Orbiter: a Space Shuttle twin or a big Spiral?

Although NPO Energiya’s favored design was by now a delta-wing vehicle virtually identical in shape to the US Space Shuttle Orbiter, the Mikoyan engineers that had been transferred to NPO Molniya had their own ideas. In February 1976 Yuriy

Blokhin, the head of DPKO Raduga’s space design bureau in Dubna, had already written a report for the Central Committee stating that the 75 million rubles invested in Spiral were the only practical basis in the USSR for the creation of a reusable space transportation system [60]. However, by this time the designers were bound by the payload requirements and mission goals for the shuttle spelled out by the February 1976 party/government decree and the small air-launched Spiral was way below specifications. Therefore, the former Mikoyan engineers hatched a plan to build a much enlarged version of the Spiral lifting body capable of carrying the required amount of payload and launch that with the new heavy-lift rocket [61].

In the weeks after the decree was issued the “big Spiral’’ (code-named “305-1”) and NPO Energiya’s delta-wing orbiter (“305-2”) were the subject of a comparative analysis carried out by NPO Energiya, NPO Molniya, TsAGI, and TsNIIMash. There seems to have been division within the newly created NPO Molniya itself, with the former Mikoyan people strongly lobbying for the Spiral-based system and the Myasishchev branch supporting the delta-wing orbiter. In fact, NPO Energiya designers had been consulting with Myasishchev’s specialists on the delta-wing design since 1974. The former Mikoyan engineers, backed by TsAGI, pointed to the significant experience accumulated over the past ten years in research on Spiral (BOR missions, wind tunnel tests, etc.), while the NPO Energiya people argued that copying the shape of the American vehicle could save at least two years, reasoning it made no sense “to re-invent the wheel’’. The whole matter turned into a fierce debate between Lozino-Lozinskiy and Sadovskiy, which was eventually put to rest by MAP minister Dementyev, who left the final decision to Glushko. Being no expert in aerodynamics, Glushko in turn delegated the decision to the Council of Chief Designers, which by a simple majority of votes selected NPO Energiya’s delta-wing vehicle on 11 June 1976 [62]. However, one source claims the final decision was not made until late 1978 [63].

The January 1976 OK-92 plan was taken as the basis for the orbiter’s design, but a couple more changes were made. The solid-fuel emergency separation motor was removed from the orbiter and the hypergolic propellants for the orbital propulsion system were replaced by LOX/vintin, with all the engines drawing their propellant from common tanks. The two D-30KP turbojet engines were replaced by a pair of Lyulka AL-31 turbojet engines, already under development at the time for use on the Sukhoy Su-27 fighter. They were mounted in special niches on either side of the vertical stabilizer and covered with thermal protection material. The engines were eventually installed on a full-scale test model of Buran (BTS-002) used for approach and landing tests in 1985-1988, which also had two additional afterburner-equipped versions of the engine to take off on its own power. However, only months before the maiden space mission of Buran, it was decided not to install the AL-31 engines (see Chapter 7).