For the record-tying eighth time in a single calendar year, SpaceX has successfully launched one of its Falcon 9 boosters to deliver a payload into orbit. At 3:10 p.m. EDT on Friday, 23 June—60 minutes into a two-hour “window”—the Hawthorne, Calif.-based organization transported Bulgaria’s first national communications satellite into Geostationary Transfer Orbit (GTO).
Liftoff from Pad 39A at the Kennedy Space Center (KSC) in Florida came after several days, caused by technical and weather-related issues. Within minutes of launch, the first stage of the 229-foot-tall (70-meter) Upgraded Falcon 9 returned to execute a controlled touchdown on the Autonomous Spaceport Drone Ship (ASDS), “Of Course I Still Love You”, positioned about 420 miles (680 km) offshore in the Atlantic Ocean. As well as representing the second “re-used” Falcon 9 first stage, today’s mission saw the first time that a SpaceX bird has landed twice on ASDS.
Since the inaugural mission by a member of its Falcon 9 fleet, way back in June 2010, SpaceX has trodden a difficult path to establish its bird’s credentials as a frequent-flyer. Despite early pledges to launch every two to three weeks, CEO Elon Musk’s company accomplished only seven missions by December 2013, before steadily ramping up the tempo in 2014 and 2015 and reaching a peak of eight in 2016. However, last year’s high-watermark-level was stunted on 1 September by the on-pad explosion of the Amos-6 mission, which forced SpaceX to stand down for several months of inspections and repairs, pending a return to flight in January 2017.
And this year’s achievements to date have included five major satellite payloads, most notably the first SpaceX launch for the National Reconnaissance Office (NRO), and a pair of Dragon cargo flights to the International Space Station (ISS). With significant damage incurred by Space Launch Complex (SLC)-40 at Cape Canaveral Air Force Station, Fla., following last September’s incident, each 2017 mission has flown from the historic Pad 39A at KSC.
Today’s flight established another first by launching the first national communications satellite on behalf of Bulgaria. However, the nature of the payload ensconsed in the Upgraded Falcon 9’s upper shroud was an old friend: another bird modeled on Space Systems/Loral’s highly flexible SSL-1300 satellite “bus”, which SpaceX launched on five occasions between August 2014 and EchoStar-XXIII in March 2017.
The SSL-1300 for BulgariaSat-1 weighs close to 8,800 pounds (4,000 kg) and supports 30 Ku-band broadcast satellite service transponders and a pair of Ku-band fixed satellite service transponders, which will enable it to deliver Direct-to-Home (DTH) television and other telecommunications services coverage over the Balkans and the rest of continental Europe, together with parts of the Middle East and North Africa. Almost half (around 46 percent) of the satellite’s capacity will be used by companies in Serbia and Bulgaria, with a dedicated “spot-beam” affording extra capacity over the Balkans. Equipped with six electricity-generating solar panels, the satellite will perform its duties from a position at 1.9 degrees East longitude and is anticipated to remain operational for 15-20 years.
Contracts to build BulgariaSat-1 were signed in September 2014 between SSL and BulgariaSat, a subsidiary of the Bulsatcom television provider, with the expectation that the satellite would fly aboard SpaceX’s Falcon 9 by the end of 2016. However, this timeline slipped into mid-2017 in the wake of the Amos-6 failure and other technical issues. The satellite was extensively tested last year in extreme conditions to mirror high thermal, vibrational, acoustic and vacuum-induced stresses, as well as evaluating the performance of its on-board antenna suite. Earlier this spring, BulgariaSat-1 underwent a simulated deployment of its solar arrays and was delivered from SSL’s Palo Alto, Calif., facility to Cape Canaveral in early May.
It was determined that BulgariaSat-1 would ride aboard the second “re-used” Upgraded Falcon 9 first stage, which was previously flown for the Iridium NEXT mission in January 2017 and, according to Space News, has produced substantial savings for SpaceX. Launch was targeted for mid-June and the booster was transferred to the assembly building, close to Pad 39A, early on the 4th, only hours after SpaceX launched its CRS-11 mission to the International Space Station (ISS). A customary Static Fire Test of the nine Merlin 1D+ engines of the Upgraded Falcon 9’s first stage was performed on 15 June, by which time the launch had moved to No Earlier Than (NET) 19 June.
However, the need to replace a fairing valve on the rocket forced SpaceX to announce that the launch would be stood-down until no sooner than the 23rd. “SpaceX identified a problem with the pneumatic system that performs the separation of the payload fairing,” noted AmericaSpace’s Launch Tracker. “Unlike other designs the SpaceX fairings are separated pneumatically rather than pyrotechnically. There are dual systems to perform the separation in case one fails, but SpaceX would rather have two working systems on launch for mission safety.” This proved fortuitous, for the 19th was predicted to have only a 60-percent chance of acceptable weather, overshadowed by the risk of violating the Cumulus Cloud Rule, Thick Cloud Rule and Anvil Cloud Rule.
Weather conditions in Florida for the new launch attempt on 23 June were predicted to be highly favorable, with a 90-percent likelihood of acceptable conditions on Friday, deteriorating slightly to 80-percent in the event of a 24-hour scrub to Saturday. It was noted by the 45th Space Wing at Patrick Air Force Base that the effects of Tropical Storm Cindy would produce a welcome relief in thunderstorm coverage, tempered by the risk of isolated showers. “Expect a small threat for on-shore showers in the morning hours,” it was noted on Thursday, “with cumulus clouds forming mainly west of the Spaceport during the latter part of the countdown.”
Emboldened by this positive outlook, SpaceX teams set to work readying their vehicle for its second re-use. As previously outlined by AmericaSpace, today’s mission was the second time that an Upgraded Falcon 9 first stage has completed more than one flight. In March, the first stage previously employed for a mission in September 2014 was used to deliver the SES-10 communications satellite into orbit, before returning to a smooth landing for a possible third flight in the future. As for today’s BulgariaSat-1 first stage, this was previously used to deliver the first batch of Iridium NEXT satellites in January 2017 and is flying again only five months later.
However, at 1:30 p.m. EDT, SpaceX tweeted that it would delay the launch until 3:10 p.m., approximately one hour into Friday’s two-hour “window”, noting that its team was “running additional ground system checks” and highlighting that both the booster and payload remained in good health. Loading of propellants aboard the Upgraded Falcon 9 got underway around 2 p.m., a little over an hour before Friday’s revised T-0 point, with a highly refined form of rocket-grade kerosene, known as “RP-1”. Since last September’s Amos-6 failure, the booster has been put through a slightly longer-than-usual fueling regime. Forty-five minutes before T-0, at around 2:25 p.m., liquid oxygen began flowing aboard the vehicle.
Notwithstanding the planned ASDS landing attempt, SpaceX CEO Elon Musk was under no illusion that a high-velocity, high-energy re-entry of the first stage might not conclude with a successful touchdown on the drone ship. “Falcon 9 will experience its highest ever re-entry force and heat in today’s launch,” Mr. Musk tweeted at 2:07 p.m. “Good chance rocket booster doesn’t make it back.” Several past GTO-bound missions were unsuccessful in their landing attempts and the March 2017 flight of EchoStar-XXIII did not attempt an ASDS touchdown, in light of its high-energy ascent.
Passing T-10 minutes, the countdown autosequencer was initiated and the nine Merlin 1D+ engines of the first stage—configured in a circle of eight, with a ninth at the center—were chilled, ahead of the ignition sequence. At T-2 minutes, the Air Force Range Safety Officer declared all ground-side assets to be “Go for Launch” and the booster transitioned to Internal Power and assumed primary command of all critical functions, going into “Startup” at T-1 minute. Simultaneously, the Niagara deluge system flooded the Pad 39A surface with water to reduce the reflected energy. The Eastern Range declared its readiness to support the launch as “Range Green”.
Three seconds before liftoff, the nine Merlins roared to life, pumping out a combined thrust of 1.5 million pounds (680,000 kg). Following computer checks of their health, the Upgraded Falcon 9 lifted off at 3:10 p.m. EDT and thundered into the clear Florida sky. Eighty seconds into the climb, it passed through the period of maximum aerodynamic turbulence, colloquially dubbed “Max Q”, and at 2.5 minutes the engines were shut down. The first and second stages separated, with the Merlin 1D+ Vacuum engine of the latter igniting to continue the boost towards orbit.
The vacuum engine, which generates 210,000 pounds (92,250 kg) of propulsive yield, burned for almost six minutes, before shutting down and placing BulgariaSat-1 into a lengthy “coasting” phase. This lasted for a little more than 18 minutes, before the Merlin 1D+ Vacuum was lit a second time—albeit only for about 65 seconds—to complete the task of delivering its precious payload into a Geostationary Transfer Orbit (GTO) of approximately 22,370 miles (36,000 km) above Earth. Finally, BulgariaSat-1 separated from the second stage at 3:45 p.m. EDT, a mere 35 minutes after departing the Home Planet. Over the coming weeks and months, its systems will undergo rigorous checkout and it will be maneuvered into its correct orbital “slot” at 1.9 degrees East longitude.
Although SpaceX makes reference before each of its missions that the first-stage landing remains an experimental (and intrinsically “secondary”) objective, the sight of the lower half of an Upgraded Falcon 9 plunging back through the “sensible” atmosphere to alight on solid ground or on the deck of the ASDS continues to draw great attention. Today’s mission proved no exception.
Following separation, a little under three minutes after leaving KSC, the first stage effected its “entry burn” and was guided back Earthbound by a system of deployable “grid-fins”. A second (“landing”) burn was then executed, but—agonizingly, for those watching on the ground—the video feed from the rapidly descending first stage was lost. Early images from the ASDS deck offered no solace and stomachs sank with the fear that the stage had been lost. Then, all at once, came the electrifying image of a scorched and blackened lower half of the Upgraded Falcon 9, sitting perfectly on the drone ship. Touchdown occurred only eight minutes after leaving KSC.
“Rocket is extra toasty and hit the deck hard,” tweeted Mr. Musk. “Used almost all of the emergency crush core, but otherwise good.”
Remarkably, it was the first time that a first stage had achieved two landings on the ASDS, having previously done so at the end of the Iridium NEXT mission in January. And despite a mixed bag of failure and nail-biting near-misses in 2014-2015, today’s landing was the seventh time a Falcon 9 had alighted on the drone ship in just 16 months, as well as the third in 2017 alone. Next up, attention turns to the West Coast, as SpaceX aims to launch its next batch of Iridium NEXT satellite from Vandenberg Air Force Base, Calif., on Sunday, 25 June. Describing the closeness of the launches as its first “doubleheader”, SpaceX successfully concluded a Static Fire Test for the Iridium NEXT mission on Tuesday.