Astronauts who spend prolonged periods of time in microgravity experience adverse health effects such as muscle deconditioning and loss of vision due to irregular blood flow to the head. A lower body negative pressure (LBNP) device counters these effects by applying a partial vacuum to the user's legs, diluting blood vessels and drawing blood away from the upper body. In essence, LBNP devices mimic the effect of gravity on human blood distribution. Existing LBNP designs are immobile, meaning that astronauts are forced to remain stationary for hours at a time (shown left). This prevents them from moving freely to accomplish important experiments and tasks. Our task was to design a mobile LBNP device that was both flexible and comfortable to wear.

Our final LBNP prototype is made up of an airtight outer pant and a detachable rigid endoskeleton. The endoskeleton supplies structure to the suit because applying negative pressure to any airtight chamber will cause the walls (in this case the pants) to compress. These rigid structures keep fabric from compressing onto the user's skin. Vacuum tubes connect to each endoskeleton leg to supply a vacuum to the device, and the entire system is suspended by a load bearing vest that rests on the user's torso. The outer pant, endoskeleton, and vacuum assembly are all easily detachable from one another.

Our final design successfully achieved the goal of maintaining the specified pressure of 25mmHg while allowing impressive flexibility and comfort. The knee hinge allows approximately 110° of flexion from the calf to thigh, and prevents fabric from contacting the user. Straps under the user's foot also cause the device to induce spinal loading due to the compressive nature of negative pressure. If tuned correctly, these forces could mimic the loading effects of gravity on musculoskeletal systems.