A thread detailing an armchair theory as to what might have happened leading to loss of vehicle/mission.
Essentially, liquid oxygen (LOX) oxidiser loss at second stage ignition; LOX didn't appear to drop in proportion to fuel (RP-1) burn. The propulsion system then probably struggled with pressurisation leading to an unbalanced stage (turning moments about the centre of mass), consequent erratic gimbaling and then loss of flight control and thus vehicle (is the theory†).
Well, based on other people's comments elsewhere, I've reviewed the webcast for the #LauncherOne #StartMeUp failure. And I noticed a fatal bug on the telemetry screen. @VirginOrbit has generously provided data on fuel amount, line pressure, voltage etc. & sth fishy does show up.
notabird.site
† Assuming the streamed telemetry data was valid, of course.
I'll lend my support to this theory via my own armchair. I went and looked at some of the past missions streams, and watched the dashboard again this time. I put to one side all moments with completely erratic, fluctuating OX readings this time, and theories about sloshing. And with those out of the way the picture is still there of the OX reading consistently dropping quicker than the other fuel reading, unlike in previous missions.
And the theory is compatible with all the other doom data and timing I observed and mentioned previously. The OX reading was a bad sign right from the start of the second engine phase, whereas the other bad indications I noticed and mentioned previously didnt start until about half way through the second engines first burn. The other missions featured much higher speeds during the second half of that phase than we ever got to see in the data this time (comically high speed reading spikes excluded). The maximum altitudes in the data on previous streams varied quite a bit so I cant say quite how far short we fell of that this time, might have been quite close to target altitude, might have been well over 100,000 feet off the target.
The call to shutdown the second engine happened reasonably close to the time when that call would have been made if the mission had been a success, but I still think that this time the call was made because it was clear there had been an unrecoverable failure by that point. In previous streams the call to shutdown that engine was the moment of triumph, preceded by a message that mission criteria had been achieved, and swiftly followed by celebrations. This time it was just a downbeat call to switch off newton 4, with none of the other indications of success. So I will stand by my remarks about all the covering bullshit that the commentator indulged in from that point onwards this time.
The previous streams were not much better overall presentationally, but they did at least have better visuals and didnt miss the drop - doing this UK one in the dark really hampered their ability to show interesting camera shots. We probably got to see so much of the dashboard this time because there wasnt anything else to show. The call to shutdown engine 2 in the previous missions streams was about the last moment that anything interesting happened in those ones too, they didnt stick around for ages to get to the stage of deploying the payload etc. So the failure of this mission actually made very little difference to what would have happened next on the stream. We were just missing the message about operational parameters having been met, an instruction to start the BBQ roll, a few people going yay, and an instruction to remove the airspace restrictions soon after.