Space exploration has greatly advanced since the early 1960s. From the first American spaceflight of just 15 minutes, space shuttle average flight times are now 25 weeks long and space station missions can last from 6-9 months. By 2030, NASA hopes to send a manned mission to Mars; such a trip would require a 4-6 month outbound flight, an 18 month stay at 0.38g, and a 4-6 month return flight. As exposure to extended periods of microgravity cause an average bone loss of 1-2% per month and potentially slower rates of bone healing, Mars-bound astronauts would be at considerable risk of developing bone fractures and suffering from delayed healing. While current countermeasures reduce bone loss, they do not stop it nor do they promote fracture healing.

The daily life of an astronaut consists of a rigorous exercise regime along with a demanding mission schedule that places the astronaut at risks for fracture. For example, astronauts have a 16 hour work day, involving experimental testing, assembling the space station, maintaining the shuttle, and repairing satellites. In addition, astronauts must sustain hypergravity exposures of 1.5-5g during liftoff and aerobraking. Currently, the protocol for the treatment of fractured bones upon the International Space Station (ISS) involves tending to the wound and splinting the area without correcting the fracture. Only if there is no pulse or sensation in the fractured area is a surgeon contacted for instructions to set the fracture. For longer and more extensive space missions, these procedures are not adequate. For example, if an astronaut sustains a severe fracture on a mission to Mars, a splint may not provide sufficient treatment, and he or she may not be able to return to Earth to receive medical care in a timely fashion. Therefore, a more thorough system to treat fractures in space is needed.

At Rice University, senior design teams Cobra and Space Owls have created exercise countermeasures that address the issue of bone loss in a microgravity environment. HPN will build upon what has been done and design a fracture healing device that will allow for the effective healing of bone in a microgravity environment. Fixation, mechanical stimulation, electromagnetic fields, and ultrasound will be considered as potential treatments in the device. In the long run, this device will impact space exploration by providing a means for astronauts to safely travel beyond Earth's moon and explore Mars.

A detailed list of the forces driving the design of this device is as follows:

• Bone loss from long-term microgravity situations may significantly increase the risk of fracture
• Microgravity environment may inhibit or hinder normal bone healing mechanisms
• Observed immune dysfunction may complicate healing process
• Reduced muscle mass in space may increase fracture risk
• Long transit time to Mars rules out current ISS fracture protocol of splinting and returning to Earth
• Limited capacity, medical equipment supplies, etc. for diagnostic and surgical repair
• Cost per unit weight payload is expensive and space on shuttle/rocket is limited
• NASA considers fracture risk a Priority 2 issue
• Decreased healing time allows for quicker return to normal operational capacity