Mass gaging system will measure fuel transfer in zero gravity

Rudy Werlink, a fluid systems engineer in the Fluids Test and Technology Development Branch at NASA's Kennedy Space Center in Florida, has developed a sensor technology that will be tested on the early suborbital flights of Virgin Galactic's SpaceShipTwo in 2015.

From 1999 to 2005, Werlink worked at Langley Research Center in Hampton, Virginia, where he focused on the Lead Zirconate Titanate (PZT) sensors, which incorporated NASA Langley patents and created the PZT-based system to determine component vibrational signatures for health monitoring and mass/volume measurements on tanks. The technology was patented at Langley in 1999 and licensed to a company in Sarasota, Florida, in 2000.

The PZT Mass Gaging technology is a type of sensor that measures the frequency of mass vibration to detect mass and fluid levels. Researchers will use PZT sensors attached to two tanks for a fluid transfer experiment during zero gravity conditions on SpaceShiptTwo flights. The flight testing of the sensors will support on-orbit propellant storage stability technology development work being done by Embry-Riddle Aeronautical University, in Daytona Beach, Florida, and Carthage College in Kenosha, Wisconsin.

Both tanks will slowly rotate or spin, as water from one full tank is transferred to the second tank, during 5 minutes of exposure to zero gravity on the flight. Rotating the tanks makes the water collect in the bottom. The PZT sensors attached to the outside wall of the supply tank will be used to detect the amount of water remaining.

The sensors also could be used to detect the tank's rigidity or stiffness, and if there are any defects.

"To go beyond low-Earth orbit, we need to develop much greater payload capacity by lowering tank weights and deploying a fuel transfer depot," Werlink said. "This technology could provide key solutions to these engineering challenges.

Previously, the technology was tested on the Zero G commercial aircraft parabolic flights in 2010 through a Systems Engineering Education Development Program with Carthage College, with flights repeated in 2011 and 2012. Water in one tank was transferred into another tank using a pump with the PZT system data indicating water quantities in the tanks under microgravity conditions.

The University of Florida in Gainesville also will test the PZT technology on future SpaceShipTwo flights as part of their space technology experiments to demonstrate volume measurement and status in zero gravity of cryogenic-filled tanks on the space station and other flight vehicles

The SpaceShipTwo suborbital technology demonstration flights are sponsored by NASA's Space Technology Mission Directorate's Flight Opportunities program. NASA's Flight Opportunities Program provides suborbital flight testing of new space technologies before they're flown in the harsh environment of space.

Werlink currently is working to patent the health monitoring and mass gaging PZT system. The electronics and communications will be packed into one practical in-situ system.

Werlink moved to Florida in the 1960s and grew up in Orlando. He watched the Apollo 11 moon landing and immediately became interested in science and space.

He came to Kennedy in 1980 and worked for USBI on the space shuttles and the hydraulic control system for the solid rocket boosters (SRBs). In 1985, he worked at Marshall Space Flight Center in Huntsville, Alabama, where he helped design the thrust vector controls for the SRBs.

He returned to Kennedy in 1989 and worked in the Special Projects Branch of Design Engineering. Projects included two-phase flow measurements, space shuttle liquid oxygen fill and launch, and orbiter brake vibration analysis.

After his time at Langley, he returned permanently to Kennedy and the Cryogenic Test Laboratory in 2005 and continued his work on the PZT sensor technology.

"The sky's the limit," Werlink said. "We will eventually prove transfer of cryogenics in space for long-term spaceflight, whether it's to an asteroid or Mars."