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posted by martyb on Saturday September 22 2018, @01:38PM   Printer-friendly
from the powered-exoskeleton? dept.

If we wish to colonize another world, finding a planet with a gravitational field that humans can survive and thrive under will be crucial. If its gravity is too strong our blood will be pulled down into our legs, our bones might break, and we could even be pinned helplessly to the ground.

Finding the gravitational limit of the human body is something that's better done before we land on a massive new planet. Now, in a paper published on the pre-print server arXiv, three physicists, claim that the maximum gravitational field humans could survive long-term is four-and-a-half times the gravity on Earth.

Or, at least you could if you are an Icelandic strongman – and Game of Thrones monster – who can walk with more than half a metric ton on your back. For mere mortals, the researchers say, it would need to be a little weaker.

[...] For the maximum gravity at which we could take a step, the team turned to Hafþór Júlíus Björnsson, an Icelandic strongman who once walked five steps with a 1430 pound log on his back, smashing a 1,000-year-old record[*].

[*] YouTube video.

What's the Maximum Gravity We Could Survive?


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  • (Score: 2) by Arik on Saturday September 22 2018, @02:43PM (39 children)

    by Arik (4543) on Saturday September 22 2018, @02:43PM (#738544) Journal
    "It is far more likely that we can adapt to microgravities, than to higher gravities."

    And not so much a question of can we, but should we, I would think.

    Even if it's possible to adapt to a high g world, why? Why take such a massive step backwards, after escaping out own gravity well, why would we imprison ourselves in another, stronger one? The US Constitution, at least, forbids such things.

    Don't colonize high g worlds directly. If they have things you need, then colonize using High Orbital emplacements and robotics. Let the robots deal with the gravity well and pass whatever is needed back upstairs.

    "Eventually, you'll have a divergent race of humans who are well adapted to high gravity."

    Each and every member of which will dream of inventing a time machine with which to kill you before you could create them.
    --
    If laughter is the best medicine, who are the best doctors?
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  • (Score: 2) by crafoo on Saturday September 22 2018, @02:56PM (13 children)

    by crafoo (6639) on Saturday September 22 2018, @02:56PM (#738547)

    Can you imagine the "humans" from such a world after 20 or so generations? They would come back to Earth and immediately take every riot cop and prison guard job available.

    Yeah, for the first 20 or so generations everyone wears a robotic exoskeleton to deal with daily life. You'd have to keep the evolutionary pressure on to adapt to the environment though. I think even with exoskeletons, the massive strain on the heart, diaphragm, and circulatory system would kill quite a few people early in their life.

    • (Score: 2) by Arik on Saturday September 22 2018, @03:12PM (3 children)

      by Arik (4543) on Saturday September 22 2018, @03:12PM (#738554) Journal
      "Can you imagine the "humans" from such a world after 20 or so generations? They would come back to Earth and immediately take every riot cop and prison guard job available."

      What makes you think there would be any such jobs available on Earth at that time?

      "I think even with exoskeletons, the massive strain on the heart, diaphragm, and circulatory system would kill quite a few people early in their life."

      You're correct, and only scratching the surface. Forget about things that kill. Think about things that fail to kill you, but cause agonizing pain every second of your misbegotten life. Think about joints wearing out before you hit puberty. Think about having to plan each and every movement carefully, knowing that a simple misstep, a stubbed toe on earth, would be a broken ankle or worse here. Think about how that ankle would never heal unless you stay completely off it for months. Think about how if you stay off your feet for months, then once the ankle is healed, you wouldn't have the strength left to stand up on your own.

      No, this is the exact opposite of what we should do. Don't colonize high g planets. Colonize weightless spaces. Escape all of those burdens, and then adapt to freedom, not to heavier restrictions.
      --
      If laughter is the best medicine, who are the best doctors?
      • (Score: 2) by takyon on Saturday September 22 2018, @03:21PM (2 children)

        by takyon (881) <reversethis-{gro ... s} {ta} {noykat}> on Saturday September 22 2018, @03:21PM (#738557) Journal

        I think even with exoskeletons, the massive strain on the heart, diaphragm, and circulatory system would kill quite a few people early in their life.

        Think about joints wearing out before you hit puberty. Think about having to plan each and every movement carefully, knowing that a simple misstep, a stubbed toe on earth, would be a broken ankle or worse here. Think about how that ankle would never heal unless you stay completely off it for months. Think about how if you stay off your feet for months, then once the ankle is healed, you wouldn't have the strength left to stand up on your own.

        By the time we have the technology to go interstellar, we'll have great anti-aging and regenerative medicine. Meaning that you can fix your joints, bones, heart, etc. faster than it would take for them to wear out.

        The 4.5g mentioned in TFS is atypical. 1.25g is more common for exoplanets, with maybe 2g possible although exoplanets could become Neptune-like before reaching that surface gravity. 0.5g to 1g is also possible. It will be interesting to see the health effects of 0.8g. Might be a great vacation spot.

        --
        [SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
        • (Score: 2) by Arik on Saturday September 22 2018, @05:14PM

          by Arik (4543) on Saturday September 22 2018, @05:14PM (#738595) Journal
          "By the time we have the technology to go interstellar, we'll have great anti-aging and regenerative medicine. Meaning that you can fix your joints, bones, heart, etc. faster than it would take for them to wear out."

          That's your assumption, but I see no proof for it. Might turn out that way, might not.

          --
          If laughter is the best medicine, who are the best doctors?
        • (Score: 1) by ChrisMaple on Sunday September 23 2018, @05:19AM

          by ChrisMaple (6964) on Sunday September 23 2018, @05:19AM (#738775)

          Bones, joints, and muscles aren't a problem. People weighing twice as much as average already exist on Earth without problem; they have sturdier bodies because they've been grown and trained that way. One body system that doesn't automatically adapt is the circulatory system; human beings aren't far from the margins of what can be tolerated for blood pressure difference between the brain and the feet. Tall animals like giraffes have special evolved adaptations that required thousands of generations to appear; that's not going to happen quickly in humans without gene editing.

    • (Score: 4, Insightful) by takyon on Saturday September 22 2018, @03:26PM (7 children)

      by takyon (881) <reversethis-{gro ... s} {ta} {noykat}> on Saturday September 22 2018, @03:26PM (#738559) Journal

      There will be no need to wait for 20 generations before adaptation can occur.

      First of all, humans won't evolve those adaptations if natural or artificial selection isn't occurring.

      Second, you can just use gene editing to make those adaptations.

      Finally, 4.5g is not typical. And if we did need to adapt to that, we could create very tiny pygmy/dwarf humans rather than Icelandic troll-gods.

      --
      [SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
      • (Score: 0) by Anonymous Coward on Saturday September 22 2018, @03:48PM (6 children)

        by Anonymous Coward on Saturday September 22 2018, @03:48PM (#738565)

        you can just use gene editing to make those adaptations

        This is extremely delusional.

        • (Score: 2) by takyon on Saturday September 22 2018, @04:08PM (5 children)

          by takyon (881) <reversethis-{gro ... s} {ta} {noykat}> on Saturday September 22 2018, @04:08PM (#738571) Journal

          Yes you are. When do you think we will reach an exoplanet? 20 years from now?

          --
          [SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
          • (Score: -1, Troll) by Anonymous Coward on Saturday September 22 2018, @05:43PM (4 children)

            by Anonymous Coward on Saturday September 22 2018, @05:43PM (#738603)

            Is it even proven that there are exoplanets? All they see is flickering stars... If you saw a flickering star and didn't know about planets, would that be the first explanation you came up with?

            • (Score: -1, Redundant) by Anonymous Coward on Saturday September 22 2018, @10:06PM

              by Anonymous Coward on Saturday September 22 2018, @10:06PM (#738665)

              What is trolling about this?

            • (Score: 1) by khallow on Sunday September 23 2018, @04:23AM (2 children)

              by khallow (3766) Subscriber Badge on Sunday September 23 2018, @04:23AM (#738765) Journal

              Is it even proven that there are exoplanets?

              To what standard of evidence? In addition to said flickering stars, we have detected motion of the stars and spectral lines from some of the transiting planets. That doesn't mean a planet is going to be nice enough to live on. Most of it is pretty nasty.

              If you saw a flickering star and didn't know about planets, would that be the first explanation you came up with?

              If you don't know about planets, then you don't know enough to have an opinion on flickering stars.

              • (Score: 0) by Anonymous Coward on Sunday September 23 2018, @01:01PM (1 child)

                by Anonymous Coward on Sunday September 23 2018, @01:01PM (#738828)

                The standard should be that they use those methods to predict something that is verified some other way. Obviously actually getting an image of the planet would be best.

                • (Score: 1) by khallow on Monday September 24 2018, @01:25PM

                  by khallow (3766) Subscriber Badge on Monday September 24 2018, @01:25PM (#739155) Journal

                  The standard should be that they use those methods to predict something that is verified some other way.

                  I noted three such methods. The flickering of stars (usually strongly periodic, I might add) is actually a very reliable measure. And it's not like the Solar System is going to be unique in the universe.

    • (Score: 2) by krishnoid on Sunday September 23 2018, @01:54AM

      by krishnoid (1156) on Sunday September 23 2018, @01:54AM (#738728)

      I think even with exoskeletons, the massive strain on the heart, diaphragm, and circulatory system would kill quite a few people early in their life.

        ... fixing the overpopulation and social security bankruptcy problems a lot faster, anyway.

  • (Score: 2) by Runaway1956 on Saturday September 22 2018, @03:13PM (1 child)

    by Runaway1956 (2926) Subscriber Badge on Saturday September 22 2018, @03:13PM (#738555) Journal

    Each and every member of which will dream of inventing a time machine with which to kill you before you could create them.

    I think you are suffering a simple case of projection. You can't imagine a rewarding life on a high-G world, so you are projecting your expectations upon this hypothetical race of man. I suggest that we wait until we find this hypothetical race, abduct one of it's members, and probe him/her to find out how happy they are. I understand that they really like anal probes.

    https://en.wikipedia.org/wiki/Cartman_Gets_an_Anal_Probe [wikipedia.org]

    • (Score: 2) by Arik on Saturday September 22 2018, @05:22PM

      by Arik (4543) on Saturday September 22 2018, @05:22PM (#738599) Journal
      "I think you are suffering a simple case of projection. You can't imagine a rewarding life on a high-G world"

      You're wrong, and I can.

      I can definitely imagine a rewarding life on a high-G world for a species which evolved on that world. To them, it would be normal, expected. But I wouldn't expect such a species would resemble us physically, or even to resemble what we would become after some generations there.

      What I don't imagine would be very enjoyable in any case is the regression involved in first mastering weightlessness - then diving not just back onto a planet, but a high g planet at that. THAT doesn't seem like a very rewarding life at all.

      More likely, adaption will work out to be a one-way trip in practice. Once a human is adapted to zero-g, they will not willingly go back to a full g, let alone 4.5. The medical risks will be severe, not insurmountable in abstract perhaps, but who would want to face them personally? And for what gain? What is it that you need done down there that you can't build a machine to do for you remotely?

      --
      If laughter is the best medicine, who are the best doctors?
  • (Score: 2) by takyon on Saturday September 22 2018, @03:15PM (1 child)

    by takyon (881) <reversethis-{gro ... s} {ta} {noykat}> on Saturday September 22 2018, @03:15PM (#738556) Journal

    Even if it's possible to adapt to a high g world, why? Why take such a massive step backwards, after escaping out own gravity well, why would we imprison ourselves in another, stronger one? The US Constitution, at least, forbids such things.

    If we have the technology to go to another star system, we probably can get out of a stronger gravity well whenever we want to.

    It's galactic real estate. If you want to live in the far future, you can live on the overcrowded oasis that is on Earth, imperfect solar system objects such as the Moon, Mars, Ceres, and Titan, on a space station, possibly spinning to simulate gravity, or you can go interstellar if technology allows it. It may be possible for individuals to reach other star systems without generation ships by using anti-aging and suspended animation. Settling on the surface of a planet (with breathable atmosphere and correct temperature) can have a lot of advantages over an orbiting station (if I break a wall in your house, you won't die).

    As I wrote above, we probably don't need to adapt to 4.5g because there will be very few suitable exoplanets with that surface gravity. 1.25g seems more likely, and may not require any genetic modification to adapt to it, although you will get a little buffer living there.

    --
    [SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
    • (Score: 4, Funny) by Arik on Saturday September 22 2018, @05:28PM

      by Arik (4543) on Saturday September 22 2018, @05:28PM (#738600) Journal
      "If we have the technology to go to another star system, we probably can get out of a stronger gravity well whenever we want to.

      It's galactic real estate. If you want to live in the far future, you can live on the overcrowded oasis that is on Earth, imperfect solar system objects such as the Moon, Mars, Ceres, and Titan, on a space station, possibly spinning to simulate gravity"

      The last option is the one you should be thinking about.

      Oh give me a locus
      where the gravitons focus
      Where the three-body problem is solved.
      Where the microwaves play
      down at three degrees K
      and the cold virus never evolved.

      Home, Home on LaGrange
      Where the space debris always collects
      We possess so it seems
      two of man's greatest dreams.
      Solar power and zero-gee sex.
      --
      If laughter is the best medicine, who are the best doctors?
  • (Score: 3, Interesting) by wisnoskij on Saturday September 22 2018, @04:00PM (20 children)

    by wisnoskij (5149) <{jonathonwisnoski} {at} {gmail.com}> on Saturday September 22 2018, @04:00PM (#738568)

    Why would a human dislike being stronger, fitter, and more able to travel over land and through space?

    If we assume a space faring future, any humans adapted to space would be stuck in their backyard for life as they would be unable to take any acceleration. And since mass still exists in space, it would be an incredibly dangerous for anyone with the type of bones that would develop in space. To do anything in space, you need to spend 99% of your life in high Gs. And the higher the Gs, the better.

    In any space faring society. The people who grew up on the the highest G world will have an overwhelming military and space faring advantage, and will be able to subjugate or simply outperform everyone else.

    • (Score: 0) by Anonymous Coward on Saturday September 22 2018, @04:47PM (2 children)

      by Anonymous Coward on Saturday September 22 2018, @04:47PM (#738588)

      Why would a human dislike being stronger, fitter, and more able to travel over land and through space?

      Because they are American? Probably best to ask some of the fat bastards you see, I was going to say walking, but you're more likely to find them in a car, around in the USA.

      • (Score: 1) by Arik on Saturday September 22 2018, @05:36PM

        by Arik (4543) on Saturday September 22 2018, @05:36PM (#738602) Journal
        I want to mod this flamebait and insightful at the same time, so I'm going to let them balance each other and skip it.
        --
        If laughter is the best medicine, who are the best doctors?
      • (Score: 0) by Anonymous Coward on Saturday September 22 2018, @05:46PM

        by Anonymous Coward on Saturday September 22 2018, @05:46PM (#738606)

        Why would a human dislike being stronger, fitter, and more able to travel over land and through space?

        If you are fit and strong, and able to do stuff, someone might ask/force you to do something. So the best way to avoid being asked is to not look like you can achieve anything. Eg, you cant be drafted if your health is too poor.

    • (Score: 1) by Arik on Saturday September 22 2018, @05:56PM (16 children)

      by Arik (4543) on Saturday September 22 2018, @05:56PM (#738612) Journal
      "If we assume a space faring future, any humans adapted to space would be stuck in their backyard for life as they would be unable to take any acceleration. "

      Big assumptions there. Interstellar space travel will not necessarily involve great acceleration. If we're talking about sleep ships, or generational ships, they can simply accel at a constant 1g or less until they reach speed. With sleep ships in particular, it may be possible to shield the humans from the affects of the accel anyway.

      Another assumption is that those who adapt to zero-g will be 'unable to take any acceleration" there's a kernel of truth to this one obviously but that's way too far. HOMEs as planned would spin to generate effective gravity, with concentric rings with different effective levels. So up to something around 1g would still be within their regular experience - journeying to the outer ring regularly for exercise, or to perform maintenance or whatever.

      Under those conditions, we clearly would not completely lose our ability to deal with acceleration. You're right that someone from a high g world would have an advantage on that one specific measure, but I'm not convinced it would be all that important in the bigger picture. Your existence would be so much more efficient, from beginning to end. You could eat less yet be able to do more. Your body parts might last many times as long, given the lack of the constant burden that gravity represents to the circulatory system and so on. You have lower tolerance for accel? Ok, but you don't NEED to start off your journey by lifting off from a planet. What an incredible head start! Do you have any idea how many calories it takes to put a capsule capable of supporting life for a few hours on an escape trajetory? Take a look at the old Saturn V.

      "The people who grew up on the the highest G world will have an overwhelming military and space faring advantage"

      Well, if you're imagining them landing troops on a planet and going door to door, sure.

      I don't imagine conflicts between people with those levels of technology are very likely to look like that though.

      To put it in in strategy game terms;

      Landing your high-g stormtroopers on my planets is pointless - there's nothing for them to fight but my robots, who are just fine with the gravity.

      Boarding my HOMEs? Well sure, I guess if you get that close I'm probably toast anyway, but your physical advantages won't help much if you haven't spent a LOT of time training these guys to deal with low and zero-g also. Without that training, they'll be breaking their own arms, legs, and necks as they attempt to maneuver down through the inner rings, where resistance would be waiting. No, I think if you got that close you'd still be better off just to use your guns, of whatever type you possess, and destroy the HOMEs rather than try to take them.

      Defending your planet against my troops? Well obviously I am not sending anyone to the surface for you to defend against. If we really have to, we'll bombard from orbit, and send down robots afterwards to collect anything of sufficient value.

      --
      If laughter is the best medicine, who are the best doctors?
      • (Score: 2) by HiThere on Saturday September 22 2018, @06:41PM (1 child)

        by HiThere (866) Subscriber Badge on Saturday September 22 2018, @06:41PM (#738616) Journal

        I consider permanent space habitats which are mobile to be a lot more likely than sleep ships. I won't deny the possibility of sleep ships, but why?

        When I say "space habitat", think of it as a mobile city, though mobile doesn't imply able to move very fast. I expect that 0.01g would be considered excessive. It's a place to live more than a vehicle. You need to keep moving so that you can get to new resources, but you don't want to move at a speed much different from drift because you don't want to deal with high speed meteors. This does assume nuclear power, and probably fusion, and it assumes a nearly closed ecology, and it assume a long-term stable society. The last is probably the most difficult, but with a government operated by an AI and good virtual reality to allow stresses to be eliminated it seems plausible. A lot of people may spend most of their life gaming, but why not. Reproduction would be strongly controlled except when the entire community decided to build a new city and the population forked into two cities. This would only happen when in contact with an exceptionally rich source of resources.

        Note: A single habitat, even one the size of a city, probably doesn't contain enough expertise to maintain a civilization. But laser communication should be feasible. (Though maybe with an AI it could contain enough expertise.)

        --
        Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
        • (Score: 1) by Arik on Saturday September 22 2018, @07:00PM

          by Arik (4543) on Saturday September 22 2018, @07:00PM (#738622) Journal
          That's the next stage after HOMEs are established. HOMEs would be much easier and more profitable for many reasons, one of which is they don't have to be truly self-sufficient, the first one could be quite dependent on Earth but as time go on and more go up the group of them could become self-sufficient.

          At that point it really becomes feasible to exploit resources that are easily accessible from zero-g, the asteroid belt for instance. And once sufficient capital is built up there, a sort of mega-HOME could be built, large enough to be pretty darn self-sufficient.

          It would not go at a La Grange point, but into it's own solar orbit, and would be able to shift that orbit, even to escape it over time, if desired.

          --
          If laughter is the best medicine, who are the best doctors?
      • (Score: 2) by wisnoskij on Saturday September 22 2018, @07:15PM (1 child)

        by wisnoskij (5149) <{jonathonwisnoski} {at} {gmail.com}> on Saturday September 22 2018, @07:15PM (#738629)

        > Well, if you're imagining them landing troops on a planet and going door to door, sure.

        More like I imagine High G accustomed soldiers to be anywhere they want to me 10 times faster than low G accustomed soldiers. Sure, your "spend 90% of their lives in free fall" people can get to Planet X given 100 years of low acceleration. But my high G accountomed colonists can get their in their own lifetimes and with enough time to spare to erect satellite defences before you arrive.
        Acceleration is everything in space, the ship with more A wins every encounter.

        • (Score: 1) by Arik on Saturday September 22 2018, @07:45PM

          by Arik (4543) on Saturday September 22 2018, @07:45PM (#738636) Journal
          "More like I imagine High G accustomed soldiers to be anywhere they want to me 10 times faster than low G accustomed soldiers. Sure, your "spend 90% of their lives in free fall" people can get to Planet X given 100 years of low acceleration. But my high G accountomed colonists can get their in their own lifetimes and with enough time to spare to erect satellite defences before you arrive."

          Really, you now seem to be assuming not just that acceleration will not only continue to be a limiting factor in space movement, but will become even more important with time. This seems far from assured.

          Currently, the limiting factor is light speed, and while higher accel *will* cut some time off a given trip, it's really not much on a long journey when you figure the large majority spent at light speed regardless.

          There's no reason that technology to exceed light speed would not also imply technology to modify inertial forces and shield humans from extremes of it as well, but you're implicitly implying nothing of the sort develops.

          You're *also* assuming that your guys have effectively infinite resources behind them. And this is where our estimates drastically diverge. You won't have infinite resources, nowhere close. You'll have effectively *fewer* resources, because your development is planet centered, most of your resources aren't "available" properly without spending incredible amounts of energy to boost them out of the gravity well. While ours are mined, refined, and manufactured in zero-g, much more efficiently.

          And you're assuming that getting there before my humans is enough. It isn't. You need to beat my *robots* there. Robots manufactured from materials and energy gathered at greatly reduced energy costs, outside the gravity well.

          More likely, by the time your guys can afford to send a probe, we have robotic manufacturing and defenses setup already.

          --
          If laughter is the best medicine, who are the best doctors?
      • (Score: 2) by Immerman on Sunday September 23 2018, @04:07PM (11 children)

        by Immerman (3985) on Sunday September 23 2018, @04:07PM (#738878)

        There is a significant military application for high-G troops in space combat though. Unless your combat ships are all fully autonomous drones, the light-speed delays means you'll need at least some troops to be right in the thick of the fight. In which case they will be the limiting factor on the maneuverability of any ship they're on. A ship that can only accelerate at 0.1 g is a sitting duck in a fight against ships that can handle a sustained 4g.

        Even if it's only a single drone-oversight command ship with a crew in any given encounter, that ship is the limiting factor on how fast the entire fleet can move.

        • (Score: 2) by Arik on Sunday September 23 2018, @05:26PM (10 children)

          by Arik (4543) on Sunday September 23 2018, @05:26PM (#738898) Journal
          Hmm let's take this bit by bit.

          "Unless your combat ships are all fully autonomous drones"

          Why wouldn't they be? Start with off-the shelf autonomous mining drones, upgrade weapons and logic, program for mission and launch.

          "the light-speed delays means you'll need at least some troops to be right in the thick of the fight."

          Ok, I'll actually give you a point here. While of course we'd do as much of any fighting that had to be done as possible with autonomous military bots, yes there still might be a need to have a human relatively near for C&C overwatch.

          "In which case they will be the limiting factor on the maneuverability of any ship they're on. A ship that can only accelerate at 0.1 g is a sitting duck in a fight against ships that can handle a sustained 4g."

          But again, I still don't see this as being so important. Acceleration? Maneuverability, essentially, in a vacuum. Why do you think that is so blamed important?

          If there's no FTL, then c is still your speed limit. Greater accel could get you there faster, get you back down faster, but interstellar distances being what they are most of the trip would be spent at c either way, and your advantage is small. And that's assuming we don't come up with some nice sleep ships that can first suspend us and then safely accelerate more rapidly than your guys can do.

          It would be handy in a tactical situation in that it might give you the ability to flee, or to preclude flight, by the enemy. Assuming you detect them from outside of either sides effective weapons range, at least.  Ok, that's actually pretty big. But still not nearly as big as you seem to think.

          And again, if we have FTL, we almost certainly have some associated tech to render this moot.

          But beyond that it's pretty nearly useless. Space combat would be taking place at astronomical distances. The likely weapons include lasers, and there's no way to dodge a laser (short of time-machine level stuff.) And another likely sort of attack would be to launch a wave of autonomous weapons - call them suicide drones, or just guided missiles, it's the same thing. They set a collision course, get as much speed as possible, and then self destruct at the last moment, turning into an expanding cloud of shrapnel. Moving at a significant fraction of light speed, anything they touch would be toast.

          Who can detect the other first, who can launch an effective strike first, would almost certainly determine who won. Little, perhaps nothing, else matters.

          So I don't think your accel is likely to come into it, even under your best scenarios.

          --
          If laughter is the best medicine, who are the best doctors?
          • (Score: 2) by Immerman on Monday September 24 2018, @12:01AM (9 children)

            by Immerman (3985) on Monday September 24 2018, @12:01AM (#739010)

            No one's getting anywhere close to c for anything other than interstellar voyages - at 1g it'd take almost a year to get to that speed, in which time you'd have long since exited the solar system. Even at 10g you'd have traveled about 50x the diameter of Neptune's orbit before you reached relativistic speeds.

            And I'm guessing most people would want to avoid releasing fully autonomous killing machines in as free-flowing a battle-ground as space, unless they're actually conscious AIs (which brings up a whole different set of problems). It's just too easy to lie to a machine. And too easy to extract its knowledge if captured (at the very least you get it's tactical/strategic decision-making algorithm, rendering it easy to exploit.) The friend-versus-foe identification system alone would be ripe for exploitation.

            Now, for the importance of acceleration, suppose we have two armies of roughly equal size, but once can handle 10x the acceleration of the other. I'll call them F(ast) and S(low)
            F decides they want to capture a location, so they launch their entire military at a juicy-enough target in the opposite direction. S launches at least most of their military to the same spot - anything less would be a pointless suicide mission. Halfway there, F changes course to attack the original location. They get there long before S can hope to do so, capture it, and then proceed to the next target - all while S is stranded in the interplanetary void unable to do anything remotely useful

            Meanwhile, S decides to attack, and F can consolidate their armies at their destination from anywhere remotely close - when your army's movements can't be hidden, the faster army wins. F's army can effectively be in multiple places at once.

            It all boils down to the equation of motion: d=1/2*a*t^2, or t = sqrt(2d/a). 10x the acceleration, means you can traverse 10x the distance in the same amount of time, or the same distance in a third the time.

            • (Score: 1) by Arik on Monday September 24 2018, @04:38AM (8 children)

              by Arik (4543) on Monday September 24 2018, @04:38AM (#739063) Journal
              "No one's getting anywhere close to c for anything other than interstellar voyages"

              Those would be the voyages that are important here though. That's the limiting factor for exploration, for colonization, and yes for invasion.

              If you're talking about tactical mobility; again, little if any advantage actually accrues there, because our robots still don't have any difficulties with accel, and they're the tactical pieces, not manned ships.

              --
              If laughter is the best medicine, who are the best doctors?
              • (Score: 2) by Immerman on Monday September 24 2018, @02:27PM (7 children)

                by Immerman (3985) on Monday September 24 2018, @02:27PM (#739173)

                Acceleration is largely irrelevant for interstellar invasion. Unless you're imagining combat between galaxy-spanning empires - but without FTL such a thing even existing seems extremely unlikely.

                Distances are so vast that the time taken to reach cruising speed is largely irrelevant, top speed is determined by propellants specific impulse and the rocket equation. And it's relatively easy to hide in interstellar space, so nobody is going to see you coming. Well, not until your braking burn announces your position I suppose - in which case the Slows give 10x as long a warning to get ready to fight them. But that's going to be months or years even for the fasts - making it strictly relevant to how many additional defenses can be built.

                It's warfare within a solar system where acceleration matters. If you really think tactical AIs will be so advanced that human insight has no value in a military engagement, then perhaps it's not important. But with several minutes to hours of communication lag, probably relatively easily jammable locally, if human insight has anything to offer then you're going to want humans nearby.

                • (Score: 2) by Arik on Monday September 24 2018, @06:22PM (6 children)

                  by Arik (4543) on Monday September 24 2018, @06:22PM (#739314) Journal
                  "Distances are so vast that the time taken to reach cruising speed is largely irrelevant"

                  Yes.

                  "And it's relatively easy to hide in interstellar space, so nobody is going to see you coming."

                  Not so sure about that. New detection methods might be in play by that point, and even with 1960s tech we should be able to spot an incoming fleet just fine once they start their decel burn.

                  "If you really think tactical AIs will be so advanced that human insight has no value in a military engagement, then perhaps it's not important."

                  Given the distances and velocities involved I suspect ONLY a tactical AI will be able to function in traditional front line roles.

                  Yes you'll want and need human oversight at the strategic level but that's a relatively small issue. Ok, our command ships are slow beasts that can't really run. Just gives our guys more incentive to make sure they win. And if you take a command ship out, sure, that's human casualties, I'm sure it will piss us off more than losing the robots, but we lose one command ship and you lose a whole manned fleet, we're still going to feel ok about the way things are going I am thinking.

                  --
                  If laughter is the best medicine, who are the best doctors?
                  • (Score: 2) by Immerman on Monday September 24 2018, @08:47PM (5 children)

                    by Immerman (3985) on Monday September 24 2018, @08:47PM (#739392)

                    You want to spot a broad-spectrum vanta-black ship coasting against the blackness of interstellar space? Good luck - we can barely spot things the size of a planet when we get *extremely* lucky. But maybe eventually - which would rob high-acceleration ships of their advantage on that front. Until then though, they're likely invisible until they start their deceleration burn - at which point the Slows would give their target 10x as much warning as the Fasts. How much of an advantage that would really be though? How much additional military can you you really build in a year or three? Especially compared to the size of fleet necessary for a credible shot at an interstellar invasion?

                    Yeah, but you're not going to be throwing your automated fleets against their manned ones - you're going to be throwing your automated fleets against their automated fleets, in an effort to take out each other's strategically important command ships. And ultimately, while people get upset over casualties, it appears to be cost of replacing hardware that wins modern wars. Soldiers are cheap until things have been going really badly for a while.

                    • (Score: 2) by Arik on Tuesday September 25 2018, @04:21AM (4 children)

                      by Arik (4543) on Tuesday September 25 2018, @04:21AM (#739542) Journal
                      "You want to spot a broad-spectrum vanta-black ship coasting against the blackness of interstellar space?"

                      Sure, and your stealth-paint isn't going to make it any harder. If anything, it might make it easier.

                      We aren't likely to detect it directly, reflected light or radio waves or whatever, even if you mirror-polished it instead. That's just not going to be the method of detection, so the countermeasures against it won't matter either.

                      How will we spot it? One of two ways. Either via occultation (we notice that this one star blinked out at this time, and then this one a little later, and then this one a little later... ohhh I see a pattern here!) or a direct detection once the decel burn starts.

                      The decel burn, whatever type of engine you use, is still going to involve releasing massive amounts of energy, and that's visible, there's no way to avoid it.

                      "How much of an advantage that would really be though? How much additional military can you you really build in a year or three?"

                      Obviously that depends on how long ago you got the colony started and how efficiently you've worked it, what's on hand, etc. But 1-3 years might well be enough time to prepare, or to evacuate if necessary. Even with lower accel tolerance.

                      Remember we don't colonize planets. We live in HOMEs and exploit the surface robotically. We'll have a relatively small human population to worry about, and none or virtually none will need to worry about packing up or reaching escape velocity - we're already packed and ready to go. HOMEs can be moved just like any other spacecraft.

                      "And ultimately, while people get upset over casualties, it appears to be cost of replacing hardware that wins modern wars"

                      Sure.

                      And war machines made in zero-g, from materials mined in zero-g, are just going to require orders of magnitude fewer calories to produce than machines made on a planet and then boosted to space, or even those made in space using raw materials boosted from a planet.

                      --
                      If laughter is the best medicine, who are the best doctors?
                      • (Score: 2) by Immerman on Tuesday September 25 2018, @02:18PM (3 children)

                        by Immerman (3985) on Tuesday September 25 2018, @02:18PM (#739677)

                        Yes, I've twice agreed with the decel burn - that's when you light the "here we come" beacon and give the targets not only warning of your coming, but a probably pretty good estimate of your mass. Unless you approach out-of-plane with

                        And again I say - we're barely able to detect entire planets by occultation when we get very, very lucky, we don't see any of the probably billions of Oort cloud objects that way. You really think we'll be able to detect something as tiny as space ships?

                        Also, infrared would probably be the bigger giveaway, but sufficient layers of directional reflective shields should render ships effectively invisible at the distances involved.

                        And what makes you think calories will matter? If you're talking about civilizations capable of launching credible interstellar invasion fleets fast enough that their technology won't be hopelessly obsolete by the time they arrive, then the energy required to get a ship off a planet won't even be a rounding error. The limiting factor in rapidly expanding a fleet is industrial capacity and raw materials.

                        • (Score: 2) by Arik on Tuesday September 25 2018, @02:44PM (2 children)

                          by Arik (4543) on Tuesday September 25 2018, @02:44PM (#739691) Journal
                          "And again I say - we're barely able to detect entire planets by occultation when we get very, very lucky, we don't see any of the probably billions of Oort cloud objects that way. You really think we'll be able to detect something as tiny as space ships?"

                          Planets many light years away, oort cloud objects much closer but also much smaller. Your space ships can't afford to be too tiny - smaller than a planet but probably a good bit larger than a comet. Yes, I suspect that even our current feeble astronomical capabilities are quite capable of spotting something like that. Especially if you're talking about an 'invasion fleet' of dozens, even hundreds of such ships, I suspect there would be a noticeable pattern of occultation at considerable distance.

                          Today, it's my understanding that much of that data only winds up being analyzed months after it's been gathered, but that's an issue that could be solved very quickly and not very inexpensively, were there a will to do it.

                          "Also, infrared would probably be the bigger giveaway, but sufficient layers of directional reflective shields should render ships effectively invisible at the distances involved."

                          I don't see why you think infrared would be a bigger giveaway than occultation, but that aside, it is definitely another potential detection mechanism, and you CANNOT stealth it with shielding as you're proposing. You would cook. Everything you're doing in there, from biological movement to mechanical, even just powering the computers, all generates heat, and if there is no heat escaping then the temperature will rise until everyone is dead and everything is melted.

                          "And what makes you think calories will matter?"

                          What makes me think energy matters?

                          You realize that besides matter, energy is literally the only thing that matters? :)

                          Calories = joules = energy.

                          E=mc^2

                          Literally nothing else matters.

                          "If you're talking about civilizations capable of launching credible interstellar invasion fleets fast enough that their technology won't be hopelessly obsolete by the time they arrive, then the energy required to get a ship off a planet won't even be a rounding error."

                          Ok, so how did you to that level of technology to begin with then?

                          Certainly not by thinking that calories don't matter.

                          --
                          If laughter is the best medicine, who are the best doctors?
                          • (Score: 2) by Immerman on Tuesday September 25 2018, @11:29PM (1 child)

                            by Immerman (3985) on Tuesday September 25 2018, @11:29PM (#739933)

                            Hence *directional* shields - you can radiate anything you want away from enemy observation posts.

                            And yes, counting energy matters during development. But compared to the cost of getting ships out of the Sun's gravitational well, much less up to interstellar speeds, the cost of getting them off a planet is so close to zero as to make no difference. It's not going to be a limiting factor in building out additional combat capacity in a survival situation. The limiting factor will be your industrial capacity to convert non-essential resources into defenses.

                            • (Score: 2) by Arik on Wednesday September 26 2018, @01:18AM

                              by Arik (4543) on Wednesday September 26 2018, @01:18AM (#739975) Journal
                              "Hence *directional* shields - you can radiate anything you want away from enemy observation posts."

                              Perhaps, as long as you're sure where they are.

                              "And yes, counting energy matters during development. But compared to the cost of getting ships out of the Sun's gravitational well, much less up to interstellar speeds, the cost of getting them off a planet is so close to zero as to make no difference. "

                              *Perhaps* that's true, at the end of the tech tree. Even there I'm skeptical.

                              But at the tech levels we were talking about, this is just the most important thing. Because the challenge is the transition. Going from being a planet bound species to being a species that travels space and can spread from one star to the next. And the next, and the next.

                              Bridging that gap means large and intricate construction in space. And it's going to be many orders of magnitude more difficult to do if you don't get away from the idea of boosting stuff off the planet to work.

                              So we bridge the gap much more quickly than you, we have a dozen systems or more before you manage to go anywhere... that really seems a big enough advantage to cover any potential disadvantages.
                              --
                              If laughter is the best medicine, who are the best doctors?