Safety panel raises concerns about crew on first SLS launch
WASHINGTON — A NASA independent safety committee wants NASA to provide a “compelling rationale” for putting astronauts on the first flight of the Space Launch System, a proposal NASA is currently studying.
In a statement at the beginning of the Feb. 23 meeting of the Aerospace Safety Advisory Panel (ASAP), chairwoman Patricia Sanders said that if NASA decides to put a crew on the first SLS/Orion launch, Exploration Mission 1 (EM-1), it must demonstrate that there is a good reason to accept the higher risks associated with doing so.
“We strongly advise that NASA carefully and cautiously weigh the value proposition for flying crew on EM-1,” she said. “NASA should provide a compelling rationale in terms of benefits gained for accepting additional risk, and fully and transparently acknowledge the tradeoffs being made before deviating from the approach for certifying the Orion/SLS vehicle for manned spaceflight.”
“If the benefits warrant the assumption of additional risk,” she added, “we expect NASA to clearly and openly articulate their decision-making process and rationale.”
NASA announced Feb. 15 that it was beginning a study of the potential of adding a crew to EM-1. Under current plans, that mission, scheduled for launch in late 2018, would fly without a crew, with the first crewed flight, EM-2, planned for no earlier than 2021.
That study is in progress and is expected to be completed by late March or early April. “We’re going back and reevaluating the trades of why we decided what we did” regarding not flying a crew on EM-1, said Jason Crusan, director of advanced exploration systems at NASA Headquarters, during a Feb. 23 panel on human spaceflight held by the Royal Aeronautical Society at the British Embassy here. “There’s many reason why we decided to do that, a lot of the related to risk posture, and a lot of them related to budget realities.”
Under the current approach, NASA would fly a relatively demanding mission on EM-1 lasting more than 20 days, “really pushing the limits of where Orion and SLS can actually perform,” Crusan said. EM-2, with a crew, would be a more conservative mission to test the performance of the life support system. That approach, he said, would be reconsidered if a crew flies on EM-1.
“If you put crew on the first mission, you’re not going to go to distant retrograde orbit and push the limits of the vehicle on the very first flight,” he said. “So do you actually make less progress, or more progress? That’s the trade we have to go through.”
The study, Crusan said, would also look at the effects putting a crew on EM-1 would have on later missions, including plans to fly co-manifested payloads on EM-2 using additional capacity on the upgraded version of the SLS that will fly starting on EM-2. Accelerating the first crewed flight, he cautioned, may not avoid the gap that currently exists between EM-1 and EM-2 because of “uncompressible” elements of infrastructure that need to be developed.
Should NASA decide to put a crew on EM-1, he added, the launch date for the mission would slip from late 2018. The Orion capsule for that mission is already under construction without some of the life support systems that would be needed if the mission was crewed. “We’d actually have to undo what we’ve been manufacturing and modify the vehicle for the life support system that we require,” he said.
At the ASAP meeting, members noted that even if EM-1 remains an uncrewed mission, NASA is facing some issues that could create cost or schedule problems. Among them is damage suffered by Michoud Assembly Facility in New Orleans, where elements of Orion and the SLS core stage are built, from a Feb. 7 tornado.
“They still do estimate that the damage will cost us a couple of months in terms of the schedule,” said ASAP member Donald P. McErlean at the meeting, recounting a briefing given to the panel earlier in the week. He noted that no critical infrastructure, like a friction stir welding system used for making the core stages, suffered serious damage from the storm that would have resulted in longer delays.
McErlean said the program has also uncovered a problem with the solid rocket boosters. Engineers found an “anomaly” in the interaction between the propellant and a layer separating the propellant from the motor’s liner. “They found that, under certain heat conditions, there can be some outgassing of this layer, and it cause voids” in the propellant, he said.
He added it wasn’t clear if this problem would prevent the motors from being flown, but even if they cannot, a fix to avoid the problem has already been put in place for other motors being cast for the boosters. “There will be no delay in EM-1 because of this problem,” he said, since they can “pull forward” motors already being cast for EM-2 instead. “It could be a cost driver if they had to be recast.”