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.)
Planet Detectability in the Alpha Centauri System (DOI: 10.3847/1538-3881/aa9bea) (DX)
(Score: 2) by takyon on Thursday December 21 2017, @10:34PM (3 children)
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)
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)
Hopefully, centigravity will get bodily fluids moving downwards generally, avoiding the upper body pooling seen on the ISS [wikipedia.org]:
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
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.