iously worked with similar materials in developing helicopter armor. "Since it's a fabric, it can be draped around molds and shaped into specific spacecraft components." And because it's derived from polyethylene, it's an excellent radiation shield as well.
Left: Raj Kaul, co-inventor of RXF1, holding a brick of the material. [More]
The specifics of how RXF1 is made are secret because a patent on the material is pending.
Strength is only one of the traits that the walls of a spaceship must have, Barghouty notes. Flammability and temperature tolerance are also important: It doesn't matter how strong a spaceship's walls are if they melt in direct sunlight or catch fire easily. Pure polyethylene is very flammable. More work is needed to customize RXF1 even further to make it flame and temperature resistant as well, Barghouty says.
The Bottom Line
The big question, of course, is the bottom line: Can RXF1 carry humans safely to Mars? At this point, no one knows for sure.
Some "galactic cosmic rays are so energetic that no reasonable amount of shielding can stop them," cautions Frank Cucinotta, NASA's Chief Radiation Health Officer. "All materials have this problem, including polyethylene."
Cucinotta and colleagues have done computer simulations to compare the cancer risk of going to Mars in an aluminum ship vs. a polyethylene ship. Surprisingly, "there was no significant difference," he says. This conclusion depends on a biological model which estimates how human tissue is affected by space radiation--and therein lies the rub. After decades of spaceflight, scientists still don't fully understand how the human body reacts to cosmic rays. If their model is correct, however, there could be little practical benefit to the extra shielding polyethylene provides. This is a matter of ongoing research.
Because of the many uncertainties, dose limits for astronauts on a Mars mission have not been set, notes Barghouty. But assuming that those dose limits are similar to limits set for Shuttle and Space Station flights, he believes RXF1 could hypothetically provide adequate shielding for a 30 month mission to Mars.
Today, to the dump. Tomorrow, to the stars? Polyethylene might take you farther than you ever imagined.
NASA Space Radiation Shielding Program -- NASA project researching radiation shielding technologies where RXF1 was invented
Can People Go To Mars? -- (Science@NASA) Space radiation between Earth and Mars poses a hazard to astronauts. How dangerous is it out there? NASA scientists are working to find out.
NASA Space Radiation Health Project -- The purpose of NASA's Space Radiation Health Project (SRHP) is to achieve human exploration of space without exceeding an acceptable level of risk from exposure to space radiation.
Fire Away, Sun and Stars! -- article about radiation shielding technologies