Astronauts 'poop-eyed' with radiation shielding for Mars expedition

Published March 8, 2013 9:11pm

Can the "eww" effect of human poo also repel radiation from cosmic rays?

Scientists think so, as they design a feces-based shield against cosmic ray radiation for the "Inspiration Mars" mission that will fly by Earth's neighbor in 2018.

"It's a little queasy sounding, but there's no place for that material to go, and it makes great radiation shielding," Taber MacCallum, a member of the team funded by multimillionaire Dennis Tito, told the NewScientist.

NewScientist.com noted radiation from cosmic rays may be a great threat to the man and woman aboard the "Inspiration Mars" mission.

They may also face cramped conditions, muscle atrophy and potential boredom, it added.

A possible solution is to line the spacecraft's walls with water, food and the astronauts' feces.

Poo, food in bags

McCallum said the solid and liquid human waste products would be put in bags and used as radiation shield.

"Those solid waste products get put into a bag, put right back against the wall," he said.

But the food could also be used as a shield, stored around the walls of the spacecraft, and is not likely to become a radioactive source.

"[F]ood 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.

This will go along with the "state-of-the-art technologies derived from National Aeronautics and Space Administration and the International Space Station" to be used in the mission, NewScientist said.

Water walls

Meanwhile, an idea under consideration by the agency's Innovative Advanced Concepts program, which funds research into futuristic space technology, is a project called "Water Walls."

The project combines life-support and waste-processing systems with radiation shielding.

"Water is better than metals for protection (shielding)," said Marco Durante of the Technical University of Darmstadt in Germany.

He said that since nuclei are the things that block cosmic rays, water molecules made of three small atoms contain more nuclei per volume than a metal.

Another advantage of water shielding is that 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 feces," NewScientist said.

Layers of the bags can create a 40-cm-thick liquid shield. While the bags would initially be filled with drinking water, the crew would swap them for bags filled with their waste during the trip.

NewScientist said the osmosis-based processing is simpler than the automated life-support systems aboard the ISS, making it less likely to fail during the long trip to Mars.

The Water Walls concept also includes bags that scrub carbon dioxide from air, regulate temperature and grow algae for food.

"Inspiration Mars" also plans an external water tank and the aluminium skin of the spacecraft itself for extra protection.

Such shielding may protect astronauts from lower energy cosmic rays, said Ruth Bamford of the Rutherford Appleton Laboratory in Didcot, UK.

Problems with micro-gravity bags

But one problem involves the urine-to-water processing bags, which were tested in orbit on space shuttle's last flight in 2011.

The bags at the time were found to be 50 percent less efficient in microgravity than in ground-based tests.

Also, the Water Walls team noted a more basic worry: the residual sights and smells.

"Hopefully they're not clear bags," MacCallum said.

Solar danger

However, NewScientist.com said organic material or aluminium may not be enough protection against particles from the sun during a solar storm.

"For this, putting three metres of concrete may not be enough to protect the astronauts," said Bamford.

For now, "Inspiration Mars" scientists are working to keep the upper rocket stage of their launch vehicle attached to the spacecraft during the trip, and point that towards the sun if a flare occurs. – KDM, GMA News

Tags: radiationshielding, useoffeces, inpirationmars