Arianespace Soyuz ST-A launches with SES-15

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The Arianespace Soyuz ST-A rocket was in action on Thursday, tasked with the lofting of the SES-15 satellite. The launch was only the second time this rocket has lofted a GEO spacecraft from the European Spaceport in Kourou, French Guiana. Liftoff occurred at the start of a window that opened at 11:54 GMT, beginning a multi-hour mission ascent to spacecraft separation.

Soyuz ST-B Launch:

Designated Flight VS17 in Arianespace’s numbering system, SES-15 was the 40th spacecraft orbited by Arianespace for SES, and its launch marked this long-time customer’s first use of Soyuz from French Guiana.

The Boeing-built satellite has an estimated liftoff mass of 2,302 kg., with the mission’s total lift performance set at 2,447 kg. – taking into account the payload integration equipment and other hardware.

SES-15 is based on an all‐electric 702SP platform. It is to be operated from an orbital position of 129 deg. West, with the satellite offering extensive coverage over North America, Mexico and Central America – stretching from Arctic Alaska to the South of Panama, and from Hawaii to the Caribbean.

This is the first of three SES hybrid satellite to be launched and is equipped with 16 Ku-band transponders (36MHz equivalent) as well as a 10 GHz high throughput payload. The satellite will also carry the Wide Area Augmentation Systems (WAAS), a US government-funded hosted payload to augment the Global Positioning Systems (GPS).

This mission was the second flight to geostationary transfer orbit performed by Soyuz from the Guiana. The first was conducted earlier this year, with the Hispasat 36W-1 satellite successfully deployed on January 27.

Soyuz carried out a 5-hr., 18-min. mission from launch to SES-15’s separation into a sub-geostationary transfer orbit. Fregat – which was responsible for the final orbital maneuvers – performed two burns separated by a four-hour-plus ballistic phase to reach the targeted deployment point.

The more powerful Soyuz-ST configuration is the standard version launched from French Guiana, with the additional performance provided by the Soyuz ST-B variant – including a Fregat-MT upper stage. However, for this launch, they used the ST-A.

The Soyuz-2 was developed from the older Soyuz models, and features digital flight control systems and modernized engines. It first flew in 2004.

Two variants are currently in service; the Soyuz-2-1a, and the Soyuz-2-1b which features an RD-0124 third stage engine which provides additional thrust. The RD-0124 was declared operational on 3 May 2011.

A third configuration, the Soyuz-2-1v, has since debuted. It features an NK-33 engine in place of the RD-108A used on the core stages of the other configurations, and does not include the strapon boosters used by other configurations.

The Soyuz-2 forms the basis for the Soyuz-ST rocket, which is optimized to fly from Kourou, and also incorporates a flight termination system and a modified telemetry system.

With the Soyuz ST-B utilizing the RD-0124 third stage engine, an additional 34 seconds of specific impulse (Isp) significantly increases the vehicle’s overall launch performance.

Click here for other Soyuz related articles: https://www.nasaspaceflight.com/tag/soyuz/

The RD-0124 is a staged-combustion engine powered by a multi-stage turbopump, which is spun by gas from combustion of the main propellants in a gas generator. These oxygen-rich combustion gasses are recovered to feed the four main combustion chambers where kerosene – coming from the regenerative cooling circuit – is injected.

Attitude control is provided by main engine activation along one axis in two planes. Liquid oxygen (LOX) and kerosene tanks are pressurized by the heating and evaporation of helium coming from storage vessels located in the LOX tank.

Avionics for the Soyuz launcher are carried in the vehicle’s third stage, and are located in an intermediate bay between the oxidizer and fuel tanks.

As part of the Soyuz’ upgrades for its operations from the Spaceport, the launcher’s flight control system is modernized with a digital control system.

This system incorporates a digital computer and inertial measurement unit that are based on proven technology – giving the Soyuz improved navigation accuracy and control capability.

The new digital control system provides a more flexible and efficient attitude control system, and it gives the additional flight control authority required for the new, enlarged Soyuz ST payload fairing.

In addition, it improves flight accuracy for the Soyuz’ first three stages, and provides the ability to perform in-flight roll maneuvers as well as in-plane yaw steering (dog-leg) maneuvers.

The Fregat upper stage is an autonomous and flexible upper stage designed to operate as an orbital vehicle.  Flight qualified in 2000, it extends the Soyuz launcher’s capability to provide access to a full range of orbits (medium-Earth orbit, Sun-synchronous orbit, geostationary transfer orbit, and Earth escape trajectories).

Fregat consists of six spherical tanks arrayed in a circle (four for propellant, two containing the avionics), with trusses passing through the tanks to provide structural support. The stage is independent from the Soyuz’ lower three stages, having its own guidance, navigation, control, tracking, and telemetry systems.

The Fregat uses storable propellants (UDMH/NTO) and can be restarted up to 20 times in flight – enabling it to carry out complex mission profiles. It can provide 3-axis stabilization or perform a spin-up of the spacecraft payload.

The Fregat first flew in 2000, and has been used on Soyuz-U, Soyuz-FG, Soyuz-2 and Zenit rockets.

The launch was performed from the purpose-built ZLS launch facility for Soyuz – located in the Spaceport’s northern sector near the city of Sinnamary.

Construction of the launch site began in 2007, as Arianespace advanced their plans to add two launch vehicles to their family. (See large set of construction photos in L2).

The Spaceport’s Soyuz launch site combines the proven design elements from the long-existing site at Baikonur Cosmodrome with satellite integration procedures that are in concert with the spacecraft processing used for Ariane missions.

Located 12 kilometers northwest from the existing Ariane 5 launch complex, the new Soyuz facility extends the Spaceport’s operational zone further up the French Guiana coastline.

The launch vehicle’s assembly building is 92 meters long, 41 meters wide, and 22 meters tall, allowing the vehicle to be assembled horizontally, prior to rolling out to the launch site, which is configured after the Russian Baikonur and Plesetsk Cosmodromes, albeit with a new mobile launch service tower.

The Soyuz’ transfer to the Spaceport’s launch zone is performed with the launcher riding horizontally atop a transporter/erector rail car.

Soyuz was then raised into position on the pad, and in contrast with the Baikonur Cosmodrome processing flow, is protected by a gantry that moves into place for payload integration.

(Images via Arianespace and L2.)

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