Radiation dose affecting ISS crewmembers exaggerated for many years

Russian physicists have analyzed the level of radiation at MIR stations and the International Space Station (ISS) over many years, and came to the astonishing conclusion that the dose received by the crew members is well below the allowed limit. That means that astronauts can work in low earth orbit without harm to health for much longer periods than previously thought.  

Scientists from the Institute of Biomedical Problems of the Russian Academy of Sciences (IBMP RAS), together with the Scientific Research Institute of Nuclear Physics. D.V. Skobeltsyn of Moscow State University summed up the results of a large-scale study of the influence of radiation on the astronauts’ bodies. Scientists analyzed more than 30 years of data on average daily absorbed radiation doses on the MIR orbital station and the ISS.

The researchers took into account data obtained with operational dosimetric monitoring devices and the calculated values of radiation loads on various tissues and body organs of the astronauts. They concluded that crews can work in the low earth orbit for three and even four years, not up to two years, as it is commonly believed now.

However, the maximum annual dose for astronauts is about 500 mSv (millisievert - one thousandth of sievert, a radiation dose unit). According to scholars from the IBMP, for one year in orbit, a crew member does not receive that much radiation. The total dose for this period is approximately 200 mSv and, in any case, does not exceed 300 mSv. The researchers also found that the radiation levels inside the astronaut's body is lower than on the outside. This should be taken considered when developing new labor standards for orbital station employees.  

“In a joint experiment with foreign colleagues as part of the Matryoshka-R experiment on the ISS, we used a spherical tissue-equivalent phantom with radiation sensors inserted into it. According to the data obtained, the level of radiation inside the body of cosmonaut is 15% less than on the surface. So, cosmonaut can fly 15% longer, until they reach the maximum dose,” experiment lead Vyacheslav Shurshakov told Asgardia Space News.

As the researchers explained, the maximum lifetime dose of radiation is 1,000 mSv. Therefore, in near-earth orbits, a person can fly for a total of four years. But there are no such examples in the space. The longest flight in terms of the total duration of stay in space, 878 days, was made by the Russian cosmonaut Gennady Padalka. During his space career, Padalka traveled to space five times and made ten spacewalks.

Although the results of this experiment are telling, the problem of radiation safety requires further research. Until now, there have been no significant experiments on the complex effects on the organism of galactic and solar proton radiations.

“For future flights to deep space, as an expert in the field of radiation, I recommend having a spherical phantom – a mannequin onboard the ship, inside which radiation sensors are installed,” said Mr. Shurshakov. “Such spherical phantoms will help us to monitor radiation conditions during flights to deep space.”

Jessica Zeitz