Falcon 9 performs successfully even with one engine flameout

October 9, 2012

Sunday evening’s launch of the first commercial ISS resupply Dragon cargo craft appeared to go on without a hitch. However, it was discovered that, about at the point of maximum dynamic pressure, one of the nine Falcon 9 first stage engines failed. On-board video cameras recorded a gush of flame and pieces of something dropping off the booster. The onboard flight computer system ran the other engines about another 30 seconds to achieve proper speed and trajectory for the second stage to fire correctly and place the Dragon in the proper orbit. From there, a series of thruster burns by the Dragon itself will modify its orbit as it “chases” the ISS.

The flight computer did its job, but apparently a small Orbcomm satellite prototype, carried on the same second stage, was injected into too low an orbit as a result of the engine failure. There are very specific rules on orbital paths that are available in the vicinity of the ISS, and since deployment of the satellite was delayed, the second stage was not able to do an additional preplanned burn to put it in the proper orbit. Doing so would have interfered with the ISS “safety gate”window allowed for it. Remember, the previous Falcon 9/Dragon test flight was delayed several times because the launch window required to get the Dragon to the ISS was only one second long.

The Falcon booster is designed to be robust, and to have the ability to achieve its objectives despite an engine failure. The deployment of the Orbcomm satellite could have been accomplished if the ISS safety gate was not in place – there was nothing wrong with the second stage of the Falcon.

Unlike most European and American boosters, which use only one or two main engines in the first stage – often augmented by solid boosters, Russian Soyuz/Progress boosters have four rocket engines on the main central stage and four on each of the four “stage and a half” outer boosters. Solids cannot be “turned off” once they are burning – one of the safety concerns with the Shuttle and one also with the proposed/pipe dream heavy lifter NASA wants to build. That rocket could have either solid or liquid-fueled strap ons – my money is on Aerojet getting the contract to do liquid fueled boosters instead of ATK getting it for solids. ATK seems to not be the NASA favorite right now, and Pratt and Whitney Rocketdyne, one of the major liquid-fuel engine players, was recently  acquired by the parent company of Aerojet. (Aerojet builds most of the engines for the Delta rockets.)

So the booster has proven to be robust. Building and flying a rocket motor is not easy – the use of supercold liquid oxygen and high pressure/high temperature nozzle and thrust chamber make it tricky business. That is why today we rarely see a new motor designed from a clean sheet of paper. Most of the engines used today are improved varieties of designs from the 1960s, if not earlier.

I would think this flameout, despite it showing a less-than-100 per cent success rate, shows that a manned vehicle using this booster has a better chance of successfully reaching orbit than one with fewer engines. That, plus the powered escape plan using the improved Draco engines on the Dragon, should make this a safe and reliable passenger booster.


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