> A few minutes after liftoff of SpaceX's Starlink 9-3 mission, veteran observers of SpaceX launches noticed an unusual build-up of ice around the top of the Merlin Vacuum engine, which consumes a propellant mixture of super-chilled kerosene and cryogenic liquid oxygen. [...]<p>> Numerous chunks of ice fell away from the rocket as the upper stage engine powered into orbit, but the Merlin Vacuum, or M-Vac, engine appeared to complete its first burn as planned. A leak in the oxidizer system or a problem with insulation could lead to ice accumulation, although the exact cause, and its possible link to the engine malfunction later in flight, will be the focus of SpaceX's investigation into the failure.<p>> A second burn with the upper stage engine was supposed to raise the perigee, or low point, of the rocket's orbit well above the atmosphere before releasing 20 Starlink satellites [...].<p>> "Upper stage restart to raise perigee resulted in an engine RUD for reasons currently unknown," Musk wrote...<p>For Falcon 9 <i>manned</i> launches, there are a whole series of abort modes and we-didn't-get-to-orbit splashdown locations:<p><a href="https://www.nasaspaceflight.com/2020/05/examining-crew-dragons-launch-abort-modes-and-splashdown-locations/" rel="nofollow">https://www.nasaspaceflight.com/2020/05/examining-crew-drago...</a><p>It'd be interesting to know where in this mission's flight profile, <i>if</i> it had been manned, the launch director would have ordered an abort. That LOX leaks often lead to explosions is Rocket Science 101.