Educator Features

Radioactive Fred
05.13.04
Picture of radioactive Fred
Radiation is mysterious. You can't see it, smell it, hear it or feel it, but in space, it's a big concern. Radiation is energy the Sun gives off; it's part of the light spectrum, and just as people on Earth protect themselves from ultraviolet rays, astronauts have to watch out for radiation. On Earth, people can apply sunscreen to minimize the danger from the Sun's rays, but astronauts don't have any "radiation block" to use in space. If they are exposed to too much radiation, it can cause tissue damage, cancer and premature aging. Nobody wants the astronauts to be placed in jeopardy, but nobody really knows how to tell when the astronauts are reaching critical levels of radiation exposure -- then Fred comes along.

Image to right: Using a synthetic version of a human torso, scientists recorded the radiation exposure astronauts recieve while in space
Credit: NASA


Fred traveled to space on Space Shuttle Mission STS-100 in May 2001. He spent 4 months as part of an experiment aboard the International Space Station (ISS) Expedition Two. Fred wasn't an astronaut; he was a phantom -- a dummy or a mannequin. He was called a phantom because he mimicked the characteristics of a real human, but was built of man-made materials. Fred's job was to absorb radiation in the atmosphere of the ISS and to record those levels. Phantom Fred is only the upper half of the body because in humans, the critical organs are located above the waist. He has sensors installed in critical spots of his body. The readings from those sensors tell scientists how much radiation astronauts experience in space.

Closeup of the inside of the torso of Fred
Before Fred went into space, the only way to monitor radiation exposure was to use computer models or room monitors. These methods were not able to respond the way a human body would, and couldn't compensate for the way real human tissue does when exposed to unusual conditions. Though Fred was made of synthetic materials, he was able to reproduce the responses of muscle and tissue.

Image to left: Synthetic organs and actual human bones helped scientists record highly accurate radiation readings
Credit: NASA


Fred was carefully designed with his mission in mind. His "body" is made of 35 layers of material, connected with pins. His skin was made of Nomex. Nomex is a nonflammable plastic material that holds together and covers the interior of bone, tissue and organ structure. The bones were real human bones, but the tissue and organs were synthetic models, made to match the density and other characteristics of the living tissue and organs. The torso was the same height and weight as an average adult male. His radiation detectors -- called dosimeters -- measured how much radiation the brain, thyroid, stomach, colon, heart, and lungs received on a daily basis. It also recorded the radiation present in the ISS and compared that figure with readings from the torso. The data collected helps scientists determine how the body reacts to and shields its internal organs from radiation. Scientists can modify Fred's reading to specific heights and weights of individual astronauts to know how much radiation each person can tolerate. Knowing this information will be helpful as longer and longer duration space flights are planned.

Photograph of the three main parts of Fred separated out
Image to right: The phantom torso contains sensors that measure radiation and its effects on the human body
Credit: NASA


Studying radiation in space isn't new. Researchers were learning about it even before Sputnik, the first human-made satellite, launched in 1957. Devices to monitor radiation flew on the Apollo spacecraft and most successive vehicles. However, they only recorded radiation and how it affected the surface of the skin. Fred's abilities are the first that provide a clear picture of the radiation dose and how the human body's organs absorb it. Knowing how the body responds to specific levels of radiation will enable engineers to create shielding to keep people safe when there is no way to prevent prolonged exposure.

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Published by NASAexplores