More than a third of all SpaceX launches have occurred in 2017 alone, as the Hawthorne, Calif.-based launch services provider despatched its 16th Upgraded Falcon 9 of the year on Monday afternoon (30 October) to deliver the heavyweight KoreaSat-5A communications satellite to Geostationary Transfer Orbit (GTO). Liftoff of the 230-foot-tall (70-meter) booster took place at 3:34 p.m. EDT, right on the opening of a 144-minute “window”. Under near-perfect Florida skies, the Upgraded Falcon 9 rose from historic Pad 39A at the Kennedy Space Center (KSC), as SpaceX eyes at least three more missions before year’s end, including the long-awaited maiden voyage of the Falcon Heavy. Today’s flight was the second occasion in 2017 that SpaceX has launched as many as three Falcons within a single calendar month.
Since the first Falcon 9 launched, way back in June 2010, flying in its “v1.0” configuration, with Merlin 1C engines, SpaceX has delivered a total of 44 of these venerable vehicles into space. The v1.0 flew five times, wrapping up its final mission in March 2013, during which it transported three Dragon cargo ships to the International Space Station (ISS). With its retirement, the baton was passed to the v.1.1, powered by an upgraded Merlin 1D+ engine suite, which supported 15 missions between September 2013 and January 2016. With this version of the booster, SpaceX launched its first payloads to geostationary altitude and into deep space and achieved successful “oceanic” splashdowns of its first-stage hardware for the first time. Several unsuccessful attempts were made to land on the Autonomous Spaceport Drone Ship (ASDS), but it was not until the arrival of the Upgraded Falcon 9 in December 2015 that first-stage hardware was safely brought back through the atmosphere to alight smoothly on either the drone ship or on Landing Zone (LZ)-1 at Cape Canaveral Air Force Station, Fla. Today’s launch was the 24th flight of the Upgraded Falcon 9.
Overall, the success rate of the Falcon 9 fleet has been remarkably high, with a partial failure to insert a secondary payload into orbit in October 2012 and the high-altitude structural breakup and loss of the CRS-7 Dragon in June 2015. More recently, in September 2016, an Upgraded Falcon exploded on Space Launch Complex (SLC)-40 at Cape Canaveral, completely destroying the Amos-6 communications satellite and wreaking significant damage to the pad itself. After repairs and refurbishment, SLC-40 is expected to re-enter operational service with the CRS-13 Dragon mission, currently slated to launch no sooner than 4 December. Rounding out 2017 are the classified Zuma mission for an undisclosed U.S. Government sponsor in mid-November, followed by the Hispasat 30W-6 communications satellite and the long-awaited debut of the Falcon Heavy.
Preparations for today’s mission seemed blessed by an exceptionally positive weather outlook, with a chance of violation classified below 10 percent. “Tropical Storm Philippe has moved north of the Bahamas and will continue moving northeastward today,” noted the 45th Space Wing at Patrick Air Force Base in their L-1 briefing on Sunday. “Monday morning will be chilly on the Spaceport, with temperatures dipping below 10 degrees Celsius (50 degrees Fahrenheit) and lighter northerly winds. There is a very slight risk for the stronger winds to linger into Monday’s launch window.” Violation of Liftoff Winds rulings was the main factor affecting the opening launch attempt, with a risk closer to 10 percent on Tuesday, caused by an anticipated development of cumulus clouds, low-level moisture and light showers.
Primary payload for today’s mission was the 7,700-pound (3,500 kg) KoreaSat-5A communications satellite, built by Thales AleniaSpace on the Spacebus-4000B2 spacecraft “bus”. Equipped with a pair of 15.8-kilowatt-generating solar arrays and batteries, and capable of supporting a 15-year operational lifetime, the cube-shaped Spacebus-4000B2 carries an advanced avionics suite, a 100-volt electrical power bus and an integrated attitude and orbit-control system with star trackers for use at geostationary altitude, some 22,300 miles (35,900 km) above Earth. In the case of KoreaSat-5A, it will support a payload power of approximately 6.5 kilowatts. Several Spacebus-4000B2s have flown, the first in March 2006, together with the Athena-Fidus military communications satellite in February 2014 and the most recent—KoreaSat-7—having ridden an Ariane 5 to orbit in May 2017.
Contracts to build KoreaSat-5A were signed between South Korean satellite operator KTSat and Thales AleniaSpace in May 2014. Under the terms of the contract, Thales would also build KoreaSat-7, with the two satellites intended to provide fixed communications, internet access, multimedia and broadcasting services across Korea, the Philippines, Indonesia, India, Japan and the Middle East. Thales’ role as prime contractor included design, production, testing and delivery of the satellites, together with launch and early operations and on-orbit testing. They boast the largest spacecraft parts ever manufactured in Europe, in the form of 3D-printed telemetry and command antenna supports. In April 2015, Thales announced that the two KoreaSats had passed Preliminary Design Review (PDR), with confidence high that both would be in orbit by the end of 2016.
As circumstances transpired, delays to the SpaceX manifest in the aftermath of the Amos-6 failure pushed many missions to the right and KoreaSat-5A found itself moved into the fall of 2017. Meanwhile, KoreaSat-7—which had been contracted to Arianespace for launch services—ended up “leapfrogging” its sister into orbit. On 4 October 2017, KoreaSat-5A departed Thales AleniaSpace and was flown from Nice, France, to Cape Canaveral. It arrived in the United States the following morning, where it was fueled and readied for launch.
In keeping with protocols adopted in the aftermath of last year’s Amos-6 explosion, the Upgraded Falcon 9 was moved from the Horizontal Integration Facility (HIF) to Pad 39A without the KoreaSat-5A payload attached. A successful Static Fire Test of the nine Merlin 1D+ first-stage engines was conducted on 26 October, after which the booster was returned to a horizontal configuration and returned to the integration building for installation of the bullet-like payload fairing. Yesterday evening (Sunday), the stack was returned to Pad 39A and raised to the vertical to begin pre-launch preparations. Early Monday afternoon, SpaceX engineers began loading the Upgraded Falcon 9 with 793,670 pounds (360,000 kg) of liquid oxygen and 341,700 pounds (155,000 kg) of a highly refined form of rocket-grade kerosene, known as “RP-1”. First-stage RP-1 loading got underway at 2:16 p.m. EDT, followed by second-stage tanking a few minutes later. Liquid oxygen loading got underway some 35 minutes before launch, around 3 p.m.
Passing T-10 minutes, the terminal autosequencer was initiated and the nine Merlin 1D+ engines were chilled, prior to ignition. By this point, KoreaSat-5A had also been transferred to Internal Power, running off its on-board batteries until such time as it could deploy its electricity-generating solar arrays in orbit. At T-2 minutes, the Air Force Range Safety Officer declared all ground-side assets as “Go for Launch” and the booster transitioned to Internal Power, going into startup at T-1 minute as its on-board systems assumed primary command of all critical functions. At this stage, the Niagara deluge system began flooding the surface of Pad 39A with 30,000 gallons (113,500 liters) of water, per minute, to suppress the acoustic energy. Three seconds before T-0, the nine Merlins roared to life, ramping up to combined 1.5 million pounds (680,000 kg) of thrust.
Liftoff occurred precisely at 3:34 p.m. EDT and the Upgraded Falcon 9 followed a characteristically perfect ascent trajectory, its first stage providing the muscle for the first 2.5 minutes, before separating. It then commenced a six-minute descent back through Earth’s “sensible” atmosphere, guided by its hypersonic grid-fins and a pair of engine burns, to alight smoothly on the deck of the drone ship, “Of Course I Still Love You”, situated about 390 miles (630 km) offshore in the Atlantic Ocean. Touchdown occurred at 3:42 p.m. EDT, some eight minutes and 35 seconds after leaving the Space Coast.
Agonizingly, the oft-repeated loss of downlink from either the first stage or the ASDS prevented news of a successful landing for some seconds. At length, SpaceX tweeted at 3:43 p.m..: “Falcon 9 first stage has landed on the Of Course I Still Love You drone ship.” Looking “a little toasty”, in the understated words of SpaceX Lead Mechanical Engineer John Federspiel, the first stage appeared significantly blackened and scarred, yet intact, after her 2.5 minutes of ascent and six minutes of descent. SpaceX subsequently noted that initial fires had been extinguished, but it remains to be seen if this particular first stage is fit to be re-used on another mission. Yet according to former NASA astronaut Garrett Reisman, who today serves as SpaceX’s head of crew operations, the landings are developing an element of the routine. “Great indicator of huge progress,” he tweeted, “when landing a rocket on a drone ship gets a golf-clap, instead of a roar. We’ve come a long way!” Today’s landing was the 12th successful touchdown of a Falcon 9 first stage on either the East or West Coast-based drone ships, since April 2016.
In the meantime, with the first stage gone, the turn came for the second stage, whose Merlin 1D+ Vacuum engine ignited for the first of two “burns” to deliver KoreaSat-5A to geostationary altitude. Generating 210,000 pounds (95,250 kg) of thrust, the engine performed admirably. Its first burn lasted for six minutes, with the engine shutting down eight minutes and 32 seconds into ascent. After this point, the vehicle entered a prolonged phase of “coasting”, lasting almost 19 minutes, until the Merlin 1D+ Vacuum was re-lit for 67 seconds to properly position the satellite for deployment. KoreaSat-5A was finally separated from the second stage of the Upgraded Falcon 9 at 4:09 p.m. EDT, some 35 minutes and 38 seconds after launch. SpaceX confirmed its successful delivery to GTO a few minutes later.
When operational at 113 degrees East longitude, KoreaSat-5A will be devoted to communications service provision over Korea, Japan, the Philippines, Guam, Indochina and South Asia. Its 36-strong suite of Ku-band transponders—12 operating at 36 MHz and 24 at 54 MHz—will provide the capability to fulfil the satellite’s mission. Four extended steerable Ku-band transponders are expected to provide commercial direct-to-home broadcasting over North Asia by the end of 2017. KoreaSat-5A will replace KoreaSat-5, which was launched into orbit way back in August 2006, but was subsequently crippled by a solar array drive mechanism failure in 2013.