Abstract

Funded by NASA, the goal of this project was to measure cryogenic, or extremely cold, fuel levels in outer space. This is a complex problem with few solutions. Gravity is not present to simply weigh the tank. Additionally, the fuel turns to gas very easily. Creating a reliable way to measure fuel levels in zero-gravity will determine the fuel necessary for space travel. This will decrease the overall shuttle weight as less fuel will need to be stored for future launches.

To measure the cryogenic fluid in the tank, we used a Fiber Optic Sensing System (FOSS). This system included a laser and a fiber optic cable with sensors. Since the strain of the cable varied directly with the temperature of the fluid, the sensors used the cable's strain to determine if the fuel was liquid or gas. In space, the gas forms a bubble in the center of the tank, while the liquid sticks to the sides. Measuring radially outward from the center, we calculated the volume of the bubble and subtracted it from the original liquid volume.

The project scope was to design a support which holds the FOSS cable inside a dewar. The structure needed to be both structurally sound in cold temperatures and survive launch forces. Our design used support rods and rings that guided the cable in a helical shape around the tank. The structure was made from G-10 steel, which has a high tolerance for cold temperatures. The further outward the cable traveled, the more volume it measured. Covering more volume with the cable directly led to more accurate results. An accurate system will allow spacecraft to measure the fuel levels and thus cut down on excess storage, creating more opportunities to explore space in the future.