After six months of painstaking work, the NASA Mishap Investigation Board (MIB) has reported its findings, including root and proximate causes, of an incident in July 2013 when water unexpectedly intruded into the helmet of astronaut Luca Parmitano, whilst outside the International Space Station (ISS). As a result, the planned 6.5-hour EVA-23 was terminated, and Parmitano and his spacewalking partner, Chris Cassidy, were summoned back to the station’s Quest airlock after just 92 minutes. At its worst, the water entered Parmitano’s eyes, nose, and mouth, restricting his visibility, hearing, and breathing and, in the words of the MIB, created the harrowing condition of “EVA crewman exposed to potential loss of life.” Moreover, the board’s findings have illustrated worrying cultural and organizational issues within NASA itself.
At 7:57 a.m. EDT on 16 July 2013, Expedition 36 crewman Cassidy (EV1) and Parmitano (EV2) left the Quest airlock on what should have been a 6.5-hour spacewalk to attend to numerous tasks outside the International Space Station (ISS). As noted in AmericaSpace’s EVA-23 article, their work began normally and the men split up to begin their first activities. Cassidy moved to the Z-1 truss to reconfigure Y-Bypass jumper cables, which he had begun on EVA-22, on 9 July, whilst Parmitano set to work to route data and Ethernet cables in readiness for the arrival of Russia’s Nauka Multi-Purpose Laboratory Module (MLM). At 8:42 a.m.—some 44 minutes into EVA-23—Parmitano made the first reference to water inside his “Snoopy” communications skullcap, on the back of his head.
He was quickly joined by Cassidy, who verified that water was indeed visible inside the helmet. Initially suspecting a coolant leak, Parmitano reduced the flow rate and an assumption that his Disposable In-Suit Drink Bag (DIDB) had leaked seemed unlikely as it was already dry. The situation rapidly deteriorated. By 9:06 a.m., after Parmitano reported that the amount of water had increased and migrated from the back of his head onto his face and into his eyes, nose, and mouth, Flight Director David Korth terminated EVA-23 and instructed the spacewalkers to return to the airlock. Cassidy handled the closure of the hatch, which was sealed at 9:26 a.m., and repressed back up to ISS ambient pressure about 11 minutes later. At 9:38 a.m., the hatch connecting the outer “crew lock” with the inner “equipment lock” was open and Expedition 36 crew member Karen Nyberg removed Parmitano’s helmet, releasing a flurry of water droplets.
During his debriefing, the Italian astronaut—flying as a representative of the European Space Agency (ESA)—explained that he had experienced impaired visibility, hearing, and breathing. In an ESA blog, he wrote in terrifying detail of its impact on his movements: “As I move back along my route towards the airlock, I become more and more certain that the water is increasing,” Parmitano described. “I feel it covering the sponge on my earphones and I wonder whether I’ll lose audio contact. The water has also almost completely covered the front of my visor, sticking to it and obscuring my vision … At that moment, as I turn ‘upside-down’, two things happen: the Sun sets, and my ability to see—already compromised by the water—completely vanishes, making my eyes useless; but worse than that, the water covers my nose—a really awful sensation that I make worse by my vain attempts to move the water by shaking my head. By now, the upper part of the helmet is full of water and I can’t even be sure that the next time I breathe I will fill my lungs with air and not liquid … ”
With his visibility thus restricted, Parmitano was forced to “feel” his way back toward the airlock. “When returning to the airlock,” the MIB report noted, “EV2 had to rely on manual feel of his safety tether’s cable for pathway directions.” In the aftermath of the incident, it was determined that about 0.26-0.39 gallons (1.0-1.5 liters) of water had entered the astronaut’s helmet. Yet the danger was not over. During the drying of the two space suits after EVA-23, a vacuum cleaner was used and unexpectedly removed oxygen from the secondary high-pressure oxygen tank. This created a potentially hazardous mixture of electricity and pure oxygen, which could have ignited flammable materials in and around the vacuum cleaner. Fortunately, no such incident occurred. However, in addition to the Primary Undesired Outcome of “EVA crewman exposed to potential loss of life”—with specific reference to “risk of asphyxiation, impaired vision and a compromised ability to communicate”—the MIB highlighted a Secondary Undesired Outcome: “The ISS crew was exposed to a potential fire hazard, due to inadvertent activation of the suit’s secondary oxygen pack during drying-out activities.”
Less than a week after EVA-23, on 22 July 2013, Bill Gerstenmaier, NASA’s Associate Administrator for the Human Exploration and Operations Directorate, assembled the five-person investigative board, tasked with identifying the causes of the incident. Chaired by Chris Hansen, the ISS Program’s chief engineer at the Johnson Space Center (JSC) in Houston, Texas, the board included astronaut Mike Foreman, ISS safety and mission assurance lead Richard Fullerton, human factors specialist Sudhakar Rajula, and NASA Engineering and Safety Center (NESC) chief engineer Joe Pellicciotti. “I recognize that this activity will be different as the affected crew and hardware will not be directly available,” wrote Mr. Gerstenmaier in his instruction to assemble the MIB. “The lack of directly available physical evidence will require this board to work closely with the ISS Program and its ongoing activities. This information will be used to substantiate any board findings, but should not delay any board proceedings.”
The EVA-23 incident was classified as a “High Visibility Close Call,” and the MIB’s report provides harrowing reading and offers a measure of insight into how close Parmitano came to suffering serious injury or even death. In summary, the board noted that the mishap evolved from a blockage of drum holes in the fan pump separator of Parmitano’s suit, caused by inorganic materials, which resulted in water spilling into the vent loop. “The source of the inorganic materials blocking the water separator drum holes had not been experienced during an EVA before,” it was stressed, “and is still undergoing a concurrent investigation.”
Of equal, if not greater, weight was that the five root causes and three proximal causes of the incident, as identified by the MIB, offer a worrying insight into the kind of cultural and organizational problems which doomed Challenger and Columbia. Five Root Causes for the incident were identified. The first was that the ISS Program’s emphasis was upon maximizing crew time for science and utilization of the space station. “The strong emphasis on utilization was leading team members to feel that requesting on-orbit time for anything non-science related was likely to be denied,” the MIB explained. “The danger with that thought process is that lower-level team members were in effect making risk decisions for the Program, without necessarily having a Program-wide viewpoint or understanding the risk trades actually being made at a Program level.”
The second Root Cause brought to light an event about which little was known: At the end of EVA-22, a week earlier, on 9 July 2013, Parmitano removed his helmet and between 0.13-0.26 gallons (0.5-1.0 liters) of water was found. Cassidy reported that he had not seen any water during the EVA itself or during the repressurization of the airlock, when the spacewalkers were facing each other. They concluded that it was most likely caused by Parmitano inadvertently pinching the valve of his drink bag with his chin, thereby introducing water into the helmet. Mission Control accepted the crew’s judgement. The astronauts cleaned up the residual water and the ground team instructed them to use a new drink bag for EVA-23. There was no discussion of water in the helmet during briefings on 11 July and 15 July 2013, ahead of EVA-23. In its summary, the MIB noted that this automatic perception that Parmitano’s drink bag must have leaked—coupled with the EVA community not challenging this determination or investigating it further—contributed to a failure in identifying and resolving the issue before EVA-23.
Thirdly, flight controllers felt that the process of reporting anomalies was so intense that invoking it would lead to a long investigation which would interfere with necessary work on EVA-23. It was considered “that this issue would likely not uncover anything significant enough to justify the resources which would have been spent.” Additionally, the board noted that ground teams did not fully understand the behavior of water inside a space suit, simply assuming that it would cling to the helmet’s inner surface, rather than to the spacewalker’s head. In essence, “the significant hazard it presented was not anticipated.” Finally, interviews with ground personnel and reviews of earlier space suit performance records indicated that some water entering the helmet was considered normal. “Despite the fact that water carryover into the helmet presented a known hazard of creating eye irritation, due to its interaction with anti-fog agents, and also presented a potential fogging hazard,” the MIB explained, “the ground teams grew to accept this as normal behavior.” It was not perceived to be a hazardous condition, and “when the water began entering EV2’s helmet, the ground team discussed anti-fog/eye irritation concerns and visibility concerns; however, a more hazardous condition was not expected because the presence of water in the helmet had been normalized.”
In addition to these Root Causes, three further Proximate Causes—which directly caused the undesired outcome and whose elimination or modification might have prevented it—were found by the MIB. Firstly, the ISS Program had “misdiagnosed” the nature of the water leak at the end of EVA-22, and it was “not determined to be a constraint to EVA-23.” The water which emerged in Parmitano’s helmet during EVA-23 originated “somewhere behind his head, near the neck/lower heard” area, which the MIB described as having “created a condition that was life-threatening.” Troublingly, Mission Control did not terminate the spacewalk as soon as the water was reported. “The MIB determined that the time between first mention of water in EV2’s helmet and the call the terminate the EVA was roughly 23 minutes,” it was noted, and “the fact that no one on the ground or the EVA crew immediately recognized the severity of the hazard and terminated the EVA resulted in the crew member being exposed to an increased level of risk.”
Nevertheless, the MIB praised Parmitano’s “calm demeanor,” which “possibly saved his life,” and added that Mission Control also performed well, based on the knowledge that they had available at the time. “The team applied what they did know to the symptoms they saw during EVA-23,” it was added. “Several possible causes were discussed in real-time between the ground team and the crew members. Ultimately, the team came to the correct conclusion that the water in EV2’s helmet was more serious than anything that could be explained by previous experience and the EVA was terminated.” In addition to the Primary and Secondary Undesired Outcomes, the five root and three proximate causes, the MIB identified 19 intermediate causes, 30 observations, 13 contributing factors, and made 49 recommendations.
In the aftermath of EVA-23, all further U.S.-based spacewalks were placed on indefinite hold, pending the outcome of the MIB’s investigation. However, in December 2013, a pump module failure necessitated two EVAs by Expedition 38 astronauts Rick Mastracchio and Mike Hopkins, neither of which showed any water intrusion problems. “The spacewalks to repair the ISS pump module that occurred in late 2013,” it was noted, “was planned with full co-operation between the ISS Program and the MIB.” Looking ahead to 2014, current plans envisage three EVAs in the July-August timeframe—by which time Expedition 40 crewmen Steve Swanson, Reid Wiseman, and Alexander Gerst will be aboard the U.S. segment of the ISS—for maintenance and other activities.