Enlarge /. Nine Merlin engines propel the first stage of a Falcon 9 rocket.
NASA and SpaceX confirmed on Wednesday that they are targeting November 14th for the launch of the Crew 1 mission that will bring four astronauts to the International Space Station.
Originally scheduled for launch on Halloween, NASA delayed the launch after an engine problem aborted the attempt to launch a Falcon 9 rocket on October 2 at T-2 seconds with a GPS III satellite for the US Air Force.
During a conference call with reporters on Wednesday, SpaceX's Hans Koenigsmann explained what happened to the launch canceled on October 2nd and what was being done to address the problem in the future.
Two of the nine engines of the first stage of the rocket ignited in early October during the launch attempt, which triggered an automatic shutdown of the engines. (If the abort hadn't triggered, probably nothing bad would have happened, but Koenigsmann said that under certain extreme scenarios, the rattle of an early ignition could have caused significant damage to the Merlin engines.)
Replicating the problem
SpaceX technicians removed the two motors and sent them from Florida to the company's test site in McGregor, Texas, where they were able to replicate the problem. They found that a pressure relief valve in the gas generator – a tiny rocket in the engine that starts and powers its machines – was clogged with a masking varnish that looked like nail polish. They were able to show that by removing the paint from the vent hole, the motors could start normally.
This paint is applied during an anodizing process to treat aluminum components of the gas generator. It is supposed to be removed later, but on these two engines a tiny amount of the material was trapped in a borehole less than 2mm in diameter.
"With that in mind, it was a really great find that allowed us to fix something that is very subtle but can obviously have a negative impact on engine operation," said Koenigsmann.
SpaceX then inspected other engines in its fleet (the company only inspected new boosters as the Falcon 9's already flown first stages are not affected by this problem). SpaceX found that two of the Falcon 9 rocket's engines used to launch the Crew-1 also had this problem. These two engines are now being exchanged for new Merlins.
The new plan
If everything goes according to plan, SpaceX will launch two new first stages of Falcon 9 before Crew 1: the GPS III mission on November 4th and the Sentinel 6 mission for NASA on November 10th. Assuming those launches go well, NASA will likely stick with them on November 14 for the Crew 1 mission, which will feature NASA astronauts Michael Hopkins, Victor Glover and Shannon Walker alongside Japan Aerospace Exploration Agency's mission specialist, Soichi Noguchi, to be sent to the International Space Station. Her crew Dragon would meet with the space station approximately 8.5 hours after launch at 7:49 p.m. EST (00:49 UTC on November 15).
This paint problem was surprising as SpaceX had literally released hundreds of new Merlin 1D rocket engines in the past decade and hadn't seen this masking agent problem before.
"It is certainly possible that we had cases before, and they were noticeably so harmless that we completely missed them," said Koenigsmann. It is also possible that a small process has been changed so that not all of the paint has been removed as this particular treatment is done by an outside provider. But he admitted, "It's difficult to explain how this works for so many years and then all of a sudden you see it in the data."
Koenigsmann seems confident that the problem will not recur. The company's engineers now get it, know how to look for it, and won't be surprised again. "Rocket science is tough and requires great attention to detail," he said. "It's always a challenge. It's always difficult. You have to be on your toes to do it right."