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SpaceX organizes inaugural conference to plan landings on Mars
No one can deny that SpaceX founder Elon Musk has thought a lot about how to transport humans safely to Mars with his Big Falcon Rocket. But when it comes to Musk's highly ambitious plans to settle Mars in the coming decades, some critics say Musk hasn't paid enough attention to what people will do once they get there.
However, SpaceX may be getting more serious about preparing for human landings on Mars, both in terms of how to keep people alive as well as to provide them with something meaningful to do. According to private invitations seen by Ars, the company will host a "Mars Workshop" on Tuesday and Wednesday this week at the University of Colorado Boulder. Although the company would not comment directly, a SpaceX official confirmed the event and said the company regularly meets with a variety of experts concerning its missions to Mars.
This appears to be the first meeting of such magnitude, however, with nearly 60 key scientists and engineers from industry, academia, and government attending the workshop, including a handful of leaders from NASA's Mars exploration program. The invitation for the inaugural Mars meeting encourages participants to contribute to "active discussions regarding what will be needed to make such missions happen." Attendees are being asked to not publicize the workshop or their attendance.
The meeting is expected to include an overview of the spaceflight capabilities that SpaceX is developing with the Big Falcon rocket and spaceship, which Musk has previously outlined at length during international aerospace meetings in 2016 and 2017. Discussion topics will focus on how best to support hundreds of humans living on Mars, such as accessing natural resources there that will lead to a sustainable outpost.
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This Week in Space Pessimism: SLS, Mars, and Lunar Gateway
(Score: 2) by HiThere on Thursday August 09 2018, @05:33PM (7 children)
FWIW, lcd lights are efficient enough that even with normal earth sunlight available for piping people often opt to use lcd lighting in indoor green houses. See "urban farms". (I may not be convinced that they're competitive, but the technology is interesting.)
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(Score: 2) by Immerman on Friday August 10 2018, @03:45AM (6 children)
Here on Earth we've got cheap fossil fuel energy to make that possible. On Mars, *if* you've got a lot of surplus nuclear power that's great - but if you assume power is at a premium it's a much less rosy picture. High-end commercial LEDs are pushing 81% efficiency. The most efficient commercial solar panels though are only reaching 22.5%. That's only ~18% efficiency sunlight-to-artificial-light, at a much higher cost than solar focusing (in price, shipping mass, and technical complexity and failure risk)
(Score: 2) by HiThere on Friday August 10 2018, @05:35PM (5 children)
But I don't think you can depend on sunlight on Mars, because of the incredible dust storms. The reduced insolation would probably mean that you couldn't depend on solar panels. What I'm worried about is cooling the nuclear plant, but some designs don't seem to be too bothered by that. True, the produce relatively small amounts of power, but that means that everything is going to need to be designed to use minimal power. And there had better be excess generation capacity in the form of multiple plants, so that when the power needs to be repaired you don't all die. So smaller plants are a real benefit, especially if they also require less maintenance.
I'd really rather depend on solar power, but I think the dust storms will make that impossible...unless you store enough power to last for months. (I'm not sure how long. A recently observed dust storm lasted two weeks, but I see no reason to believe that was the longest. I'm also not sure how much that affects power generation at the surface, as there were multiple reasons to shut down Opportunity for the duration.)
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(Score: 2) by Immerman on Saturday August 11 2018, @01:25AM (4 children)
Yes, the worst dust storms can last many months, and block 90+% of insolation at their worst (I haven't been able to find info on how long "their worst" may be reasonably expected to last). That definitely means you need backup power options - but solar is viable most of the time, and is far lighter, cheaper, and safer than nuclear. I would imagine an outpost would want at least enough nuclear power capacity to keep things running in minimal survival mode, but a great deal of growth and other industry would be powered by solar.
The moon has related problems - though rather than dust storms it has night that last for two weeks out of every four. I would imagine the solution would be similar, with the exception that rather than erratic dust storms of unpredictable length, you'd have a regular two weeks on, two weeks off rhythm to more power-hungry endeavors.
Back on Mars, it would be worth investigating the distribution of dust storms as well - my impression is that they're mostly concentrated near the lower latitudes and become less frequent and intense near the poles - which is probably where you'd want to build your outpost anyway, to have access to the vast quantities of water frozen there. On a related note, I doubt cooling would be an issue - ambient temperatures average around -55C, and you've got plenty of water to use for heat transfer. An underground liquid-cooling loop should be quite capable of shedding waste heat, or you could use that heat more productively to melt ice directly (it takes roughly as much energy to melt ice without changing the temperature as it does to boil the resulting water). With such low ambient temperatures liquid water becomes a valuable construction material - with sufficient care you could make large domes of transparent radiation shielding, which could be easily vacuum-insulated from habitats or greenhouses within them.
(Score: 2) by HiThere on Saturday August 11 2018, @05:27PM (3 children)
I'm not at all sure that what you're proposing would work. The caps are largely dry ice, so the water may be very thinly spread. For cooling you don't just need a temperature difference, you need a way of distributing it. E.g. you can touch the outside of a working ceramic kiln without getting burned, because the kiln is a thermal insulator.
Now liquid water on the surface of Mars sublimes, and so does dry ice, what's left behind is probably not a good conductor of heat. Likely you'd need to depend on radiant cooling (slow!!) or drill down and circulate a working fluid through a long heat pipe. You could also use some of the "waste heat" to warm the living quarters, which would provide you with additional cooling surface, but not allow a very high temperature for the cooling, and, IIRC, radiant cooling is not only more efficient when hotter, but there's a 4-th power law involved, so you want your radiant surface to be as hot as feasible.
P.S.: On Earth the nuclear plants use flowing water to cool themselves. That's why they tend to be situated along the banks of rivers. I believe that there are some that use large "cooling ponds", which largely depend on evaporative cooling, i.e., losing a lot of the water. Not good for Mars.
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(Score: 2) by Immerman on Sunday August 12 2018, @01:56AM (2 children)
My understanding is the dry ice is mostly seasonal glaciers, with numerous more permanent water glaciers having been identified. Dry ice would work fine for cooling too though.
Sure, for cooling you need thermal transfer - ambient heating is a great use. and geothermal heat pipe would certainly work. My suggestion was to run it through a big "hot plate" on which you steadily pile crushed ice. And while sublimation consumes even more heat than melting, if you want to capture the water as a useful resource you probably want to perform the process inside a pressurized chamber. Fortunately you can get away with a CO2 atmosphere, so you need only pressurize ambient air. Radiant is also an option, I believe that's what the NASA reactors use - but they're only dealing with a few kW, and if you're trying to establish a colony rather than just a research outpost you probably want to work closer to the MW range.
As for the difference in scale between rivers and crushed ice - there's also a difference in reactor scale - reactors on Earth typically operate in the GW scale, which would definitely present some unique cooling challenges on Mars.
If you were particularly clever, and managed to find fairly pure water ice glaciers, you could potentially even use the waste heat for tunneling: Dig an initial cave and airlock (to maintain a reasonable working pressure) into the side of a glacier, then use waste heat to generate steam that you blow against whatever walls you want to excavate. As steam melts the ice it cools, condensing if you balance flow rates just right, and you can then recapture condensed steam along with the melt-water. With a little luck, cooler steam that flows into cracks in the ice would freeze before reaching the surface, gradually "repairing" the glacier into a more airtight structure for future use.
(Score: 2) by HiThere on Sunday August 12 2018, @05:44PM (1 child)
Well, if you kept things in an enclosed chamber, that would produce a larger radiation surface, so cooling would be more effective at lower temperatures...but "continually packing on ice" doesn't sound to me like a feasible strategy. And how large would your cooling chamber need to be to allow sufficient heat to dissipate? I know we're talking about smaller reactors, but it doesn't sound workable. If you make the chamber long and thin to allow enhanced cooling, you're heading in the direction of a heat pipe, but I think that requires an internal circulation mechanism to work, which means it *is* a heat pipe. Horizontal is cheaper to build than vertical, which involves digging (drilling!) a pit to put the pipe in, but vertical pipe have more direct connection with conductive surfaces (i.e., base rock). A glacier would work until it evaporated, but that would happen pretty quickly to any ice in contact with the cooling element. And vertical or at a steep angle is probably easier to drill than a shallow angle. If you've got spare water, you dump it in the hole and seal the top (with provision to add more water as needed). That provides a better thermal contact between the pipe and the base rock. This will be a problem if there isn't a lot of subsurface water.
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(Score: 2) by Immerman on Sunday August 12 2018, @08:15PM
Well, if you assume you want lots of water for growing food and making methane for rocket fuel and energy storage you'll need to be melting it all anyway.
Easy enough to see how feasible it is - the heat of fusion for water is 334J/g - if we completely ignore all heating, and assume 100% of the energy goes to melting ice at 0C to water at 0C, and assume a smallish, but still impressive 1MW (waste heat) reactor, then we'd need to supply 1MW *1g/334J = ~3kg/s of ice to melt to dissipate the 1MW of heat. That doesn't sound too ridiculous. at first glance. Of course it does add up - 3kg/s =~ 11,000 kg/hour, which sounds considerably more extreme - but at 0.934g/cm^3 that only translates to 11 cubic meters. Still pretty impressive for an hour of mining - but if you could perform "steam mining" that could just mean you're creating new ice-habitats very quickly, though that probably wouldn't be sustainable for more than a few... months? years?
Still, it could consume quite a bit of energy relatively quickly - especially if you figure you're heating the ice/water as well - Ice has a specific heat of ~2J/gK, and water of ~4J/gK, so if you heated ice at -55C into water at 100C you'd consume an additional ~500J/g. And if you boiled the resulting 100C water without heating it any further (which could be quite handy for distillation), that'd add water's whopping 2230J/g heat of vaporization. Combined, that'd total about 3,000J/g, reducing the necessary ice input to only a bit over 1 cubic meter per hour to dissipate 1MW of heat. That sounds pretty feasible to me.