Good to go for GTO: Soyuz to launch SES-15 satellite from French Guiana
Arianespace‘s Europeanized variant of the workhorse Russian Soyuz rocket stands ready to launch the SES-15 telecommunications satellite. The medium-class launch vehicle, known for decades of reliable launches to low-Earth orbit, is being tapped for its second mission to geosynchronous transfer orbit (GTO) from the Guiana Space Center.
Liftoff is currently targeted for 7:54 a.m. EDT (11:54 GMT) May 18, 2017, from Arianespace’s South American launch complex in French Guiana.
Riding atop the Soyuz is the SES-15 communications satellite.
The satellite marks the first hybrid spacecraft in SES’ as it will provide both wide-beam and high-throughput coverage, for the Luxembourg-based operator.
The spacecraft, SES’ first all-electric satellite, is equipped with four electric propulsion engines capable of both raising the spacecraft’s orbit and maintaining its orbital slot at 129 degrees West. From that position, the satellite will provide Ka- and Ku-band coverage to North and Central American markets.
“Thanks to its extensive coverage, SES-15 will be the first satellite to enable airline passengers to access full, seamless HTS coverage from New York all the way to Hawaii – or from Alaska to Mexico,” noted SES, in a release issued by the company. “SES-15 is also equipped with a dedicated wide beam that will allow IFEC providers to provide live broadcast of TV content on all flight routes across the entire region. This unique combination of beams enables IFEC providers to optimally utilize HTS capacity for internet traffic and wide beam coverage for broadcasting content.”
Beyond supplying digital communications services, the satellite is also outfitted with a Wide Area Augmentation System (WAAS) payload. WAAS is designed to supplement traditional GPS-based navigation, greatly enhancing the accuracy of the system.
SES-15 tips the scales at 5,075 pounds (2,302 kilograms), and has an on-orbit design life of 15 years.
SES-15 will launch atop a Europeanized Soyuz ST-A launch vehicle, which is an upgraded version of the venerable family of Soviet and Russian launchers that has seen decades of successful use.
The Soyuz, in its various incarnations, has tallied up more than 1,800 launches over 60 years and is capable of sending more than 6,190 pounds (2,810 kilograms) to GTO in the ST-A variant used on this mission.
The rocket’s first stage is composed of a core, surrounded by four liquid-fueled strap-on boosters – an iconic design that is immediately recognizable by the distinctive look of the four boosters as they taper to meet the core stage.
The core stage and side boosters make use of slightly different versions of the same family of the Russian-manufactured engine – the RD-107A on the boosters and the RD-108A on the core. Both engine models are powered by a single turbopump assembly feeding liquid oxygen (LOX) and highly refined kerosene (RG-1) into four independent combustion chambers.
While the side boosters don’t need to provide a large amount of control over the vehicle, the core stage needs a full range of attitude adjustment. This variation of control requirements is reflected in the number of vernier engines per propulsion module and is the reason for a different model designation per engine even though they are otherwise largely similar. The core stage’s RD-108A is outfitted with four verniers, while the RD-107A in the boosters have two.
The difference in verniers isn’t the only thing setting the two engines apart. While they both burn the same mixture of fuel and oxidizer, their output is slightly different.
The RD-107A in the boosters each provide 188,500 pounds-force (838.5 kilonewtons) of sea-level thrust during their two-minute burn time, while the RD-108A in the core clocks in a slightly lower 178,100 pounds-force (792.5 kilonewtons).
Powering the second stage is the Russian-made RD-0110. Like its larger RD-107A/180A cousins, the RD-0110 has four combustion chambers, into which is fed LOX and RG-1 from a single turbopump system. The smaller RD-0110 provides 67,000 pounds-force (298 kilonewtons) of vacuum thrust.
The Russian-made Fregat-MT is the upper stage for the SES-15 mission. Although the Fregat-MT has had a less-than-perfect record, it has seen several successful missions since its redesign and was most recently responsible for placing the Hispasat 36W-1 satellite into its proper transfer orbit.
Arianespace will provide launch coverage via their website.
Curt Godwin has been a fan of space exploration for as long as he can remember, keeping his eyes to the skies from an early age. Initially majoring in Nuclear Engineering, Curt later decided that computers would be a more interesting - and safer - career field. He's worked in education technology for more than 20 years, and has been published in industry and peer journals, and is a respected authority on wireless network engineering. Throughout this period of his life, he maintained his love for all things space and has written about his experiences at a variety of NASA events, both on his personal blog and as a freelance media representative.