Another 'Successful Failure' for SpaceX
On its last trip to the International Space Station (ISS), the SpaceX Falcon 9 rocket lost an engine in ascent, losing a little performance but achieving orbit anyway. On Friday’s flight, the Falcon seems to have performed flawlessly in delivering the Dragon capsule to orbit.
This time, it was the Dragon itself that failed, at least initially. Normally, after initial orbit insertion the solar panels would be deployed, but SpaceX personnel delayed deployment because they were having problems with the orbital maneuvering thrusters needed to circularize the orbit and to match it with that of the ISS. Only one of the four was working, and NASA rules required at least three of them to be functional before attempting an approach to the station.
They had limited time to solve either the thruster or solar panel problem -- they were in an orbit with a low perigee and relatively high drag that wouldn’t have lasted more than a day or two, and their batteries were likely to die in about the same time frame. It seemed to be a problem with a propellant valve (the four propulsion systems are cross connected to share propellant tanks). So for a time, it was nerve wracking for the team. If they were unable to fix the problem it would have meant an early end to the mission, without delivering or retrieving cargo from the ISS, and a forfeiture of at least part if not all of the payment for the flight. It may also have resulted in the loss of the vehicle if the propulsion system was unable to perform a proper entry or orientation, with the vehicle potentially burning up in the upper atmosphere.
But shortly after, they made the decision to deploy the arrays while they worked the propulsion issue. Eventually, after cycling the valves and blasting them with pressurant to clean them out, first one more propulsion pod came up, and then the other two.
The working theory as of this writing was that it was frozen oxidizer in one of the lines. By late afternoon they were go for rendezvous with ISS, though the delay cost them their window for their planned berthing early Saturday morning, pushing it off until Sunday instead. The company celebrated a slightly belated but happy “berth day,” with a delivery of a ton of equipment and supplies -- with a bonus of fresh fruit -- to the ISS crew.
Like that of the previous flight, it was a valuable failure in that it identified a potential problem with either the design or operations but didn’t cost them the mission. On the first successful Dragon flight, Elon Musk, the company’s founder and chief executive, noted that it made him a little nervous because it was almost too perfect, and provided nothing to learn from or room for improvement.