SpaceX has launched the Koreasat-5A communications satellite for South Korea’s KT SAT on Monday, with a Falcon 9 lifting off from the Kennedy Space Center to carry the satellite into geosynchronous transfer orbit. Launch occurred on time at 15:34 local time (19:34 UTC), at the opening of a two-hour, 24-minute window. Landing of the first stage was also successful, albeit resulting in a “toasty” engine section.



SpaceX Launch:

Monday’s launch – the sixteenth of the year for SpaceX – deployed KT SAT’s Koreasat-5A spacecraft, which is also known as Mugungwha 5A. Replacing a faulty satellite in the South Korean operator’s fleet, Koreasat-5A will begin a fifteen-year mission with its journey to orbit aboard Falcon 9.

The three-and-a-half-tonne (7,700 lb) KoreaSat-5A satellite was built by Thales Alenia Space and is based on the SpaceBus-4000B2 platform. Equipped with thirty-six Ku-band transponders, the satellite will support broadcasting and internet services in Korea, Southeast Asia and the Middle East from geostationary orbit at a longitude of 113 degrees East. Koreasat-5A is expected to operate for at least fifteen years.

Koreasat-5A is one of two which KT SAT ordered from Thales in May 2014. The second satellite, Koreasat-7, was successfully deployed by an Ariane 5 rocket earlier this year. Koreasat-5A will replace the Koreasat-5 spacecraft, which was deployed in 2006, flying aboard a Zenit-3SL rocket from Sea Launch’s Odyssey launch platform in the Pacific.

Koreasat-5, another Thales-built satellite, was designed for a fifteen-year lifespan but is being replaced ahead of schedule because of a problem with its solar arrays. In 2013 the drive mechanism, which rotates the solar arrays to face the sun – maximising their exposure to sunlight – stopped operating correctly, reducing the satellite’s available power.

Koreasat-5A will join the Koreasat-7 and Olleh 1 (or Koreasat-6) satellites in KT SAT’s fleet. Formerly known as Korea Telecom, KT SAT’s first satellite was Koreasat-1, deployed in August 1995 by a Delta II rocket. During its ascent to orbit, one of the Delta’s nine solid rocket boosters failed to separate – one of only two blemishes on the Delta II’s otherwise exemplary record – with the satellite attaining a lower orbit than had been planned.

Koreasat-1, along with its sister craft Koreasat-2 and the later Koreasat-3, have since been sold to other operators and the original two satellites have been decommissioned. In addition to its own satellites, KT SAT has leased capacity on other spacecraft, including Asia Broadcast Satellite’s ABS-2 satellite which it markets as Koreasat-8.

Monday’s launch was the first that SpaceX has made for KT SAT, and involved a new-build Falcon 9 rocket, B1042.

Uniquely among rockets currently in service, Falcon 9 is partially reusable, with the first stage designed to make a controlled landing after completing its role in boosting the rocket’s payload into orbit. After landing, stages can be reflown on subsequent launches.

A two-stage rocket, Falcon 9 first flew in June 2010 and Monday’s launch will mark its forty-fourth flight. Since its debut, Falcon 9 has completed 41 missions with complete success. The rocket has failed once – during June 2015’s launch of the CRS-7 Dragon mission to resupply the International Space Station.

The second launch that was not entirely successful was an early mission, which aimed to deploy the CRS-1 Dragon spacecraft and an Orbcomm communications satellite. A first stage engine failure left the rocket unable place the Orbcomm payload into a usable orbit, although Dragon was deployed successfully as planned. A Falcon 9 was also lost along with its payload during a ground test – a static fire a few days before the planned launch of the Amos 6 spacecraft – last September.

The rocket that launched Koreasat-5A is a Falcon 9 v1.2, or Falcon 9 “Full Thrust” model, a revision of the original Falcon 9 which was introduced in 2015 to increase the rocket’s performance – improving maximum payload capacity and making first stage recovery possible on a greater number of missions, including geosynchronous launches.

Falcon 9’s first stage is powered by nine Merlin-1D engines, burning RP-1 kerosene propellant and liquid oxygen. These ignited three seconds before launch, with Falcon 9 lifting off when the launch countdown reached zero.

Climbing away from the Kennedy Space Center, Falcon flew downrange on an easterly azimuth, passing through the point of maximum dynamic pressure – max-Q – seventy-six seconds into its flight.

The first stage provides the initial kick to carry the rocket off of the ground and out of the atmosphere. It burned for two minutes and thirty-three seconds before reaching main engine cutoff (MECO), at which point its role in launching Koreasat-5A was complete.

Three seconds after MECO, Falcon underwent stage separation with Core 1042 separating and falling away from the second stage and payload to begin its return to Earth, deploying its grid fins shortly after separation.

The second stage ignited its single Merlin-1D Vacuum (MVac) engine two seconds after staging, continuing the ascent towards orbit. About sixty-two seconds into the second stage burn the payload fairing separated from around Koreasat-5A at the nose of the rocket.

The second stage, making the first of two planned burns for Monday’s ascent, fired its engine for five minutes and 58 seconds to establish an initial parking orbit. While this burn was ongoing, the first stage will complete its descent, culminating in a planned landing on the deck of Of Course I Still Love You, one of SpaceX’s two Autonomous Spaceport Drone Ships (ASDS).

An ASDS is deployed for Falcon 9 launches which have sufficient fuel reserves to allow the first stage to attempt a landing, but not for it to perform a boostback maneuver to return to the launch site, which is the case for most geosynchronous missions. A large converted barge, the ASDS is positioned downrange to catch the stage as it descends back to Earth.

Of Course I Still Love You was last used to recover the first stage of the Falcon 9 rocket that launched SES-11 earlier this month. Despite recovering the core successfully, a fire broke out aboard the drone ship shortly after landing, damaging both the barge and the robotic “OctaGrabber” or “Roomba” that is designed to secure the first stage to the deck following touchdown. SpaceX was able to carry out repairs quickly to allow OCISLY to participate in Sunday’s launch.

During its descent, Core 1042 made two additional burns. The first, three minutes and 46 seconds after stage separation saw three engines ignite to slow the core as it begins to enter the denser regions of Earth’s atmosphere, reducing heating that would cause damage during reentry.

The second burn began just in advance of landing, slowing Core 1042 to a soft touchdown aboard the drone ship. The landing came about eight minutes and 35 seconds mission elapsed time – just three seconds after the end of the second stage’s first burn.

The aft of the booster was observed to be on fire, although hoses on the drone ship will have put out the flames shortly after landing.

Recovery of the first stage is a secondary objective of any Falcon 9 launch: the primary concern is always the successful deployment of the payload into its planned orbit. For Koreasat-5A, this is a geosynchronous transfer orbit.

To complete insertion, the second stage made a second burn, beginning 26 minutes and 45 seconds after liftoff and lasting for 67 seconds. Spacecraft separation came seven minutes and 46 seconds after the conclusion of this second burn.

Monday’s launch was the sixteenth of the year for SpaceX and the Falcon 9, which has flown more times in 2017 than any other rocket worldwide. Up to four more Falcon 9 launches are planned before the end of the year – along with the Falcon Heavy’s debut that is still targeting a date no earlier than December. Falcon’s next launch will come on 15 November when it deploys the mysterious Zuma payload under contract from Northrop Grumman.

Flight Proven for CRS status:

Looking further ahead, at the beginning of December Falcon will return to at the Cape Canaveral Air Force Station with the launch of Dragon’s CRS-13 resupply mission to the International Space Station – the first launch from SLC-40 since the pad was damaged last September.

According to L2 coverage of extensive reviews, NASA has internally cleared SpaceX to begin using flight-proven Falcon 9 vehicles to launch Dragon.

While NASA’s official stance remains one of no decision being made, information has pointed to CRS-13 being the first mission, re-using the first stage of the rocket that carried CRS-11 to orbit earlier this year. NASA has already approved the use of previously flown Dragon hardware on ISS resupply missions.

The NASA review into flight proven boosters has been ongoing for months, involving a final review and approval process at NASA HQ to asscertain if flight proven boosters could be used on ISS resupply missions.

Towards the end of December, SpaceX’s last planned West Coast launch of the year will carry a further ten Iridium communications satellites into orbit: Falcon’s fourth launch for Iridium in the last twelve months.

This will use another flight-proven booster, which was used on one of the previous Iridium missions back in June. Spain’s HispaSat 30W-6 communications satellite is slated to launch no earlier than December, while the Falcon Heavy’s demonstration flight could also launch late in the year or slip into 2018.

(Images via SpaceX and L2/Chris Gebhardt for NASASpaceFlight.com – to join L2, click here)