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Briz-M: Russia's workhorse space tug
First introduced in 1999, the Briz-M space tug replaced the veteran Block-D series as the fourth stage of Russia's workhorse Proton rocket in the 21st century. In 2016, Briz-M got its first opportunity to fly a deep-space mission aimed to send the ExoMars-2016 spacecraft on a path to the Red Planet.
General architecture of the Briz-M stage.
The Briz-M (breeze) stage derived from a smaller Briz-K and Briz-KM variants, which previously flew on the light-weight Rockot launcher. To match the capabilities of larger Proton rockets, Briz-K was upgraded with a thorus-shaped external propellant tank to form the 22.9-ton Briz-M under an industrial designation 14S43. In addition, all the avionics on the upgraded stage were re-designed to work in vacuum of space, unlike previous-generation systems on Briz-K, which required pressurized containers.
The full-scale development of the Briz-M started after its proposed design had been declared a winner in a tender which the Russian government conducted in 1993 and 1994 for the new upper stage of the Proton rocket. The project was funded by the Ministry of Defense for prospective military missions.
Moscow-based GKNPTs Khrunichev, which also built the Proton rocket, advertised such advantages of Briz-M as its very compact size and the capability to function in space for prolonged periods of time. Briz-M stood just 2.6 meters high, comparing to 6.5 meters of Proton's older upper stage Block D. As a result, the new stage would leave much more volume available for potential payloads onboard the launch vehicle. Briz-M's main engine was promised to be able to fire up to eight times during its mission, while the stage was to survive in orbit up to 24 hours. In combination with a cluster of smaller engines onboard, the stage could perform carefully choreographed maneuvers when delivering single or multiple payloads.
The design arm of GKNPTs Khrunichev -- KB Salyut -- completed the preliminary design for Briz-M in 1996. A year later, a set of blueprints for the first flight vehicle and for as many as 10 development prototypes of the stage was issued.
According to Khrunichev, the introduction of Briz-M would enable Proton to carry between 3.2 and 3.5 tons of payload directly into the geostationary orbit (instead of previous 2.5 tons with Block D) or to deliver from 5.5 to more than six tons into the geostationary transfer orbit. Proton/Briz-M combination could place around 15 tons into the low Earth orbit, the company's documents said.
Briz-M was also designed to be compatible with the next-generation Angara family of launch vehicles including Angara-A3 and Angara-A5. During the 1990s, the stage was also proposed for the European Ariane-5 rocket, the Ukrainian-built Zenit and, even possibly, for the Russian Soyuz-2 launcher.
The Briz-M stage is composed of a central core and an auxiliary propellant tank. The external tank is depleted first during the flight, after which all its fuel and electric links to the core stage are severed with pyrotechnics and springs push the empty tank away from the core stage along two guides. A special cone structure inside the external tank helps to distribute loads from the payload to the rest of the stage during the launch.
A special transfer ring with a diameter of 4.1 meters, also known as spacer, serves as an interface between the third stage of the Proton, its payload fairing and the external tank of Briz-M. The transfer ring remains on the third stage when its separates from Briz-M around nine minutes after launch.
Briz-M is powered by a pump-fed S5.98 main engine developed at Isaev KB Khimmash design bureau in Korolev, Russia. Capable of producing around 20 kilonewtons of thrust, the engine has a special gimbal suspension system, which allows to steer the vehicle in flight under commands from an onboard computer. To protect the engine from harsh environment of space during prolonged periods of unpowered flight, its exposed nozzle is closed with a special movable thermal cover.
In addition, Briz-M is equipped with four 11D458M settling thrusters, which are used to give the stage an initial acceleration, in order to cause the propellants to shift toward the bottom and thus ensure that the main engine would have an uninterrupted flow of propellant at the time of its ignition. The same engines can also be used to fine tune the maneuvers performed by the main engine. Finally, the stage also sports twelve 17D58E thrusters used for attitude control. All auxiliary thrusters are mounted in four clusters on the dome-shaped aft bulkhead of the core stage: one propellant settling thruster and three attitude-control thrusters in each cluster. The entire propulsion system burns self-igniting mix of nitrogen tetroxide and unsymmetrical dimethyl hydrazine.
Along with the engines, the dome-shaped aft bulkhead of the core stage is used to attach a pair of tanks containing helium for pressurization of the propellant tanks, as well as some pneumatic and hydraulic hardware. Two other ball-shaped high-pressure tanks on the aft bulkhead are used to store propellant components for the ignition of the main engine and for feeding orientation and stabilization thrusters, SOiS. Other components for pneumatic and hydraulic systems are located inside propellant tanks. The "waist" of the core stage is enveloped in the lines of the thermal control system. The external tank has four own helium pressurization vessels.
The Briz-M's flight control system includes an on-board computer, a three-axis gyro stabilized platform, and a navigation system. Most of the space tug's avionics and its power batteries are housed in the unpressurized equipment section at the top. A series of antennas for telemetry transmission, trajectory tracking and satellite navigation extend from the core stage.
A cone-shaped adapter for the spacecraft is attached to the top of the equipment section via a 2.49-meter ring. The payload then can be attached to an adapter with a special release mechanism, which is designed to gently separate the satellite at the conclusion of its orbital insertion.
In the course of its operational life, various components of the Briz-M underwent upgrades. Phase IV upgrade of the Proton-M rocket inaugurated in June 2016, also marked the introduction of the new Pirit-RBs multi-functional radio-telemetry system employing modular architecture. According to AO RKS, which developed Pirit-RBs, its mass was reduced to eight kilograms comparing to the previous 14-kilogram version, while relying on domestically built avionics. The five-unit system also used pocket telemetry principles compatible with an international standard CCSDS. Pirit-RBs also has a unique capability to simultaneously downlink real-time data and pre-recorded telemetry stored in its memory, AO RKS said.
Phase IV also saw the removal of two high-pressure tanks from the instrument compartment.
Known specifications of Briz-M stage:
Briz development team:
14D30 engine specifications:
The Briz-M lifted off for the first time on June 5, 1999, but it never had a chance to fire during that mission due to the second-stage failure of its Proton-K rocket. The second attempt to test the stage was made on June 6, 2000, when the rocket successfully delivered the Gorizont-45 satellite into its planned orbit. On April 7, 2001, the Briz-M flew for the first time on the modified Proton-M rocket. Finally, at the end of 2002, the space tug was employed for the first time to deliver a commercial payload, which became its main job.
By mid 2000s, as its production expanded, Briz-M mainly replaced the Block DM upper stage on the Proton rocket. In 2008, KB Khimmash manufactured 10 engines for Briz.
By March 2016, Briz-M logged 91 flights, during which the stage failed or experienced serious technical problems seven times. This number includes seemingly anomalous performance of Briz-M during the first test launch of the Angara-5 rocket in December 2014, even though official Russian sources have not yet disclosed any problems during this flight.
Prior to the launch of the TGO orbiter and the Schiaparelli lander for the ExoMars-2016 mission in March, Briz-M completed eight increasingly accurate satellite deliveries, demonstrating the maturity of its flight control and navigation systems.
A complete list of Briz-M missions:
Read much more about the history of the Russian space program in a richly illustrated, large-format glossy edition:
Test integration of the Briz-M stage (top) with its external tank (bottom). Credit: GKNPTs Khrunichev
A front (top) and aft view of the Briz-M upper stage integrated with its external tank. Red protective boxes, which are removed before launch, cover acceleration thrusters. Credit: GKNPTs Khrunichev
Scale models of Briz-M's 14D30 engine (S5.98) (left) and its predecessor S5.92. Copyright © 2011 Anatoly Zak
Artist rendering of the Inmarsat-5 F2 satellite and its Briz-M upper stage in the initial parking orbit.
Artist rendering of Briz-M's second firing.
Briz-M sheds its empty external tank between its third and fourth engine firings.
Typically for an upper stage operating in weightlessness, Briz-M first fires its small thrusters to give the vehicle initial acceleration to ensure a reliable propellant supply into the main engine during prolonged orbit correction maneuvers.
Briz-M conducts 4th orbit correction with its main engine.