Scientists at NASA have created Fred the Phantom Torso, a 95-pound, 3-foot high recreation of the human upper body that will spend four months on the International Space Station in order to monitor the effect of radiation of the body.
Beneath Fred’s artificial skin are real bones. Fred’s organs — the heart, brain, thyroid, colon and so on — are made of a plastic that is said to closely match the density of human tissue.
‘We believe the current dose [of radiation to the crew of the ISS] is too small to be of concern,’ said Dr. Gautam Badhwar, the study’s principal investigator at the Johnson Space Centre. ‘The one possibility for radiation sickness might be an EVA situation during a solar event, if perhaps a crew member couldn’t be brought back inside safely.’ But there is still a lot to learn, he added.
The Phantom Torso has been designed to perform three tasks. First, it will determine the distribution of radiation doses inside the human body at various tissues and organs. Second, it will provide a way to correlate these doses to measurements made on the skin. ‘In the past we’ve typically recorded doses only on the skin,’ said Badhwar, ‘whereas the risk to crew members is established by exposure to internal organs.’ Finally, the Phantom will help check the accuracy of models that predict how radiation moves through the body.
In order to measure space radiation as it propagates through Fred’s body; Badhwar and his team have sliced Fred horizontally into 35 one-inch layers. In each section they’ve made holes for dosimeters.
The torso carries 416 lithium-crystal based passive dosimeters, which record the total radiation dose received throughout the mission. Fred is also equipped with five active detectors. These, placed at the Phantom’s brain, thyroid, heart, colon, and stomach, can track the times that the radiation exposures took place.
‘With the active detectors, we can correlate the time the radiation was received with the position of the spacecraft,’ explained Badhwar.
Radiation models devised by Badhwar and colleagues will be able to estimate how much radiation reaches an astronaut’s internal organs simply by looking at the dose on his or her skin. That’s important, because while the permissible radiation limits are based on internal exposures, practically speaking, all that can be measured is what occurs on the skin.
Such models are also said to be scalable. Rather than giving a blanket risk assessment for all crew members, they can be customised to each individual in terms of height, weight, and even personal histories: how the astronaut flies an aircraft, or what medical tests he or she might have taken. All this contributes, said Badhwar, to total radiation exposure.