of a single fixed thrust chamber producing a thrust of 23 ton-force and two smaller gimbaled thrust chambers mounted on the frustum-shaped bottom of the fuel tank producing a total of 3 ton-force thrust. The engine was ignited using a squib and burned a hypergolic propellant combination, dinitrogen tetroxide and unsymmetrical dimethylhydrazine, which was delivered into the combustion chamber via turbopumps. The 4D10's main chamber operates on a highly-efficient oxidiser-rich staged combustion cycle to maximize fuel efficiency, while the two smaller chambers use the more ordinary gas-generator cycle. Both the larger chamber and the smaller chambers could be throttled by either regulating the single propellant line leading to the main chamber or a shared oxidiser line leading to the smaller chambers. One of the most important novelties on this missile is that the main chamber of this rocket motor was integrated into the missile by permanently welding it inside the fuselage instead of mounting the rocket motor onto a thrust structure below the fuselage, which is the usual practice in rocket design. 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. When the R-27 was fired underwater, the container housing them was first overpressurized before the container was flooded and the pressure was equalized. 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 two smaller chambers are ignited first, before finally igniting the main chamber. The missiles were fired from a depth of 40 to 50 meters under the sea. Preparations for launch would take 10 minutes, and a salvo could be fired with an interval of 8 seconds between each launch. Variants R-27 Total Mass: 14,200 kg Diameter: 1.50 m Total Length: 8.89 m Span: 1.50 m Payload: 650 kg Warhead: single nuclear: 1.0 Mt Maximum range: 2400 km CEP: 1.9 km Launch platform: project 667A submarines R-27U (RSM-25) Total Mass: 14,200 kg Diameter: 1.50 m Total Length: 8.89 m Span: 1.50 m Payload: 650 kg Warhead: 3 : 200 kt Maximum range: 3,000 km CEP: 1.3 km Launch platform: project 667AU submarines R-27K 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.