WASHINGTON — Boeing and United Launch Alliance say they remain committed to launching future CST-100 Starliner commercial crew missions on Atlas 5 missiles, even after that vehicle is effectively retired for other missions.
Similar to the Orbital Flight Test (OFT) mission in late 2019, an Atlas 5 Starliner launched on the OFT-2 mission on May 19. Boeing has a contract with ULA to launch both the Crew Flight Test (CFT) mission, the first Starliner mission to carry astronauts, and six operational or post-certification missions on Atlas 5 vehicles.
With NASA plans to alternate between Boeing’s Starliner and SpaceX’s Crew Dragon for International Space Station crew rotational missions once Starliner is certified, each flying once a year, it means Atlas 5 launches from Starliner will extend well into could continue into the second half of the decade. ULA, which has stopped selling Atlas 5 launches, has previously talked about phasing out Atlas 5 in favor of Vulcan Centaur around the middle of the decade.
NASA’s Aerospace Safety Advisory Panel at its May 12 meeting expressed concerns about how delays in Starliner development could affect the Atlas 5’s availability. “Any further delays to Starliner launches would add to these concerns,” said David West, a member of the panel, adding that certifying Vulcan for manned launches “could take years.”
At a prelaunch briefing on May 17, NASA and ULA officials said all remaining Starliner missions under contract, including CFT and the six post-certification missions, would remain on Atlas 5 regardless of schedule.
“From a resource perspective, we’ve taken steps to protect the talent and ensure we retain the critical skills to fly an Atlas as late as needed,” said Gary Wentz, vice president of government and commercial programs at ULA. “We are in talks with Boeing and other customers about that possibility.”
But even at the rate of one mission per year and with no other customers for Starliner, the Atlas vehicle stock would be exhausted before the ISS’s planned retirement in 2030. or to enable other flights for Boeing,” said Steve Stich, NASA commercial crew program manager. “We would look for a new system.” He added that NASA would support human assessment of a new system “when Boeing and ULA are ready.”
ULA has not announced any plans to human-grade Vulcan. However, Wentz said “more than 90%” of the Vulcan Centaur hardware already flies on Atlas 5, simplifying any human review process. A major change, he said, would be moving the emergency detection system currently on Atlas, which alerts the spacecraft of problems with the missile to activate the break-down system, to Vulcan. The other big change, he said, would be the human assessment of the BE-4 engines used on Vulcan’s first stage.
Boeing may not be the only customer, or even the first, seeking a human assessment of Vulcan. Sierra Space plans a manned version of its Dream Chaser cargo spacecraft. The cargo version will be launched on Vulcan missiles from 2023 and a manned version could be ready as early as 2026.