NASA says space station's batteries safer than 787's
BY STEPHEN CLARK
Posted: April 30, 2013
NASA officials are confident lithium-ion batteries due to launch to the International Space Station in 2016 will not overheat like the batteries that grounded the Boeing 787 Dreamliner earlier this year.
Pratt & Whitney Rocketdyne - NASA's space station battery contractor - tapped GS Yuasa Lithium Power Inc., a U.S.-based subsidiary of GS Yuasa Corp. of Japan, to supply the cells for the space station's next-generation lithium-ion batteries.
GS Yuasa is also the supplier for batteries used on the Boeing 787 airplane, which was grounded in January after batteries aboard two of the jumbo jets smoldered and caught fire.
No crew members or passengers were injured in the incidents, but one firefighter received minor injuries while responding to the fire on a Japan Airlines 787 on the ground in Boston.
Kirk Shireman, NASA's deputy space station program manager, said earlier this month that the space station batteries should not be affected by the problem.
Engineers working on the Dreamliner have devised ways Boeing says will prevent similar problems in the future, but investigators have not found the root cause of the battery overheating. The suspect batteries provide electricity to the Dreamliner's auxiliary power unit. The Dreamliner batteries include eight cells arranged in a four-by-two matrix.
Engineers at Boeing, GS Yuasa and Thales, one of the 787's electrical system subcontractors, redesigned the batteries to prevent overheating in one cell from cascading into other sections of the battery. The contractors beefed up the battery's casing to contain a fire.
The Dreamliner returned to commercial service Saturday with an Ethiopian Airlines flight, two days after the Federal Aviation Administration approved Boeing's battery fix. Other carriers will resume Dreamliner flights over the next couple of months as national regulatory agencies grant approvals following the installation of redesigned batteries.
Boeing is also the top industrial contractor for the U.S. side of the International Space Station, and it oversees engineering and maintenance projects aimed at sustaining the complex orbiting more than 200 miles above Earth.
"We had in place, prior to this issue with the 787 battery, a bunch of design features to protect us against this same phenomena," Shireman told a NASA Advisory Council committee April 18. "We have been actively, both from a contractor standpoint and from a NASA standpoint, participating in that investigation. So far, we haven't learned anything out of that that affects the design of our battery."
"If one cell runs away, it doesn't dump a lot of heat into another cell and cause a chain reaction," Shireman said. "Some of the things they're learning on the 787, we already had in place."
Lithium-ion batteries, each with 30 cells, will replace the space station's nickel-hydrogen batteries on the outpost's truss backbone. The new batteries are lighter, more efficient and will last at least 10 years, according to NASA.
The station's oldest existing batteries will reach the end of their design lives in 2016, about the same time the new units are due to arrive. The nickel-hydrogen batteries were built by Space Systems/Loral.
The batteries store energy generated by the space station's solar panels.
Judy Jeevarajan, group lead for battery safety at NASA's Johnson Space Center, said lithium-ion batteries have been used on human-rated NASA missions since 1999.
"The lithium-ion battery chemistry is the highest in energy density, at this time, of all rechargeable battery systems," Jeevarajan told members of the National Transportation Safety Board in an April 23 hearing into the Dreamliner grounding.
"However, it is not the safest due to the catastrophic failures that are usually associated with them, like electrolyte leakage, fire and thermal runaway," Jeevarajan said, adding potential risks include internal shorts, high temperatures and overcharges.
Jeevarajan said NASA will do stringent testing on all of the space station's new batteries, including checks on their performance in the unpressurized environment outside the outpost.