Video SpaceX has confirmed that one of the engines on its Falcon rocket flamed out mid-flight during the launch of its resupply mission to the International Space Station.
Around one minute after takeoff, the SpaceX team noted an anomaly on one of the first stage Merlin engines and shut it down. The Falcon is equipped with nine Merlin 1C engines and the team used the eight remaining power systems to adjust for the lack of thrust, and successfully drove the craft and its Dragon cargo capsule into orbit.
Rockets such as the European Space Agency's Ariane 5 only use a single, powerful engine (albeit augmented with two booster sections) to loft cargo into orbit, making failure a terminal disaster. The Falcon design allows it to ride out such issues, since it uses multiple smaller engines rather than a few big ones, which gives the Falcon a little more leeway when gremlins strike.
"We know the engine did not explode, because we continued to receive data from it," a SpaceX spokeswoman told El Reg in an emailed statement. "Our review indicates that the fairing that protects the engine from aerodynamic loads ruptured due to the engine pressure release, and that none of Falcon 9's other eight engines were impacted by this event."
Judging from this statement and slow-motion video of the launch, it appears the nozzle of one of the Merlin engines exploded. At around 1:19 in, there is a gush of flame followed by what looks like pieces of the nozzle falling away from the craft, but without causing any further damage to the other engines.
The Merlin 1C has had problems in this area before, with cracking found in its niobium-alloy nozzles in testing. The nozzles have to be built tough, since their task is to first compress all the thrust developed by the engines and then direct the expanding gases into the atmosphere in the most efficient way possible.
This puts the materials involved under enormous strain, and nozzle failure is a significant factor in many failed launches. NASA was so concerned about the issue it designed the Saturn V rocket that launched Apollo to still function with one engine dying in flight by allowing four of the five nozzles to move and give directed thrust.
According to SpaceX, the Falcon system handled the issue with barely a stutter, and the flight systems compensated with slightly extended burn times from the remaining engines. The Dragon capsule is still on schedule to dock with the ISS on October 10, whereupon the astronauts will unpack its 1,000 pounds of supplies and repack it with scientific materials and station hardware ready for return to Earth.
While SpaceX hasn't yet received clearance to carry human cargo, Monday's little mishap may make NASA happier about giving it clearance to do so. Very few people in the US are happy about relying on the Russians for ISS resupply, now that the Space Shuttle is a museum piece, and are keen to have an American company doing the job. ®