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Microbes may help astronauts transform human waste into food
Human waste may one day be a valuable resource for astronauts on deep-space missions. Now, a Penn State research team has shown that it is possible to rapidly break down solid and liquid waste to grow food with a series of microbial reactors, while simultaneously minimizing pathogen growth.
"We envisioned and tested the concept of simultaneously treating astronauts' waste with microbes while producing a biomass that is edible either directly or indirectly depending on safety concerns," said Christopher House, professor of geosciences, Penn State. "It's a little strange, but the concept would be a little bit like Marmite or Vegemite where you're eating a smear of 'microbial goo.'"
[...] "Each component is quite robust and fast and breaks down waste quickly," said House. "That's why this might have potential for future space flight. It's faster than growing tomatoes or potatoes."
Today, astronauts aboard the International Space Station recycle a portion of water from urine, but the process is energy intensive, said House. Solid waste management has been a bigger hurdle. This currently is ejected into the Earth's atmosphere where it burns up.
"Imagine if someone were to fine-tune our system so that you could get 85 percent of the carbon and nitrogen back from waste into protein without having to use hydroponics or artificial light," said House. "That would be a fantastic development for deep-space travel."
Coupling of anaerobic waste treatment to produce protein- and lipid-rich bacterial biomass (DOI: 10.1016/j.lssr.2017.07.006) (DX)
(Score: 2) by JoeMerchant on Tuesday January 30 2018, @01:49PM (5 children)
AC, I think you got that complicated radiation shower thing wrong - the nuclear physicists I've worked with claim that, pound for pound, lead is worse for shielding than hydrocarbons because of the scatter effect. They did agree, it's a complicated thing - and thin aluminum is worse than no shielding at all (well, except that you really want something to hold an atmosphere in...), but, all in all, you're best off with a couple of miles of low density atmosphere between you and the cosmic source, after that, pound for pound, the thinner the shield, the worse the scatter effect.
My preferred Earth-Mars transit [arxiv.org] vehicle would be a converted asteroid [nasaspaceflight.com], preferably one large enough and with enough structural integrity [nasaspaceflight.com] to be spun for some gravity on the inside [newworldencyclopedia.org].
🌻🌻 [google.com]
(Score: 2) by Immerman on Tuesday January 30 2018, @04:21PM (1 child)
A Mars-Cycler is an interesting idea, and would be an interesting orbital habitat location, but it seems to me that it would be of dubious utility for actually transporting things between Earth and Mars. The problem is that a simple transit between Earth and Mars orbits is useless on it's own, you have to actually pass near the planets themselves to transport passengers. Which makes the orbits considerably more complicated, and the cycle considerably slower.
Probably the simplest and fastest is the Aldrin Cycler, with a cycle time of 783 days (2.14 years), making a cycle with every relative planetary alignment. Starting at Earth at t=0 it reaches Mars in roughly 5 months (t=150 days). So far, so good. But then it takes another 21 months to get back to Earth (t=783 days). So, it's going to be a long trip home if you don't build a second inbound cycler. Most damning, it also requires a significant course correction on every orbit to create the necessary 55-degree precession of the cycler's elliptical orbit on every pass. https://www.youtube.com/watch?v=qCVfUlFZQ4U [youtube.com]
It's that correction that's going to make things rough - without it we could just hollow out a big asteroid and set it on its way. But regular significant course corrections are going to put a serious cramp in that plan because it means that the mass is still extremely relevant - even if a gravity assist is used for the bulk of the acceleration, fine-tuning will still be necessary. Of course, such fine tuning will be relatively minor compared to getting the thing into the proper orbit in the first place, so maybe it's not such a major concern. There's also some orbits that require minimal ballistic corrections, Wikipedia mentions the VISIT 1 which encounters Earth 3 times and Mars 4 times over the course of 15 years. Ignoring the one Mars-Mars trip in that cycle, which would presumably sit unused, that's an average of one interplanetary trip every 2.5 years. https://en.wikipedia.org/wiki/Mars_cycler [wikipedia.org]
The common theme, from what I can see, is that you end up building a nice big well-shielded habitat, that mostly sits empty waiting for passengers on the "good" legs of the journey. Whereas, if you're going to build a habitat it seems a shame to not actually have people living there full time. Could perhaps be an excellent location to work on developing asteroid mining technologies - have a full-time industrialized mining facility, conveniently cycling between Mars and Earth, with recreational facilities etc. for both residents and passengers. After all you don't need to spin the asteroid for gravity - which not only does that require untested structural integrity of the asteroid, but also robs you of all the benefits of microgravity. You could instead just hollow out a disc within the asteroid in which a "traditional" spinning space station could be built.
Or, I suppose, you could just make a big hollow within the asteroid within which you park your rockets, and everybody just stays in their ship for the journey, with the cycler offering nothing but shielding. That seems like an awful waste of potential, but might make for a decent starting point.
(Score: 2) by JoeMerchant on Tuesday January 30 2018, @04:47PM
See, that's my thought, exactly. Make each transit-habitat a colony onto itself, say 100K residents, with capacity to host another 30K transit passengers on every useful leg. If you're going to transit lots of people between Earth and Mars, having a large, comfortable, well radiation shielded way to do it would seem to be a worthy goal. And, I can't imagine that life in such a habitat would be any less appealing than a Mars surface colony.
🌻🌻 [google.com]
(Score: 1, Informative) by Anonymous Coward on Tuesday January 30 2018, @04:46PM (1 child)
As a cosmic ray physicist, I want to point out that yes it is indeed a complicated problem, and what makes it so complicated is that shielding effectiveness is dependent upon the energy of the particle. For certain charges and energies, thin aluminum is worse because you can create more ionizing radiation secondaries (knock-on particles, "delta rays", etc.) in the aluminum, but that effect goes down as the particle incident energy goes up. And we cosmic ray physicists scoff at what nuclear physicists think are very high energies.
I remain very pessimistic about the prospects for a reasonably safe trip to Mars from the standpoint of radiation exposure. Apart from ideas mentioned like boring out an asteroid, it will be very expensive and massive to get a sufficient amount of shielding material up. You can't shield against the galactic cosmic rays, but fortunately the fluxes of those particles are orders of magnitude lower than the solar cosmic rays (but though it will be low, they will be a source of constant radiation). It will be an optimization problem where you'll be shielding against anticipated solar storms. It will probably be a trade-off between the expected background vs. the worst case. The astronauts will probably also need luck in avoiding going through any major storms.
(Score: 2) by GreatAuntAnesthesia on Wednesday January 31 2018, @09:37AM
In your opinion, is there any hope in shielding astronauts by means of magnetic fields? I don't think the tech is there yet to create a powerful enough artificial magnetosphere, but theoretically it could be done. Would that be sufficient?
(Score: 0) by Anonymous Coward on Tuesday January 30 2018, @08:47PM
Hydrogen is tiny, and carbon isn't much more. The hydrogen is great, and the carbon isn't bad. Water and polyethylene are OK.
The bad ones are aluminum, titanium, and similar.
It gets better again with heavier stuff like iron, copper, and nickel.