The "smoking gun" behind the spacesuit leak that allowed water to invade the helmet of European Space Agency astronaut Luca Parmitano during a July 16 U.S. spacewalk outside the International Space Station eluded experts in NASA's Mission Control during a round of troubleshooting over the U.S. Labor Day weekend.
A suspect water relief valve and gas trap extracted from the leaky, shuttle-era NASA Extravehicular Mobility Unit (EMU) will be returned to Earth late Sept. 10th aboard Russia's Soyuz TMA-08M crew transport for more extensive analysis. The Soyuz capsule is undergoing preparations to descend into Kazakhstan with Russians Pavel Vinogradov and Alexander Misurkin as well as NASA astronaut Chris Cassidy. The three men are concluding a more-than-five-month tour of duty aboard the ISS.
Efforts by NASA's spacesuit and life support system experts to establish a cause for the July 16 seepage seemed to point to the valve, an associated filter or the gas trap as the most likely source of a problem that might force water from the suit's cooling system into the airflow apparatus. An estimated 1 to 1 1/2 liters of water entered an airflow vent at the back of Parmitano's head between his communications cap and the top of the helmet. The liquid seeped over the communications cap and gathered around his eyes, ears and nose.
His scheduled six- to seven-hour spacewalk with Cassidy was called to a halt by NASA's Mission Control after 92 minutes. U.S. spacewalks were suspended in the aftermath, while investigations on two fronts search for a root cause, contributing factors as well as a repair strategy.
At the direction of NASA troubleshooters, Cassidy and NASA astronaut Karen Nyberg removed the water relief valve, then the gas trap from the faulty space suit’s Primary Life Support System (PLSS), or backpack, on Aug. 31. After each of those steps -- carried out in the space station airlock -- the EMU was re-activated by Cassidy and Nyberg without Parmitano in it. Each time the helmet leaked again, a sure sign the root cause remained elusive. The troubleshooting took seven hours.
"So, we have not isolated the exact component that failed on Luca's helmet,” Dina Contella, a NASA lead flight director involved in the troubleshooting, said Tuesday. "But we did a lot of good work recovering those elements. We bagged them all up for return on the Soyuz."
Parmitano, a 36-year-old Italian Air Force test pilot, made his way back to the ISS air lock on July 16, though largely blinded and unable to hear because of the water buildup.
The troubleshooting has been hindered by the close proximity and intricacy of the suspect PLSS hardware, said Contella. The filter, for instance, may have trapped fine particles in the water flow that diverted the coolant into the air ventiliation system. Working with small components in the absence of gravity is also a limiting factor.
"It's difficult to pinpoint the issue when you can't just go grab the items off the suit, then have your experts take a look at them," noted Contella. "It takes a lot of effort to get them out."