The design is useful by testing the astronaut’s reflexes so they can test if their reflexes are strong. Astronauts will become weaker when they come down from space because the bones do not have a body to support when there is no gravity. Astronauts lose 1% to 2% bone mineral density a month in space. Their reflexes are going to weaken too, causing legs to feel hard to move, control, and feel very slow. My design is the closest to the real thing I can get. A reflex hammer will test so astronauts can just double check their reflexes, and try to improve.