RP-318 and RP-318-1 (РП-318, РП-318-1) by S.P.Korolev

RP-318-1 (on the photo) differed from the RP-318 by the engine type
(courtesy of )

On June 16, 1936, S.P.Korolev presented project of the "Object 218", powered by liquid fuel rocket engine and intended for stratospheric flights. Most calculations for the project and preliminary design were ready, but many important components were still under development. There were no reliable ZhRD (ЖРД) with required thrust and weight. Pumps for fuel components were still under development, as well as pressurized pilot's cockpit.

S.P.Korolev was aware of all those problems, and prepared a reliable testbed for new powerplant trials - SK-9 glider (flown in 1936), capable for 7g loads - too much for common light-weight sailplane. Aircraft was a 2-seater, second seat was added as a provision for rocket fuel tanks in planned developments.

Practical work on rocket powered aircraft began in early 1936. Designation RP-318 is means "Rocketnyj Planer [Rocket Glider], department 3, project 18".

S.P.Korolev planned to install the OR-2 engine designed by Tsander. This engine relied on liquid oxygen. The RNII leadership did not favor engines with cryogenic fuel components, and development of such engines was not among high priority programs. As a result, the ORM-65 (nitric acid and kerosene) engine by V.P.Glushko was selected for its high readiness and suitability for other projects, including cruise missiles. Nonetheless, S.P.Korolev considered liquid oxygen the best option and tried to encourage L.S.Dushkin to continue his work on the "Type 12K" engine.

Once the engine and fuel components were selected, S.P.Korolev and his team started rebuilding the SK-9 for new role. Space of the second cockpit was occupied by aluminum baths protecting the fuel tanks: two with nitric acid and one with kerosene. Baths were used to prevent wooden airframe from being damaged (or even ignited) by fuel component during occasional leak.

RP-318 cutaway showing the fuel system. From Raketnyj planer RP-318-1 (Slovak)

No fuel pumps were used - components were supplied to the engine by compressed nitrogen (35kg/cm²).

Extensive study of fuel system was performed. Liquid flows and hydraulic pressure losses were studied with water instead of aggressive components. Results were re-calibrated for kerosene and acid. Special attention was paid to guarantee simultaneous supply of both components to the engine during the ignition. Reliable sealing of fuel system also took a lot of efforts...

All firing trials were performed under control from pilot's cockpit. On the first stage engine was separated from the aircraft by armor plate. Once system was proven reliable, engine was moved to its place in the tail of RP-318 and trials continued. More than 30 fire trials were performed.

In April 1938 PR-318 successfully passed ground trials. At the time Stalin's policies started taking tall on the RNII team. In 1937 on the RNII Director I.T.Kleimenov and leading engineer G.E.Langemak were fired and arrested, chief of engine department V.P.Glushko - arrested and transferred to "specialized" OKB. In June 1938 S.P.Korolev himself was arrested as "the enemy of the people" and work on the RP-318 came to a complete halt for 6 months. Later the project re-emerged as RP-318-1.

Predecessors	Following	Related project
SK-9	RP-318-1	"Object 218"