The Russian Proton-M was back in action on Tuesday, tasked with lofting the Ekspress-AM6 communications satellite on a multi-hour flight to a geostationary orbit via its Briz-M Upper Stage. The Russian workhorse launched on schedule from its traditional home at the Baikonur Cosmodrome in Kazakhstan at 15:09 UTC and apparently successfully deployed the satellite. However, half a day later, questions were raised about its initial orbit.
The Proton booster 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). Overall height of the three stages of the Proton booster is 42.3 m (138.8 ft).
The Proton vehicle has a heritage of around 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 sent 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 The Rokot-K has since been replaced by the Rokot-KM, with a modernised Briz-KM upper stage.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.
Spacecraft separation occurred at 00:31 UTC on Wednesday morning. There wasn’t any live webcast of the mission, per a late decision by Roscosmos.
UPDATE: Sources note the satellite was deployed into the wrong orbit, but officials have not confirmed this issue and have apparently claimed it is in the correct orbit. It is possible the orbit parameter problem – if confirmed – can be solved during the satellite’s propulsive trip to its designated orbital home.
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The Ekspress-AM6 satellite has a mass of 3,200 kg and sports 14 C-band, 44 Ku-band, 12 Ka-band and 2 L-band transponders and is expected to have a service life of 15 years. It has 284 kg of xenon and 75 kg of hydrazine for its onboard propellant needs.
The satellite built around ISS-Reshetnev’s heavy-class Express-2000 platform. It was manufactured under a contract with the national operator RSCC (Russian Satellite Communications Company).
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 of this satellite follows a recent loss in its family, namely the Ekspress-AM4R, that was lost during a launch in May of this year. The failure was due to a problem 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 Proton-M successfully returned to flight in late September with a Russian military launch.
(Images via ILA, Roscosmos and ISS Reshetnev).