For only the second time in spaceflight history, Cape Canaveral was rocked by the roar of rocket engines on Thanksgiving, as SpaceX’s Falcon 9 v1.1 came close—but not quite close enough—to embarking on its second mission to deliver its first payload to geostationary transfer orbit. Liftoff from the Cape’s storied Space Launch Complex (SLC)-40 was dramatically halted at T+2 seconds, after the ignition of the nine Merlin-1D engines on the rocket’s first stage, and although the countdown clock was recycled out to T-13 minutes in hopes that another attempt might be viable, later in tonight’s “window,” it was not to be. Like Monday’s attempt, tonight’s second effort to get the Falcon airborne fell foul to technical troubles and the time limits of an ever-diminishing launch window. Ironically, weather conditions were near-perfect, and according to Falcon 9 Product Director John Insprukter, the SpaceX may make another attempt “probably in a few days.”
In a similar vein to Monday’s nail-biting launch attempt, the countdown proceeded with exceptional smoothness, tracking a liftoff, just after local sunset, at the 5:39 p.m. EST opening of the 65-minute “window.” At T-13 minutes, all stations were polled and confirmed their state of readiness as “Go” to proceed with the Terminal Count at T-10 minutes. As planned, the Terminal Count got underway at 5:29 p.m., and shortly afterward the flight control system was enabled and the nine Merlin-1D engines on the first stage began a “chill-down” protocol as part of pre-launch conditioning. Autosequence Start occurred at T-6 minutes, with the rocket’s propellant tanks verified to be at the proper flight pressures, and the launch pad’s “strongback” was completely retracted by T-4 minutes. The Flight Termination System (FTS)—tasked with destroying the Falcon in the event of a major accident during ascent—was placed onto internal power and armed, and by T-2 minutes and 15 seconds the first stage was confirmed to be at pressure.
“Range Green” came the call from Air Force Range personnel at T-2 minutes. Ironically, like Monday’s attempt, meteorological conditions were near-perfect, with barely a 10 percent probability of violating weather constraints. According to Patrick Air Force Base meteorologists, primary concerns were liftoff winds “from the north-northeast, gusting to 25 knots … diminishing to 10 knots after sunset,” and cumulus clouds. At T-1 minute, the flight computer was confirmed to be in control of the vehicle, with the second-stage tanks pressing to flight pressures. SLC-40’s “Niagara” deluge system began to flood the pad surface with 30,000 gallons (113,500 liters) of water per minute to suppress acoustic waves radiating from the Merlin-1D exhaust plumes. The vehicle’s propellant tanks were pressurized, and at T-3 seconds the nine engines roared to life.
Under computer control, their start-up sequence was tightly monitored and, assuming the ignition protocol is normal, hold-down clamps would have been commanded to release the vehicle at T-0. As circumstances transpired, that ignition protocol was not normal, for with the clock displaying T+2 seconds—and with all nine engines up and burning—the launch was dramatically aborted, ahead of the command to release the hold-down clamps. In the next few seconds, a flurry of communications could be heard over the SpaceX loop, as the FTS was safed, engine prevalves were closed, and the strongback was returned to the vehicle. The countdown clock held at T+2 seconds for some time, until it was eventually recycled back out to T-13 minutes, which is the normal recycling point from which the Terminal Count may begin again. “Launch aborted by autosequence due to slower than expected thrust ramp,” noted Elon Musk on Twitter. “Seems OK on closer inspection. Cycling countdown.”
With all minds keenly aware that today’s 65-minute window closed at 6:44 p.m. EST, it seemed likely that the attempt would be scrubbed. At 6:10 p.m., speaking on SpaceX’s live webcast, Falcon 9 Product Director John Insprukter noted that no decision had yet been made by engineers about whether or not to proceed with a second launch attempt. Then, at 6:17 p.m., a new T-0 time of 6:44 p.m.—right at the very end of the window—was announced and the countdown clock resumed. During this second period of counting, the customer for today’s launch, Orbital Sciences’ SES-8 communications satellites, operated by SES World Skies, confirmed that it was prepared to support an extension of 20 minutes beyond the nominal closure of today’s window. This made a launch attempt as late as 7:04 p.m. a distinct possibility, should further technical issues arise.
This mission is a pivotal one for SpaceX. Whereas the CASSIOPE spacecraft was inserted into a polar orbit with an apogee of 920 miles (1,480 km), tonight’s planned flight of the Falcon 9 v1.1 has been described by the company as its “First GEO Transfer Mission,” delivering SES-8 into a geostationary transfer orbit, whose apogee of 50,000 miles (80,000 km) is one-quarter of the distance to the Moon. SES-8 has been built by Orbital Sciences Corp. and will ultimately be co-located with the 2002-launched NSS-6 communications satellite at 95 degrees East longitude. Its primary purpose is to utilize its high-performance beams to support bandwidth-growth capability in the Asia-Pacific region, with specific focus upon emerging markets in South Asia and Indochina. Equipped with 33 Ku-band and Ka-band transponders, SES-8 will also provide expansion capacity for direct-to-home, very-small-aperture terminals and government applications. Operated by Dutch-based operator SES World Skies, it should remain operational for about 15 years.
Tracking a revised T-0, the countdown continued normally, entering the Terminal Count at T-10 minutes, passing Autosequence Start at T-6 minutes, completely retracting the strongback from the vehicle by T-4 minutes, arming the Flight Termination System at T-3 minutes, confirming “Range Green” at T-2 minutes and handing off control to the flight computer at T-1 minute. Shortly thereafter, at T-48 seconds, a “Hold, Hold, Hold” call was made and the clock stopped. At length, it became untenable for engineers to properly evaluate their data, when balanced against the time limits of the rapidly diminishing launch window. A scrub was formally called at 6:49 p.m., citing that the team simply “ran out of time to complete the data review” in the time available to them. Summing up, John Insprukter remarked that another attempt will take place “probably in a few days,” indicating that the anomaly experienced tonight will likely require longer than a 24-hour recycle to be resolved.
Looking ahead to the mission, at the instant of liftoff the nine Merlin-1D engines will generate 1.3 million pounds (590,000 kg) of thrust, about 200,000 pounds (90,000 kg) greater than the Falcon 9 v1.0, and will push the vehicle uphill for 180 seconds. Their propulsive yield will gradually rise to 1.5 million pounds (680,000 kg) in the rarefied high atmosphere. “Unlike airplanes, a rocket’s thrust actually increases with altitude,” noted SpaceX. “Falcon 9 generates 1.3 million pounds of thrust at sea level, but gets up to 1.5 million pounds of thrust in the vacuum of space. The first-stage engines are gradually throttled near the end of first-stage flight to limit launch vehicle acceleration as the rocket’s mass decelerates with the burning of fuel.”
With around 1,970 seconds of test time and a lengthy qualification program, SpaceX has expressed supreme confidence in the Merlin-1D. During a full-duration-mission firing in June 2012 in McGregor, Texas, the engine operated at or above the power (147,000 pounds of thrust) and duration (185 seconds) required for a Falcon 9 launch. The Merlin-1D has a vacuum thrust-to-weight ratio in excess of 150:1, making it the most efficient liquid-fueled rocket engine in history. The ignition system for the v1.1’s first stage was tested in April 2013. The stage also includes four extendible landing legs, manufactured from carbon-fiber and aluminum honeycomb, to support a series of tests which SpaceX CEO Elon Musk hopes will lead to vertical-takeoff-vertical-landing (VTVL) capability by the latter half of the present decade.
Immediately after clearing the SLC-40 tower, the Falcon 9 will execute a combined pitch, roll, and yaw program maneuver to establish itself onto the proper flight azimuth for the injection of the SES-8 communications satellite into geostationary transfer orbit. Eighty seconds into the ascent, the vehicle will pass Mach 1 and experienced a period of maximum aerodynamic stress (known as “Max Q”) on its airframe. The Merlin-1Ds will continue to burn hot and hard, finally shutting down at T+2 minutes and 58 seconds, and the first stage will be jettisoned five seconds later. The turn will then come for two “burns” by the Falcon’s restartable second stage, which will ignite for the first time at T+3 minutes and 10 seconds. Its single Merlin-1D Vacuum engine, with a maximum thrust of 180,000 pounds (81,600 kg), will burn for 320 seconds to establish the vehicle and SES-8 payload into a “parking” orbit.
A minute into the second-stage flight, the two-piece Payload Fairing (PLF)—a 43-foot-long (13.1-meter) protective cover which encapsulates the SES-8 satellite—will separate from the vehicle. “Like the inter-stage between the first and second stages,” explained AmericaSpace’s Launch Tracker in its notes for the inaugural Falcon 9 v1.1 launch on 29 September, “a pneumatic system is used to separate the two halves, rather than the traditional pyrotechnics.” Fabricated from carbon-fiber and aluminum-honeycomb, the PLF was extensively tested by SpaceX in April 2013 within the confines of the Reverberant Acoustic Test Facility at NASA’s Plum Brook Station in Sandusky, Ohio, part of the Cleveland-based Glenn Research Center.
The first shutdown of the second-stage engine is scheduled to occur at T+8 minutes and 30 seconds, after which the vehicle will coast for 18 minutes, ahead of a second “burn”—lasting about one minute—to carry SES-8 into geostationary transfer orbit. And five minutes after the Merlin-1D Vacuum shuts down for the second time, at 32 minutes and 53 seconds after liftoff, the satellite will be released into its 180 x 50,000-mile (300 x 80,000 km), 20.75-degree-inclination transfer orbit. This process will be monitored closely, for SpaceX was unsuccessful in restarting the Merlin-1D Vacuum during the 29 September maiden flight of the Falcon 9 v1.1. A propulsive-return-over-water test is not planned to occur on the SES-8 flight, or on next month’s launch of the Thaicom-6 communications satellite, but will be attempted on the February 2014 flight of the third dedicated Dragon mission (SpX-3) to the International Space Station.
Tonight’s abort comes as a bitter disappointment for SpaceX, which had earlier noted on its webcast that this would have been only the second space-bound mission to be launched from the Cape on Thanksgiving, coming 54 years since the 26 November 1959 flight of the ill-fated Pioneer (P-3) lunar probe. Yet tonight, SpaceX can express its own thanksgiving, for the uprated Falcon 9 v1.1 and its Merlin-1D engines appear to have performed nominally in response to an unanticipated abort situation, after first-stage ignition.
Fifty-four years ago, on Thanksgiving Day in 1959, the world was a quite different place. At that time, only the Soviet Union and the United States had successfully flown artificial satellites, and both nations were striving to launch a man into orbit—the former through its Vostok program and the latter through Project Mercury. The mission known today as Pioneer P-3 was lofted from the Cape’s Launch Complex 14, atop an Atlas Able booster, and was tasked with journeying to the Moon. It would utilize a payload of scientific instruments to image the Moon’s surface and shed light upon the mass characteristics and topography of our closest celestial neighbor. The spherical spacecraft would also study micrometeorites, radiation, magnetic fields, and electromagnetic waves. Unfortunately, just 45 seconds into the flight, the fiberglass payload shroud broke away from the ascending rocket and the payload was subjected to crippling aerodynamic overloads. Less than two minutes after leaving Cape Canaveral, all communications were lost, along with the payload and the vehicle.
“We called manual abort,” Elon Musk tweeted in the aftermath of the abort. “Better to be paranoid and wrong.” Tonight, a launch eluded SpaceX, but it is fortuitous that the Falcon 9’s safety systems kept it safe, and she remains primed to fly another day.