Falcon 9 Engine-Out Anomaly Raises Concern and Relief

Under the combined thrust of the nine Merlin-1C engines on its first stage, SpaceX’s fourth Falcon 9 roars away from Space Launch Complex (SLC)-40 at Cape Canaveral Air Force Station at 8:35 pm EDT on Sunday. Eighty seconds into the flight, its redundancy capabilities would be put to the test in truly dramatic fashion. Photo Credit: Julian Leek/Blue Sawtooth Studios

As SpaceX’s second Dragon cargo flight to the International Space Station – the first under its $1.6 billion Commercial Resupply Services (CRS) contract with NASA – closes in on a rendezvous and berthing at the outpost tomorrow morning, further details have arisen over an ‘engine-out’ anomaly just 80 seconds into Sunday night’s ascent. According to SpaceX, one of the nine Merlin-1C engines on the Falcon 9 rocket’s first stage experienced a sudden loss of pressure and a shutdown command was automatically issued. During this process, panels designed to relieve engine pressure were jettisoned to protect the first stage and the other eight engines burned an additional 30 seconds to compensate for the reduced thrust. Although Dragon was inserted into its proper orbit, the fate of the small Orbcomm ‘piggyback’ satellite remains unclear. The incident raised questions about the reliability of the Falcon 9 on only its fourth flight, but also served to vindicate SpaceX’s assertion that the rocket can recover from as many as two engine ‘flame-outs’.

Seven minutes ahead of launch, the Dragon craft in the Falcon’s nose transitioned to its internal power supplies, followed, two minutes later, by the booster itself. As personnel within the SpaceX control room watched pensively – none more so than CEO Elon Musk himself – the final ‘Go’ for launch was received at 8:33 pm EDT. All of the Falcon’s propellant tanks were verified to be at their correct flight pressures by the T-30-second point and the 227-foot-tall vehicle roared spectacularly into a darkened Florida sky at 8:35 pm. The nine first-stage Merlin-1Cs, producing a combined 1.1 million pounds of thrust, provided the impulse for the first three minutes of the climb to orbit. It was during this initial boost that the ‘Engine 1 Anomaly’ appeared.

“Falcon 9 detected an anomaly on one of the nine engines and shut it down,” Musk noted after the launch. “As designed, the flight computer then recomputed a new ascent profile in real time to reach the target orbit, which is why the burn times were a bit longer.” He added that Falcon is the only rocket currently in service which can endure an engine ‘flame-out’ and still successfully complete its assigned mission. The Merlin-1Cs on the first stage – each capable of 125,000 pounds of thrust at sea level – are powered by a mixture of rocket-grade kerosene (RP-1) and liquid oxygen. No previous anomalies of this nature have been experienced on the vehicle’s previous missions in June 2010, December 2010 or the triumphant first Dragon cargo flight to the station last May.


Casting an eerie glow upon the watery landscape of Cape Canaveral Air Force Station, SpaceX’s Falcon roars aloft. Photo Credit: Jason Rhian

The flame-out caused some consternation when launch video revealed the highly-visible ‘incident’ and speculation arose that an explosion might have occurred in the aft compartment of the Falcon. However, SpaceX were quick to verify that Engine 1 “did not explode, because we continued to receive data from it”. Engineering analyses are currently ongoing, although speculation has centred on the possible fracture-related failure of the engine’s fuel dome. It would appear that debris seen falling from the rocket into the exhaust plume was related to the jettisoned pressure-relief panels.

Its secondary passenger, the Orbcomm, appears not to have been quite so lucky. Original plans called for the Falcon’s second stage to execute a short second burn of its single Merlin-1C engine to raise its orbit, ahead of deploying the Orbcomm, about 62 minutes after launch. This burn, however, was dependent upon the stage being sufficiently healthy and a propellant mass check shortly after the first engine cutoff failed to pass the requirements to ensure a safe injection of Orbcomm into its correct orbit. Consequently, no second engine burn was conducted and the small satellite was deployed into an insertion orbit of 125 x 200 miles, far lower than the planned 220 x 470 miles. SpaceX President Gwynne Shotwell initially told journalists at Sunday’s first post-launch conference that the Orbcomm had been successfully released, but it later became clear that the insertion orbit is “unworkable”.

The Falcon 9’s nine Merlin-1C engines are each capable of producing 125,000 pounds of thrust and fail-safe capability allows the vehicle to recover from as many as two engine failures and still successfully complete its primary mission. Photo Credit: SpaceX

Although the 313-pound Orbcomm is alive and functional, and presently occupies a low elliptical orbit, its planned five-year lifespan is expected to be seriously impaired. Built by Sierra Nevada Corporation, the satellite is the first in a new second-generation class of Orbcomms, officially designated ‘O2G’, to be launched. It is intended to serve as a prototype testbed for future missions and, indeed, two further satellites in the series are currently scheduled to ride another Falcon 9 into space next year. Both Orbcomm and Sierra Nevada Corporation have established contact with the satellite and are presently working to determine if the orbit can be raised with its small on-board propulsion system.

As for Dragon itself, a successful insertion into a preliminary orbit of 122 x 203 miles was confirmed at 8:45 pm EDT. Two minutes later, the cargo ship parted company from the second stage of the Falcon 9 and at 8:51 pm its twin solar arrays were deployed, followed later by the opening of the critical Guidance, Navigation and Control (GNC) bay door. Aboard the Dragon are over 1,000 pounds of usable items, including equipment, experiments and supplies for the International Space Station’s Expedition 33 crew – currently at its three-member level of Commander Sunita Williams and Flight Engineers Yuri Malenchenko and Aki Hoshide – and arrival in the vicinity of the multi-national research facility is scheduled in the early hours of Wednesday.

In a view which will hopefully be repeated early tomorrow morning, this view from May 2012 – during SpaceX’s demo mission to the International Space Station – reveals the Dragon cargo ship, grappled by Canadarm2, a few minutes away from berthing at the Harmony node. Photo Credit: NASA

Grappling of the cargo ship by the Canadarm2 robotic arm will occur under the control of Hoshide and the Dragon will be berthed for almost three weeks at the Earth-facing (‘nadir’) port of the Harmony node. Measuring 19.3 feet long and 12 feet wide, the Dragon has the capability to ferry pressurised and unpressurised cargo to the station. Although no unpressurised payloads are being carried on this flight, subsequent operational missions under the CRS contract – which requires SpaceX to fly 12 cargo deliveries and truck 44,000 pounds of research and other supplies by 2015 – will exploit this capability. Assuming that tomorrow’s berthing goes well, Dragon is expected to return to a parachute-assisted splashdown in the waters of the Pacific Ocean, off southern California, on 28 October.

Despite the mixed results of the launch, it must be borne in mind that the accomplishments of the Falcon 9 and the Dragon are truly astonishing. They have restored the United States’ capacity to launch its own cargo-delivery missions, from its own soil, for the first time since last year’s retirement of the Space Shuttle fleet. When Dragon returns to Earth in three weeks’ time, it will bring back over 1,670 pounds of cargo, including frozen samples from space station experiments. Moreover, the Falcon 9 rocket performed exactly as it was designed to do in the event of an off-nominal ‘engine-out’ scenario.

After all, this is rocket science.

Or as the charismatic Elon Musk put it: Rocket science is “super-frickin’ damn hard.”


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  1. I am confused did the second stage not complete a second burn because of the engine issues with the first stage…was the first stage using fuel that was originally planned for the second stage?

    • Good question. Another is if you have suffered a pressure loss why do you need to jettison pressure relief panels to protect the first stage?

  2. Tracy, according to an Orbcomm statement: “The rocket did not comply with a pre-planned International Space Station (ISS) safety gate to allow it to execute the second burn.” It would appear therefore to be some kind of trajectory/guidance-related issue which precluded the second burn.

    Joe, I’m not sure on this point. Only last night there were still suggestions that an explosion had occurred! I am sure SpaceX will reveal more detail in time.

    Thanks both for your comments.

    • Hi Ben,

      Thanks for the response.

      “Only last night there were still suggestions that an explosion had occurred!”

      Were those suggestions before are after the Space X assurances there was no explosion?

      What was the source of the suggestions?


      • Joe, there was both internet chatter and comments from onlookers at CCAFS when debris was observed in the first stage plume at around T+80 seconds. I wasn’t at the Cape, but several of my colleagues were present and it was speculated that an engine had malfunctioned or perhaps even disintegrated. Obviously, when SpaceX provided assurances that there was no explosion, those concerns went away.

        • Thanks again.

          I would hope the CCAFS-Range Safety Office is going to want a lot more detail on the anomaly before the Falcon 9 flies again, so more details will (hopefully) be coming forward in the weeks ahead.

          Keep us posted.

    • Tracy, at present it’s not clear, but my guess that they are both related to the thrust shortfall in the first stage and its aftereffects. A follow-up article will appear on AmericaSpace as more information becomes available.

  3. http://www.aviationweek.com/Blogs.aspx?plckBlogId=Blog:04ce340e-4b63-4d23-9695-d49ab661f385&plckPostId=Blog%3A04ce340e-4b63-4d23-9695-d49ab661f385Post%3Afdf0d27c-fdf2-4efb-a71f-8272017dbfc3


    I held back from commenting on this quote from your article: “No previous anomalies of this nature have been experienced on the vehicle’s previous missions in June 2010, December 2010 or the triumphant first Dragon cargo flight to the station last May.” Until I discovered the article linked above.

    That may technically be true (though the incident from the Dec. 8, 2010 flight seems similar though less severe).

    Never the less there have been significant anomalies on at least three to the four Falcon 9 flights to date and now Space X seems to be on the verge of moving (after only four flights) to a basically new vehicle that they intend to still call the Falcon 9.

    From the linked article:
    “It is worth noting that this is not the first time Falcon 9 has experienced an engine anomaly. During a Dec. 8, 2010 launch that orbited a Dragon qualification unit for NASA’s Commercial Orbital Transportation Services (COTS) program, one of the rocket’s engines experienced an “oxygen-rich shutdown,” according to Ken Bowersox, a retired NASA astronaut and former SpaceX vice president for astronaut safety and mission assurance. Bowersox revealed the anomaly in a September 2011 interview with Space News shortly before leaving the company.

    Falcon 9 also suffered an anomaly during its inaugural flight June 4, 2010, though flight data from the mission was never made public. The rocket appears to have experienced a slight roll at liftoff, visible in a video of the launch. And in a post-launch interview I did for Space News, SpaceX founder, CEO and CTO Elon Musk said he was surprised by a pronounced roll that occurred following the rocket’s upper stage firing.
    “We didn’t expect the roll,” Musk said, adding that it did not affect the payload’s insertion vector and had no adverse impact on the mission.

    It is also worth noting that next year SpaceX plans to fly an upgrade to the Falcon 9 rocket that will effectively replace the existing launch vehicle. They’ve cleverly dubbed it Falcon 9 v1.1, a name that suggests only minor modifications to the current version. But the upgrade will feature a new engine — the Merlin 1D — to be arranged in an octagonal, rather than the current tic-tac-toe configuration. The rocket will also be longer, to accommodate stretched fuel tanks, and incorporate a wider payload fairing, meaning v1.1 will bear little resemblance to the Falcon 9 of today.”

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