NASA is working with Elon Musk's SpaceX to redesign part of the fuel system for the company's Falcon 9 rockets and then will demand at least seven successful unmanned flights before allowing astronauts on board.
Those requirements, spelled out during a House space subcommittee hearing Wednesday, highlight safety and schedule challenges confronting the National Aeronautics and Space Administration's commercial crew-transportation program.
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With routine flights ferrying U.S. astronauts to the orbiting international space station slated to begin in fall of 2019, the agency's top outside safety watchdog has raised new questions about potential hazards in testimony to the House panel. The safety of internal helium tanks, needed to keep fuel flowing properly during ascent, has been identified as one of the most prominent unresolved risks for SpaceX.
Space Exploration Technologies Corp., as Mr. Musk's company is called, and Boeing Co., which is separately developing what are intended to be privately operated spacecraft, both face the "very real possibility of future schedule slips," said Patricia Sanders, who heads NASA's independent Aerospace Safety Advisory Panel.
Commenting on the likelihood that neither company will be able to fully comply with all of NASA's longstanding safety standards, Ms. Sanders said ending current U.S. reliance on Russian capsules for crew transportation may "require decisions to accept a higher risk" on next-generation U.S. systems than anticipated.
The hearing also disclosed that the statistical limit for a "failed mission" remains approximately one in 55 launches, despite several years of intense development, NASA expenditures of about $5 billion and significant additional investment by the two companies. That limit applies to mission failures in which the vehicle doesn't reach the space station but the crew uses emergency procedures to survive.
NASA's statistical standard for crew fatalities is no greater than one in 270 flights, though Ms. Sanders and NASA officials have signaled neither Boeing nor SpaceX is on track to meet that precise mandatory benchmark.
In the end, on-orbit inspection safeguards combined with certain NASA waivers are expected to provide the green light for initial crewed flights.
During her testimony, Ms. Sanders also said that given the agency's expertise and history of close collaboration with the two companies, "NASA will be able to make a reasonable decision" to balance mitigating hazards while avoiding extensive delays.
The hearing was marked by repeated lawmaker comments expressing concern about the fall 2019 deadline to start ferrying astronauts to the space station.
In his prepared opening statement, Texas Republican Rep. Brian Babin, the subcommittee chairman, said, "We are here today looking at not one, but two companies that are behind schedule, may not meet safety and reliability requirements and could even slip into cost overruns."
Mr. Babin added that the challenges heighten the "risk that the [space station] cannot be successfully or gracefully transitioned" out of service in the middle of next decade.
SpaceX's top flight-reliability official told the panel the company is working in tandem with NASA to fully understand and alleviate risks associated with the helium tanks, which have been identified as the cause of two previous accidents.
William Gerstenmaier, NASA's top human-exploration official, testified that a redesign of the tanks is under way. "We will identify the most likely contributors" that led to the previous catastrophic accidents, he said.
He also said NASA is methodically assessing, but hasn't signed off on, controversial SpaceX plans to load fuel into its rockets on the launchpad, while astronauts are strapped into the capsule on top.
John Mulholland, who oversees Boeing's commercial crew program, testified that Boeing considered but rejected a similar fueling procedure years ago. "We never could get comfortable with the safety risks," he said. The Boeing official said his experts continue to have "significant concerns" about the procedure.
Hans Koenigsmann, the SpaceX reliability official, countered that his company's unorthodox fueling procedures provide additional safety partly because ground personnel leave the pad during the process.
The pending decision means NASA managers "are about to learn a bunch of new lessons" about managing risk while giving industry the lead in designing and operating crew vehicles, NASA's Mr. Gerstenmaier told the panel.
(END) Dow Jones Newswires
January 17, 2018 18:59 ET (23:59 GMT)