SpaceX Thanksgiving Day Launch Attempt Aborted at T plus 2 Seconds

Back to the Hanger

It was back to the hanger for SpaceX, as the second attempt to launch the Falcon  9 SES-8 mission made it all the way through a smooth countdown and right up until the moment of engine ignition when launch computers aborted the count at t plus 2 seconds.  After going back into a hold to diagnose the problem, SpaceX announced that computers had detected a lower than expected ramp-up in engine thrust, which under normal conditions would have seen hold down clamps released as the engine reached full power at t plus 3.5 seconds.

As engineers continued to study the data, Elon Musk tweeted that the launch team would try again by increasing the helium spin start pressure, but then went on to caution that the odds were less than 50% of passing all aborts.  With the launch window closing once again,  the countdown re-started, targeting a 6:44 pm EST liftoff.  It reached approximately t-60 seconds when it was halted for the final time, bringing the Thanksgiving day launch effort to a close.

This time SpaceX cited a lack of time to complete the necessary data review from the first abort.  In a subsequent update via Twitter, Musk observed that it was “better to be paranoid and wrong,”  going to say that the launch will probably be delayed for several days as engineers bring the booster back into its hanger for closer examination of the engines via boroscope.

Close observers will recall that in the course of SpaceX’s historic first mission to ISS, the COTS 2/3 mission, a similar last second abort after engine ignition also resulted in a delay of several days  as SpaceX sought to identify  why computers detected the number 5 center mounted engine trending badly.  In that case, the source of the problem was traced to a safety check valve on the fuel line for the gas generator stuck in the open position.  At the moment of ignition, as fuel began to flow to the gas generator to build the thrust to drive the turbo pump, the open valve allowed some of the fuel to return to tank, changing the delicate balance between fuel and oxidizer in favor of the latter, leading to an oxygen “rich” fuel combustion causing a spike in temperature and pressure, and triggering the shutdown.

Though frustrating to those eager to see the commercial debut of the Falcon 9 v1.1,  just as in the case of the NASA COTS 2/3 mission, it ia the like, it is rather encouraging to see a launch monitoring system sophisticated enough to “abort with authority,” protecting both vehicle and payload to fly another day.

More updates as information becomes available.

Oh, and Dallas beat the Raiders 31-24