“The students are helping to solve one of the most perplexing problems in rocket science: How much fuel is left in the tank,” explains Carthage physics professor and team advisor Kevin Crosby. “In the weightless environment of space, conventional fuel sensors simply don’t work. To date, there is no such thing as a fuel gauge for the propellant tanks on a spacecraft, so engineers must be extremely conservative with fuel use. At $10,000 launch-cost per pound of fuel, having extra fuel in the tank is a costly mistake.”
The solution the Carthage students are studying is to listen to the tank. They are using non-invasive PZT technology to create vibrations in the tank wall, which are then recorded and analyzed in real time using a software technique called modal analysis. “Much like the ring of a wine glass struck by a spoon, a spacecraft’s propellant tank will ‘ring’ at different pitches as the fuel volume inside changes,” Dr. Crosby states. “We can tell with great precision how much fluid is in the tank.”
The Carthage Microgravity Team first investigated this technology during the 2011 SEED program and continued its research during the summer of 2011, to great success. “What’s surprising is the accuracy of this approach. We believe it surpasses the accuracy of every alternative method of fuel gauging,” Dr. Crosby says. “The solution Carthage students are proposing could save millions of dollars each year if widely implemented.”
The success of the project has already attracted the attention of space flight managers at Johnson Space Center in Houston, who have selected this technology for further investigation on an upcoming Delta IV rocket flight.
Says Dr. Crosby: “Given the rapid pace of NASA technology transfer into the consumer market, you may well find this technology built into the fuel tank of your next automobile.”