic place it could happen would be deep in the galactic core, where the radiation and the influence of the central black hole could prove overwhelming. But in the galactic disk, any star that isn't in immediate danger of going supernova is a good place to live.
(Score: 2) by Arik on Sunday January 19 2020, @04:06PM (26 children)
https://www.lcas-astronomy.org/articles/display.php?filename=home_on_lagrange (HOME on Lagrange)
If laughter is the best medicine, who are the best doctors?
(Score: 0) by Anonymous Coward on Sunday January 19 2020, @07:45PM (25 children)
It seems peculiar to suggest we'd have little reason to return to planets, when the long-term goal of a space station would be largely to provide passable replications of the 'real thing' - fresh air, biodiversity, atmosphere, weather, oceans, various activities such as exploring unknown areas, rock climbing, etc. Obviously we'll develop new interests, desires, and recreation in space. Yet at the same time I would not just assume all options are equal, let alone better. If you look at the pros and cons of a planet versus a station, one is going to turn out superior. And I don't think it's going to be the station.
(Score: 3, Informative) by Arik on Monday January 20 2020, @05:08AM (24 children)
If you mine an asteroid, you won't be digging through crust and you won't be working in a gravity well, it's many orders of magnitude easier, it takes far less energy, and the end result isn't trapped in a gravity well - it can be moved about freely.
If laughter is the best medicine, who are the best doctors?
(Score: 0) by Anonymous Coward on Monday January 20 2020, @06:04AM (23 children)
Ah! You have a major bias in your thought process there. You are assuming energy usage and production will remain at all comparable in the future. Many people do this and it makes absolutely no sense whatsoever. You, individually, now consume many orders of magnitudes of energy than individuals in the past and there's no reason to think that this trend will not continue.
It's really remarkable that only 200 years ago the light bulb did not exist, let alone any source of energy to power it. It's the same reason that sci-fi didn't really exist as a genre until something along a similar time-line. The things we take for granted today were simply unimaginable to people of times past. Things like flying machines were the breadth of their imagination. Being able to communicate, instantly, from one side of the planet to the other or see people remotely would have been viewed as little more than fantasy and magic.
And there's no reason to think that today we're not living in a similar time of ignorance. And while we cannot predict the future, one thing that remains certain is that technologies will become more 'energetic' over time. Our musing over the extreme energies of the cost to extract ore will probably be comparable to those of time past musing on the extreme energies of the cost to move a man faster than a horse, or to create a machine capable of engaging in such complex tasks as adding 15 + 18.
(Score: 2, Insightful) by khallow on Monday January 20 2020, @03:32PM
The laws of physics won't change. So yes, it will remain comparable in the future.
For example, aluminum costs about 15 MJ per kg to smelt [world-aluminium.org] from the nicest ores (bauxite) we have. Presently, it costs well over 100 MJ per kg to put in low Earth orbit (the energy cost of the propellant plus portion of vehicle construction). But even with perfect technologies that reduce that to energy cost alone, you're speaking of 10 MJ per kg - basically making Earth-based aluminum at least two thirds more expensive, energy-wise, than aluminum from elsewhere. Iron alloys would typically be much less energy intensive (since iron, nickel, and chromium would all be vastly easier to extract from iron-nickel asteroids) so the energy markup of launching from Earth would be much larger.
You can talk about how cheap energy will be in the future, but it'll still remain that it costs substantially less energy to move massive amounts of material from asteroids to where you want them to be than to launch from Earth, even to Earth orbit!
(Score: 3, Informative) by Arik on Monday January 20 2020, @03:49PM (21 children)
No, I'm really not. I expect the amount of energy we can control and use will continue to increase, just as you are.
All I'm assuming is that it will remain finite, a limited resource. As another poster already pointed out, there's a huge difference between having a high energy economy and being able to change the laws of physics. Having a very high energy economy might make such endeavors *possible* but it's never going to make them *attractive* relative to the alternatives that take orders of magnitude less energy to produce the same result.
Once the initial cost of getting that space-based operation going has been paid once there's going to be very little reason to go back to a planet, and some very good reasons not to.
If laughter is the best medicine, who are the best doctors?
(Score: 0) by Anonymous Coward on Monday January 20 2020, @05:51PM (20 children)
Let me elaborate on the point of exponential energy increase. Do you know how much energy is in a gallon of gas? It's around 132 million joules. Now a days we don't even blink about a regular person using up billions of joules for extremely mundane tasks. But in a time before we had the things that consume these levels of energy, it would have seemed not only unacceptable but simply unimaginable. How in the world could you generate that much energy for billions of people?
The same will likely be true in the future as personal energy usage continues to scale exponentially with the average person continuing to consume exponentially more energy. And so speaking of saving some energy as a motivation for living an otherwise likely undesirable existence makes no sense. It's like deciding to forgo with a phone today to try to save 20k joules a day. It would make no sense.
Perhaps you think this is where the requisite of finite energy kicks in. It doesn't. That shiny little star we revolve around generates about 3.8 x 10^26 joules each and every second. The entirety of Earth's energy consumption in 2013 was about 5.67 * 10^20 joules. In other words, each and every second the sun generates around about a million times more energy than we use per year. So our potential energy remains relatively unlimited for an extremely long time to come.
(Score: 2) by takyon on Monday January 20 2020, @06:57PM (3 children)
I'm responding to your comment out of context but it looks like Jevons paradox has been largely averted today. Home heating and cooling is more efficient, LED lighting is more efficient, massive computing performance is available in smartphone/SBC/laptop/SFF form factors, people are driving less and in some cases can work remotely (although you have to account for whether services like Amazon or grocery delivery consume more or less energy per user), etc.
U.S. electricity consumption per capita has been flat since 2000. Oil consumption per capita peaked in 1978 and has dropped significantly since 2007.
If the typical $0.12/kWh dropped to $0.01/kWh through use of solar or fusion, will we get 12x the energy consumption per household or capita? I'm not sure. Maybe the energy usage increase won't be in households directly but in server farms or factories, with more wasteful products and services being consumed by households. And we could come up with hyperadvanced technologies like Star Trek style replicators or use plasma gasification on every piece of trash or whatever.
Even if you were to get a world population of 20 billion people using 5x the 2014 Canadian electricity consumption [google.com], that would be an increase of about... 68.41x. Just over six doublings. Does this count as exponential scaling? Will we not hit a plateau like the one we're already living in?
(20 billion / 7.271 billion) * (15545.54 / 3125.29) * 5
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 0) by Anonymous Coward on Wednesday January 22 2020, @04:15AM (2 children)
Context matters. ;-)
It was a fun discussion anyhow. We were talking about the long-term growth in energy consumption and how that relates to energy saving in the future. There was a time in programming that saving a cycle or two on a square root was a really big deal. Now, even if such things weren't already optimized away in hardware, it wouldn't really matter*.
* - Okay, just adding an asterisk because I'm going to hijack my own post. What I said is true, but I think this is paradoxically the same reason that software today is, generally, shit. A single micro-optimization is foolish. A million? Now your program is running vastly more efficiently, even if you only improved O(1) tasks! As "we" neglect more and more optimizations at all levels, we're seeing a death (of performant software) by a thousand cuts. The reason I put "we" in quotes is because this is happening at all levels. The compilers, the JIT systems, the OS, and while outside of my domain I would not be surprised if even the hardware itself is taking some "minor" liberties granted the pool of resources at its disposal.
(Score: 2) by takyon on Wednesday January 22 2020, @04:35AM (1 child)
Jevons paradox [wikipedia.org] Wikipedia article links to Wirth's law [wikipedia.org] in the "See also" section.
The tremendous increase in hardware capabilities has allowed higher-level languages to be used, which makes things more convenient, accessible, and portable for programmers (or script kiddies). This is the "positive" side of the negative, unless it means more bugs and security holes.
I still think we have a clear net positive from hardware advancements. And if some piece of software *really* needs every little optimization or bare-metal programming, somebody will pay for that expertise.
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 0) by Anonymous Coward on Wednesday January 22 2020, @05:28AM
This is all a huge tangent, but I agree completely. However, the one thing I think those articles all miss is the production side motivation for obsolescence. Both hardware and software manufacturers benefit from systems that are performant enough to attract consumers, but no more. Because these systems will become obsolete as rapidly as possible which means another cycle of purchasing. This is the reason we've seen all the big tech companies now a day start to migrate to rent seeking behavior. It's becoming difficult to force the next cycle because we've reached a point where a machine built a decade ago is still fine for literally 100% of tasks for your average user. So now we get "perfectly logical" business models like paying a monthly fee for your word processing program...
There almost certainly is at least a grain of truth to 'they just don't build things like they used to.' And it's no accident. You make *vastly* more money from a coffee maker that breaks in 2 years than one that breaks in 50.
(Score: 2) by Arik on Monday January 20 2020, @07:56PM (15 children)
What makes no sense is your bizarre assertion that life outside the gravity well would somehow be undesirable. Quite the contrary, to those born there it would probably be obviously undesirable to 'return' to coping with crushing gravity and such an uncontrolled environment full of potentially dangerous organisms.
"But in a time before we had the things that consume these levels of energy, it would have seemed not only unacceptable but simply unimaginable."
To the contrary, the ancients both conceived of it and certainly did not universally consider it unacceptable. Plato spoke rather strikingly on the subject, and he was a completely unoriginal thinker.
"In other words, each and every second the sun generates around about a million times more energy than we use per year."
And so what?
If we somehow had all of that energy harvested and stored in a convenient form and ready to use, it would *still* make sense to use it efficiently, rather than for potlatch.
If laughter is the best medicine, who are the best doctors?
(Score: 0) by Anonymous Coward on Wednesday January 22 2020, @05:07AM (14 children)
You're somewhat shifting the goal posts with your post here, but I think it's a much more reasonable shift. The energy argument is dubious. What makes sense is what we always do - whatever is the easiest to get the job done. It's the reason we squander energy like crazy today, because it makes things more convenient.
So let's get to what I think is probably the bigger issue. Would living in an orbital station itself be more desirable than living on a planet? Well I think the most logical approach here is to look at pros/cons. For benefits I'm really struggling to see any. I guess 0G and a gorgeous view? Yet 0G is kind of a mixed blessing since it causes our bodies and minds to turn to mush pretty quickly so you'll need to spend most of your time in artificial gravity anyways. The downsides are countless: extremely limited size, a million new risks, extreme dependence on various systems for just basic survival, 0 direct access to minerals necessary not only for building things but growing them, and much more.
The sustainability issue is probably one of the biggest problems. Star Trek sidestepped it by coming up with replicators and having the largest station still be tiny. For instance DS9's was the biggest 'elaborated' station in the series to my knowledge. And it had a capacity of 7,000! On Earth you need multiple acres per person for self sustainability. How is a station going to sustain even a million people, let alone billions? It'd need to start scaling up to the size of a planet itself and then, somewhat ironically, you're starting to create your own gravity well. On the bright side you can then start to create a 'real' atmosphere, but we're starting to talk about literally building a planet at this point which was kind of the whole point. The long-term vision for a station effectively turns it into a planet. So why not start at the finish line?
(Score: 2) by Arik on Wednesday January 22 2020, @06:55AM (13 children)
HOME's would have multiple rings with varying levels of 'artificial gravity' simulated via rotation. Only at the centre of the HOME would you have zero-g. The outside ring might be about 1g.
The idea is not to live in 0g, it's to live in reduced g, and controlled g. There will be many health benefits to this. Many people die of heart conditions, for a single example, and even *just moving* people with those problems to a slightly more interior ring after the problem develops would extend their lives. The entire circulatory system would benefit from the reduced stress, at any point in life. Placing heavy machinery in lower-g rings would greatly reduce the human toll of workplace accidents, as it makes it easier for people to maneuver heavier objects with less risk.
The gorgeous view would be icing on a cake packed full of benefits like that.
"extremely limited size"
True that they would be limited in size. The early ones, in particular, might only house the population of a small town.
But some people like that, and everyone can survive it easily enough. And it's not like the HOMEs wouldn't have communication and transportation between them.
Space travel is quite cheap, if you don't have any gravity wells to enter and exit.
"a million new risks"
Of course there's the spectre of the unknown, as there is on any frontier.
But again, once we've spent a generation there, we may well look back at the planet and shudder in fear, at the thought of subjecting ourselves to its weather, its volcano, its earthquake and flood and so on.
And also of being permanently bound 1g constantly, without even an occasional escape to an inner ring for a little r & r?!?
"0 direct access to minerals"
Sure, sure.
But just assume for a moment that basically everyone in the space industry and academia are correct when they tell you that asteroid mining is going to be a big thing whenever we actually get around to it. All sorts of minerals are available, plentiful, just hanging out in space waiting to be mined. From Earth, they're still pretty unattractive really, just because of that enormous energetic cost of getting your people and machinery out of the gravity well to begin the journey to go get anything from them. But if you're already living in a HOME, you pay none of that. You just go get what you want from asteroids.
"The sustainability issue is probably one of the biggest problems. Star Trek sidestepped it by coming up with replicators and having the largest station still be tiny. For instance DS9's was the biggest 'elaborated' station in the series to my knowledge. And it had a capacity of 7,000!"
Wasn't DS9 also dependent on Bajor for regular shipments of consumables?
"On Earth you need multiple acres per person for self sustainability."
Indeed, well, using well-established techniques that's typically true. Carefully planned and using modern technologies, you could shrink that a good bit using hydroponics and carefully planned niche gardening techniques, taking advantage of a completely tailorable environment including growing season. But I'd argue you want to give back what you save there in nature preserves as well; at least personally I'd strongly prefer to live in a HOME with such a place.
So you need to enclose quite a bit of space; but remember it's not just an empty cell, it's kind of like a russian nesting doll actually. You have level after level, each slightly smaller than the next, and in the case of a HOME with slightly reduced 'gravity' as well. Russian nesting dolls have very large surface areas in relation to their apparent dimensions, when you add up the layers.
"How is a station going to sustain even a million people, let alone billions?"
Well, in the short term, the first ones at least I wouldn't expect to house anywhere near that many.
Once the technology has been in use for some time, however, it might easily become possible to build such large habitations as well. But it's not necessary to the idea, nor necessarily desirable.
Remember, travel and communication between HOMEs will be relatively cheap and easy. Even with airplanes, you often spend most of the fuel for the flight on the task of initially countering gravity and getting up to your cruising altitude. There's none of that involved, if both your destination and starting point are already outside of the gravity well.
"'real' atmosphere"
In what way would the atmosphere in a HOME not be "real?" It would be recycled the same way as on Earth, with animals taking in oxygen and plants exchanging it for carbon dioxide, just like always.
"The long-term vision for a station effectively turns it into a planet."
No, it doesn't, that's just... not the vision at all. That's just a strange idea.
If laughter is the best medicine, who are the best doctors?
(Score: 0) by Anonymous Coward on Thursday January 23 2020, @07:45PM (12 children)
Late reply here. You said quite a lot and I didn't want to responds hastefully. Let's start with one important thing. The health stuff you were talking about is highly speculative, and on the end making it more likely to be incorrect than not. It's completely intuitive that lower gravity would be good on a dysfunctional heart - less work on a strained muscle. But of course intuition is often wrong. Low gravity is bad on the heart, somewhat seriously. Here [nature.com] is a research article on the topic (there are quite a lot). You can sci-hub it for the full version. Arterial hardening and increased arrhythmia alongside the predictable increased weakening. Again, it's basically a rule that low g just causes our bodies to turn to mush.
Completely agreed on the manufacturing benefits. There was an awesome video here [youtu.be] of some Russian astronauts handling a docking shield on the ISS. 1000 pounds moved about like a styrofoam toy. That entire series is awesome by the way. Such a shame modern NASA sucks at edutainment. We used to do similar things back in the Apollo days.
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Have you ever seen the ISS? NASA has a really cool site here [nasa.gov] where you can sign up for alerts when it's traveling overhead. Incidentally that station is undoubtedly incapable of supporting even a single person. In space you have three dimensions to garden with, but you also have to contend with many other issues, such as energy generation, that will invariably bump your volume requirements up far larger than I think you may be expecting.
The next time you see the ISS, multiply its size by tens of thousands. It'd be a whole heck of a lot larger than the moon. That's what you need to support around 10,000 people. Now that you have that super-moon imagine your mind, multiply it by a million. That's what varies swarms of these supporting merely 10 billion people, a single planet's worth of population, would look like. This alone can already refute the energy thing from earlier as well. The station keeping and other energy costs in this scenario are going to be like nothing we can even imagine, constantly. You can't just move between the stations - things orbits naturally deteriorate over time and need adjustment. With the size of these things you will be executing and planning extremely expensive burns literally years in advance. Not only the energy cost, but the fuel cost here is hard to even imagine!
And all of this isn't for the grand vision - this is just the most bare bones stuff: keeping people alive, and orbital station-keeping.
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I want to hit on the atmosphere stuff as well, but this is already lengthy and it's 2:30am here. The gist being the difference between closed and managed systems vs open and self sustaining systems.
(Score: 2) by Arik on Friday January 24 2020, @05:33AM (11 children)
Yes there are, and most (like this one) are concerned with long exposure to zero gravity or microgravity. Not a daily routine taking advantage of reduced gravity. Very different things.
But of course you're correct that my arguments in that vein are somewhat speculative. We have no definitive proof because we have never run the experiment.
Seen the ISS? Like with my own eyes? Or pictures. Of course I've seen pictures, and video...
Your estimate of the size needed for a HOME makes no sense, however. The surface area of the moon is 14.6 million square miles. A HOME that size would have many times that much surface area, even calculating for large cutaways on some levels. Let's call it, very conservatively, 10x. 146 million square miles of surface area and you're talking about needing something LARGER than that to support 10k people? If I haven't missed a zero that's over 14k square miles per person, many times the space needed by hunter gatherers in the most barren deserts. And we have hydroponics. You might want to re-check your estimate.
"You can't just move between the stations - things orbits naturally deteriorate over time and need adjustment."
This seems like a non-sequitur - how on earth would a need to adjust orbits interfere with transport? That makes no sense.
Having to adjust an orbit occasionally is no huge catastrophe, and even that can be almost eliminated by taking advantage of LaGrange points between gravity wells. Certainly I would expect HOMEs to appear first in a place like L5.
"The station keeping and other energy costs in this scenario are going to be like nothing we can even imagine, constantly."
Well they *would* be, if you did it the way you seem to be imagining it. Grossly oversized.
"With the size of these things you will be executing and planning extremely expensive burns literally years in advance."
Depending on where you want to go, sure. But from L4 to L5 needn't be a particularly long trip, even with current tech. It's like a moonshot in terms of total distance, but remember there's no drag and no gravity, so it's actually nothing like that at all in terms of energy used.
On the other hand getting out to the vicinity of Mars or the asteroid belt, likely future hot spots, well that's still a significant journey. But again, it's far far less of a challenge if you don't have to escape from a planet to get it started. A fraction of the fuel would be needed, and the entire vehicle could be much smaller yet have more usable space. Would it take a long time? Well, yes, but it's not going to take any longer from L4 than it would from Terra Firma.
If laughter is the best medicine, who are the best doctors?
(Score: 0) by Anonymous Coward on Friday January 24 2020, @07:23AM (10 children)
Oh man, definitely go check out SpotTheStation. Yes, you can easily see the ISS with the naked eye - even with light pollution. It's big and bright. It's an awesome feeling too, especially for anybody at all interested in space. When I said supermoon, I meant in terms of relative perceived size. Of course the moon would be much larger, because it's about 900x further from Earth than the ISS. But in perceived size, a single station (at ISS orbit height) would appear to be many times larger than the moon.
I think you've made one significant mistake in all your assumptions here: orbits in real life are not stable. This includes orbits within the L4/L5 points. The points themselves are stable but everything within them, not so much - other than that they'll probably stay within the points. There are two big reasons for this. The first is that gravitational mechanics are themselves not stable. Everything exerts gravity on everything else in a system that is dynamic and changes every single continuous moment. So any orbit is always an approximation. The other reason is that in space there is lots of matter - solar winds, micrometeorites, and just various particles. This exerts drag on everything akin to a really thin atmosphere. Similar to the reason that when we send a probe to some planet it's not just a approach burn and then an insertion burn, but a countless series of little adjustments all along the way. Part of the reason I'm dubious on the Starshot project as much as I'd love for it to be possible.
Anyhow this means that even the Earth is constantly slowing down and will eventually fall into the sun. However, planets have enough momentum/mass that the effect is not too relevant. Last time I looked into it it will take Earth something like 10^15 years to fall into the sun. But since the sun will probably become a red giant and absorb us on the order of 10^10 years, it's somewhat of a nonissue. However, for things that weigh less, and especially things with higher volume, this is a serious issue. For example, this [heavens-above.com] is a graph of the ISS height/thrusts. It's doubly affected since even at 430km Earth's atmosphere is poking out a bit. Nonetheless, it's remarkable how rapidly its orbit decays over time. These things are the same reason, if you didn't know, that all satellites also have little thrusters on them. A satellite put in a 'perfect' geostationary orbit (such that it always faces the same point on Earth) would leave it relatively quickly without constant adjustments. The ISS primarily uses docked soyuz crafts who intentionally bring loads of extra fuel as its thrusters. Only difference here in L4/L5 is that stuff would probably stay within the points, yet their internal orbits would be constantly shifting.
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The stations as you've described them would be high volume and low (compared to a planet) mass. This means they're going to be constantly experiencing a pretty substantial orbital decay. Presumably this decay would be magnified within the L4/L5 points since they tend to be dust magnets. And of course you also will need to engage in maneuvers just to avoid regular space stuff - comets, meteors, and what would undoubtedly be far more space junk. Again, another problem that is magnified within an L4/L5 point. And given the mass of these things you're going to need to plan and execute these never-ending burns well ahead of time. This is what I was talking about in the difference between just keeping the stations up and traveling between them.
I do expect the total energy cost here is probably going to be substantially larger than any saving from orbital launches. However, this is also a generalization of the previous point. I expect Earth will be using many orders of magnitude more energy on the same sort of time frame we're talking about. This is the whole point I was getting at - things that seem like high energy to us today will be the equivalent of a flash-light in the future. Actually I haven't even asked you how you plan to get fuel, presumably water, and maintain your hydrogen. The most logical is to probably grab a comet, or a big piece of one, but now your mass just went supersonic meaning you are definitely burning unimaginably more energy than some surface launches, just for basic operation - station keeping, electrolysis, etc.
(Score: 2) by Arik on Friday January 24 2020, @03:06PM (9 children)
Spot it, sure. Not the same thing as seeing it at a range where details can be made out. You're not making out much detail on that with the naked eye.
"When I said supermoon, I meant in terms of relative perceived size. Of course the moon would be much larger, because it's about 900x further from Earth than the ISS. But in perceived size, a single station (at ISS orbit height) would appear to be many times larger than the moon."
That seems pretty irrelevant. You wouldn't put a HOME there. The nearest likely locations are at lunar distance, not ISS distance, from Earth.
"I think you've made one significant mistake in all your assumptions here: orbits in real life are not stable. This includes orbits within the L4/L5 points."
And I don't understand why you continue to misunderstand me like that. Not only have I not posited perfectly stable orbits, I explicitly said already that they do have to be maintained, and that using L4 or L5 would *minimize* that, not eliminate it.
"And of course you also will need to engage in maneuvers just to avoid regular space stuff - comets, meteors, and what would undoubtedly be far more space junk."
Of course the chance of a comet or decent sized meteor hitting such a small object (compared to the moon and planets, it will be a very tiny target) is low, but not zero, so of course you have to be ready for that. But as we have both pointed out, the station will have to have the ability to maneuvre a bit just to maintain it's orbit, so this is not a huge problem. Smaller objects are likely to be a fairly regular annoyance, but the station doesn't necessarily need to move for those, it would be easier just to capture the smaller objects or deflect them.
"And given the mass of these things you're going to need to plan and execute these never-ending burns well ahead of time. This is what I was talking about in the difference between just keeping the stations up and traveling between them."
They will need to be calculated ahead of time, and controlled by computer, but so what? And what does that have to do with travel between them?
"For example, this [heavens-above.com] is a graph of the ISS height/thrusts."
And it says right there: "the gradual decrease is caused by atmospheric drag." I'm talking about an L4 or L5 orbit and you keep pointing me at the ISS which occupies a MUCH lower orbit. The cases are not the same.
"but now your mass just went supersonic"
What are you talking about?
There's no atmosphere, there's no sonic, there's no transsonic, there's no supersonic. These labels are all meaningless in space. There's no drag, there's no turbulence, there's no sonic boom. Just thrust and inertia.
"meaning you are definitely burning unimaginably more energy than some surface launches"
Not at all. You seem horribly confused.
If laughter is the best medicine, who are the best doctors?
(Score: 0) by Anonymous Coward on Friday January 24 2020, @04:41PM (8 children)
The visualization point on the size of these things was because I find imagery often more useful than words. What's the difference between a million and a trillion? Well obviously an absolutely vast amount, but for our little minds it's hard to grasp the difference beyond simple mathematics. So things like something the size of the ISS suddenly being multiplied to the [perceived] size of a moon gives a much better mental model of what we're talking about. And not just one of them, but millions to support the equivalent of a single planet's population. I mean your idea sounds perfectly reasonable when you just say it, obvious even. But when you actually start looking more deeply into things is where the issues emerge.
The point on station keeping is getting back to what we were talking about from the very beginning. Moving a station is extremely expensive. A tiny station of the sort you're describing would be on the order of thousands of times larger than the ISS. The ISS currently uses around 10,000 pounds of propellant per year just for the ~30m/s of deltaV it requires. Even if you can get the deltaV requirements (and atmosphere is just one factor in orbital deterioration) down you're likely to be spending millions of pounds of propellant per year per station just for basic survival.
To put more specific numbers to the game here, it takes about 7,600m/s of deltaV to get off Earth. Energy requirements are of course linearly proportional to mass. So the bigger (and heavier) these stations get, the less you gain any energy benefit from them. To give an example imagine we only wanted to move 1/7,60th the mass of a station in goodies off of Earth. That means if the station requires more than 10m/s of deltaV per year, you're in the net negative. For a single station, such a notion very much on the efficiency of the station side, though it's probably surprisingly close for reasons I'll get to in a minute. But for a million stations the exact opposite becomes true where that's probably rather more than we'd be moving into space.
---
Getting back to the mass, one of the most important parts is what you ignored from the last post. How do you plan on getting your fuel and whatever's needed for your internal life support systems (probably hydrogen)? I think the most obvious answer is to grab some comets. But this is where you start to see some real problems. You suffer from the Tyranny of the Rocket Equation, even when you're already in space. You're going to want to grab a pretty big comet, but that's going to dramatically increase you mass - and thus the amount of energy you're burning to get those all-so-precious deltaV.
And that also now means your station is becoming increasingly unable to maneuver. So you're probably going to want to provide collision shielding so a mid sized piece of space junk doesn't just destroy your station. Incidentally you'd also need such shielding anyhow since part of the reason the ISS stays fairly close to Earth is because of our magnetic shielding. It helps minimize radiation exposure. Out in open space, you're going to need substantial shielding to avoid frying everything and everybody on board. Yet this shielding is now going to add even more mass to your station. You're getting really really big, really really slow, and really really expensive (in terms of energy to maneuver). The ultimate effect of this all is that you're burning just unimaginably large amounts of energy for basic survival. This is what I was referring to with your mass going supersonic. I thought it was obviously figurative. Incidentally your station continues to slowly approach becoming a small planet!
---
Space stations in space have been a sort of pet peeve of mine. It sounds so simple at first - 'blow up a Bigelow Style capsule or two, get some greenery going on, and you're 90% of the way there!' But that's just not true at all. I expect we'll have military, industrial, and leisure stations - but I do not expect to see any significant number of residential stations. The costs and complexities involved are many orders of magnitude away from what they seem at a glance.
(Score: 2) by Arik on Friday January 24 2020, @07:35PM
I'm sorry, I don't share your finding.
But if you're trying to visualize a HOME and failing, I guess the best easy reference would be to the Babylon 5 station from the series of the same name. Not perfectly represented, but a decent idea of what a particularly grand and impressive HOME might look like after we have, oh perhaps a couple centuries or so of experience building them.
It's a series of cylinders, one containing the next, rotating around the common central axis. Airlocks are located at either end of that central axis to accommodate arrivals and departures. That area is zero/microgravity, and subjectively it is the "top" of the structure, as moving in any direction (other than directly along the central axis itself) is subjectively "down."
"And not just one of them, but millions to support the equivalent of a single planet's population."
But you have to think about how such changes occur. It starts with one station, in L4 or L5, conveniently placed to profit from any traffic between Earth and or the Moon with any other destination. Initial problems are encountered, and resolved, the technology matures, another one goes up in the other point. Maybe the next one is intended to service Mars, or the asteroids, etc. As long as they are advantageous they will continue to be built, larger as technology improves, but perhaps smaller to fill new niches as well. You keep talking about how we'll have more energy available as technology increases, and that's true, but that helps the HOME at least as much as the planet. It makes overcoming all the difficulties you mention that much less difficult.
It might take a century or more for the population in HOMEs to exceed that of Earth. You might well see diversification, with increase in technology allowing for quite mobile HOMEs that can be moved around quite easily and perhaps follow asteroids or comets that they specialize in exploiting existing side by side with larger ones that tend to stay in relatively stable spots and serve more as hubs of trade, perhaps also hosting specialized industries and so forth. It wouldn't necessarily involve any mass-migration, or as I think you may have alluded to earlier a rule of absolute self-sufficiency inside a single HOME. There would be trade, and specialization. Of course you want each and every HOME to have basics - like enough plants to sustain the environment - but not every HOME has to be capable of producing everything and anything they might want or need on their own station. There's plenty of room for specialization.
And there's even room for disaster - because at that point we no longer have all our eggs in one basket. A comet hitting a HOME might be horrible, but it wouldn't end the species like a good strike on Terra might do right now.
"The ISS currently uses around 10,000 pounds of propellant per year just for the ~30m/s of deltaV it requires."
And again, the ISS is nowhere near the same position. The ISS is in a low orbit. The HO part of HOME stands for High Orbital. The ISS would use a tiny fraction of that to maintain position if it were located at L4.
"How do you plan on getting your fuel and whatever's needed for your internal life support systems (probably hydrogen)? "
I expect the first station would be located at L4 or L5 and be able to rely on Earth and/or perhaps a Lunar station for some supplies at first, as the technologies are tested and refined. It would be premature and perhaps even hubris to presume to know exactly how that would best be done now, before anyone has done that work. And again, even late stage, I'm not positing that anyone will feel the need to build a station which is perfectly self-sustaining and never requires any sort of external input, ever. That's just not necessary. Every station needs to be able to scrub oxygen and water and supply staple foods, but not every station needs to be able to fabricate a new reactor, for instance.
"You're going to want to grab a pretty big comet, but that's going to dramatically increase you mass - and thus the amount of energy you're burning to get those all-so-precious deltaV."
I think I'd start with a small one and see how that went to start with.
Again, we're not talking about jumping to the final stage immediately, we're talking about something that would start with a single station and grow over time because of the economic advantages. They don't have to all apply from the moment the first station is in place - I'd expect something on the order of a century or two of rapidly developing technology and rapidly expanding opportunities as a result.
"Incidentally you'd also need such shielding anyhow since part of the reason the ISS stays fairly close to Earth is because of our magnetic shielding. "
The Earth's magnetic field is quite weak at that height, and there's some connection between a rotating cylinder and magnetic fields.
But yes, despite that, you'd certainly want to maintain an ability to maneuver as well, and whatever level of shielding or other protection becomes feasible. But again, any object large enough to cause a problem is going to be MUCH more likely to fall into a nearby gravity well and strike either Terra or Luna than it is to strike a much smaller station located in L4 or L5.
Also, reading back on this, it seems like you're imagining /the station/ itself going out to capture a comet, physically. Well, no, I don't see that. Not with the sort of tech we have now or reasonable extrapolations from it, perhaps after some wild breakthrough we cannot anticipate. But no.
What you would do in the case you're occupying a relatively small HOME which is specialized in hunting comets, I would expect to go more like this:
Move the HOME, not to the comet, but to a spot the comet will be passing by at some point in the future. Simultaneously, launch transports to intercept the comet itself, carrying your mining equipment. Use the time between interception and the later approach near the waiting HOME to get your 'package' ready. You haven't changed the path of the comet whatsoever, you're simply collecting what you want up to this point. Then, you still don't try to deflect the remainder of the comet, just your transports with the added mass of your package. They need to match back up to the HOME and dock for unloading.
The same comet might be harvested many times, with better technology available each time.
I expect asteroid mining might be easier to start with, but much of the technology developed there would be applicable either way, no?
"You're getting really really big, really really slow, and really really expensive (in terms of energy to maneuver)."
Which is why I expect the early ones, and later the largest ones, would primarily maintain an easy orbit in L4 or L5 instead of trying to go anywhere else.
Nonetheless, when we get to 'generation ships' of course a large HOME would be the ideal basis for such a thing. You'd want to upgrade your propulsion system and pile on a ton of fuel, assuming we're still using rockets for thrust at that point. But again that's something that would happen very late stage, probably not until the solar system starts to feel a little too crowded, and much more efficient mechanisms for generating thrust have been developed.
"Incidentally your station continues to slowly approach becoming a small planet!"
But only because you keep insisting it requires things it does not!
;)
"I expect we'll have military, industrial, and leisure stations - but I do not expect to see any significant number of residential stations. "
You're overlooking the obvious. The cost of commuting from Earth to orbit and back again regularly would dwarf the cost of residential accommodations on the station. I know, I know, the ISS - but again the ISS is a LOW ORBIT station, and simply not large enough to operate any other way. Why don't they leave them longer than 6 months? Among other reasons because, as you're obviously already aware, zero/micro g is harmful to humans over time. We're talking about a totally different sort of station, in a high orbit, with gravity of or near 1g (experienced.) Of course it would be much expensive to construct initially, but long term it would be much more productive - and remove the requirement for that expensive commute. You could stay on such a station as long as needed. You could even be born on one and die on one.
If laughter is the best medicine, who are the best doctors?
(Score: 2) by Arik on Friday January 24 2020, @10:23PM (6 children)
This is actually what brings us right back to the start of what's become a very long digression.
When/if a generation ship, a human 'colony ship,' sets out for another star, what's more likely? That they will go out of their way to get to a system with a 'habitable' planet or that they will set out for Proxima Centauri, the nearest destination?
Sure, it's a class M star, probably not the sort of place you'd find a 'habitable' planet, but why would they care? They're looking to take on raw materials and energy. The star itself is unfortunately unstable, and it's only known planet a bit close for comfort, but it's still likely to have all manner of debris in the form of asteroids and comets available, and if it once had gas giants they should have left rocky cores behind to provide L points, accumulate and concentrate asteroids, and do all that at a reasonably safe distance from Proxima. They don't need a 'habitable planet' just reasonably safe L points for larger stations, a star of some kind for energy, and sufficient resources outside of large gravity wells. I'm not even saying they would never enter them, just that I expect they would prefer to avoid them, and if pressed for some reason to take up on a planetoid of some form they'd be more likely to choose a moon than a planet. (And by the same token it's very strange to be talking about colonizing Mars when the low-hanging fruit of Luna sits untouched, but I have digressed enough for now.)
By the time humans actually see another habitable planet, it might not even strike them to *consider* 'returning' to the surface of one. It's a long ways down the road, and I'm considering the most likely road to get there and the way it will affect us along the way.
If laughter is the best medicine, who are the best doctors?
(Score: 0) by Anonymous Coward on Saturday January 25 2020, @08:33PM (5 children)
There are a lot of things I want to point out here, and I did. I'm going to erase that (my) wall of text to try to what I see as the most core issue: scale. That's what I was talking about with visualization. It's fun to imagine how a station might look, but I was talking about size. I don't think you're entirely appreciating this factor. So let's hit on one of the most basic necessities: water. Your comments on the comet make me suspect you're radically underestimating what's going on here.
It's surprising how much water we use. Let's consider two things - how much a person on Earth uses and how much a person on the ISS uses and try to get some meet in the middle figure that might tell us how much water we'd need if we can't just go balls out like on Earth, yet also don't want to like an ultra-spartan lifestyle such as on the ISS.
- On Earth we use around 140 [usgs.gov] gallons per person per day. Let's call it 100. That's 36,500 gallons or about 305,000 pounds per year. I'd emphasize that that is also only indoor usage. Usage in outside food production, etc is in no way considered there. Whatever. I suspect it won't matter.
- The ISS has a pretty horrible standard of living which involves basically 0 non-necessary usage of water. "Showers" are moist cloths (granted - probably required by 0g anyhow), brush your teeth and swallow if you're an American or spit if you're a Russian - no water in either case. Shave gets a moist cloth. And so on. That lifestyle nonetheless still runs about about 10,000 [nasa.gov] pounds of water per person per year.
So let's imagine a relatively small station - 10,000 people. How much water might they want to use? I mean presumably you want something vaguely resembling comforts like being able to take a shower or bath in the artificial gravity, perhaps making some 'beverages', and so on. Let's say 50k pounds? The ISS manages to recycle about 90%. We'll bump ours down to 70% because it might be nice to actually be able to have things like air with a bit of moisture in it and there's going to be some loss of efficiency due to huge scale. So we're at about 15k pounds of water needed per person per year.
That's 150,000,000 pounds of water we need per year. And that's before we even consider fuel. In reality fuel would likely bump that up several orders of magnitude due to the tyranny of the rocket equation - but just to show the issue I'm going to dramatically low ball as I've done for some other measurements throughout this. It doesn't matter. Let's just bring that up to a billion pounds, a nice easy number to work with. How big is a billion pounds of ice. Yeah ice is bigger (volume) than water, but doesn't need to be kept heated up and is generally easier to work with than literally billions of pounds of water.
A square meter of ice weighs about 2000 pounds. So a billion pounds of ice would be about 500 square kilometers of ice! And keep in mind this is a serious lowball. But I think it should start to hopefully make the issues more clear. You're not having a few transport ships go bring back hundreds of kilometers of ice. These issues of scale are what make stations, as a base for living, so unreasonable. The sheer scale of many things are vastly larger than you would intuit. This is what I've been getting at all along in that a "real" sustainable station, and not a sci-fi one, rapidly just starts becoming a small planet that will ultimately just leave you itching for the real thing because of all the sacrifices you'll have to make along the way.
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Couple of asides I did point out that I think are tangential to this core point:
1) Earth's magnetic field does strongly protect the ISS. It's huge and even hits the L4 point for a fraction of its orbit.
2) L4 is not a haven, it's a trash magnet. See: Kordylewski clouds. You can literally see the dust in L4/L5 with the naked eyes. We also already know of some dangerous sized asteroids cruising about in them. Dangerous place with a high probability of screwing your orbit. You're not going to be using less fuel station keeping - but likely much more.
(Score: 2) by Arik on Saturday January 25 2020, @09:16PM (4 children)
Sure, it works for both. One mile diameter, one rotation for minute, for about .9g in the lowest levels. About 11 miles long.
Of course it would need lots of water. But water is not something that's used once and then disintegrates and escapes into the ether. You drink a litre of water, you excrete a litre of water - some through the skin some as urine and so on. In this environment, it would (virtually) all be captured and recycled. So you definitely need to bring a lot of water on board at the start to meet the needs, but it's not like you need to keep re-importing all that water every day as it is 'used up.' Of course it's not possible to keep everything perfectly sealed - over time a few molecules will sublimate here and there, a little humidity will be lost each time an airlock is cycled and the like - but these are very small fractions of the total, so occasional imports to 'top up' the system should be fine.
This would inevitably be much MORE efficient than the ISS, not less as you posit, in part because of scale! The inverse square law applies here.
"1) Earth's magnetic field does strongly protect the ISS. It's huge and even hits the L4 point for a fraction of its orbit."
Oh, it does indeed protect it, I wasn't questioning that at all. And you could say it's a strong field, in that it obviously has a huge amount of energy, so it reaches a very long ways. But it's quite a weak field nonetheless, at the distance we're talking about, in comparison to fields we routinely generate ourselves. So one might consider simply generating your own field, sized to fit. You need an enormous electric motor to rotate the lower levels anyway, so you have a rotating cylinder and a bunch of electromagnets, it's not such a huge stretch to generate your own magnosphere in the process.
"2) L4 is not a haven, it's a trash magnet.
Oh, it is indeed a bit of a trash magnet. It would need to be cleaned up, and regularly monitored and maintained. But that's not such a bad thing, monitoring and maintenance of the area should go without saying, it's needed anywhere.
If laughter is the best medicine, who are the best doctors?
(Score: 0) by Anonymous Coward on Sunday January 26 2020, @03:57PM (3 children)
The number I gave was, as mentioned, after recycling! That's the amount of new water you'll need each and every year, and a dramatic lowball due to fuel requirements.
There's no such thing as 100% efficiency in recycling, and bigger doesn't inherently mean easier or cheaper. You can get the best water recycler that money can buy and if it gives you 93% (as it does) then you're only going to get less than that the more complex your system gets. For instance every useage of your ice other than directly becoming water is going to result in inefficiencies. As an example - air scrubbing. You'll probably use the Sabatier reaction: hydrogen + CO2 = water + methane. That hydrogen is going to come from electrolysis and the entire reaction, along many others, is going to be a regular drain on your water resources. There's also the water reclamation itself. You're going to do a better job of collecting all the water in your bathtub than in your house than in your neighborhood, etc. Bigger = worse in cases like this. I gave us an overall 70% efficiency which I think is very fair.
You also now start to get into energy requirements. Even the act of processing billions of pounds of water is going to be extremely expensive. This is the reason the fear of a shortage of fresh water is even a thing on Earth. We have effectively infinite salt water, but recycling/desalinating that water is incredibly expensive. I'm not much in the mood now but you could try to ballpark exactly how many square miles of solar panels you'd need simply to sustain this system. For comparison the ISS only generates about 0.25MW when directly angled towards the sun with its giant flaps. You'd probably need to go nuclear, yet now you're introducing a whole new host of issues.
I mean these are not just 'yeah we'll just solve it things' - these are some real show stoppers. A "small" station of the sort you're describing is going to be literally to thousands of cubic miles large just to provide the most basic necessities, with a fraction of the quality of life you'd have on a planet. The ideal of a space station and the reality of one are very different. I definitely think tiny entirely dependent stations for tourism will be a huge thing though. Who wouldn't want to try some 0g poon, alongside all the other novel forms of recreation possible.
(Score: 2) by Arik on Sunday January 26 2020, @08:26PM (2 children)
Actually it does. Double the dimensions of a three dimensional object - it's surface area increases by the square, it's volume by the cube.
Leakage from the closed system is proportionate to surface area, from a base proportionate to volume. So increasing the size of the structure decreases the amount of leakage relative to volume.
"As an example - air scrubbing. You'll probably use the Sabatier reaction: hydrogen + CO2 = water + methane.
Try 6CO2+6H20=C6H12O6+6O2.
Look, some of your points aren't totally off. It's not like it's going to be an easy thing. But you're just dead set on making it seem impossible, and you keep distorting the idea until it becomes impossible, which is kind of interesting, but not very meaningful.
If laughter is the best medicine, who are the best doctors?
(Score: 0) by Anonymous Coward on Monday January 27 2020, @04:41PM (1 child)
I'm not sure what reaction you're describing there. If you combine CO2 and H20 you're going to get H2CO3. Also known as... soda water! :) And there you'd already need the CO2 extracted so you can supersaturate the water, so it doesn't have anything to do with scrubbing.
Here, I think you're entirely misunderstanding my position. I would love for nothing more than a self sustaining station to be viable. The main reason (and source) of my critiques here is specifically because I'm so interested in this topic. I would like to be one of the first settlers on Mars. Most of my critiques here have come from trying to determine whether settling Mars is even possible. I came to the conclusion that it probably is but it's going to require vastly more work than most people are aware. And even then it's a "probably" because it may simply be the case that e.g. 0.4G = 15 year life expectancy. But it's of course going to be extremely dependent on many of the things you simply don't have on a ship: effectively infinite water, land, and material/elemental resources to start with.
I think for things like this, which I assume you also aspire to, you should be as critical and objective as possible for otherwise you are simplying lying to yourself.
(Score: 2) by Arik on Monday January 27 2020, @05:01PM
Photosynthesis. The process by which living plants keep turning carbon dioxide and water into sugar and oxygen, to oversimplify a bit for brevity. I was expecting you to be familiar with the process.
"Here, I think you're entirely misunderstanding my position. I would love for nothing more than a self sustaining station to be viable."
Well I don't think I volunteered any opinion or speculation on your motives, I was just referring to the /actions/ so to speak. You seemed to repeatedly insist on a station large enough to hold todays planetary population but I don't see why that would be required or even necessarily desirable frankly.
"Most of my critiques here have come from trying to determine whether settling Mars is even possible. I came to the conclusion that it probably is but it's going to require vastly more work than most people are aware."
I agree completely with you on that. It will be very difficult and there isn't (yet) an economic case to do so. Logically it should be proceeded by a lunar colony and a transit station occupying one of the earth-moon L points. Unless there's some enormous advantage to the Mars colony that I'm unaware of.
If laughter is the best medicine, who are the best doctors?
(Score: 1) by khallow on Sunday January 19 2020, @04:34PM (5 children)
Or perhaps to create a stable ecosystem that doesn't require active maintenance. Here on Earth, we're actively perturbing the global ecosystem in a variety of negative ways and it's still holding together. Try that trick on a space station and you're dead.
(Score: 0) by Anonymous Coward on Sunday January 19 2020, @04:57PM (2 children)
I'm not sure what the purpose of that would be, except as a multi million year science experiment or a colossal vanity project.
It seems like what you're saying is equivalent to "no one can live in a city because if the plumbing and roads stopped working people would die!" They would, so people keep them working.
(Score: 1) by khallow on Sunday January 19 2020, @05:06PM
Or a failsafe.
(Score: 1) by khallow on Monday January 20 2020, @06:04AM
As an aside, yes, that can happen as any post-apocalypse zombie documentary would show you. When everyone is a zombie, they stop caring about the plumbing and roads.
(Score: 0) by Anonymous Coward on Sunday January 19 2020, @05:42PM (1 child)
OMG! Did khallow just cop to Anthropogenic Global Warming?
(Score: 1) by khallow on Sunday January 19 2020, @06:08PM
(Score: 2) by FatPhil on Sunday January 19 2020, @06:28PM
There are no resources on space stations. They were resources before you mined them and put them on the space stations, now they're very finite supplies.
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves