October 8, 2012
Redundancy Counts
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.
It turns out that there was an unintended side-effect of the engine loss. For safety reasons, NASA has refused SpaceX permission for a second stage burn that was needed to put the Orbcomm satellite into the proper orbit. So this launch was only a partial success.
Comment by JohnD — October 9, 2012 @ 9:41 am
In a later press release, it was stated that the Orbcomm satellite was not boosted further because of a safety lock enforcing a rule that the second stage was not allowed to reignite if there were problems during the initial boost phase. . . which there were. This rule was to prevent a potentially defective booster from getting yet closer to the ISS.
Comment by Rick Papo — October 9, 2012 @ 9:55 am
In other words, the mission could have been completed completely successful for both NASA and Orbcomm if SpaceX had been allowed to by NASA. IMHO, Orbcomm therefore has a case against NASA, not SpaceX.
Also, as the satellite can achieve its orbit using onboard fuel, albeit, with a shorter lifespan, any claim against any agency, or insurance company, should not be for the full cost of the satellite/launch cost.
It would be a good/nice gesture if SpaceX were to launch the next satellite for Orbcomm gratis though.
Comment by Oliver McDonald — October 10, 2012 @ 10:52 am
It turns out that Orbcomm’s satellite was a test satellite and they knew of this possibility when they signed on to “piggyback” on the NASA launch for a lesser fee. Since the satellite was not going to stay up, just gather data for the operational models to come later, they were saying that they likely would gain enough data for a successful flight. When they launch their operational satellite later on a Falcon 9, they will be one of the primary payloads and will not have the same constraints. Expectation is that SpaceX will perform fine in this case, since they have just demonstrated their fine redundancy features.
Comment by gregg givens — November 3, 2012 @ 9:50 pm