By Kendra Chamberlain
France’s Arianespace will launch its second mission of year on February 14, at the Guiana Space Center (GSC) located in French Guiana. Arianespace will use its expendable Ariane 5 rocket to launch two commercial telecom satellites into orbit from the spaceport’s ELA-3 launch zone.
The Ariane 5 family of rockets are heavy lifters, and have large fairings that measure 17 meters high — with an external diameter of 5.4 meters — that make the rockets suitable to launching larger satellites for both commercial use and research. The Ariane 5 ECA model can carry payloads weighing over 10 metric tons into orbit. Its heavy lifting capabilities enables Arianespace to offer “dual launches” of two telecommunications satellites. It’s also the rocket model the European Space Agency (ESA) used in 2008 for launching the Herschel and Plank scientific observation mission.
Arianespace’s upcoming VA235 launch will carry two commercial telecom satellites: the SKY Brasil-1, which will be operated by DirecTV Latin America for pay TV, and the Telkom 3S, which will be operated by Indonesia service provider PT Telkom for voice and data services. The SKY Brasil-1 satellite will ride in the upper position of the payload dispenser system, and the Telkom 3S will sit in the lower position.
The other Ariane 5 model, called the Ariane 5 ES, can carry 20 metric tons into low Earth orbit (LEO). It’s used for Automated Transfer Vehicle (ATV) missions, such as cargo supply missions to the International Space Station (ISS).
The Ariane 5 rocket contains a Main Cryogenic Stage, two strap-on solid rocket boosters and an upper stage, and the ECA has an additional Cryogenic Upper Stage.
The lower composite of the rocket includes the two solid EAP (Etage d’Accélération à Poudre) boosters and the cryogenic EPC (Etage Principal Cryotechnique) Vulcain 2 main engine. During a launch, the Vulcain 2 is ignited first. Once it reaches its nominal operating level, the two booster engines are ignited.
On the ECA model, the two boosters hold 10% more propellant, weighing some 2.5 metric tons, to help it accommodate the extra large load. The extra propellant delivers an additional 50 metric tons of thrust during the first 20 seconds after liftoff. All together, the two boosters deliver 1,300 metric tons of thrust at liftoff. They burn for 135 seconds before separating from the main stage via pyrotechnic devices and separation motors. The boosters then re-enter the atmosphere over the Atlantic ocean, and they can either be recovered for analysis (if equipped with parachutes) or left to settle at the bottom of the ocean.
The cryogenic EPC Main Core Stage is powered by the Vulcain 2 gas generator cycle engine, which means a portion of its liquid propellant is used to generate hot gas that powers the engine’s pumps. The Vulcain 2 engine is made by France-based manufacturer Snecma, a subsidiary of Safran.
The EPC holds 175 metric tons of propellants — 25 metric tons of liquid hydrogen and 150 metric tons of liquid oxygen. The Vulcain 2 engine provides 136 metric tons of thrust, and burns for 540 seconds.
The EPC then separates from the upper composite at altitudes between 160 km and 210 km. Once separated, the EPC performs its destructive re-entry into the Earth’s atmosphere over the Atlantic.
The upper composite of the Ariane 5 ECA contains the ESC-A Cryogenic Upper Stage (Etage Supérieur Cryotechnique de type A), the vehicle equipment bay (VEB), and payload-supporting infrastructure. The Cryogenic Upper Stage includes 14.7 metric tons of propellant and the HM7-B engine, which delivers 6.5 metric tons of thrust and runs for 945 seconds. The VEB, which holds the flight computers and electronics, autonomously controls the entire vehicle and transmits flight data to the ground station.
The Launcher Upper Part is comprised of the fairing and the Sylda 5 and Speltra structures that house the two satellites. The Speltra is slightly larger than the Sylda 5, and the two are used to accommodate satellites of different sizes. Around three minutes after lift-off, the fairing is jettisoned from the remaining structure via pyrotechnic charges. The upper satellite is separated from the Sylda/Speltra structure and released. Then the Sylda/Speltra is jettisoned, and the second satellite is released.
Arianespace says its rockets are able to “fast-track” payloads into orbit. The Ariane 5 rockets can reach geostationary transfer orbit (GTO) in 25-35 minutes, depending on the separation phase events.
Arianespace’s launch window for Feb 14 is 4:39 pm to 6:05 pm EST (21:39 to 23:05 GMT).
