(Photo by Paul Hennessy/SOPA Images/LightRocket via Getty Images)
SpaceX is aiming to restart Starlink satellite launches as soon as tomorrow after addressing the cause behind the faulty Falcon 9 flight on July 11.
In a new report, SpaceX confirms that a liquid oxygen leak led to the malfunction that failed to place 20 Starlink satellites into orbit. "During the first burn of Falcon 9’s second stage engine, a liquid oxygen leak developed within the insulation around the upper stage engine,” it says. SpaceX then traced the leak to a crack in a “sense line for a pressure sensor attached to the vehicle’s oxygen system.”
These sense lines are used to accurately measure and regulate an electronic component’s voltage. However, fatigue caused a sense line on the pressure sensor to crack due to “high loading from engine vibration and looseness in the clamp that normally constrains the line,” SpaceX says.
Despite the leak, the Falcon 9’s second stage was able to operate during its first engine burn. But during the second engine burn, the liquid oxygen leak caused excessive cooling of the engine components, including the ignition fluid to the engine.
“As a result, the engine experienced a hard start rather than a controlled burn, which damaged the engine hardware and caused the upper stage to subsequently lose attitude control,” SpaceX says.
The malfunction derailed SpaceX’s effort to send all 20 Starlink satellites into the correct orbit. Instead, the satellites were deployed into a lower-than-expected elliptical orbit, which eventually caused them to fall back to Earth and burn up in the atmosphere.
The malfunction is a rare misfire for the Falcon 9, which has completed 364 missions. However, the company says it was able to quickly identify the root cause and provide a fix.
“For near term Falcon launches, the failed sense line and sensor on the second stage engine will be removed. The sensor is not used by the flight safety system and can be covered by alternate sensors already present on the engine,” SpaceX says. "An additional qualification review, inspection, and scrub of all sense lines and clamps on the active booster fleet led to a proactive replacement in select locations."
SpaceX has also tested the design changes at a rocket development facility in Texas with oversight from the Federal Aviation Administration, which is investigating the malfunction.
SpaceX has since submitted its official “mishap” report to the FAA to help close the investigation. Although the probe remains open, the FAA granted SpaceX clearance to essentially resume the Falcon 9 launches because the malfunction doesn’t pose a threat to public safety.
“This public safety determination means the Falcon 9 vehicle may return to flight operations while the overall investigation remains open, provided all other license requirements are met,” the government agency said in a statement.
In response, SpaceX is preparing to send up another batch of 23 Starlink satellites on Saturday, July 27, pending weather conditions. This also means the company can continue deployment of satellites meant for the cellular Starlink system, which is aiming to kick off service with T-Mobile this fall.