Antares failure. We are going to know soon what triggered the Antares/Cygnus explosion on Tuesday based on hints that Orb-Sci dropped today. Looking frame-by-frame at NASA’s HD raw feeds from the launch and listening closely to audio, I’m moving away from my initial theory that the problem was a failure of one or both of the first-stage powerplants to build adequate thrust, followed by an automated destruct program.
Based on launch control callouts, it sounds as if the AJ26… engines were running at the intended 108% of rated thrust as the rocket climbed away from the pad. I still think I see an issue with yaw control during the first 6-9 seconds of climb-out, which could point to failing avionics and/or engine gimbal actuator under-performance and/or winds buffeting the rocket. I no longer think the yaw action alone precipitated the failure.
What seems absolutely certain is that the first-stage powerplants blew-up (not the rocket, not the self-destruct system) but one engine followed immediately by the other. That comes across from the audio and the visuals (synched up to adjust for speed-of-sound lagtime). The stack (the entire rocket) does not appear to have broken apart until impact with the ground. So, no self-destruct sequence but definitely complete, instantaneous failure of the engines. That points to three possible triggers for the event that ended the flight: (1) catastrophic metallurgic failure anywhere along one of the powerplant’s fuel/oxidizer flow lines and turbo pumps; (2) a fuel/oxidizer mixture imbalance due to obstructed or leaking fuel lines or valves feeding into the powerplant, resulting in a reaction imbalance outside of engine tolerances; (3) a software error that resulted in unintended upstream valve closure or flow restriction on the fuel or oxidizer side.
Watching and listening: the powerplants blow up at 15-16 seconds in rapid succession; 7 seconds for the rocket to return to Earth remarkably vertical resulting in a substantial blast and sonic wave as the engines hit the ground; followed 2 seconds later by a massive explosion (the fireworks display) and sonic wave as either: (1) the first-stage tanks and second-stages tanks collapse, mix, and cook-off; or (2) the Range Safety Officers’ destruct order kicks in, effectively blowing up the tanks.
Right or wrong, interesting to thinking through the mechanics of the failure.