Redundancy Counts

SpaceX’s Falcon 9 rocket keeps on chugging, despite an engine loss

A SpaceX employee -- Mohawk Girl? -- watches the launch in Hawthorne, Calif. (Photo: SpaceX)

A Dragon supply ship is now en route to the International Space Station, after launching last night on a SpaceX Falcon 9 rocket. Docking of the vehicle is scheduled for Wednesday morning.

In the video below, at about the 1:30 mark, you can see  a problem develop with one of the engines, which immediately shuts down.Yet the rocket keeps going.

That’s the beauty of the Falcon design, which has 9 clustered engines. From our article on SpaceX that ran last January:

The choice of nine engines for the first stage was made with reliability in mind: From the moment of liftoff, Falcon 9 can suffer an engine shutdown and keep flying; after about 90 seconds, it can tolerate a second engine shutdown. Even if an engine explodes…the others will not be affected.

Update: SpaceX put out the following statement on Monday afternoon:

Approximately one minute and 19 seconds into last night’s launch, the Falcon 9 rocket detected an anomaly on one first stage engine. Initial data suggests that one of the rocket’s nine Merlin engines, Engine 1, lost pressure suddenly and an engine shutdown command was issued. We know the engine did not explode, because we continued to receive data from it. Panels designed to relieve pressure within the engine bay were ejected to protect the stage and other engines. Our review of flight data indicates that neither the rocket stage nor any of the other eight engines were negatively affected by this event….

Falcon 9 did exactly what it was designed to do. Like the Saturn V (which experienced engine loss on two flights) and modern airliners, Falcon 9 is designed to handle an engine out situation and still complete its mission. No other rocket currently flying has this ability.

It is worth noting that Falcon 9 shuts down two of its engines to limit acceleration to 5 g’s even on a fully nominal flight. The rocket could therefore have lost another engine and still completed its mission.

October 9 update: It also has become clear that, due to the first stage anomaly, the Falcon 9 sent a smaller secondary payload owned by Orbcomm into the wrong orbit. SpaceX wasn’t exactly forthcoming with this information, which trickled out on various space websites yesterday. As a private business, they’re not required to tell us anything, of course. But with all the uninformed criticism of “new space” ventures these days, companies like SpaceX might do themselves a favor by being open and upfront when something does go wrong. NASA always has been — and it’s one of the agency’s many strengths.

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