It can only be started once, and as a high altitude engine it has a thrust of 78.45 kN (17,640 lbf) and a specific impulse of 342 s (3.35 km/s).[5][6] It is the first ever steering engine to use the staged combustion cycle, and as such is the basis for a family of planned engines for the Mayaklaunch vehicle family.[3]
The engine itself is built like a hollow cylinder, with a cylindrical space in the center so the RD-120 nozzle can pass through.[9]
Whilst Yuzhnoye's propulsion experience had been mostly on hypergolic propellants engines, like RD-855orRD-861, they are considered too toxic for current ecological standards.[7][8] While Yuzhnoye still offer to develop hypergolic propulsion, such as RD-843 for the Vega's AVUM stage or the Tsyklon-4 project, Yuzhnoye selected a more environmentally friendly LOX and kerosene propellant for the Mayak launch vehicle family.[3]
Not only had Yuzhnoye mastered the most complex cycle for the propellant (oxidizer rich staged combustion cycle) with the RD-8, but they had worked closely with NPO Energomash during the RD-120 program. The manufacturing is done at its sister company of Yuzhmash in Dnipropetrovsk, and the RD-120 thrust augmentation project of 2001 to 2003 had been a mixed project between the three companies.[3]
On the base of this experience, a family of derivatives engines were proposed. While the RD-801 and RD-810 are really just based on the general technology, the other members of the family are related enough that they reuse many components of the RD-8.[3] One characteristic of this family is the limitation of keeping the preburner output temperature below 500 °C (932 °F).[3]
RD-805 (orRD-802): A proposed upper stage engine of just 19.62 kN (4,410 lbf) of thrust, it would use a single chamber of the RD-8.[10] While many new components would be required, it is considered a low technological risk since it only needs smaller versions of already developed component.[3]
RD-809 (sometimes identified as RD-809M): It is an RD-8 re arranged to minimize its diameter. It would use practically every single component of the RD-8, but arranged without the big hollow section in the middle. It was a proposed engine for a proposed liquid upper stage of the Antares rocket, then named Taurus II.[3] It would be capable of five engine burns in a single mission.[11]
RD-809K: A proposed single nozzle version of the RD-8. It would mix most principal elements of the RD-8 like the turbopumps with a main combustion chamber and nozzle adapted from the RD-861K.[3][12] It would be capable of 4 starts in a single mission.[12] It is expected to be used in a dual engine configuration in the Mayak upper stage.[3]
