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Good news: Data collected on ISS for the past decade now suggests that the human body does a better job of shielding its internal organs from space radiation than previously believed.
For an astronaut working inside the space station, the overestimate was about 15 percent — a fairly close correlation given that the station’s exterior shell provides much of the protection needed.
But for astronauts working outside the station, the radiation absorption measured was substantially less than what had been registered by the personal dosimeters worn by astronauts. “Measurements of a personal dosimeter dramatically overstate the exposure of an astronaut, in the worst case by a factor of three,” according to a summary of the results by a Euro-Russian team. “[I]n an outside exposure the self-shielding of the human body is very effective. … [T]he effective dose equivalent is less than 30 percent higher than in an inside exposure.”
In other words, humans could fly 30 percent longer in space with the present shielding and suffer far less exposure than expected. Though this data is for operations in low Earth orbit, it still provides a strong counter to the bad news recently released about the high amounts of dangerous radiation expected in interplanetary space due to the Sun’s recent low sunspot activity. Even if radiation levels are higher, the human body is more resilient than expected. Interplanetary space travel is still possible.