The US space agency has placed a “no-go” on extravehicular activity (EVA) outside the ISS due to a persistent problem of water intrusion into the bulky spacesuits used for them, called extravehicular mobility units (EMUs).
"Until we understand better what the causal factors might have been during the last EVA with our EMU, we are no-go for nominal EVA (spacewalk)," Dana Weigel, deputy manager of the space station program at NASA’s Johnson Space Center, said at a Tuesday press conference. "So we won't do a planned EVA until we've had a chance to really address and rule out major system failure modes."
The decision came after a March 23 spacewalk by European Space Agency (ESA) astronaut Matthias Maurer, after which a circle of water and dampness was found inside his helmet following the completion of the spacewalk. Nearly half of his visor was coated in water, but ground control said there was "no danger" to him.
"It's a little bit difficult to judge the volume because it's spread across the front of his visor," NASA astronaut Kayla Barron, who spotted the water, said about the incident. "But I think we should accelerate the steps to get him out of his suit here."
The problem has been known since at least 2013, when ESA astronaut Luca Parmitano nearly drowned in his EMU when his helmet rapidly filled with 1.5 liters of water during a spacewalk. According to the NASA report, the problem wasn’t with his drinking water system, but one of several other water-based systems in the massive EMU suits that keep the astronaut cool and store urine.
Since then, NASA has installed small sponges to soak up any moisture that might get into the helmet.
NASA hasn’t said if the March problem is believed to be related to the previous one.
"So far, we haven't found anything unusual," Weigel said of inspections aboard the space station. "We're looking for any obvious signs of contamination or fouling or something else that might have gotten into our system. We're not seeing that yet."
The space agency plans to send Maurer’s suit back to Earth in July for further study.
According to Space.com, the EMU suits date to the late 1990s, and as of 2017, only 11 of the 18 EMUs were available for use on the ISS. NASA is developing several new suits, including the Artemis lunar spacesuits intended for a future manned mission to the Moon.