[5] Directly beneath the warhead, the instrumentation necessary for guidance of the missile was housed inside of a hemispherical compartment formed by the upper bulkhead of the oxidiser tank.

The engine was ignited using a squib[4]: 87  and burned a hypergolic propellant combination, dinitrogen tetroxide and unsymmetrical dimethylhydrazine, which was delivered into the combustion chamber via turbopumps.

As a result of this design practice, most of the engine could not be tested, repaired or maintained as soon as it was permanently welded inside the missile.

To reduce the effect of water hammer when igniting the rocket engine, the nozzles were housed inside of a watertight air-filled adapter connecting the bottom of the missile with its container.

The 4K18 was a Soviet medium-range anti-ship ballistic missile (also known as R-27K, where "K" stands for Korabelnaya which means "ship-related") NATO SS-NX-13.

The missile was a two-stage development of the single-stage R-27, the second stage containing the warhead as well as propulsion and terminal guidance.

After a number of delays caused by several malfunctions, test firings were finally carried out between 11 September and 4 December 1973.

[6] Although the R-27K could fit in the launch tubes of the Project 667A (NATO Yankee class), the subs lacked the necessary equipment to target and fire the missile.

[7] In 1992, the Makeyev Rocket Design Bureau signed a contract with North Korea regarding the creation of a R-27 derived launch vehicle.

As a result of this, the very similar North Korean Hwasong-10 "Musudan" IRBM was derived from the R-27,[8] the only major change from the original being a slightly extended fuselage.