Masys says that, so far, NASA hasn’t been surprised by anything the committee has said—“other than their mild surprise that we have anchored radiation as the deal breaker,” he says. “It is the showstopper for what NASA calls exploration-class missions.”
Both NASA’s and the Academy’s documents say that long-term missions will be radiation-risky for the foreseeable future—maybe forever.
Masys doesn’t use the words “deal breaker” and “showstopper” lightly. According to NASA’s reports and the Academy’s evaluation, cancer-inducing radiation can also cause cardiovascular and degenerative diseases—like cataracts, premature aging, and endocrine problems—a risk “of much greater concern than previously believed.” It can also rejigger the central nervous system, screwing with everything from cognition to spatial perception to hand-eye coordination. Then there’s the infertility, the cataracts, the slow wound healing, and the problems that astronauts could pass on to future children if they make it back from the long trip to Mars and manage to procreate.
For several of these medical matters, scientists don’t understand the underlying mechanisms. And so far, their research into those mechanisms, and their manifestations, has mostly involved the low-energy particles from Earth or near-space—not the high-energy cosmic rays from farther off—and radiation exposure that falls in one fell swoop, like the swoop of a nuclear bomb. Often, too, researchers base their conclusions on animal models that they haven’t translated to humans. Both NASA’s and the Academy’s documents say that long-term missions will be radiation-risky for the foreseeable future—maybe forever.
“For as long as there have been catalogs of health effects, radiation has been the most intractable, most severe, hardest problem to solve,” Masys says. “Now, 20 or more years into advances in space technology and propulsion and systems and vehicles, radiation is still the deal breaker. It has never changed.”