This bone density tester helps astronauts see if they are at risk for fractures due to lack of stress on their bones. The test is used on an astronaut’s shinbone and can be used to tailor exercise routines. Before launch, the dimensions of the 3D model will be tweaked to factor in the thickness of the skin on the shin and the spring constant of the built-in spring. The bone density test can be self-administered. First, apply a local anesthetic to the shin, then place the needle against the shin. Squeeze the actuator until the lip touches the outer cylinder, then release. How deep the needle goes depends on the porosity of the bone. Record the results based on what line the outer lip rests on when the needle is in the bone. My first idea involved a DXA machine, but it was too complicated. My model is an original working interpretation of a research project from the University of Southampton. The model should be printed with metal so the needle and spring are stronger and more sterile.