The Space Dynamics Laboratory Completes Floating Potential Measurement Unit

October 14, 2003

LOGAN –– Utah State University’s Space Dynamics Laboratory Floating Potential Measurement Unit (FPMU), designed to monitor safety when astronauts are outside of the International Space Station (ISS), was completed and accepted by NASA on Friday, Oct. 10, 2003.

“The FPMU is designed to enhance crew safety with regard to a plasma arcing hazard,” said Marybeth Edeen, Flight Projects Office deputy manager at NASA’s Johnson Space Center (JSC). “That is a catastrophic hazard to the crew.”

Because FPMU is so critical to crew safety, Edeen worked with the crew and NASA’s Public Affairs Office to get the crew’s special Silver Snoopy logo attached to the FPMU. Edeen said the Silver Snoopy is the crew’s special award and is presented only when a person has done something to markedly improve crew safety.

“While the award is given only to people, because of the resemblance of the FPMU’s electronics box to a dog house and the critical safety function the hardware will provide, it seemed appropriate to affix the Silver Snoopy logo to the FPMU to indicate how important this hardware is to enhancing crew safety,” Edeen said.

FMPU is composed of four sensors that will monitor the electrostatic charging of the ISS as well as the surrounding ionospheric plasma density and temperature. This instrument is vital to ensure the safety of the astronauts during their space walks, known as Extra Vehicular Activity (EVA).

“A similar situation is created when a person walks across a carpet, building up a static electrical charge,” said Charles Swensen, Ph.D., principal investigator for FPMU and USU professor. “When the person touches an object that is at a different charge, such as a doorknob, there will be a discharge – shocking him or her.”

In much the same way, astronauts charge to a potential different from the Space Station as they perform their EVA. This creates a voltage difference between them and the Station. If the differential charging becomes severe enough, it may discharge, upsetting spacecraft electronics, damaging surface coatings, burning holes in thermal blanketing or causing failure of an astronaut’s space suit or even the death of an astronaut.

Within two years, SDL developed, built, integrated, tested and delivered four FPMU units and a ground station. One unit has already been delivered to NASA; the last three flight-ready FPMUs and the ground station will be delivered to NASA this month. One of the instruments is scheduled to launch on the second Space Shuttle once NASA resumes shuttle missions.

“The FPMU team has learned some hard lessons about communication, expectations and the politics of our business,” said Ames. “Because of this newfound understanding about quality assurance, configuration management and document control, we have positioned ourselves for future NASA work, specifically work associated with ISS safety and crew health instrumentation.”

JSC awarded SDL a $2.5 million contract in 2001 to build FPMU for the ISS. The SDL team included scientists from Utah State, engineers, technicians, designers, contamination control scientists, quality assurance personnel, technical writers, a program coordinator and management.

“Our congratulations to the FPMU crew for their dedication to get this job done right according to the customer demands,” said Ames. “We will look back on FPMU as a valuable learning experience.”