As the two companies developing commercial crew vehicles prepare for test flights in the next 12 months, a NASA official said the agency expects those companies to be able to meet, or come close to, stringent safety requirements for those spacecraft.

At a Nov. 29 meeting of the NASA Advisory Council's human exploration and operations committee, Lisa Colloredo, deputy program manager for NASA's commercial crew program, said Boeing and SpaceX were making good progress towards achieving a "loss of crew", or LOC, requirement established by NASA at the beginning of the program.

The LOC requirement states that the odds of an accident killing or causing serious injury to a crewmember be no more than 1 in 270 flights for a 210-day mission at the International Space Station. That covers all aspects of the mission, including launch and re-entry.

"We have a very difficult LOC requirement to meet, and we knew that when we going in," Colloredo said. The 1-in-270 LOC requirement for commercial crew is more stringent than the 1-in-90 value at the end of the shuttle program. "I would say that we've made a lot of progress, and the providers have both done a lot of redesign work to improve their LOC numbers."

Those changes, she said, include "more robustness" to the thermal protection systems on the spacecraft and additional parachute testing. "It's served its purpose of getting the right look at the top drivers for LOC," she said, including making design changes to improve those values.

Colloredo said she expected that both companies would meet the 1-in-270 LOC requirement, or come close enough that NASA would be willing to accept the vehicles as safe enough for its astronauts. "It's pretty likely in the end that SpaceX and Boeing will come in with their evidence that they meet the requirement or close to it," she said. Ultimately, she said, it will require NASA due diligence to either confirm they meet the requirement or be willing to accept a variance from the requirement in a specific area.

Another NASA committee has also monitored the ability of Boeing and SpaceX to meet the LOC requirement. At the October meeting of the Aerospace Safety Advisory Panel (ASAP), committee members discussed the progress both companies were making on addressing key risk issues for their systems.

"The ASAP believes that NASA is judiciously continuing to address the risk drivers with the providers for the most serious scenarios through continued analysis, modeling, testing, and design development. It remains challenging," the panel noted in the minutes from that meeting. "Nevertheless, the focus on worst case scenarios has driven positive design decisions for both providers, as well as other aspects such as increases in systems testing for some of the systems that carry notable risks."

The biggest challenge, ASAP reported, was meeting micrometeoroid and orbital debris protection requirements. NASA was working to improve the modeling of the risks posed to those spacecraft from micrometeoroids and orbital debris through experiments mounted on the station as well as on Dragon cargo spacecraft.

At the NASA Advisory Council committee meeting, Colloredo said the LOC requirement was the biggest programmatic issue facing the overall program, but not the only one. She said NASA was assessing if it had included all the costs of various government-provided services for commercial crew missions. It was also working to ensure that search and rescue training for Air Force personnel supporting commercial crew launches would be ready in time for the first missions.

Both companies are working to schedules that call for both uncrewed and crewed test flights in 2018, although later in the year than previously planned. SpaceX is planning an uncrewed test of its Crew Dragon in April, previously scheduled for February. The crewed test flight is now planned for August, instead of June. Between the two flights will be an in-flight abort test.

Boeing's uncrewed test flight of its CST-100 Starliner is now scheduled for August, two months later than previously planned. The crewed test flight has shifted from August to November, although the company said earlier this fall that the crewed test flight might slip into early 2019.

"We're making a lot of progress with the providers," Colloredo said. "We're getting prepared for flight and we acknowledge that we have a lot of work ahead of us."

Source:
courtesy of SPACE

by Jeff Foust

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