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    Quote Originally Posted by Grey_Wolf_c View Post
    A few years back, there was a "space elevator climbers" yearly competition (it also had a ribbon competition, but that never went anywhere). By the end, the teams where bringing in climbers that were powered by lasers. I honestly don't think that car propulsion would be a problem, if we did have the ribbon. Which, as I and you both agree, we don't.

    Grey Wolf
    Yeah, as far as I'm concerned the big problem with the climbers is that we don't know if they'll hold up when we get to full scale, we can already make proof of concept climbers or scaled down versions if we need to. We don't know if the ribbon is even possible, we have theoretical materials that might be able to maintain the strength needed at the required length, but it's definitely a 'might' not a 'will'.
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    Quote Originally Posted by Zelphas View Post
    So here I am, trapped in my laboratory, trying to create a Mechabeast that's powerful enough to take down the howling horde outside my door, but also won't join them once it realizes what I've done...twentieth time's the charm, right?
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    Quote Originally Posted by factotum View Post
    There aren't any resources on Mars that we can't find here on Earth
    Yes but mars has tgem in raw form, where as pretty soon the ones on earth are all going to be tied up in things that have already been manufactured and purchased. We're going to need more if we're going to continue to make more.

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    Quote Originally Posted by Anonymouswizard View Post
    IIRC there are massive engineering problems with massive space stations.
    Plus, I don't think many people would want to live in such a place permanently, not even trekkies like me.

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    Quote Originally Posted by Bohandas View Post
    I don't think many people would want to live in such a place permanently, not even trekkies like me.
    Most people would also not want to live permanently in a place with no sanitation, clean water or access to reliable sources of food, and yet over a billion people do so anyway. If being on the space station means having a job and a future for your kids, there'd be queues, no matter how bad the living conditions were, so long as they were better than the ones on Earth.

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    Quote Originally Posted by ArcticMoue View Post
    animals going extinct before their time
    Since there are no animals native to Mars, there is no chance of them going extinct....
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    Quote Originally Posted by Grey_Wolf_c View Post
    Speaking of, I understand we could build a space Elevator on the Moon out of steel. Unfortunately, it doesn't sound like there is anything we'd want to mine in the moon that'd need a Space Elevator.

    Grey Wolf
    How high would that elevator reach? Generally a space elevator terminates at the "Geo"synchronous orbit, as I understand it. But for the tidally-locked Moon, that's a point roughly 385,000 km away (Earth is in a "Geo"stationary orbit around the moon). For the lunar elevator, are they looking at a tower rather than a ribbon?
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    Quote Originally Posted by MikelaC1 View Post
    Since there are no animals native to Mars, there is no chance of them going extinct....
    Precisely


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    Quote Originally Posted by Lord Torath View Post
    How high would that elevator reach? Generally a space elevator terminates at the "Geo"synchronous orbit, as I understand it. But for the tidally-locked Moon, that's a point roughly 385,000 km away (Earth is in a "Geo"stationary orbit around the moon). For the lunar elevator, are they looking at a tower rather than a ribbon?
    Oh, yes, ludicrously long. That said, it seems I mispoke - wikipedia does not susgest steel as a construction material, so wherever I read that was probably wrong. Interestingly, I see in the wikipedia that the design calls for a double elevator, anchored (as it must) at the equator, but with a secondary ribbon going to the pole, where the lunar base is more realistically to be placed. I had not seen that design before, but it makes sense, if it is achievable.

    As to ribbon vs tower, (assuming "ribbon" hangs from the planet and "tower" rests on the planet), it would still be a ribbon, held taut by the moon's 28-day long spin on its own axis. Although I suspect that to a certain degree, the elevator might also be assisted by Earth's gravity pull on its end.

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    Quote Originally Posted by Grey_Wolf_c View Post
    2.4 GPa is insufficient
    So? You were arguing that we can't get more than "a few millimetres". But we never expected to make one huge molecule, it's the fibre we were always after - and it is the technology that already exists. Now we simply need to perfect it.

    "2.4 GPa" demonstrates that Pasquali fibre is not some mush. We've got to 5.6 GPa by 2015 (Kumar), and will keep on improving it for years to come - despite not even spending any significant amount of money on this research. If we'll get serious, we may even have space elevator in a decade. But we can't have that, can we? Which is why "space elevator is a pipe dream" is being repeated endlessly.

    Quote Originally Posted by Grey_Wolf_c View Post
    Hardly anything new. Moreover, it is the _existing_ (circa 2006) technologies that are investigated.

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    Quote Originally Posted by Lazymancer View Post
    So? You were arguing that we can't get more than "a few millimetres". But we never expected to make one huge molecule, it's the fibre we were always after - and it is the technology that already exists. Now we simply need to perfect it.
    Single walled nanotubes is not equivalent to multiwalled nanotubes. Being able to produce the latter doesn't do squat for the prospects of the space elevator, that cannot use them. Only the former count. And I stand by my statement that we have not figured that out yet. Your claim that we are now making it by the meter and that only "politics" stands in the way is particularly misdirecting if not outright wrong.

    So yes, we have not produced more than a few millimeters (a few dozen, as it turns out) of a material capable of building the space elevator. You telling me that a similar, but much weaker, material also exists is irrelevant.

    Quote Originally Posted by Lazymancer View Post
    "2.4 GPa" demonstrates that Pasquali fibre is not some mush. We've got to 5.6 GPa by 2015 (Kumar), and will keep on improving it for years to come - despite not even spending any significant amount of money on this research.
    No, we won't. The upper theoretical limit for multi-walled carbon nanutubes is significantly below the minimum necessary for the space elevator. Just because single and multiwall nanotubes are both carbon nanotubes, the research into one does not mean we have figured both out.

    Quote Originally Posted by Lazymancer View Post
    If we'll get serious, we may even have space elevator in a decade. But we can't have that, can we?
    And this just reads like the ravings of a conspiracy theorist, so I'm done with you.

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    Quote Originally Posted by Lazymancer View Post
    "2.4 GPa" demonstrates that Pasquali fibre is not some mush. We've got to 5.6 GPa by 2015 (Kumar), and will keep on improving it for years to come - despite not even spending any significant amount of money on this research.
    The bolded part is an assumption, this is somewhere where we're not sure where the practical upper limits are. Maybe we can create magical 200GPa carbon nanotubes, maybe doing so takes more energy than launching 1030 rockets and high sophisticated nanofabrication, we don't actually know.
    Last edited by Anonymouswizard; 2017-12-04 at 03:27 PM.
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    Quote Originally Posted by Zelphas View Post
    So here I am, trapped in my laboratory, trying to create a Mechabeast that's powerful enough to take down the howling horde outside my door, but also won't join them once it realizes what I've done...twentieth time's the charm, right?
    Quote Originally Posted by Lord Raziere View Post
    How about a Jovian Uplift stuck in a Case morph? it makes so little sense.

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    Quote Originally Posted by Anonymouswizard View Post
    Note: any long term Martian living or colonisation would require us to know how plants develop in low-g environments, and it's theorised that long term exposure to Martian gravity would even stop Earth born humans from being able to tolerate 1g of gravity, let alone those who grow up on Mars. For all we know a martian society might be impossible.
    Research stations (basically like the ISS) seem perfectly reasonable, but I don't think Mars could be regarded as habitable for any permanent settlers. Microgravity does really strange and uncomfortable things to a body and even though Mars has some gravity, I don't think the human body will work properly in such an environment. But that's just for healthy adults. When you think of permanent settlement you also have to include developing children and I actually don't even want to imagine what it would do to them. Bone, muscle, and nerve development would all probably turn our very funky, likely leading to severe disabilities.
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    Quote Originally Posted by Anonymouswizard View Post
    The bolded part is an assumption, this is somewhere where we're not sure where the practical upper limits are. Maybe we can create magical 200GPa carbon nanotubes, maybe doing so takes more energy than launching 10[sup]30[sup] rockets and high sophisticated nanofabrication, we don't actually know.
    Sun rising tomorrow in the east is also an assumption. It simply happens every morning. Day after day. We aren't sure whether it will do so tomorrow. Maybe it will magically rise again, maybe not. We don't actually know, do we?

    To put it another way: instead of putting the label of "assumption" on anything and pretending the each and every possible event has the same chance to happen, we need to evaluate how probable the "assumption" is - since every potential event can be called an assumption.

    In this specific case, we have new technology that not only did not exhaust basic approaches (we literally get new methods every year), but didn't even perfect any of the existing. Thus, it is practically certain we will get much better at making carbon nanotubes, and we will be getting better soon. Leaps of qualitative improvement (more than doubling within 2 years) suggest that improvement will be significant.

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    Quote Originally Posted by Yora View Post
    , I don't think the human body will work properly in such an environment. But that's just for healthy adults. When you think of permanent settlement you also have to include developing children and I actually don't even want to imagine what it would do to them. Bone, muscle, and nerve development would all probably turn our very funky, likely leading to severe disabilities.
    Or they could turn out like John Carters child (Edgar Rice Burroughs version please) and turn out to be Superman
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    Quote Originally Posted by Lazymancer View Post
    Sun rising tomorrow in the east is also an assumption. It simply happens every morning. Day after day. We aren't sure whether it will do so tomorrow. Maybe it will magically rise again, maybe not. We don't actually know, do we?
    No, it is an expectation. There are reasons it might not rise in the East (international consensus to exchange the directions of east and west, suddenly being put out by a highly advanced alien race), but it is expected it will.

    To put it another way: instead of putting the label of "assumption" on anything and pretending the each and every possible event has the same chance to happen, we need to evaluate how probable the "assumption" is - since every potential event can be called an assumption.

    In this specific case, we have new technology that not only did not exhaust basic approaches (we literally get new methods every year), but didn't even perfect any of the existing. Thus, it is practically certain we will get much better at making carbon nanotubes, and we will be getting better soon. Leaps of qualitative improvement (more than doubling within 2 years) suggest that improvement will be significant.
    Ah, here we're getting into the fact that one of our things, the sun rising in the East, is based on lots of previous data, while the other, that we'll keep getting better at making carbon nanotubes, is based on the fact that we haven't stopped yet.

    Let me put it this way, we might be able to make carbon nanotubes that strong. However, there is literally no guarantee that a) we will do it within the lifetime of any poster on this forum, and b) that we won't hit a roadblock in say 17 months that caps the tensile strength of the carbon nanotubes due to the manufacturing methods not being precise enough or some other problem. Instead of looking at things that are decades to centuries away, like space elevators and fusion plants, why don't we look at stuff that is years away, like better fission reactors?
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    Quote Originally Posted by Zelphas View Post
    So here I am, trapped in my laboratory, trying to create a Mechabeast that's powerful enough to take down the howling horde outside my door, but also won't join them once it realizes what I've done...twentieth time's the charm, right?
    Quote Originally Posted by Lord Raziere View Post
    How about a Jovian Uplift stuck in a Case morph? it makes so little sense.

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    One problem with living on Mars that I have not seen mentioned yet: Dust. It will be everyplace. And it will be a much bigger problem on Mars than it is here on Earth.
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    Quote Originally Posted by Anonymouswizard View Post
    No, it is an expectation. There are reasons it might not rise in the East (international consensus to exchange the directions of east and west, suddenly being put out by a highly advanced alien race), but it is expected it will.
    And how is it different from expectation of technological progress?

    Quote Originally Posted by Anonymouswizard View Post
    Ah, here we're getting into the fact that one of our things, the sun rising in the East, is based on lots of previous data, while the other, that we'll keep getting better at making carbon nanotubes, is based on the fact that we haven't stopped yet.
    It's like saying that we should account for sun rising only during November of 2017. And that happened only a few times so far.

    Why isn't expectation of improvement based on the fact that we've been getting better things we were doing for centuries?

    Quote Originally Posted by Anonymouswizard View Post
    Let me put it this way, we might be able to make carbon nanotubes that strong. However, there is literally no guarantee
    Before making statements such as this, you need to remember the sun: is it possible to say "there is literally no guarantee that sun will rise tomorrow in the east"? If it is - then your statement is meaningless.

    Quote Originally Posted by Anonymouswizard View Post
    that we won't hit a roadblock in say 17 months that caps the tensile strength of the carbon nanotubes due to the manufacturing methods not being precise enough or some other problem.
    As I've pointed out, we have multiple approaches and none had been developed exhaustively. I.e. the technology is not mature. Consequently, chances of some critical roadblock are negligible.

    Quote Originally Posted by Anonymouswizard View Post
    Instead of looking at things that are decades to centuries away, like space elevators and fusion plants, why don't we look at stuff that is years away, like better fission reactors?
    What does this have to do with the topic?

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    Quote Originally Posted by factotum View Post
    There's also the point that the population on Mars would be very small for a long time, given the costs of getting people there, so you'd need to be comparing this with small communities here on Earth, not inner cities and the like. When everyone knows everyone else there are fewer opportunities for theft, murder and the like, if only because of the extreme likelihood of being caught.
    Crime rates in small communities are vastly higher than they're often depicted, and corruption in general is yet more common.

    Quote Originally Posted by Lazymancer View Post
    As I've pointed out, we have multiple approaches and none had been developed exhaustively. I.e. the technology is not mature. Consequently, chances of some critical roadblock are negligible.
    The maximum material strength being lower than the necessary minimum is a critical roadblock, and their presence is hardly a negligible chance.

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    Quote Originally Posted by Knaight View Post
    The maximum material strength being lower than the necessary minimum is a critical roadblock, and their presence is hardly a negligible chance.
    There is no "maximum material strength" as such. There is maximum theoretically possible (which is in low hundreds of GPa and cannot be a "critical roadblock"), and the maximum which we can do/will be able to actually achieve. The latter heavily depends on the production method used.

    I.e. there is no one single maximum. For each approach the maximum will be different.

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    Quote Originally Posted by Anonymouswizard View Post
    Note: any long term Martian living or colonisation would require us to know how plants develop in low-g environments, and it's theorised that long term exposure to Martian gravity would even stop Earth born humans from being able to tolerate 1g of gravity, let alone those who grow up on Mars. For all we know a martian society might be impossible.
    A surface centrifuge can provide spin gravity to compensate for this. Large habitats could be suspended on air cushions and/or with magnetic levitation, and the rotations/minute necessary to produce Earth-like gravity should drop as their sizes increase. They could also avoid needing to endure long term exposure to Martian gravity by combining telepresence, virtual reality, and humanoid robots that are 1/(cube root of 0.377) times taller than their users.

    Quote Originally Posted by Taro View Post
    I don't get people who want to live there, it looks so dull and boring.
    Amen to that. I'm more interested in asteroid and comet habitats, personally.

    Quote Originally Posted by Grey_Wolf_c View Post
    Most people would also not want to live permanently in a place with no sanitation, clean water or access to reliable sources of food, and yet over a billion people do so anyway. If being on the space station means having a job and a future for your kids, there'd be queues, no matter how bad the living conditions were, so long as they were better than the ones on Earth.

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    Wouldn't exposing Martian permafrost to sunlight in a low pressure chamber cause it to rapidly boil, and therefore provide easier access to clean water? I also think that cultured meat becoming a mature technology would make it much easier to feed Mars colonies, though they'd probably want to bring some live animals to ensure a steady supply of tissues.

    Quote Originally Posted by HandofShadows View Post
    One problem with living on Mars that I have not seen mentioned yet: Dust. It will be everyplace. And it will be a much bigger problem on Mars than it is here on Earth.
    With the right setup, there's no reason to personally go outside of the habitats, and a sufficiently scaled manufacturing network could probably turn craters (or even the Hellas Planitia) into megahabitats. If dust is still somehow a problem, pressurized air streams and vacuums could be used to get dust off most equipment, and keeping those chambers at lower air pressures would significantly reduce the amount of dust that gets into the rest of the habitats.

    Quote Originally Posted by Lazymancer View Post
    As I've pointed out, we have multiple approaches and none had been developed exhaustively. I.e. the technology is not mature. Consequently, chances of some critical roadblock are negligible.
    Do you know if the tensile strength of carbon nanotube fiber twisted into helices, much like rope or metal wire, has been tested? If so, how much stronger is that arrangement when compared to straight fibers?
    Last edited by WhatThePhysics; 2017-12-06 at 07:43 AM.

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    Quote Originally Posted by WhatThePhysics View Post
    Do you know if the tensile strength of carbon nanotube fiber twisted into helices, much like rope or metal wire, has been tested? If so, how much stronger is that arrangement when compared to straight fibers?
    I think the point of twisted rope is more about getting the strands interconnected. If you have a long rope of a hundred strands, and each strand is broken, but each one in a different spot, the rope still has 99% of its original strength, while just a bundle of straight fibers would have been completely severed by that point. Something as tiny as carbon nanotubes, which we probably can't make long enough to individually go all the way up to geosynchronous orbit anyway, would most likely benefit quite a lot from some sort of twisting/braiding/webbing.
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    Quote Originally Posted by WhatThePhysics View Post
    Wouldn't exposing Martian permafrost to sunlight in a low pressure chamber cause it to rapidly boil, and therefore provide easier access to clean water? I also think that cultured meat becoming a mature technology would make it much easier to feed Mars colonies, though they'd probably want to bring some live animals to ensure a steady supply of tissues.
    ...
    You quoted me to talk about this, but not sure why. I was talking about conditions on Earth, not on Mars, and how some people would find life in a space station an upgrade to their conditions here.

    I can't comment on the generating water from permafrost - would need to know how much of it is present in likely landing sites (I'm aware one of the poles has plenty of frozen brine, but poles make for very poor base locations). We are also quite proficient at this point at water recycling, so it's not usually a concern (and it might be that any ship that takes humans outside the magnetosphere for any amount of time will use water as radiation shielding anyway, so you'd end up with plenty of water when you got to Mars).

    Quote Originally Posted by WhatThePhysics View Post
    Do you know if the tensile strength of carbon nanotube fiber twisted into helices, much like rope or metal wire, has been tested? If so, how much stronger is that arrangement when compared to straight fibers?
    As I understand it, it's not any "stronger" by MPa measures. Braiding means you need a longer thread to cover the same distance, which means that it is overall heavier, which if anything reduces its ability to be a space elevator tether.

    However, as Lvl 2 Expert points out, you braid because real life is a bitch, and braiding allows a form of redundancy and safety that means any stress due to breaking is kinda shared by all the threads at once, which leads to an overall stronger cord by the measure that matters (likelihood of snapping). It also may be the only way to create the tether. I doubt we will ever create strands of anything 100,000 km long, so braiding is the only way we will get tethers that long.

    So, returning to your question: yes, braiding carbon nanotubes is being done, whenever the practical applications of them are discussed, vs. the single-strand properties.

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    Quote Originally Posted by Grey_Wolf_c View Post
    ...
    You quoted me to talk about this, but not sure why. I was talking about conditions on Earth, not on Mars, and how some people would find life in a space station an upgrade to their conditions here.

    I can't comment on the generating water from permafrost - would need to know how much of it is present in likely landing sites (I'm aware one of the poles has plenty of frozen brine, but poles make for very poor base locations). We are also quite proficient at this point at water recycling, so it's not usually a concern (and it might be that any ship that takes humans outside the magnetosphere for any amount of time will use water as radiation shielding anyway, so you'd end up with plenty of water when you got to Mars).
    Sorry, I misconstrued your post, and thought you were commenting on potentially negative living conditions on Mars.

    Quote Originally Posted by Lvl 2 Expert View Post
    I think the point of twisted rope is more about getting the strands interconnected. If you have a long rope of a hundred strands, and each strand is broken, but each one in a different spot, the rope still has 99% of its original strength, while just a bundle of straight fibers would have been completely severed by that point. Something as tiny as carbon nanotubes, which we probably can't make long enough to individually go all the way up to geosynchronous orbit anyway, would most likely benefit quite a lot from some sort of twisting/braiding/webbing.
    Quote Originally Posted by Grey_Wolf_c View Post
    As I understand it, it's not any "stronger" by MPa measures. Braiding means you need a longer thread to cover the same distance, which means that it is overall heavier, which if anything reduces its ability to be a space elevator tether.

    However, as Lvl 2 Expert points out, you braid because real life is a bitch, and braiding allows a form of redundancy and safety that means any stress due to breaking is kinda shared by all the threads at once, which leads to an overall stronger cord by the measure that matters (likelihood of snapping). It also may be the only way to create the tether. I doubt we will ever create strands of anything 100,000 km long, so braiding is the only way we will get tethers that long.

    So, returning to your question: yes, braiding carbon nanotubes is being done, whenever the practical applications of them are discussed, vs. the single-strand properties.

    Grey Wolf
    I'm not really a fan of space elevators on planetoids, due to the massive risks they can pose if they collapse, but these are good points. Maybe carbon nanotube rope would be more practical with regards to momentum exchange tethers?

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    Quote Originally Posted by WhatThePhysics View Post
    Do you know if the tensile strength of carbon nanotube fiber twisted into helices, much like rope or metal wire, has been tested? If so, how much stronger is that arrangement when compared to straight fibers?
    I might be unaware of some exceptions, but AFAIK all macro-scale fibers are spun.

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    Quote Originally Posted by Grey_Wolf_c View Post
    ...
    I can't comment on the generating water from permafrost - would need to know how much of it is present in likely landing sites (I'm aware one of the poles has plenty of frozen brine, but poles make for very poor base locations).
    I always thought the Martian polar caps were dry ice--e.g. frozen carbon dioxide? Or is this frozen brine underneath the CO2?

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    Visible at the north pole, present but under CO2 ice at the south pole:

    https://en.wikipedia.org/wiki/Water_on_Mars
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    Quote Originally Posted by WhatThePhysics View Post
    I'm not really a fan of space elevators on planetoids, due to the massive risks they can pose if they collapse
    ... they don't? The tether is absurdly light. That's the point, and the problem of why we can't build it. It's like being hit with a feather in freefall... except it is much, much, much lighter than a feather.

    Yes, the whole thing will weight tons, but stretched out over 100,000 km. The scenarios I have seen for collapse suggest that it will mostly burn up in the atmosphere, or get blown all over the place by the winds. But it's not going to hurt much, because it doesn't have the density. Admitedly, I haven't seen similar scenarios modeled for, say, Mar's thin atmosphere or the Moon's no atmosphere, but I can't imagine that even in vacuum freefall a feather would hurt that much.

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    Quote Originally Posted by Grey_Wolf_c View Post
    but I can't imagine that even in vacuum freefall a feather would hurt that much.
    Depends how long it has to accelerate in vacuum freefall. Given sufficient distance, a featherweight object left to fall on the Moon would reach a speed of 2.38km/sec (Lunar escape velocity) or nearly so. A typical feather might mass 0.01g, and travelling at 2380m/s would have a kinetic energy of about 56J. Doesn't sound like much, but it's in the same ballpark as an arrow fired from a short bow, and since we're not talking about an actual feather but a broken fragment of the space elevator, it'll probably be quite sharp as well, and may also be heavier than that 0.01g figure I mentioned above--we only have to increase that to 0.1g to have an object with the same kinetic energy as a .45 ACP round fired from a pistol.

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    Quote Originally Posted by ArcticMoue View Post
    Hey!
    I read an article recently about how scientist have discovered how to potentially grow plant life on mars by replicating the soil as best they can and they've successful so far, this got me thinking about what it'd be like if we moved there - as in would it be anything like Earth? Considering nothing went wrong, that is. My theory is that it'd be no different, especially as the population there grows, because humans don't change; the only thing changing is the location and we can still *******s half way across the world so we'd be the same on mars.
    I still suspect there'd be corruption, crime, pollution and all that other stuff that gives us a bad name on earth. But I have no idea how it'd be set up on mars, would there be measures put in place to stop us from ruining society and mars like we are the earth? I think it'd be really cool to live on another planet and it'd be cool to be alive to see it happen but I think we should only planet-jump if we/the governments actually decide to take proper care of this place and make it a safe and decent place to live.
    To put it bluntly, human civilization is based on massive agricultural investment in narrow bands of prime land and then sent to large population centers. Almost the entire population is located within subtropical and temperate zones with arable land, all major nations require major ports to be economically viable, and the ecological fertility of Earth is at the boiling point in many places despite those places being little more then camps for people to live in while receiving grain out of more fertile zones.

    Civilization, in other words, cannot be exported to other planets because grain shipments from Kansas can't reach there. If we want to make Mars habitable we might at least try settling the Sahara desert first.
    Now if everyone could please "Sig" something along the lines of "Gosh 2D8HP, you are so very correct (and also good looking)", I think that would be good progress.

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    Quote Originally Posted by factotum View Post
    Depends how long it has to accelerate in vacuum freefall. Given sufficient distance, a featherweight object left to fall on the Moon would reach a speed of 2.38km/sec (Lunar escape velocity) or nearly so. A typical feather might mass 0.01g, and travelling at 2380m/s would have a kinetic energy of about 56J. Doesn't sound like much, but it's in the same ballpark as an arrow fired from a short bow, and since we're not talking about an actual feather but a broken fragment of the space elevator, it'll probably be quite sharp as well, and may also be heavier than that 0.01g figure I mentioned above--we only have to increase that to 0.1g to have an object with the same kinetic energy as a .45 ACP round fired from a pistol.
    Fair enough. I haven't double checked your math, but it sounds reasonable. Now, on the moon that wouldn't concern me much (since th tether would be unlikely to hit anything), but I do wonder how much the thin atmosphere of Mars would manage to slow down a Mars tether.

    Quote Originally Posted by Tvtyrant View Post
    To put it bluntly, human civilization is based on massive agricultural investment in narrow bands of prime land and then sent to large population centers. Almost the entire population is located within subtropical and temperate zones with arable land, all major nations require major ports to be economically viable, and the ecological fertility of Earth is at the boiling point in many places despite those places being little more then camps for people to live in while receiving grain out of more fertile zones.

    Civilization, in other words, cannot be exported to other planets because grain shipments from Kansas can't reach there. If we want to make Mars habitable we might at least try settling the Sahara desert first.
    I don't disagree with any of this, except in a general "we really should stop taking over ecosystems and turning them into our private farms"... but I make an explicit exception to the Sahara, because It'd be nice to turn its expansion around.

    That said, do you have an opinion on the development of urban vertical farms? A recent article went through the history of the approach, saying that it looks like tech is almost there to make them economically viable*. We may soon have the ability to grow food at the population centers, which would be an interesting development in the nature of human civilization, although I'm ambivalent of how big the consequences would be.

    Grey Wolf

    *It also admits to having said so 5 years ago, but the cost curve is definitely trending in the right direction, so they should be viable in our lifetimes, even if this particular one also fails
    Last edited by Grey_Wolf_c; 2017-12-07 at 11:33 AM.
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