Firefly: Software caused failure of upper stage in December
According to the rocket startup Firefly, a software issue prevented the engine on the upper stage of its Alpha rocket from firing its final burn, leaving a Lockheed Martin satellite in the wrong orbit.
In a Feb. 20 statement, Firefly said an error with the guidance, navigation and control (GNC) software for the upper stage of the Alpha on the company’s “Fly the Lightning” mission Dec. 22 kept the upper stage from firing as planned to circularize its orbit. That left the upper stage and its payload, a Lockheed Martin technology demonstration satellite, in an orbit with a low perigee.
The investigation, which included the company’s own mishap team as well as an independent review, found that the error in the GNC software algorithm “prevented the system from sending the necessary pulse commands to the Reaction Control System (RCS) thrusters ahead of the stage two engine relight.” Firefly didn’t elaborate on the issue, but the RCS thrusters likely would have been used to ensure the stage was in the proper orientation and to settle its tanks so propellant would flow from them into the engine.
From this description it appears the attitude thrusters (RCS) had not worked correctly, and this made it impossible for the main engine to fire, either because the computer sensed it was in the wrong orientation, or its fuel could not flow properly to the engine.
The company says it has made corrections, and still expects to launch four times this year.
According to the rocket startup Firefly, a software issue prevented the engine on the upper stage of its Alpha rocket from firing its final burn, leaving a Lockheed Martin satellite in the wrong orbit.
In a Feb. 20 statement, Firefly said an error with the guidance, navigation and control (GNC) software for the upper stage of the Alpha on the company’s “Fly the Lightning” mission Dec. 22 kept the upper stage from firing as planned to circularize its orbit. That left the upper stage and its payload, a Lockheed Martin technology demonstration satellite, in an orbit with a low perigee.
The investigation, which included the company’s own mishap team as well as an independent review, found that the error in the GNC software algorithm “prevented the system from sending the necessary pulse commands to the Reaction Control System (RCS) thrusters ahead of the stage two engine relight.” Firefly didn’t elaborate on the issue, but the RCS thrusters likely would have been used to ensure the stage was in the proper orientation and to settle its tanks so propellant would flow from them into the engine.
From this description it appears the attitude thrusters (RCS) had not worked correctly, and this made it impossible for the main engine to fire, either because the computer sensed it was in the wrong orientation, or its fuel could not flow properly to the engine.
The company says it has made corrections, and still expects to launch four times this year.