Falcon 9 conducts second launch this week with SES-11 mission

by William Graham

SpaceX launched its third re-flown Falcon 9 rocket Wednesday, carrying the EchoStar-105/SES-11 communications satellite into geosynchronous transfer orbit for SES and EchoStar. Liftoff, from Launch Complex 39A at the Kennedy Space Center took place at the opening of a two-hour window at 18:53 Eastern Time (22:53 UTC), with the booster landing successfully.

SpaceX Launch:

Flying less than sixty hours after another Falcon 9 lifted off from California’s Vandenberg Air Force Base and successfully deployed ten Iridium-NEXT communications satellites, Wednesday’s mission saw Falcon carry the SES-11 communications satellite to geosynchronous transfer orbit for SES of Luxembourg.

The spacecraft will be operated by SES in conjunction with US telecoms company EchoStar, as EchoStar-105/SES-11.

SES-11 is the second satellite that SpaceX has launched for SES this year, and the fourth overall. Wednesday’s launch followed March’s successful deployment of SES-10, and earlier missions in 2013 and 2016 which deployed the SES-8 and SES-9 satellites.

SES-8 was the first geostationary satellite to be launched by SpaceX, while March’s SES-10 launch was the first to make use of a “flight-proven” first stage – one which had been recovered following a previous launch.

In the case of March’s launch, the first stage had boosted a Dragon mission to the International Space Station the year before.

Another previously-flown first stage will be used for Wednesday’s mission to deploy SES-11: Core 1031 was part of the rocket that carried Dragon’s CRS-10 mission into orbit in February.

Following a successful landing at Cape Canaveral’s Landing Zone 1 – the former Launch Complex 13 at the Cape Canaveral Air Force Station – Core 1031 was refurbished for the SES-11 launch.

Falcon 9 is the only rocket currently flying that incorporates reusability: after separating from the second stage, which carries the rocket’s payload the rest of the way to orbit, the core uses its remaining propellant to make two or three additional engine burns – the last of which guides it to a controlled landing either on land near to the launch site, or at sea aboard an Autonomous Spaceport Drone Ship (ASDS) barge.

The Space Shuttle is the only other orbital rocket that has demonstrated partial reusability.

Wednesday’s launch was the third Falcon 9 mission to re-use a previously-flown first stage. In addition to March’s SES-10 launch, a second re-use occurred in June when BulgariaSat-1 was boosted by a core stage that had previously been used to deploy ten Iridium communications satellites.

Like the previous missions, Wednesday’s launch used a first stage that previously flew a low Earth orbit mission to carry a satellite into geosynchronous transfer orbit on its second flight.

To date, SpaceX has only re-flown first stages recovered from low Earth orbit missions; geosynchronous launches see the stages separate at higher velocity and subject them to more extreme conditions as they reenter the atmosphere.

Core 1031 was previously used during February’s launch of CRS-10, a Dragon mission that delivered supplies and experiments to the International Space Station. CRS-10 was the first mission that SpaceX launched from the Kennedy Space Center, having flown their previous Falcon 9 missions from Space Launch Complex 40 (SLC-40) at the nearby Cape Canaveral Air Force Station.

Wednesday’s launch again used Launch Complex 39A (LC-39A) at Kennedy, making Core 1031 the first Falcon 9 core to fly twice from the same launch pad.

SpaceX leased Launch Complex 39A from NASA in 2014 to support manned Dragon launches to the International Space Station, the company’s Falcon Heavy rocket which is due to make its debut late this year or early next, and future vehicles such as the formerly named Interplanetary Transport System (ITS) and its “Big Falcon Rocket” (BFR).

Space Launch Complex 40 was damaged when a Falcon 9 exploded during fuelling ahead of a static fire test last September, so LC-39A has been used for all of SpaceX’s East Coast launches in 2017 while that pad is repaired. SLC-40 is not expected to be ready to support a launch until at least the end of November.

LC-39A is the same pad from which Apollo 11 launched in 1969, becoming the first manned mission to land on the moon. The pad, which was built in the 1960s along with nearby Launch Complex 39B and the NASA’s Vehicle Assembly Building, was constructed as the primary launch pad for the Apollo program.

The Saturn V made twelve of its thirteen launches from LC-39A, a number that included all of the manned missions to orbit or land on the moon except for Apollo 10 – which flew from LC-39B due to a short turnaround after Apollo 9.

After the end of the Apollo program, the final Saturn V launch from LC-39A carried the United States’ first – and so far, only – space station, Skylab, into orbit.

The pad was then converted for the Space Shuttle, with Columbia making the program’s first launch – STS-1 – from the pad in April 1981. In all, eighty-two of the Space Shuttle’s 135 missions began at Pad 39A, including Atlantis’ STS-135 mission in July 2011 which brought the curtain down on the Shuttle program.

A Falcon 9 made the one-hundredth launch from LC-39A in June, while Wednesday’s launch marks the 105th from the pad overall and the eleventh to be made by a Falcon 9.

Saturn and Space Shuttle launches from LC-39A saw the rockets integrated vertically atop a Mobile Launcher Platform within the Vehicle Assembly Building, with the platform and rocket then moved to the launch pad atop a Crawler Transporter.

SpaceX has opted instead to continue with horizontal integration – as it has used at SLC-40, Space Launch Complex 4E at Vandenberg Air Force Base and in its earlier operations with the smaller Falcon 1 rocket out of Omelek Island in the Pacific.

To facilitate this, a large hangar has been assembled at the foot of the Crawlerway. Falcon is integrated in the hangar before rolling to the launch pad atop a Strongback, or transporter-erector-launcher (TEL), which also raises the rocket to vertical and provides umbilical connections to the vehicle up until liftoff.

The SES-11 satellite continues a partnership between SES and EchoStar, replacing the AMC-15 satellite – located at 105 degrees West – whose capabilities EchoStar have leased since it was launched aboard a Proton-M/Briz-M rocket in October 2004. AMC-15, which was built by Lockheed Martin around the A2100AXS bus, carries 12 Ka-band and 24 Ku-band transponders.

Originally launched for SES subsidiary SES Americom, internal mergers saw it transferred to the short-lived SES World Skies in 2009 before this was absorbed into its parent company two years later.

Like AMC-15, SES-11 carries twenty-four Ku-band transponders, although it does not have a Ka-band payload. EchoStar will lease the spacecraft’s Ku-band capacity to deliver services to North America as EchoStar-105. EchoStar’s involvement with the SES-11 spacecraft goes beyond this lease, however, with both companies having worked together to define their requirements, design the spacecraft and select contractors.

The companies signed an agreement with Airbus Defence and Space in September 2014 to build the SES-11 satellite. Built around Airbus’ Eurostar E3000 bus, the satellite has a mass of 5,200 kilograms (11,500 lb) and is designed to operate for at least fifteen years.

In addition to its Ku-band payload, the satellite also carries 24 C-band transponders which SES will use for television distribution through North America, Hawaii and the Caribbean. In this role, SES-11 will replace another former SES Americom satellite, AMC-18, which launched aboard an Ariane 5 in December 2006.

Wednesday’s launch was the fifteenth that SpaceX has performed in 2017, following Monday’s successful mission for Iridium Communications. The SES-11 launch had initially been scheduled to fly before Iridium. However, an attempt scheduled for Saturday was called off to resolve an issue with a first stage engine.

The two-stage Falcon 9 rocket will carry SES-11 into a geosynchronous transfer orbit. After being deployed into this orbit, SES-11 will raise itself into its final geostationary orbit, high above the Earth’s equator, to begin its mission.

First flown in June 2010, Falcon 9 has conducted forty-two missions prior to Wednesday’s launch with a record of forty successful launches, one failure and one partial failure which deployed its primary payload successfully but lost a secondary payload that was to have been deployed into a different orbit.

Another Falcon 9 was lost, along with its payload, during a pre-launch test at Space Launch Complex 40 last September.

Both stages of the Falcon 9 rocket burn RP-1 kerosene propellant, oxidized by liquid oxygen. The first stage powers the rocket at liftoff – igniting its nine Merlin-1D engines about three seconds before the countdown reaches zero – and propels the rocket through the dense lower reaches of the atmosphere. Falcon passed through the area of maximum dynamic pressure, or Max-Q, 78 seconds after liftoff.

The first stage – Core 1031 – burned for the first two minutes and thirty-five seconds of Wednesday’s flight. Three seconds after main engine cutoff, or MECO, the first and second stages separated. The second stage ignited its single Merlin-1D engine two seconds after stage separation, beginning the first of two planned burns to inject SES-11 into orbit.

One minute into the second stage burn, Falcon’s payload fairing separated. The second stage’s first burn lasted five minutes and 58 seconds and was followed by a 16-minute, 21-second coast.

At the end of the coast, a 59-second burn raised the orbit ahead of spacecraft separation. SES-11 was deployed eight minutes and nine seconds after the second burn concludes.

While the second stage continued to orbit with SES-11, the first stage – Core 1031 – began its return to Earth. With Wednesday’s mission targeting a geosynchronous transfer orbit, the core did not have enough fuel remaining to return to Cape Canaveral.

Instead, as normal for such a launch, SpaceX stationed its Autonomous Spaceport Drone Ship (ASDS) – named Of Course I Still Love You – downrange to make the landing attempt at sea. With the ASDS catching the core downrange, no boostback burn was required.

Shortly after it separated from the second stage, the core deployed its gridfins to provide additional control as it plummeted back through the atmosphere. About three minutes and 46 seconds after separation, Core 1031 performed its entry burn, firing three engines to slow its descent as it began to enter the denser regions of Earth’s atmosphere.

Landing on the deck of Of Course I Still Love You occurred about two minutes and nine seconds later, with three engines re-igniting for their landing burn seconds before touchdown. This burn, which began at the last possible moment in order to conserve propellant, slowed the rocket’s descent so it could make a survivable landing on the drone ship. In contrast, low earth orbit missions would use a longer, single-engine burn to provide greater control and a softer landing.

Wednesday’s launch was the fifteenth to be conducted by SpaceX in 2017, with up to six further launches still to come before the end of the year. The next mission is slated for 30 October, with a Falcon 9 flying from LC-39A to deploy the Koreasat-5A communications satellite. Another SES satellite, SES-16, also known as GovSat, is slated to launch no earlier than December atop another Falcon 9.

(Images: SpaceX, SES, NASA and L2 imagery via Brady Kennison, Chris Gebhardt, Jay Deshelter for NASASpaceFlight.com. To Join L2, which includes access to a vast dump of hi-res L2 SpaceX photos, *click here*)

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