Cosmic Radiation Less Of A Risk To Astronauts Than Previously Thought

Chuck Bednar for redOrbit.com – Your Universe Online
Cosmic radiation from space travel could be less harmful to astronauts than previously believed, data from experiments conducted on board and outside of the International Space Station (ISS) has revealed.
The MATROSHKA experiment, the first comprehensive measurement of long-term exposure of space travelers to cosmic radiation, brought together researchers from the European Space Agency (ESA) and colleagues from other institutions to determine precisely how much radiation astronauts are exposed to during long-term space travel.
The goal was to determine how long astronauts could remain in space without their health being threatened due to exposure to ionizing radiation. To do so, they developed a type of mannequin that was outfitted with several thousand detectors that recorded the doses of cosmic radiation from inside and outside the ISS over the course of several years. The data collected by those sensors has been analyzed, the researchers called the results surprising.
“One may say that we found open space to be a bit less hostile to humans than expected. The effective doses, related to the health risk of the astronauts and calculated from measurements with our detectors, were lower than those indicated by dosimeters worn by the astronauts,” Dr. Paweł Bilski from the Henryk Niewodniczański Institute of Nuclear Physics (IFJ PAN), said in a recent statement.

The mannequin, a legless torso described by the researchers as “a specially adapted humanoid phantom used in medical research,” contained real human bones places inside a plastic shell simulating the shapes and densities of soft tissues and lungs in an astronaut’s body. It consisted of 33 slices 2.5 cm thickness each, and each of them contained measuring equipment and sets of passive thermoluminescent detectors placed in plastic tubes.
Using a total of six thousand thermoluminescent detectors, the researchers created a three-dimensional rectangular grid of measurement points inside the phantom. The design allowed the authors to accurately determine how much radiation would be absorbed by each of the body’s organs, and to calculate “the so-called effective dose, which is considered to be an estimate of the radiation hazard to humans,” IFJ PAN explained.
“The main hazard to the astronaut’s health due to exposure to cosmic radiation is the increased probability of developing cancer in his or her body,” the institute added. “This probability however is quite dependent on the type of radiation the astronaut is exposed to. Most of the natural sources of ionizing radiation on Earth produce electromagnetic radiation of high energy – gamma rays. On the other hand, in cosmic rays, energetic protons or heavier ions dominate, which are much more effective in creating cancer cells.”

The thermoluminescent detectors used in the phantom are unable to distinguish between gamma rays or ions, meaning that it also had to be equipped with plastic track detectors in which tracks of protons or heavier ions could be measured. The mannequin was also dressed in a poncho-type outfit with additional detectors, simulating the personal dosimeters worn by members of the ISS crew and other astronauts for the sake of comparison.
“Over the years 2004-2009 the MATROSHKA mannequin underwent three exposures to cosmic radiation, each lasting a year of more,” the IFJ PAN said. “Two of these exposures occurred inside the Russian modules of the space station and for one exposure the phantom, in a container imitating the shielding properties of a spacesuit, was placed in open space outside the ISS. Such measurements have never been done before.”
“After returning the detectors to Earth, their painstaking readout and analysis of the complete data set gathered within the MATROSHKA experiment were carried out by teams of scientists at the IFJ PAN in Kraków, the German Aerospace Center (DLR) in Cologne and at the Technical University of Vienna,” it added. “Their overall conclusion was that the individual dosimeters worn by the crew inside the ISS overestimated the actual dose measured inside the phantom by about 15 percent. However, in open space this overestimation exceeded 200 percent.”
Based on the results of the experiment, the study authors conclude that traveling to the Moon or Mars could be safer than previously believed in terms of exposure to hazardous radiation. Even so, they said that the doses the space travelers are likely to receive, while lower than previously thought, would still be dangerously high.
In October, researchers from the University of New Hampshire published research that indicated that, due to a highly abnormal and extended lack of solar activity, the solar wind exhibits extremely low densities and magnetic field strengths which causes dangerous levels of hazardous radiation to spread throughout the space environment.
Those conditions have resulted in the highest intensities of galactic cosmic rays ever during the space age, the study authors said, and the increasing intensity has worsened the radiation hazards that could threaten future deep-space astronaut missions. While the UNH researchers said this was not necessarily “a showstopper for long-duration missions,” it remained “a significant and worsening factor” that could limit mission durations.
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