The SpaceX Falcon 9 rocket launched the first West Coast return-to-launch-site mission Sunday. The launch, whose primary mission was to deploy Argentina’s SAOCOM 1A radar imaging satellite, took place from Vandenberg Air Force Base’s Space Launch Complex 4E at 19:22 Pacific Time (02:22 UTC on Monday). Falcon’s first stage successfully touched down at the nearby Landing Zone 4 about seven and three-quarter minutes after liftoff.
From the outset, SpaceX has aimed to drive down the cost of access to space, in a large part by making as much or their rockets reusable as possible. While the company’s initially planned to recover their rockets’ first stages with parachutes, this proved impractical. Instead, Falcon 9 was upgraded, giving it additional performance that can be used – where mission requirements allow – to make a powered landing of the first stage.
Depending on the mass of its payload and the orbit it is aiming for, the first stage can either fly back to its launch site, or it can land aboard a floating platform – known as an Autonomous Spaceport Drone Ship (ASDS) – positioned downrange to catch the vehicle on its existing trajectory. SpaceX made its successful return-to-launch-site landing at Cape Canaveral in December 2015, followed a few months later in April 2016 by the first successful landing atop the ASDS.
Until now, all booster recoveries at SpaceX’s West Coast launch site, Vandenberg Air Force Base in California, used an ASDS which is named Just Read The Instructions. The West Coast drone ship was first employed in January 2016 to try and recover the first stage of a rocket that had deployed the Jason 3 ocean research satellite – however, the booster’s landing gear failed to lock into position and it toppled over on touchdown. Success followed a year later on the first mission of a multi-launch contract to deploy Iridium-NEXT communications satellites.
Prior to Sunday’s launch, SpaceX had successfully landed the first stage of a Falcon 9 rocket 27 times: nine via return-to-launch-site at Cape Canaveral, thirteen on the East Coast ASDS, Of Course I Still Love You, and five aboard Just Read The Instructions on the West Coast.
In addition, the two side boosters of the first Falcon Heavy rocket – launched from Florida’s Kennedy Space Center in February – also made landings at Cape Canaveral although its center core’s landing aboard Of Course I Still Love You was unsuccessful. Falcon Heavy uses three modified Falcon 9 cores strapped together to provide additional thrust in the early stages of its flight.
The landing pad that was used for Sunday’s mission is designated Landing Zone 4 (LZ-4).
The landing zone has been constructed on the site of Space Launch Complex 4W (SLC-4W). Originally part of the US Navy’s Point Arguello launch site, Launch Complex 2-3 as it was then designated was built for the Atlas-Agena rocket in the early 1960s. It saw its first launch in July 1963 with an Atlas LV-3 Agena-D deploying the first KH-7 Gambit reconnaissance satellite. Point Arguello was merged into the adjacent Vandenberg Air Force Base in July 1964, with LC-2-3 being redesignated SLC-4W in 1966. The twelfth and final Atlas launch from the pad took place in March 1965.
Just sixteen months later, SLC-4W began its long association with the Titan family of rockets when it hosted the maiden flight of the Titan IIIB. A series of different Titan IIIB configurations – pairing the first and second stages of the Titan III (without boosters) and the Agena-D upper stage – flew out of SLC-4W from July 1966 until February 1987, all on missions for the National Reconnaissance Office. Fifty-four of its sixty-eight launches carried KH-8 Gambit photoreconnaissance satellites, while the remainder deployed Quasar communications satellites and Jumpseat signals intelligence (SIGINT) spacecraft.
Between 1988 and 2003, thirteen Titan II(23)G rockets flew from SLC-4W. These consisted of decommissioned Titan II missiles that were used to deploy satellites, with or without the aid of solid-fuelled upper stages. The Titan II(23)G missions deployed a mixture of payloads for military and civilian government agencies – with about half of its launches carrying weather satellites. The final launch from SLC-4W took place on 18 October 2003, with the last Titan II carrying a Defense Meteorological Satellite Program (DMSP) spacecraft into orbit. In all, 93 rockets were launched from the pad during its time in service.
Space Launch Complex 4 was a two-pad launch complex, with SLC-4W accompanies by the nearby Space Launch Complex 4E (SLC-4E). Formerly Point Arguello’s Launch Complex 2-4, SLC-4E was also used by Atlas-Agena rockets from 1964 onwards. However, these continued after SLC-4W had been converted for the Titan IIIB.
SLC-4E would later be used by Titan IIID, Titan III(34)D and Titan IV rockets, supporting the final launch of a Titan vehicle in October 2005. SpaceX took over the complex in 2011 and rebuilt it to launch Falcon 9 rockets. It is from SLC-4E that Falcon will lift off for Sunday’s mission to deploy the SAOCOM 1A satellite.
Satélite Argentino de Observación Con Microondas, or SAOCOM, is a constellation of radar-imaging satellites that is being established by Argentina’s national space agency, Comisión Nacional de Actividades Espaciales (CONAE).
The constellation, whose name means Argentine satellite for microwave observation, will consist of two satellites, which will be interoperated with Italy’s COSMO-SkyMed system. COSMO-SkyMed is a four-satellite constellation that was deployed between 2007 and 2010, with a new generation of satellites slated to begin launching next year.
CONAE was an early customer for the Falcon 9, signing a contract for SpaceX to launch both of the SAOCOM satellites in April 2009: over a year before the rocket made its maiden flight and still three months before the smaller Falcon 1 made SpaceX’s first successful launch with a functional payload. At the time, the two launches were scheduled to take place between 2012 and 2013.
SAOCOM 1A is a 3,000-kilogram satellite. Built by INVAP, it is based around the same platform used for the SAC-C remote sensing satellite which launched aboard a Delta II rocket in November 2000. Designed to operate for five years, the satellite will use L-band synthetic aperture radar (SAR) to image the Earth in any weather or lighting conditions. SAOCOM 1B is an identical satellite which will join SAOCOM 1A in orbit next year.
The radar-imaging sensor aboard the two satellites is SAOCOM SAR. This can operate in two different modes: strip mapping and terrain observation with progressive scans (TOPSAR). In strip mapping mode, SAOCOM SAR can image at resolutions of up to 10 meters (33 feet) per pixel, or 25 meters (82 feet) in medium-resolution mode. Configured for TOPSAR, the instrument has a resolution of 25 meters (82 feet) per pixel in narrow mode and 50 meters (164 feet) in wide mode.
CONAE expect to be able to use the SAOCOM constellation to monitor Earth resources, agriculture and urban development, for cartography and to assist in the management and response to natural and man-made disasters. The satellite will also be used to map soil moisture in the Earth’s surface.
Sunday’s launch was the sixty-second for SpaceX’s Falcon 9 rocket and the sixty-eighth for SpaceX overall. The Falcon 9 first flew in June 2010 and has undergone a series of upgrades to reach the Block 5 configuration that will perform the SAOCOM 1A launch. Falcon 9 is a two-stage rocket, with its first stage powered by nine Merlin-1D engines. A tenth Merlin-1D, in Merlin Vacuum (MVac) configuration powers the rocket’s second stage. SAOCOM 1A sat atop the second stage enclosed within a payload fairing, which protects it from the Earth’s atmosphere as the rocket ascends towards space.
The first stage that powered Sunday’s mission had already completed one launch successfully. Core 1048 was previously used as the first stage of the Falcon 9 that deployed ten Iridium-NEXT satellites in late July, making a successful landing aboard Just Read The Instructions after that launch. Sunday’s launch marked its second flight, however the Block 5 first stage, unlike previous versions, is capable of flying more than two missions before retirement.
Fuelling of the Falcon 9 in preparation for liftoff occurred at about the thirty-five minute in the countdown, having been given a go-ahead by the launch director about three minutes earlier. The rocket burns RP-1 propellant – rocket-grade kerosene – oxidized by liquid oxygen.
Initial propellant loading consisted of RP-1 for both stages of the rocket and liquid oxygen for the first stage only. Loading of liquid oxygen onto the second stage commenced about sixteen minutes before launch.
The final ten minutes of the count saw lots of activity as the final preparations for launch took place. With about seven minutes to go liquid oxygen passed through the rocket’s first stage engines to chill them ready for ignition.
The strongback, a structure that is used to transport Falcon 9 from its hangar to the launch pad, raise it to vertical and provide support and umbilical connections during the countdown, began to retract away from the rocket about four minutes before liftoff. The strongback at Vandenberg is older than the ones that SpaceX use on the East Coast and uses a different retraction process, moving to its launch position ahead of liftoff instead of falling away from the rocket as it begins to climb.
The last minute of Sunday’s countdown saw a number of final key checks conducted by Falcon’s onboard computers. The rocket’s propellant tanks were pressurized for flight and at the forty-five second mark the launch director gave the final “go” for launch. About three seconds before liftoff Core 1048’s nine Merlin-1D engines ignited, undergoing checkout and building up thrust before the rocket was released at T-0.
Falcon began to climb vertically away from Vandenberg’s Space Launch Complex 4E before pitching over to fly downrange to the South. Fifty-nine seconds after lifting-off, Falcon reached the area of maximum dynamic pressure, or Max-Q, where the combination of the rocket’s increasing velocity and the decreasing atmospheric pressure at altitude gave the moment of peak mechanical stress on the vehicle.
The rocket’s first stage burned for two minutes and twenty seconds, at which point the nine Merlin-1D engines shut down. This event is designated Main Engine Cutoff (MECO). Four seconds later the first stage detached from the second, and the two stages went their separate ways. The second stage continued on to orbit with SAOCOM 1A, while the first stage made a series of further engine burns to return to California.
Seven seconds after separation, the second stage ignited its Merlin Vacuum engine. Sunday’s mission called for the second stage to make only a single burn ahead of payload deployment, although the engine will be fired a second time after spacecraft separation in order to dispose of the second stage.
A major milestone in the flight occurred shortly after the second stage ignited. Separation of the payload fairing, 17 seconds into the burn, exposed the SAOCOM 1A spacecraft to space for the first time. The fairing splits into two halves which will fall away from the vehicle.
On recent flights from Vandenberg SpaceX has been conducting trials aimed at recovering the payload fairing under parachute as it descends back into the atmosphere.
Although they have been able to recover intact fairing halves from the water following a parachute descent, these cannot be reused as they have been contaminated by salt water.
A ship, Mr. Steven, has been outfitted with a large net and is sailed out into the Pacific Ocean for each launch to try and catch the fairing as it descends.
While this has not yet been completed successfully, SpaceX did confirm another attempt was called off for Sunday’s mission.
— Pauline Acalin (@w00ki33) October 6, 2018
The second stage’s first burn lasted seven minutes and thirty-six seconds. This placed SAOCOM 1A directly into its deployment orbit. Spacecraft separation occurred two and a half minutes after shutdown, at twelve minutes and 37 seconds mission elapsed time.
Sometime after spacecraft deployment of the second stage will restart for its deorbit burn, which will result in the destruction of the stage as it reenters the atmosphere on its second orbit of the Earth, to the south of Hawaii.
While the second stage continued to orbit with SAOCOM 1A, Falcon’s first stage made three burns of its own as it returns to Vandenberg Air Force Base. Immediately after separating from the second stage, the booster flipped around to point its engines in the direction of flight.
Twelve seconds after staging the boostback burn began, with the first stage firing to change its course back towards the launch site. The stage will continued to gain altitude until it reached the apogee – or highest point- of its trajectory before it began to descend back towards the atmosphere.
The next burn began three minutes and 34 seconds after staging. This was the entry burn, which slowed Falcon’s first stage as it passed back into the denser layers of Earth’s atmosphere, protecting it from heating. Finally, about a minute and a half later a single engine restarted for a landing burn, guiding Core 1048 to touchdown at Landing Zone 4.
Sunday’s launch marked the sixteenth Falcon 9 mission of 2018. The rocket’s next launch is currently scheduled for mid-November with a multitude of small satellites under Spaceflight Industries’ SSO-A Smallsat Express charter.
Qatar’s Es’hail-2 satellite is also slated to fly no earlier than November. However, a precise launch date has not yet been set.
Argentina’s SAOCOM 1B satellite, which will partner SAOCOM 1A in orbit, is currently slated for launch no earlier than June next year.