Upper stages

Since the core stage was suborbital, another element that needed to be developed for Buran-T besides the GTK were the upper stages to place payloads into orbit. One of these was a modification of the Proton rocket’s Blok-DM upper stage. Having a diameter of 3.7 m and a length of 5.56 m, it was to carry between 11 and 15 tons of LOX/kerosene. Its engine was to have a thrust of up to 8.5 tons and have the capability of being ignited up to seven times. It could also act as a retro- and correction stage for long-duration deep-space missions, in which case it would need a special propellant-cooling system.

The other upper stage, known as 14S40 or Smerch (“Tornado”), was to use liquid oxygen and hydrogen. It was only one in a family of cryogenic upper stages that the KB Salyut design bureau (part of NPO Energiya in the 1980s) had been tasked to develop by a government decree in December 1984. The others were Shtorm (“Gale”) for the Proton rocket, Vikhr (“Whirlwind”) for Groza (an Energiya with two strap – ons), and the 11K37 (a “heavy Zenit’’) and Vezuviy (“Vesuvius”) for Vulkan (an Energiya with eight strap-ons). Manufacturing was to take place at the Krasnoyarsk Machine Building Factory.

By late 1985 KB Salyut came up with a plan for using the cryogenic 11D56M engine, an improved version of the 11D56 engine developed back in the 1960s by KB Khimmash for the N-1 rocket. With its thrust of 7.1 tons and specific impulse of 461 s, it was well suited for KB Salyut’s own Proton, but did not meet the requirements that NPO Energiya had laid down for Smerch. In July 1988 Minister of General Machine

Building Vitaliy Doguzhiyev directed NPO Energiya and its Volga Branch to propose its own upper stages for Buran-T and Vulkan. NPO Energiya set its sights on the RO-95, an open-cycle LOX/LH2 engine under development at KBKhA in Voronezh.

With a thrust of 10 tons and a specific impulse of 475 s, the RO-95 outperformed the 11D56M by a considerable margin and was also optimized for use in Vulkan’s Vezuviy upper stage. Unlike the upper stage that KB Salyut had proposed, NPO Energiya’s Smerch had the LOX tank on top, which was more favorable in terms of center-of-gravity requirements and also made it easier to ignite the engine in zero gravity. In this configuration Smerch was 5.5 m wide and 16 m long with a propellant mass of up to 70 tons. The engine could be re-ignited up to ten times. Technical requirements for the RO-95 were sent to KBKhA in December 1988 and test firings of the engine were expected to begin in 1991-1992. Yet in February 1989 Doguzhiyev seems to have turned around his earlier decision by limiting work on cryogenic upper – stage engines to KB Khimmash’s 11D56M, arguing that there were no payloads in the pipeline for Buran-T and Vulkan that justified the development of an entirely new engine.

Initially, three upper-stage configurations were studied for Buran-T: only the Blok-DM derived stage for low-orbiting payloads (up to 1,000 km), only the Smerch for payloads destined for geostationary orbit, lunar libration points, and lunar orbit, and the two stages combined for lunar-landing missions, flights to Mars and Jupiter. Payload capacity would have been about 88 tons to low Earth orbit, 18-19 tons to geostationary orbit, 21.5-23 tons into lunar orbit, 9-10 tons to the lunar surface, and 10-13 tons into Martian orbit [57].