CAPE CANAVERAL, Fla. - Two US astronauts finished a 6-1/2-hour spacewalk on Wednesday to prepare parking spots for new commercial space taxis then discovered water had leaked into a spacesuit helmet, a problem that led to the near-drowning of another astronaut in 2013, officials said.
Unlike the 2013 incident, astronaut Terry Virts was not in any danger, said NASA mission commentator Rob Navias.
Virts discovered a small amount of water was floating in his helmet after he and spacewalk partner Barry "Butch" Wilmore had returned to the station's airlock following a successful outing.
"I really can't see any immediate danger," station flight engineer Samantha Cristoforetti of Italy radioed to ground control teams at Mission Control in Houston.
In July 2013, NASA hastily aborted a spacewalk when the helmet worn by Italian astronaut Luca Parmitano began filling with water. By the time he returned to the airlock, his vision was blocked and communications equipment had stopped working.
NASA suspended spacewalks while engineers searched for the cause of the problem.
Engineers do not yet know why Virts' helmet leaked, nor if the issue is related to the previous problem, Navias said.
NASA managers plan to meet on Friday to decide whether to proceed with Sunday's outing, he added,
During Wednesday's spacewalk, the astronauts removed a cover protecting the space shuttle's docking port, one of two sites being reconfigured for new spaceships under development by Boeing and Space Exploration Technologies, or SpaceX.
The work paves the way for the arrival later this year of two international docking port adapters, which will be installed during four more spacewalks NASA plans in 2015.
The spacewalkers finished routing two power and data cables on Wednesday then greased the grapple fixture at the end of the station's robot arm.
They also prepared the Tranquility connecting node for the September arrival of an experimental inflatable habitat built by privately owned Bigelow Aerospace. Sunday's spacewalk is devoted to setting up a new communications system for the visiting vehicles.
The station, a partnership of 15 nations, is a collection of laboratories and platforms for materials and life science experiments, Earth studies, physics and other investigations that take advantage of the microgravity environment and unique vantage point of space. The Russian space agency Roscosmos said on Tuesday it would remain part of the international outpost until 2024, a four-year extension proposed by the United States.