ORLANDO — Boeing and SpaceX, who have been struggling to meet safety thresholds established by NASA for commercial crew vehicles, now believe their vehicles can meet those requirements as they prepare for test flights scheduled in the next several months.

A key issue in the development of Boeing’s CST-100 Starliner and SpaceX’s Crew Dragon has been their ability to meet a “loss-of-crew” requirement — a measure of the probability of death or permanent disability of one or more people on a spacecraft during a mission — of 1 in 270. The companies have faced problems meeting that requirement, significantly more stringent than that of the space shuttle.

“The number one safety-related concern for the program is the current situation with respect to the estimate of loss of crew,” Donald McErlean, a member of NASA’s Aerospace Safety Advisory Panel, said at a meeting of the panel last year. The U.S. Government Accountability Office has also warned in reports that the companies were having problems meeting that loss-of-crew requirement.

However, during a panel discussion at the American Institute of Aeronautics and Astronautics (AIAA) Space Forum here Sept. 18, executives of the two companies said they now believed their vehicles met that and related safety requirements.

John Mulholland, vice president and program manager for the commercial crew program at Boeing, said the company was assessing three separate requirements, including the overall loss of crew as well as ascent and entry risks and loss of mission. “Our teams have been working that for a number of years,” he said, noting those analyses have driven changes to the vehicle design, such as increased micrometeoroid and orbital debris protection.

“Where we are now is that our analysis shows we can exceed the NASA requirements for all three of those criteria,” he said.

Benjamin Reed, director of commercial crew mission management at SpaceX, said his company was in a similar situation. “We’re looking right now to be meeting the requirements,” he said.

Kathy Lueders, NASA’s commercial crew program manager, didn’t confirm that the companies have, in fact, met those safety requirements. “We’re learning from a NASA perspective about how to understand the assessments that we’re getting from each of the contractors and how to apply it,” she said. “We at the NASA team are assessing the modeling that each of the providers has done.”

She cautioned, though, about using the loss-of-crew figure as the sole figure of merit of the safety of either vehicle. “I sometimes struggle when people say that the loss-of-crew number is the safety number,” she said. “I don’t believe that that’s true.”

Test flight preparations

Those assessments come as test flights for both companies’ vehicles are approaching. Updated schedules released by NASA in early August said that SpaceX planned to perform an uncrewed test flight in November, followed by a crewed flight in April 2019. Boeing would perform its uncrewed test flight late this year or early next year, with a crewed flight in mid-2019.

SpaceX Chief Executive Elon Musk, though, hinted at a slight delay in his company’s schedule during the Sept. 17 announcement of the company’s plans to fly a Japanese billionaire and a group of artists around the moon on the company’s Big Falcon Rocket (BFR) under development.

“We’re hoping to do a test flight of Dragon 2 in December, and then a crewed flight next year, hopefully in the second quarter of next year,” he said, calling commercial crew the “top priority” for the company.

Reed declined to comment on any potential slip in that schedule. “We’re working closely with NASA to find the right dates,” he said after the panel. He said during the panel that the Dragon that will fly that initial uncrewed test is in Florida for final integration work, while the first and second stages of the Falcon 9 that will launch it were being tested at the company’s McGregor, Texas, test site. Final certification reviews for that mission, he said, have been scheduled with NASA.

Mulholland said Boeing has three Starliner vehicles in various stages of development, one each for the uncrewed and crewed test flights and a third that will be used for a pad abort test that will take place early next year between the two flights. Construction of the two Atlas 5 rockets by United Launch Alliance for those test flights are also almost complete. The schedule announced in August for the Starliner test flights is unchanged, he said after the panel.

Reusing crew vehicles

The panel discussion also addressed plans by both companies to reuse their crew vehicles. That issue gained attention last month when, at an Aug. 27 meeting of the human exploration and operations committee of the NASA Advisory Council, Lueders said SpaceX would use a new vehicle for each of its crewed flights. “Right now, what they proposed was a new vehicle every time for us,” she said then.

At the AIAA panel, Reed said SpaceX still had plans to reuse its Crew Dragon vehicles, as it does now with the cargo version of the spacecraft. “Crew Dragon, just like Cargo Dragon, was designed from the beginning to be a fully reusable vehicle, and it’s certainly still our intent” to reuse them. That includes the vehicle flying the first, uncrewed demo mission, which will be quickly turned around for use on an in-flight abort test that will take place before the crewed flight test.

For the operational commercial crew missions, Reed said SpaceX plans to use new vehicles for each mission initially as it builds up a “stable” of vehicles. The company would then work with NASA on how to certify those vehicles for reuse.

That approach, he said, is similar to the cargo version of Dragon, where SpaceX initially used new vehicles for all its flights but, after discussions with NASA, won approval for reuse of vehicles, which now account for all recent Dragon cargo missions. “That was a very successful approach,” he said. “We’re following the same basic plan.”

Boeing plans to reuse its Starliner crew capsules from the beginning. Mulholland said the company has defined what inspections, tests and vehicle refurbishments will be needed for the capsule between flights, a process he said should take about four months.

That desire to reuse the capsule drove Boeing’s decision to land the spacecraft on land, at one of five selected locations in the western United States, rather than splashing down at sea. “For us, in our baseline, we need to land on land to support capsule reuse,” he said. Starliner does have the ability to splash down in an emergency, but “if we end up aborting and ditching into the ocean, then we wouldn’t reuse that capsule.”

Reed said that, given SpaceX’s experience with cargo Dragons, landing in water was not a major obstacle to reusability. “It is different, for sure,” he said of water landings. “I don’t know if it’s much more difficult, though.”

Non-NASA markets

A key foundation of the commercial crew program is that NASA would not be the only customer for these vehicles, with the companies free to use them for other customers and thus spreading out costs. Both Boeing and SpaceX said they’re optimistic about the non-NASA demand for those vehicles.

“I think there’s a lot of opportunity out there,” Reed said, including commercial missions to the ISS and to other destinations in low Earth orbit that have been proposed but yet to be developed. “We see a lot of opportunity out there. We’re working on a number of interesting opportunities with various commercial partners,” he said, not identifying any specific opportunities.

Mulholland said a Boeing marketing team has been “actively engaged” with other countries and entities about potential commercial Starliner flights. However, he said the company is holding off on deals until the Starliners are flying for NASA. “I’ve been hesitant to sign anything, or for the company to sign up, until we actually go fly,” he said.

Quelle: SN