A loss occurring after a nominal lift-off, on the stage that delivers the final orbit, destroying the payload although the flight appeared successful.
The upper stage is the one that, after the atmosphere has been crossed, gives the payload its final velocity and orbit, often through several burns separated by long ballistic coasts. It accounts for a large share of launch failures for three compounding reasons: it operates in vacuum and cold, far from any possibility of full ground testing, it must reignite after a wait that testing reproduces poorly, and its failure comes too late for any range safety procedure to protect the payload. In insurance terms this profile produces the costliest configuration, a total loss occurring after every visibly dangerous phase has been passed, which makes the event both rare and without gradation. Contractual characterization is by contrast straightforward, the launch policy responding without argument once separation has not occurred or the orbit reached will not support the mission, and the debate shifts to the relaunch clause and to the anomaly investigation that governs the vehicle's return to flight.
Flight VV22 of the Vega-C launcher, on 20 December 2022, failed after a nominal first stage burn, degradation of the Zefiro-40 motor nozzle throat leading to the loss of the two Pléiades Neo 5 and 6 observation satellites.
upper stage failure, défaillance du dernier étage, panne d'étage supérieur