Virgin Orbit has started modifying its air-dropped rocket vehicle after analysis indicated that abnormal heating of the second-stage engine, following a filter displacement, caused loss of thrust during the company’s failed inaugural UK satellite launch.
Investigators have analysed data suggesting that a fuel filter in the LauncherOne vehicle – dropped from a Boeing 747-400 carrier – was “dislodged” from its position in the fuel feedline at the beginning of the initial second-stage burn.
The inquiry reveals a fuel pump, operating downstream of this filter, was running at a “degraded” efficiency level and that this led to fuel starvation to the rocket engine.
“Performing in this anomalous manner resulted in the engine operating at a significantly higher-than-rated engine temperature,” it states. “Components downstream and in the vicinity of the abnormally-hot engine eventually malfunctioned.”
This caused premature termination of second-stage thrust, and the launch vehicle to fall short of its target orbit. The vehicle and its payload fell back to Earth and landed in the Atlantic Ocean.
“Our investigation is not yet complete,” says Virgin Orbit chief Dan Hart. “However, with many clear clues from extensive data assessment now understood, we are modifying our next rocket with a more robust filter.”
He insists that the company will “proceed cautiously” towards its next launch, as it works to ensure that contributing elements to the mission’s failure are “rooted out”.
Virgin Orbit quickly initiated an investigation into the failure which followed the inaugural departure of the carrier aircraft and LauncherOne from Spaceport Cornwall, located in Newquay, on 9 January.
It states that the inquiry has examined “extensive telemetry” and obtained “robust” data from ground stations in the UK, Ireland and Spain as well as systems on board the 747.
This information has enabled Virgin Orbit to confirm that the pre-flight preparations, take-off, cruise, and release of LauncherOne were conducted successfully, and that the vehicle’s first-stage ignition, stage separation, and second-stage ignition were “nominal”.
Virgin Orbit says that, while the fuel filter is undergoing modification, the inquiry is still investigating all potentially-credible scenarios.
“Numerous tests are underway to support the investigation and help lead to definitive conclusions,” it states.
Virgin Orbit is planning to carry out its next space launch for a commercial customer from California’s Mojave air and space centre.