Further Explanation of NASA “Safety Gate” Which Resulted in Incorrect Orbcomm Deployment

SpaceX provided the following update today, shedding a little more light on the specific circumstances regarding NASA requirements which ultimately forced SpaceX to deploy an Orbcomm satellite in a lower than desired orbit.

Update on SpaceX CRS-1 Mission: October 10

The SpaceX CRS-1 mission reached a critical milestone today, October 10, with the Dragon spacecraft successfully attaching to the space station.

The mission, the first of at least 12 to the International Space Station under the company’s cargo resupply contract with NASA, began with a Sunday, October 7 launch from Cape Canaveral, FL. As a result of shutting down one of its nine engines early shortly after the launch, the Falcon 9 rocket used slightly more fuel and oxygen to reach the target orbit for Dragon. For the protection of the space station mission, NASA had required that a restart of the upper stage only occur if there was a very high probability (over 99%) of fully completing the second burn. While there was sufficient fuel on board to do so, the liquid oxygen on board was only enough to achieve a roughly 95% likelihood of completing the second burn, so Falcon 9 did not attempt a restart. Although the secondary payload, the Orbcomm satellite, was still deployed to orbit by Falcon 9, it was done so at the lower altitude used by Dragon in order to optimize the safety of the space station mission.

SpaceX and NASA are working closely together to review all flight data so that we can understand what happened with the engine, and we will apply those lessons to future flights. We have achieved our goal of repeatedly getting into orbit by creating a careful, methodical and pragmatic approach to the design, testing and launch of our space vehicles. We will approach our analysis in the same manner, with a careful examination of what went wrong and how to best address it.  Additional information will be provided as it is available.

End Press Release

Apparently, the safety issue involved whether or not the second stage could be absolutely depended upon to boost itself well out of the orbit being  occupied by ISS and therefore not pose any safety risk.  What seems confusing is that even if the Falcon 9 second stage did not fully complete its planned second burn, presumably the orbit still would have been easily raised sufficiently to preclude any future risk to ISS while still placing the secondary payload in a higher, and potentially more useful orbit.   As the specifics are explained  more fully,  it will be interesting to note the extent to which this appears to be an isse of NASA overcaution versus a reasonable requirement.

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