The man and woman aboard the Inspiration Mars mission set to fly-by the Red Planet in 2018Movie Camera will face cramped conditions, muscle atrophy and potential boredom. But their greatest health risk comes from exposure to the radiation from cosmic rays. The solution? Line the spacecraft’s walls with water, food and their own faeces.
“It’s a little queasy sounding, but there’s no place for that material to go, and it makes great radiation shielding,” says Taber MacCallum, a member of the team funded by multimillionaire Dennis Tito, who announced the audacious plan earlier this week.
McCallum told New Scientist that solid and liquid human waste products would get put into bags and used as a radiation shield – as well as being dehydrated so that any water can be recycled for drinking. “Dehydrate them as much as possible, because we need to get the water back,” he said. “Those solid waste products get put into a bag, put right back against the wall.”
Food too, could be used as a shield, he said. “Food is going to be stored all around the walls of the spacecraft, because food is good radiation shielding,” he said. This wouldn’t be dangerous as the food would merely be blocking the radiation, it wouldn’t become a radioactive source. The details of Inspiration Mars’s plans have yet to be clarified, but the team has said it will be using “state-of-the-art technologies derived from NASA and the International Space Station”. One idea that is already under consideration by the agency’s Innovative Advanced Concepts programme, which funds research into futuristic space technology, is a project called Water Walls, which combines life-support and waste-processing systems with radiation shielding.
Water has long been suggested as a shielding material for interplanetary space missions. “Water is better than metals for protection,” says Marco Durante of the Technical University of Darmstadt in Germany. That’s because nuclei are the things that block cosmic rays, and water molecules, made of three small atoms, contain more nuclei per volume than a metal.
Water shielding also has another benefit – you can drink it. Such dual use is essential aboard a spacecraft, where space is at a premium. Applying this rationale, the Water Walls concept involves polyethylene bags that use osmosis to process clean drinking water from urine and faeces. …
Lining the walls of a spacecraft with layers of these bags creates a 40-centimetre-thick liquid shield. All of the bags would initially be filled with drinking water. The crew would then fill other bags with waste during the trip to Mars and swap them out for the now-empty water bags.
The osmosis-based processing is much simpler than the automated life-support systems aboard the International Space Station, making it less likely to fail during the long ride to Mars. However, there are problems to be ironed out. The urine-to-water processing bags were tested in orbit on the last ever flight of the space shuttle in 2011 and found to be 50 per cent less efficient in microgravity than in ground-based tests. Besides testing that the various bags work properly, the Water Walls team points out the more basic worry of dealing with the residual sights and smells. MacCallum made a similar point about the system to be used on Inspiration Mars: “Hopefully they’re not clear bags,” he said. …
Not all bags need be equally unpleasant, though. The Water Walls concept also includes bags that scrub carbon dioxide from air, regulate temperature and grow algae for food – although NASA hasn’t yet taken those to space.
Inspiration Mars also plans to have an external water tank and the aluminium skin of the spacecraft itself for extra protection. This kind of shielding should keep astronauts safe from lower energy cosmic rays, says Ruth Bamford of the Rutherford Appleton Laboratory in Didcot, UK, who is working on creating magnetic “deflector shields” for spacecraft.
Organic material or aluminium is no defence against the burst of particles that occasionally spew out from the sun during a solar storm, however. “For this, putting three metres of concrete may not be enough to protect the astronauts,” says Bamford. Inspiration Mars say they should be able to keep the upper rocket stage of their launch vehicle attached to the spacecraft for the whole of the trip, and point that towards the sun in the event of a flare.
Read the rest on 01 March 2013 – New Scientist.
This idea sounds better than the Poo Shield to me… Electrostatic Active Space Radiation Shielding:
Must be careful speaking about radiation in space. Can’t let on that radiation would have killed anyone who tried to travel 234,000 miles to moon.
*NASA gives the distance from the center of Earth to the center of the Moon as 239,000 miles. Since the Earth has a radius of about 4,000 miles and the Moon’s radius is roughly 1,000 miles, that leaves a surface-to-surface distance of 234,000 miles. The total distance traveled during the alleged missions, including Earth and Moon orbits, ranged from 622,268 miles for Apollo 13 to 1,484,934 miles for Apollo 17. All on a single tank of gas.
To briefly recap then, in the twenty-first century, utilizing the most cutting-edge modern technology, the best manned spaceship the U.S. can build will only reach an altitude of 200 miles. But in the 1960s, we built a half-dozen of them that flew almost 1,200 times further into space. And then flew back. And they were able to do that despite the fact that the Saturn V rockets that powered the Apollo flights weighed in at a paltry 3,000 tons, about .004% of the size that the principal designer of those very same Saturn rockets had previously said would be required to actually get to the Moon and back (primarily due to the unfathomably large load of fuel that would be required).
To put that into more Earthly terms, U.S. astronauts today travel no further into space than the distance between the San Fernando Valley and Fresno. The Apollo astronauts, on the other hand, traveled a distance equivalent to circumnavigating the planet around the equator nine-and-a-half times! And they did it with roughly the same amount of fuel that it now takes to make that 200 mile journey, which is why I want NASA to build my next car for me. I figure I’ll only have to fill up the tank once and it should last me for the rest of my life.
Here’s one estimate of the amount of radiation the Apollo astronauts would have experienced:
The Spacecast 2020 Technical Report puts the space weather radiation hazard to human life in perspective:
“…at geostationary orbit, with only 0.1 gm/cm2 of aluminum shielding thickness, the predicted radiation dose (REM) for one year continuous exposure, with minimum-moderate solar activity, is estimated to be about 3,000,000…”
At geosynchronous orbit, doses are “still low compared to interplanetary space due to geomagnetic shielding”, according to Radiation Hardening In Space.
A radiation dose value from a low energy flare is provided from NASA Mooned America, p. 134: “On page 256 of ‘Astronautical Engineering’ there is a chart that shows the dosage of four different flares. On August 22, 1958 there was a low energy flare that could have been reduced to 25-rem with 2-cm of water shielding.”
So, being conservative and using 25 rems per flare, we have 25 rems x 15 flares/day = 375 rems / day for the Apollo astronauts.
For occupational exposure dose limits, the International Atomic Energy Agency states that the “occupational exposure of any worker shall be so controlled” that the limit of an “effective dose of 50 mSv” “in any single year” “be not exceeded”. 50 mSv converts to 5 rems.
How were the Apollo astronauts able to withstand 375 rems per day when the IAEA occupational exposure dose limit is only 5 rems in any single year?