Radiation Poses Greatest Threat to Humans in Space

A new report commissioned by NASA’s Exploration Systems Mission Directorate said that cosmic radiation poses cancer and other health risks for years after astronauts return to Earth, and that a lack of understanding of the biological responses to space radiation is the biggest limiting factor to future missions.

The report, authored by the National Research Council, one of the independent National Academies of Science that advises the federal government, said that cosmic rays are so dangerous and poorly understood that people are unlikely to get to Mars or return to the moon until better ways to protect the astronauts are found.    

"The committee finds that lack of knowledge about the biological effects of and responses to space radiation is the single most important factor limiting prediction of radiation risk associated with human space exploration," the report reads.

However, NASA currently lacks the proper funding for such an undertaking, the council committee said Monday.

"One of the big issues is they have really cut funding for biology issues," retired space shuttle astronaut James van Hoften, the committee’s chairman, said during a telephone interview with Reuters.

"It is tough on them when they don’t have any new money coming in. They are using old data," he added, referring to research done on survivors of the World War Two nuclear bombings of Japan.

"Given today’s knowledge and today’s understanding of radiation protection, to put someone out in that type of environment would violate the current requirements that NASA has."

Here on Earth, the planet’s bulk, atmosphere and magnetic field protect life from the solar radiation and the cosmic rays traveling through space. However, out in space astronauts have only a thin layer of shielding to protect them.

"My introduction to space radiation came first-hand as a crew member aboard the Space Shuttle Challenger in April 1984. ‘What the heck was that?’ I blurted out after seeing what looked like a white laser passing quickly through my eyes," Van Hoften wrote, speaking of his personal experience, in the report’s introduction.

"’Oh, that’s just cosmic rays,’ said Pinky Nelson, my spacewalking partner and space physicist. The thought of extremely high-energy particles originating from a distant cosmic event passing easily through the space shuttle and subsequently through my head made me think that this cannot be all that healthy. The truth of the matter is that it is not," Van Hoften said.

Such cosmic rays include galactic cosmic radiation, or GCR, along with other solar particles.

"You can put on very thick walls and they just won’t protect you from that," Van Hoften said. "The younger you are the worse it is," he added. As with exposure to many types of radiation, it can take years for resulting disease to develop.

"It might be OK if you just send a bunch of old guys like me," he laughed.

According to Van Hoften, any mission to Mars using current technology would take three years, a long enough time to expose the astronauts to excessive amounts of radiation.

"It hasn’t really gotten the airing that it needs. In the committee we stewed over this for a long time before we said anything," he added.

The committee said that although experts can forecast the amount of ejections of dangerous particles from the sun, astronauts must shelter in specially shielded areas of shuttles or space stations and may miss important parts of their mission. The addition of more shielding would be too costly and could make the spacecraft too heavy, added the council’s report.  

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