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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.

Genesis cover

On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.

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  • Barry

    I wonder why they don’t fix their software problem and fire the engines when they get to apogee on any of the orbits? There must be deeper problems.

  • Edward

    I don’t know why they could not do remote operations and do as you suggested without a software fix, but I’m sure that they would have if it were practical and didn’t endanger the rest of the mission.

    The SpaceNews article describes that Lockheed Martin accelerated its test schedule and accomplished many of the mission’s objectives. The satellite reentered a couple of weeks ago, so it is too late to rescue that mission even if they already have the solution ready to go. Since Firefly says it is still correcting the problem, I don’t think they have the updated software ready yet.

    I don’t know whether the satellite can operate with the upper stage still attached. If they had to separate for the satellite to operate properly, then it would have been unable to make corrective actions even if the software was ready before reentry. I’m pretty sure that they made the best of a bad situation. Lemonade, anyone?

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