Astronauts are exposed to a number of risks during space travel including freezing temperatures, crushing pressures, isolation – even in low Earth orbits – and while each of these risks is huge, radiation risk could emerge as a huge one in future missions.
There is no quantification possible for the amount of radiation that astronauts could be exposed to during their space missions. Space agencies design and build space labs that would protect astronauts from as much radiation as possible, but because of technological limitations a 100 per cent radiation proof spacecraft isn’t a possibility as of now – even in case of low Earth orbits.
Researchers at Texas A&M, NASA and UT Medical Branch researchers set out to explore and estimate radiation risks for low Earth orbits using supercomputers and advanced computing models. The study found that even in case of low-Earth orbit missions – specifically those that have polar orbits – will be susceptible to high radiation exposure.
For the study researchers used as a test case the Manned Orbiting Laboratory (MOL), about which mission documents were recently declassified. The MOL was conceived in 1963 and underwent planning from 1965 to 1969, but never actually flew. The MOL had relatively minimal shielding and its high inclination polar orbit would have left the crew susceptible to high exposures of cosmic radiation and solar particle events. Had the mission continued through 1972, astronauts would have faced toxic doses of radiation during a massive solar event.
The researchers focused on radiation from two sources: solar winds and galactic cosmic rays. Some space radiation is believed to pass through the walls of shuttles, while some barrages the shielding and causes a cascade of loose metal ions. A portion passes through the body; the rest deposits its energy on the skin or even inside the body, affecting the organs.
Determining the radiation levels that MOL pilots would have experienced behind the vehicle’s light-weight shielding entailed a good deal of data mining, extrapolation and simulation. Jeffery Chancellor, a research scientist in the Department of Physics and Astronomy at Texas A&M University, and his collaborators modeled the MOL’s orbit profile, the space weather and geomagnetic forces from those years, and the particle and heavy ion transport that such a trajectory would have encountered.
Combining these factors, sampling them, and simulating them thousands of times on TACC’s Lonestar5 supercomputer, Chancellor and his collaborators found that, under normal conditions, the MOL crew would have endured 113.6 millisievert (mSv; a measure of radiation dosage) to their skin and 41.6 mSv to blood forming organs (for instance, bone marrow or lymph nodes) during a 30-day flight — well within the exposure limits for NASA astronauts.
However, during the “worst-case scenario” of the 1972 solar storm, their skin would have been exposed to 1,770 mSv, while their organs would have experienced 451 mSv, both of which exceed NASA exposure limits.