How a Tiny Bit of Lacquer Grounded New Falcon 9 Rockets For a Month
On October 2, SpaceX automatically aborted the launch of a Falcon 9 rocket (with just two seconds left in the countdown) after two of its first-stage engines ignited early. Investigating the problem ended up delaying the October 31st launch of four astronauts to the International Space Station until November 14, reports Ars Technica, citing a teleconference with SpaceX's Hans Koenigsmann. "Had the abort not triggered, it is likely that nothing bad would have occurred, but Koenigsmann said that under certain extreme scenarios, rattling from an early ignition may cause significant damage to the Merlin engines." SpaceX technicians removed the two engines and shipped them from Florida to the company's test site in McGregor, Texas, where they were able to replicate the problem. They found that a relief valve within the gas generator — a tiny rocket within the engine that starts up and powers its machinery — was clogged with a masking lacquer akin to nail polish. They were able to show that removing the lacquer from the vent hole allowed the engines to start up normally. This lacquer is applied during an anodizing process to treat aluminum components of the gas generator. It is supposed to be subsequently removed, but in the case of these two engines, a tiny amount of the material had been trapped within a bore hole less than 2mm across... After this, SpaceX inspected other engines across its fleet (the company inspected new boosters only, as Falcon 9 first stages that have already flown are not subject to this issue). SpaceX found that two of the engines on the Falcon 9 rocket that will be used for the Crew-1 launch also had this problem. Those two engines are now being swapped out for new Merlins... This lacquer issue came as a surprise given that SpaceX has literally launched hundreds of new Merlin 1D rocket engines over the last decade and, until now, had not seen this problem with the masking agent. "It's certainly possible that we had cases of it earlier, and they were appreciably so harmless that we completely missed them," Koenigsmann said. It is also possible that a small process was changed so that all of the lacquer was not removed, as this particular treatment is done by an outside vendor. But, he admitted, "It's difficult to explain how this works for so many years and then, suddenly, you see this coming up in the data." What Koenigsmann seems confident in is that the issue will not occur again.
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