SpaceX recently posted the launch video of the ill-fated Falcon 1, flight 3 launch on August 2nd. At the time, I was glued to the screen watching the live video broadcast of the event seeing the launch unfold. The first launch attempt was terminated due some minor parameter fluctuations, but the rocket was re-fuelled and prepped for a second attempt within the hour. However, although Falcon 1 made it to well above 200 km altitude, a very small thrust anomaly during stage separation had huge consequences for the space vehicle and payload…
So what did happen on that sunny day above the Pacific Ocean? According to the SpaceX press release, it was something very small that caused the failure of this commercial launch. At an altitude of 217 km everything appeared to be going to plan. The first stage Merlin 1c engine performed excellently (even after the one hour launch abort-restart), but a small quirk called a transient thrust was the undoing of the mission.
As can be seen in the launch video and the sequence of images at the top of this article, stage separation occurred as planned, the spent first stage separating and falling toward Earth. But something happened as it was being pushed away. Almost as if it was still attached to the second stage by elastic, the first stage seemed to rebound, colliding with the rocket after it had been ejected.
Elon Musk, SpaceX CEO, confirmed this anomaly stating that a tiny amount of fuel inside the stage one engine had ignited after the main burn. Although it only produced a tiny thrust (of 10 psi), it caused first and second stage re-contact. The reason why this thrust remained undetected was due to the small pressures involved. In the SpaceX test facility, the ambient pressure exceeds 14 psi, thereby masking the effect of this post-main burn transient thrust. In the vacuum of space, the full effect of the 10 psi thrust had catastrophic consequences, causing stage collision and launch failure.
However, SpaceX remains upbeat and is determined to push ahead with another launch next month. All going well, the fourth Falcon 1 launch will be a success, putting the first commercial space vehicle into orbit.
For more, read Video of SpaceX Falcon 1 Flight 3 Launch Shows Stage Separation Anomaly over at the Universe Today.