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posted by martyb on Wednesday December 20 2017, @11:27AM   Printer-friendly
from the say-hi-to-Vir-Cotto-for-me dept.

NASA thinks that the technologies needed to launch an interstellar probe to Alpha Centauri at a speed of up to 0.1c could be ready by 2069:

In 2069, if all goes according to plan, NASA could launch a spacecraft bound to escape our solar system and visit our next-door neighbors in space, the three-star Alpha Centauri system, according to a mission concept presented last week at the annual conference of the American Geophysical Union and reported by New Scientist. The mission, which is pegged to the 100th anniversary of the moon landing, would also involve traveling at one-tenth the speed of light.

Last year, Representative John Culberson called for NASA to launch a 2069 mission to Alpha Centauri, but it was never included in any bill.

Meanwhile, researchers have analyzed spectrographic data for the Alpha Centauri system and found that small, rocky exoplanets are almost certainly undiscovered due to current detection limits:

The researchers set up a grid system for the Alpha Centauri system and asked, based on the spectrographic analysis, "If there was a small, rocky planet in the habitable zone, would we have been able to detect it?" Often, the answer came back: "No."

Zhao, the study's first author, determined that for Alpha Centauri A, there might still be orbiting planets that are smaller than 50 Earth masses. For Alpha Centauri B there might be orbiting planets than are smaller than 8 Earth masses; for Proxima Centauri, there might be orbiting planets that are less than one-half of Earth's mass.

In addition, the study eliminated the possibility of a number of larger planets. Zhao said this takes away the possibility of Jupiter-sized planets causing asteroids that might hit or change the orbits of smaller, Earth-like planets.

(For comparison, Saturn is ~95 Earth masses, Neptune is ~17, Uranus is ~14.5, and Mars is ~0.1.)

Also at BGR and Newsweek.

Planet Detectability in the Alpha Centauri System (DOI: 10.3847/1538-3881/aa9bea) (DX)


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  • (Score: 2) by HiThere on Wednesday December 20 2017, @05:50PM (9 children)

    by HiThere (866) Subscriber Badge on Wednesday December 20 2017, @05:50PM (#612405) Journal

    Unfortunately, we've got a long way to go on the closed eco-system front. And it doesn't get anywhere near the attention it deserves. With a real closed eco-system (probably impossible) you could send mice anywhere in the galaxy...at, admittedly, and extremely slow speed. But it would need to maintain itself for aeons. Not feasible.

    A reasonably closed eco-system would allow human habitation of space, even though you need occasional space walks to scavenge an asteroid for gases and metals. The habitat would probably need to spin rather rapidly, and would need lots of mass for shielding, but it could be done. But you'd need to be able to fab your own solar cells, etc., as well as the other work of maintaining a civilization. This isolated scenario would probably require a population in at least the hundreds of thousands with current technologies. OTOH, with current technologies there's no requirement of isolation, as laser communication is cheap.

    Other technological developments would allow other scenarios, and I've totally left out living on other planets, as that has a larger number of unknowns. But in all the scenarios an improved "nearly closed" ecosystem would be a strong advantage.

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  • (Score: 2) by Immerman on Wednesday December 20 2017, @07:01PM (8 children)

    by Immerman (3985) on Wednesday December 20 2017, @07:01PM (#612451)

    True. We have a long way to go on truly closed ecosystems, but also no particular need for them when colonizing resource-rich planets or large asteroids. Mars is such a desirable target specifically because it's incredibly rich in easily accessible water, CO2, and nitrogen. That, some imported trace elements, and a big greenhouse will get you almost everything you need, ecology wise, and quite a bit in terms of industrial materials (nanocellulose for example is gas impermeable, transparent, and as strong as aluminum. Lots of potential there. And it can be made from plant waste using only thermomechanical processes, so no need to introduce toxic substances into the recycling stream.) And of course a planet has many other useful materials that become available as your available effort and industrial base expands.

    Technology wise - yes, there's likely going to be a long period of dependency on imports. However, there have been a lot of advances in cheap down-scalable manufacturing techniques. Solar panels and electronics that can be printed with a minimally-modified ink-jet printer for example. Heck, it wouldn't surprise me if Tesla's highly adaptable car-manufacturing plant weren't designed with an eye towards general-purpose offworld factories in the future - Musk clearly has a dream, and early colonies won't need a large quantity of production potential nearly as much as a wide *range* of it. The vast majority of current production goes to creating "disposable" goods - it could as easily go to creating far more durable and (cost-effective) goods instead, while radically reducing the amount of production required to maintain our standard of living (consider - your great-great-grandma's cast-iron skillet is probably still around somewhere, and is superior to pretty much anything made today.)

    And of course planets also provide gravity and radiation/meteorite shielding extremely cheaply - a few yards of sand or rock overhead do wonders in that regard.

    As for your mouse - the fact that expanding into space will undoubtedly (eventually) lead to excellent closed ecosystem management is one of the reasons I assume our species will eventually colonize other stars. Once you have a stable closed-loop ecology and industry base, all you need is enough nuclear fuel reserves to keep everything powered until you reach the next star, and the desire to get away from your neighbors. The first is unlikely to be a big problem, and the latter has been a rallying cry throughout human history - be it the immigrants escaping oppressive governments, or the oppressive governments trying to isolate themselves from destabilizing outside interference.

    • (Score: 2) by HiThere on Thursday December 21 2017, @01:32AM (7 children)

      by HiThere (866) Subscriber Badge on Thursday December 21 2017, @01:32AM (#612663) Journal

      I disagree about the need. A "resource rich" asteroid won't be resource rich very long if you don't close your eco-system, and supplying things from outside gets quite expensive, even if they're close by.

      In the case of a planet things are a bit less clear, because most of the waste hangs around for a long time. Mars is still holding onto lots of CO2, even though it keeps getting ionized and the Oxygen heading off into space. But it used to have a lot more water, before the same thing happened to the water, except that Hydrogen escapes even without an energy boost (from the incoming radiation) so the angle at which the split happened was a lot less significant. It would still be a bad (i.e. short term) plan to terraform Mars without putting a lid on the atmosphere. I know it's probably doable, but it would be a massive waste for a short-term gain.

      That said, even for a planet running everything through the ecosystem once is a costly and stupid way to do things. Often the waste gets into places where you really don't want it, and a planet is finite. Large isn't the same thing as unlimited.

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      • (Score: 2) by Immerman on Thursday December 21 2017, @02:43PM (6 children)

        by Immerman (3985) on Thursday December 21 2017, @02:43PM (#612796)

        I agree - terraforming is a completely different problem. But if you're making a mostly-closed ecosystem on (or under) the surface of Mars then you'll have essentially unlimited resources with which to grow and replace incidental losses for a *very* long time. And obviously waste is one of the first things you want to eliminate - waste is just another name for raw materials you haven't recycled.

        Similarly even a mid-sized asteroid a few tens of miles across contains a LOT of raw materials - not limitless, but if you never intentionally throw anything away it should be quite capable of supporting a large city for centuries at least. And as recycling improves that number should grow towards infinity. Along with how to manage a closed ecosystem, how to effectively eliminate the creation of waste will likely be one of the biggest and most valuable lessons learned from space colonization - both will potentially be of immense benefit to Earth as well. Pretty much anything we can do in space, we can do here as well - it's less immediately necessary, but would drastically reduce our ecological footprint and help restore the health of this rare oasis of life.

        • (Score: 2) by HiThere on Thursday December 21 2017, @06:44PM (5 children)

          by HiThere (866) Subscriber Badge on Thursday December 21 2017, @06:44PM (#612888) Journal

          Centuries is a short time for a population. Even the US is over 2 centuries old...closer to 3, really, since change of government doesn't signify in this context, and it's a new comer.

          Also the easily extracted resources tend to be used first, but that's your volatiles. Once those are gone, they're gone. So you need to start recycling from the start, and otherwise work to limit your losses. The idea is that all you need to import is energy (or, if you've got a good fusion engine, hydrogen). That's not going to happen, but it's important to get as close to that as possible. Importing things is expensive.

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          • (Score: 3, Interesting) by Immerman on Thursday December 21 2017, @07:42PM (4 children)

            by Immerman (3985) on Thursday December 21 2017, @07:42PM (#612921)

            I absolutely agree. But, centuries *is* a long time to work on perfecting your closed system to the point that you need minimal, if any, further imports to sustain yourself. And there's lots of other asteroids around, too small to justify colonizing, to scavenge for additional materials.

            Besides, even a paltry 10 mile diameter asteroid is an equivalent volume of raw materials to all of California to a depth of 17 feet, or the entire US to a depth of 9 inches. That's a LOT of raw materials to support a single city. Even a big one. Especially if you're recycling essentially everything.

            • (Score: 2) by takyon on Thursday December 21 2017, @10:34PM (3 children)

              by takyon (881) <reversethis-{gro ... s} {ta} {noykat}> on Thursday December 21 2017, @10:34PM (#612992) Journal

              Ceres has 2.9% of 1g surface gravity, Vesta has about 2.5%, Pallas has about 2.2% (Vesta and Pallas are not rounded).

              We should probably check those out as spots to colonize. Obviously 2-3% of Earth's gravity is not a lot, but it might be enough to counteract some health effects of microgravity.

              Unfortunately, Pallas has a steeper orbital inclination that will make it more expensive to reach. Vesta orbits closer to the Sun than Ceres and doesn't have an internal ocean that we wouldn't want to contaminate. So while Ceres is probably in the top 10 rocks we want to colonize, Vesta might be a good first choice (for asteroids).

              7 Iris (~213km) is down to 1.1% of 1g, and as for smaller 'roids, the largest near-Earth asteroid 1036 Ganymed [wikipedia.org] (~32 km) is at 0.09% of 1g which is negligible (it also has an aphelion of 4.0847 AU which may be undesirable).

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              • (Score: 3, Interesting) by Immerman on Friday December 22 2017, @01:58AM (2 children)

                by Immerman (3985) on Friday December 22 2017, @01:58AM (#613076)

                It will be interesting to see if "centigravity" is substantially better for human health than microgravity. I suspect it will still be close enough to freefall that it won't be much better, other than for for keeping stuff where you left it.

                On the other hand, I've thought it would be interesting to actually build a rotating space station within an asteroid - it can provide whatever range of artificial gravity is desired for residential quarters, while non-rotating modules would have all the benefits of microgravity. You could even tunnel all the way down to the center of mass for true freefall.

                I do hope Ceres gets left alone long enough to study carefully - though I fear such a large mass of liquid water and assorted minerals might prove too tempting a target, especially since the first group to claim it will have a fare shot at staking a long-term claim to one of the most valuable pieces of real estate in the solar system - if they can defend it. At 2.77 million km of surface area it's only about the size of Argentina - the 8th largest country on Earth.

                • (Score: 2) by takyon on Friday December 22 2017, @02:32AM (1 child)

                  by takyon (881) <reversethis-{gro ... s} {ta} {noykat}> on Friday December 22 2017, @02:32AM (#613081) Journal

                  Hopefully, centigravity will get bodily fluids moving downwards generally, avoiding the upper body pooling seen on the ISS [wikipedia.org]:

                  The second effect of weightlessness takes place in human fluids. The body is made up of 60% water, much of it intra-vascular and inter-cellular. Within a few moments of entering a microgravity environment, fluid is immediately re-distributed to the upper body resulting in bulging neck veins, puffy face and sinus and nasal congestion which can last throughout the duration of the trip and is very much like the symptoms of the common cold. In space the autonomic reactions of the body to maintain blood pressure are not required and fluid is distributed more widely around the whole body. This results in a decrease in plasma volume of around 20%. These fluid shifts initiate a cascade of adaptive systemic effects that can be dangerous upon return to earth. Orthostatic intolerance results in astronauts returning to Earth after extended space missions being unable to stand unassisted for more than 10 minutes at a time without fainting. This is due in part to changes in the autonomic regulation of blood pressure and the loss of plasma volume. Although this effect becomes worse the longer the time spent in space, as yet all individuals have returned to normal within at most a few weeks of landing.

                  [...] Because weightlessness increases the amount of fluid in the upper part of the body, astronauts experience increased intracranial pressure. This appears to increase pressure on the backs of the eyeballs, affecting their shape and slightly crushing the optic nerve.

                  The small amount of gravity will let normal strength building exercises like weight lifting work, even if comically big weights are needed, perhaps fashioned directly out of asteroid rock.

                  Finally, it should cut down on motion sickness. Not sure if any was experienced by lunar astronauts.

                  The real action will be at the Moon and Mars for many decades - rather than Ceres. A subsurface ocean hasn't been ruled out on Mars:

                  https://news.nationalgeographic.com/news/2010/12/101214-mars-liquid-water-life-bacteria-human-mission-science-space/ [nationalgeographic.com]
                  https://www.universetoday.com/117502/meteoric-evidence-suggests-mars-may-have-a-subsurface-reservoir/ [universetoday.com]

                  We will have to live with the fact that people will be contaminating Mars while we are trying to study it. But it shouldn't be too bad as they will be constrained to a small area due to radiation concerns. Can they even wander 100 km away from home base without compromising their health?

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                  • (Score: 3, Insightful) by Immerman on Friday December 22 2017, @03:55PM

                    by Immerman (3985) on Friday December 22 2017, @03:55PM (#613227)

                    It might help with biological issues - but I'm less confident. 10m/s^2 of acceleration is enough to easily overcome most incidental bodily forces. 0.1m/s^2 on the other hand could easily be dwarfed by normal turbulence and viscosity. Doesn't help you that much that your inner ear eventually settles down if you have to remain motionless for 10 minutes before it does so. You're also unlikely to get the regular micro-impacts from walking that seem to be important for maintaining skeletal strength - the energy to climb a single ladder step here would be enough to launch you a hundred feet in the air, and it would take five seconds for an initially stationary object to fall a single yard from rest - so moving around would probably be far more similar to doing so in freefall than under "real" gravity.

                    Ceres 0.03g *might* be enough to be somewhat useful - but is proportionally about as much lower than the moon's as the moon's is lower than Earth's, so I'm not sure that positive results on the Moon would be at all relevant.

                    As for exercising - I don't see that as any benefit at all. Those comically large weights will still have normal inertia, and won't care that you didn't *mean* to throw them through the ceiling and crush your upstairs neighbor to death. And they wouldn't seem to offer any major advantage over resistance bands, which operate completely independently of mass and gravity. If anything you'd have to develop whole new exercise regimes that exploit inertia rather than weight, since the weight would be essentially nonexistent in comparison.