A Russian Proton-M was in action on Wednesday, lofting the Ekspress-AM7 communications satellite on what was a multi-hour flight to a geostationary orbit via its Briz-M Upper Stage. The Russian workhorse launched from its traditional home at the Baikonur Cosmodrome in Kazakhstan at 22:05 UTC on a nominal first leg of the flight, before successfully deploying the spacecraft.
The Proton booster tasked with launching the satellite was 4.1 m (13.5 ft) in diameter along its second and third stages, with a first stage diameter of 7.4 m (24.3 ft).
The overall height of the three stages of the Proton booster is 42.3 m (138.8 ft).
The Proton vehicle has a heritage of over 400 launches since 1965 and is built by Khrunichev Research and State Production Center, one of the pillars of the global space industry and the majority owner of ILS.
The first stage consists of a central tank containing the oxidizer surrounded by six outboard fuel tanks. Each fuel tank also carries one of the six RD-276 engines that provide first stage power.
Total first stage vacuum-rated level thrust is 11.0 MN (2,500,000 lbf).
Of a conventional cylindrical design, the second stage is powered by three RD-0210 engines plus one RD-0211 engine and develops a vacuum thrust of 2.4 MN (540,000 lbf).
Powered by one RD-0213 engine, the third stage develops thrust of 583 kN (131,000 lbf), and a four-nozzle vernier engine that produces thrust of 31 kN (7,000 lbf).
Guidance, navigation, and control of the Proton M during operation of the first three stages is carried out by a triple redundant closed-loop digital avionics system mounted in the Proton’s third stage.
The mission was tasked with sending the spacecraft to its transfer orbit via the Upper Stage called the Briz-M, which carries out multiple burns to deploy the satellites into their respective orbits.
The Briz-M was developed from the Briz-K stage, which was used on the Rokot-K carrier rocket. The Rokot-K has since been replaced by the Rokot-KM, with a modernised Briz-KM upper stage.
The core of the Briz-M which contains the engines, propellant tanks, avionics and electronic equipment, is based on the Briz-K.
Mounted around the outside of the core is the Auxiliary Propellant Tank, which contains up to 14.6 tonnes of propellant. Fuel is drained from the APT first, and once empty it is jettisoned to reduce the vehicle’s mass.
A single 14D30 engine powers the Briz-M, with four 11D458 vernier engines and twelve 17D58E thrusters being used to provide attitude control. It can make up to eight burns, and produces 19.6 kilonewtons of thrust.
The Briz-M for this mission had the classification 14С43, and was the Phase 3 version which sports improved energy-mass characteristics. As per the mission plan, the spacecraft/upper stage separation took place 9 hours and 13 minutes after liftoff.
The Ekspress-AM7 satellite is a Eurostar E3000 platform and has a mass of 5,712 kg and sports 24 C-band, 36 Ku-band and 2 L-band transponders.
It is expected to have a service life of 15 years. It also holds xenon and hydrazine for its onboard propellant needs.
The spacecraft is intended to provide digital television and radio broadcasting services across Russia, mobile presidential and government communications, multimedia services (telephony, video conferencing, data transmission, Internet access) as well as solutions based on VSAT network technologies.
The launch success for this satellite follows a patchy success rate in lofting this breed of spacecraft, following the loss of Ekspress-AM4R, after a failure during third stage flight.
An investigation into that failure identified the probable cause of the failure was the loss of structural integrity of a bolted interface that attaches the Stage III steering engine turbopump to the main engine structural frame.
The loss of integrity led to an excessive steering engine turbo pump vibration environment that damaged a fuel inlet line to the oxidizer gas generator, resulting in a fuel leak. The loss of fuel led to the premature shutdown of the turbopump and loss of stage control authority and ultimately loss of mission approximately 545 seconds into the flight.
The Ekspress-AM4 satellite was also lost in 2011, after an issue during the fourth burn of the upper stage.
The most recent launch of the Ekspress-AM6 satellite also suffered issues during its ride on the Briz-M and was deployed into a lower than planned orbit. However, it will eventually get to its designated orbit under its own propulsion.
(Images via Roscosmos)