Surrounding the living quarters with water or UHMW-PE (Ultra High Molecular Weight PolyEthelyne) would ruther reduce transmitted radiation through the hull--perhaps to reduce the risk to acceptable levels.
What has not yet been addressed (well, it certainly was only poorly addressed as of a 2004 space exploration conference I attended) is muscle atrophy for such long duration missions. Remember--once you've got these guys out to Mars, they've been in zero-G for almost a year. How are they going to be able to stand up and walk around? Now, Mars' gravity is only about 3/8 of Earth gravity, but these guys are going to be wearing heavy space suits, life support gear, and be carrying equipment. Having them ride makeshift stationary bicycles, ellipticals and treadmills will not be sufficient.
They'll need a large, habitable centrifuge.
A committee tasked by the White House with reviewing NASA’s plans for human space flight suggested that Mars is “the ultimate destination for human exploration; but it is not the best first destination” and suggested that sending astronauts to one of Mars’s moons, Phobos or Deimos, may be a better idea.
From there, astronauts could use remote-controlled robots to explore the Martian surface and retrieve samples for study.
But the suggestion is still dangerous, according to the New Scientist.
Why? Because the galactic radiation that barrels through the solar system poses a significant health risk.
The radiation, which is made up of protons, gamma rays and cosmic rays, can slice through DNA molecules when it passes through living cells. The resulting damage can make cells behave erratically and lead to cancer.
NASA outlined the problem itself way back in 2004:
NASA weighs radiation danger in units of cancer risk. A healthy 40-year-old non-smoking American male stands a (whopping) 20% chance of eventually dying from cancer. That’s if he stays on Earth. If he travels to Mars, the risk goes up.
The question is, how much?
“We’re not sure,” says Cucinotta. According to a 2001 study of people exposed to large doses of radiation–e.g., Hiroshima atomic bomb survivors and, ironically, cancer patients who have undergone radiation therapy–the added risk of a 1000-day Mars mission lies somewhere between 1% and 19%. “The most likely answer is 3.4%,” says Cucinotta, “but the error bars are wide.”
The odds are even worse for women, he adds. “Because of breasts and ovaries, the risk to female astronauts is nearly double the risk to males.”
Researchers who did the study assumed the Mars-ship would be built “mostly of aluminum, like an old Apollo command module,” says Cucinotta. The spaceship’s skin would absorb about half the radiation hitting it.
“If the extra risk is only a few percent… we’re OK. We could build a spaceship using aluminum and head for Mars.” (Aluminum is a favorite material for spaceship construction, because it’s lightweight, strong, and familiar to engineers from long decades of use in the aerospace industry.)
“But if it’s 19%… our 40something astronaut would face a 20% + 19% = 39% chance of developing life-ending cancer after he returns to Earth. That’s not acceptable.”
Here on Earth, people are protected by the planet’s atmosphere and magnetic field. That’s also the case for astronauts in the low-Earth orbit International Space Station.
But for a Mars mission, it would take impractically thick and heavy aluminum shields to stop high-energy galactic cosmic rays. And alternative technologies — such as a plasma radiation shield — are still not fully developed.
NASA’s existing rules stipulate that each astronaut’s lifetime risk of fatal cancer from space radiation must be below 3 percent:
Shield design studies based on nominal biological response models are highly questionable in their result and may lead to designs in which astronaut risk are much higher than anticipated on the basis of such models…current technology is adequate for a single lunar mission for casual astronauts. Revolutionary technology needs to be developed for human space missions to Mars for NASA’s vision.
The problem is that the White House panel expects a round-trip mission to a Martian moon to take 750 days, potentially exposing astronauts to more radiation than is currently allowed.
The panel asked NASA if it would consider accepting higher risks, but it’s unclear what the agency’s next move will be.
What do you think?
