William and Mary chemists cook up radiation shield bricks for Mars habitats

Tamara Dietrich
Contact Reportertdietrich@dailypress.com
W&M chemistry profs cook up bricks that could one day shield astronauts from radiation on Mars

In a chemistry lab in Williamsburg, a pair of emeritus professors and their students are cooking up Mars bricks.

Literally.

Desks and tables are stocked with kitchen supplies — mortar and pestle, bread molds, glass jars, coffee grinder, microwave oven, etc. — so chemists Richard Kiefer and Robert Orwoll can measure and mix simulated Martian soil with an assortment of polymers to find just the right recipe to bake up safe habitats for astronauts when they finally reach the Red Planet.

Something not too moist, not too dry and capable of withstanding massive doses of cosmic radiation blasting the Martian surface.

Their success could be key to visiting — and colonizing — the planet one day.

"If you want to stay there a while, you have to have something to shield you from the radiation," explained Kiefer, a nuclear chemist at the College of William and Mary. "One way to do it, instead of having to take a lot of material up there, you could simply use the regolith, the topsoil."

Martian simulant

When it comes to space flight, every ounce counts. So building with Martian dirt would save the prohibitive expense of trying to fly tons of construction material hundreds of millions of miles for astronauts to assemble into condos onsite.

There are no samples of Mars regolith to experiment with here on Earth, but unmanned NASA missions to the surface decades ago determined the chemical and mechanical properties of the local soil.

A close match, as it happens, is the glassy volcanic ash found in the Pu'u Nene cinder cone located between Hawaii's Mauna Kea and Mauna Loa volcanoes.

From quarrying that, NASA developed a Martian regolith simulant, then contracted with a private company to provide tons of the material for research. Orbital Technologies Corporation (Orbitec), based in Madison, Wis., also makes it available for purchase to researchers like Kiefer and Orwoll.

Bowls of the stuff sit in their laboratory, sorted by size, ranging from a coppery powder to rough brown pebbles that resemble Grape-Nuts cereal.

Since last summer, Kiefer and Orwoll have been combining the simulant with various binding polymers, or plastics, in various amounts, spreading it into kitchen molds and heating it.

Results range from dusty, crumbly "brownies" to a firm, dark chocolate loaf. Others look a lot like the red bricks found at any home improvement store.

The exact makeup of the polymers is protected, but the chemists say they do contain "a lot of hydrogen," which not only is lightweight but also provides the best radiation shield for bricks.

"I'm not even sure what it is about the polymer that we want to look for — what is in it, the chemical structure," said Orwoll, a polymer chemist. "But we want one that would wet the granules so that, when they're squeezed together, they hold together well."

Bricks will also undergo compression and other tests to make sure they're tough enough for the job.

A hard nut to crack

NASA has been planning a crewed mission to Mars for the 2030s, but first it has to crack the radiation problem.

Radiation exposure can cause serious acute health effects for astronauts, as well as increase their lifetime cancer risk.

The Earth has a magnetosphere — basically, a big magnetic bubble around the planet — that provides natural shielding from most radiation particles from the sun and from supernova explosions and other high-energy events outside the solar system.

But Mars has no global magnetic field and an atmosphere too thin to deflect most solar or cosmic particles.

"The space radiation environment will be a critical consideration for everything in the astronauts' daily lives, both on the journeys between Earth and Mars and on the surface," NASA's Ruthan Lewis said last fall. "You're constantly being bombarded by some amount of radiation."

Lewis is an architect and engineer with the human spaceflight program at Goddard Space Flight Center in Greenbelt, Md.

When the Curiosity science rover landed on Mars in 2012, it gave NASA the radiation data it needed to begin designing systems to protect deep-space explorers.

The agency has been soliciting private partners to find solutions.

Last month, for instance, NASA announced it was seeking industry proposals for prototypes that will give astronauts "a place to call home" during deep-space flights and while on alien soil.

It's the second phase of the agency's NextSTEP initiative, or Next Space Technologies for Exploration Partnerships, launched in 2014 to solicit industry concepts.

Now, NextSTEP-2 is looking for commercial development of those concepts for what NASA calls "more extensive human spaceflight missions in the proving ground of space."

Getting it down

Kiefer and Orwoll say their research isn't part of NextSTEP, but as subcontractors with International Scientific Technologies Inc., a small company based in Dublin in Pulaski County.

That company is working under NASA's Small Business Innovative Research program, said senior research scientist Eugene Aquino in a recent phone interview. It has worked on other NASA radiation shielding projects in the past, he said.

A graduate of William and Mary, Aquino has been with International Scientific since its founding in 2002.

While he enjoys the research, Aquino said he has no interest in actually going to Mars one day to see the radiation bricks in action.

"I'll leave that to the astronauts," Aquino said. "I'll leave that to Matt Damon."

Damon starred last year in the film "The Martian."

Last year, too, NASA began soliciting radiation shield concepts, including ways to process regolith with polymer binders.

Orwoll has worked for decades on radiation shielding with other polymer chemists at NASA Langley Research Center in Hampton, so was well-versed in the effort.

Their regolith work now is being monitored out of NASA Langley by Sheila Thibeault, a senior research physicist and radiation shielding expert.

"I think this is exactly what we should be doing," Thibeault said. "I think it makes a lot of sense — the radiation doses on Mars are significant."

The six-month first phase to develop concepts to submit to NASA wrapped up in December. Thibeault said those development contracts were each funded at $125,000.

Now the second phase — to deliver actual test specimens within two years — has begun. That contract is worth $750,000.

Once the technology is ready, one idea is to install the bricks around an inflatable habitat. Ideally, said Orwoll, such work would be completed by robots before astronauts even reach the surface.

"We're still kind of feeling our way," Kiefer said. "We've got a couple of years to get this down."

Dietrich can be reached by phone at 757-247-7892.

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