Light as a Brick! On Earth, the layers of our atmosphere help protect us from the sun’s most lethal forms of radiation. Two hundred and fifty miles above the Earth, dangerous forms of ionizing radiation constantly bombard Space Station Alpha.  The Earth’s atmosphere does not shield the Space Station as effectively from the sun’s radiation bombardment, especially during the violent solar storms called solar proton events. The space station’s walls can deflect or absorb some low energy-forms of radiation. High-energy radiation, however, has the power to zoom through the space station’s outer layers. On Earth we shield ourselves from ultraviolet light, one form of dangerous radiation that penetrates Earth’s atmosphere, by applying sunscreen to our skin. Sunscreen acts as a shield and deflects the ultraviolet photons. On the space station, the astronauts can decrease their exposure to dangerous radiation by working and sleeping in areas of the space station that are shielded from the radiation. The Shielding Challenge The most important areas of the spacecraft to shield are the crews’ sleeping quarters and their workspace because this is where they spend the most time. Finding a type of shielding that could be shaped to fit into the Space Station’s few non-essential areas and yet “fit” around the astronauts while they sleep was a challenge. An effective radiation shield depends on the material used and its thickness. Different types of radiation require different shielding materials. There is no one shielding material that can block all radiation. Finding a shielding that would protect the astronauts from the specific ionizing radiation found in space was a challenge. One of the challenges of working with radiation shielding is to determine exactly the right amount.  Too much shielding would take up too much space and be too difficult to transport to the space station. Too little shielding would be like no shielding at all. Materials used for shielding On Earth, scientists, nurses, technicians, and engineers are exposed to dangerous forms of ionizing radiation during some medical treatments and experiments and while working with nuclear power and some military weapons. These scientists and technicians shield themselves during their work with heavy materials such as concrete and lead. Lead and concrete are too heavy for the Space Station. To provide the astronauts with shielding, a dense, light material had to be found.  Researchers found that any material rich in hydrogen makes very good radiation shielding material. One material rich in hydrogen is water.  Consequently, water serves a dual purpose and is stored in strategic places on Space Station Alpha. Engineers decided that additional shielding would be a valuable addition to the crew’s sleep quarters. Another material rich in hydrogen is polyethylene. There are over 800 different polyethylenes.  The polyethylene selected for space shielding was C2H4, which is also used for kitchen cutting boards. It is very light and provides adequate shielding.  It is made into a brick that measures 1”X14”X14.” This size permits it to be transport easily into space in a rack that can be transferred from the Shuttle to the Space Station.  Once at the Space Station, all the bricks are strapped together to provide a three-sided shield.  One side of the sleeping “shelf” is left open for ventilation.