ENERGIYA GUIDANCE AND CONTROL

With Buran being only one of many possible payloads of Energiya, flight control functions were divided between the rocket and the orbiter, each using their own set of computers. This is very different from the integrated US Space Shuttle system, where the Orbiter’s General Purpose Computers are in control of all flight events. Being the most complex rocket ever built by the Russians, flight control proved to be a daunting task, facing designers with many unprecedented problems.

Originally, the flight control systems for both Energiya and Buran were to be built at NPO AP (Scientific Production Association of Automatics and Instrument Building), a Moscow-based organization headed between 1948 and 1982 by Nikolay A. Pilyugin. However, in 1978 the development of Energiya’s control system was entrusted to NPO Elektropribor, an organization based in the Ukrainian city of Kharkov and originally founded as OKB-692 in 1959 (now called NPO Khartron). Since the early days it had been headed by Vladimir Sergeyev, replaced in 1986 by A. G. Andryushchenko. The chief designer of the Energiya control system was Andrey S. Gonchar and a leading role in its development was also played by Yakov E. Ayzenberg, who would go on to lead the organization in 1990. Production of the hardware took place at the Kiev Radio Factory. NPO AP built the orbiter flight control system and remained in overall charge of the Energiya-Buran flight control system [5].

The core stage had a primary computer (called M6M) and a computer charged with continuously monitoring the operation of all Energiya’s engines and shutting any one of them down if needed. Each Blok-A strap-on booster had a M4M computer in its nose section. There was continuous interaction between the com­puters in the core stage and the strap-on boosters. Crucial commands such as nominal or emergency shutdown of both core stage and Blok-A engines and separation of the boosters were issued by the core stage computers [6].

Each booster had a single inertial guidance platform (17L27) built by NPO Elektromekhanika in Miass (Chelyabinsk region). The core stage’s intertank area housed three inertial guidance platforms (KI21-36) developed by NPO Rotor in Moscow and based on similar systems built for the 15A35 (SS-19 “Stiletto”) and 15A18 (SS-18 “Satan’’) missiles. Pre-launch alignment of the booster platforms took place with an optical system (17Sh14) (precision 7′) and that of the core stage platforms with an automatic system (17Sh15) (precision 45”) The automatic system consisted of three instruments mounted on a black plate outside the intertank area of the core stage. The plate was detached from the core stage and retracted to the launch tower with less than a minute to go in the countdown after the final pre-launch alignment. Failure of the plate to properly disengage led to the abort of the first Buran launch attempt on 29 October 1988 [7].

With the N-1 failures fresh in their memories, Soviet designers went to great lengths to protect the rocket against the consequences of leaks and engine failures. There was a so-called Fire and Explosion Warning System, consisting of gas and fire detectors and a system to purge the tail sections of the core stage and boosters with nitrogen and extinguish fires with freon. This was activated both during the count­down and launch. Installed on the pad was a hydrogen burnoff system to eliminate hydrogen vapors exhausted into the RD-0120 engine nozzles during the start sequence. This differed from the hydrogen igniters on the Space Shuttle launch pads in that the hydrogen was burnt off well away from the engine nozzles [8].

Energiya was also equipped with a so-called Engine Emergency Protection System, comprising a wide range of sensors in the engine compartments to monitor pressures, temperatures, turbine rates, etc. In case an anomaly was detected, any of the engines could be shut down immediately before failing catastrophically. Depend­ing on the moment when the shutdown took place and the type of payload carried (an orbiter or unmanned payload canister), the flight control system could then decide on a further course of action. This could involve shutting down the diametrically opposed engine to continue controlled flight, increasing the burn time of the remain­ing engines to deploy the payload in a lower or even nominal orbit, initiating a return to launch site maneuver, guiding the rocket to a safe impact area, etc. This would not only ensure the safety of the crew, but also facilitate post-flight analysis of the failure. The system was designed to deal with over 500 types of anomalies and was said to be a major improvement over the analogous “KORD” system on the N-1 rocket.

The safety systems were not only used during launch countdowns and ascent, but also during bench tests of the RD-170 and RD-0120 engines and test firings of the core stage and strap-ons. The bench tests, especially those of the RD-170, showed that the Engine Emergency Protection System could not always respond to rapidly escalating problems such as turbopump burn-throughs or cracks in the turbopump rotors, a problem that had not been fully solved by the time Energiya made its two missions [9].