The Starlink 10-9 mission takes off early Saturday morning from Florida.
Enlarge / The Starlink 10-9 mission takes off early Saturday morning from Florida.
SpaceX Webcast
Early Saturday morning, at 1:45 a.m. local time, a Falcon 9 rocket lifted into orbit from its launch site at the Kennedy Space Center in Florida.
From a technical standpoint, this was a routine mission; after all, it was SpaceX’s 73rd launch this year. And like many other Falcon 9 launches this year, the “Starlink 10-9” mission carried 23 of the high-speed internet satellites into orbit. However, after a rare failure earlier this month, this particular Falcon 9 rocket was making a return to flight for the company, attempting to get the world’s busiest booster back into service.
And by all accounts, it succeeded. The first stage booster, B-1069, completed its 17th orbital flight before landing back on Earth. Just read the instructions A drone ship took off into the Atlantic Ocean. Then, just over an hour after liftoff, the rocket’s second stage released its payload into a healthy orbit, from which the Starlink spacecraft will use its onboard thrusters to reach operational altitudes in the coming weeks.
A crack in the line of meaning
The Falcon 9 rocket failed just over 15 days ago, during a Starlink launch from Vandenberg Space Force Base in California at 7:35 p.m. PDT (0235 UTC) on July 11. During that mission, just minutes after stage separation, an unusual buildup of ice was observed on the Merlin vacuum engine that powers the vehicle’s second stage.
According to the company, the Merlin vacuum engine successfully completed its first burn after the second stage separated. However, during this time, a liquid oxygen leak occurred near the engine, leading to the ice buildup observed during the webcast.
Engineers and technicians were quickly able to identify the cause of the leak, a crack in a “sensing line” of a pressure sensor connected to the vehicle’s liquid oxygen system. “This line cracked due to fatigue caused by high load from engine vibration and loosening of the clamp that normally constrains the line,” the company said in an update released ahead of Saturday morning’s launch.
This leak excessively cooled the engine and caused a decrease in the amount of ignition fluid available before reigniting the Merlin for its second burn to circularize the rocket’s orbit before releasing the Starlink satellites. This caused the Merlin engine to have a difficult start. Eventually, the satellites were released into a lower orbit, where they burned up in Earth’s atmosphere within a few days.
The failed sensor line is redundant, SpaceX said. It is not used by the flight safety system and can be covered by alternative sensors already on the engine. In the near term, the sensor line will be removed from the second stage engine for Falcon 9 launches.
At a press conference Thursday, SpaceX CEO Sarah Walker said the sensor line was installed in response to a customer request for another mission. The only difference between the component and other commonly used sensor lines is that it has two connections instead of one, she explained. That may have made it a little more sensitive to vibration, leading to the small crack.
Come back quickly
SpaceX identified the cause of the outage within hours of the anomaly and worked with the FAA to find a quick fix. On Thursday, the launch company received clearance to resume flights.
“It was amazing how quickly the team was able to identify the cause of the accident and then the associated corrective actions to ensure success,” Walker said.
Before the July 11 overnight failure, SpaceX had not experienced a mission failure in 297 previous Falcon 9 launches, dating back to the Amos-6 launch pad explosion in September 2016. The short time between the failure earlier this month and Saturday’s return to flight appears unprecedented in spaceflight history.
The company now plans to launch two more Starlink missions aboard the Falcon 9 rocket this weekend, one from Cape Canaveral Space Force Station in Florida and one from Vandenberg Space Force Station in California. It will then fly three more missions before a crucial NASA flight, Crew-9, which could take place as early as August 18.
That’s why NASA was involved in the investigation into the second stage failure. Steve Stich, NASA’s commercial crew program manager, said SpaceX did an “extraordinary job” of identifying the root cause of the failure and then quickly examining its Dragon spacecraft and the Falcon 9 rocket’s first stage to make sure there were no other sensors that could cause similar problems.
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