Secrets of the Soviet SLBMs

by Christian Lardier

For more than 30 years, Soviet SLBMs have been using technologies that are unique in all the world. Among these are "immersed" engine technology and nuclear warheads in "inverted" position.

Nowadays, Russia is fielding about 30 nuclear submarines armed with SLBMs. These missiles, designated RSM- 50, RSM-52, and RSM-54 were developed by the Makeyev Design Bureau at Miass, near Chelyabinsk (in the Urals), while the Soviet Union was still in existence (during the period 1973-1986). But, only the RSM-52 employs a solid-propellant engine, following the lead of the American, French, or Chinese SLBMs. The two other Russian SLBMs make use of liquid-propellants maintained at an ambient temperature (by means of nitrogen peroxide and unsymmetrical dimethyl hydrazine (UDMH)). They make use of three original technologies which have just recently been unveiled.

The first is that of an engine that has been "immersed" in its liquid-propellant reservoirs. This technology was employed for the first time aboard the RSM- 25 missile, developed over the period 1962-1968. The engine, rated at 23 T of thrust, was immersed in a UDMH (or Heptil) reservoir. The RSM-40, developed over the period 1964-1974, was the first two-stage missile, at once, devoid of an interstitial compartment between stages, having a guidance system making use of azimuthal stellar correction, and equipped with a nuclear warhead in the inverted position.

These techniques were, at the time, unique in all the world. Since then, stellar guidance has been installed aboard the American SLBMs TRIDENT-C4 and D5 (beginning in 1979) and perhaps aboard the Chinese JL-2 SLBM (beginning in 1983). The RSM-40's stellar guidance system had been developed by the designer, V.S. Kuzmin, from Central Design Bureau No. 589 (also known as the "Geofizika" Scientific Production Facility). But, "immersed" engine technology has as yet no peer in all the world. The justification for its existence is the need for designing a compact missile without mechanical interfaces. The missile's skin is completely sealed (combining aluminum and embossed steel) and its reservoirs are filled with propellants that can be stored there at the KRASMASH manufacturing plant itself, in Krasnoyarsk (Siberia). The missile is then containerized to prevent toxic fuel leaks aboard the submarine.

The engines of the Khimmash Design Bureau in Kaliningrad are manufactured by the Ust-Katav railcar plant (in the Urals). First-stage engines are immersed in UDMH with maneuvering provided by four vernier engines. Second- stage engines are immersed in nitrogen peroxide. The upper segment of the nosecone encloses the guidance system (computer, gyroscopes, stellar sensor, etc.), while the lower segment, consisting of the nuclear warhead, takes up a conical cavity over the second stage. The decoy bays are located in the second-stage UDMH reservoir. The development of these technologies took a long time since the in-flight testing of the RSM-40 had been carried out between March 1969 and December 1971 but was subsequently resumed with the RSM-50 and RSM-54 models.

The RSM-50 can accommodate three different nosecone configurations, having either one, three, or seven nuclear warheads. The nosecone is equipped with a propulsion system having four chambers, providing guidance for each of the warheads to its individual target. Roll attitude adjustment is provided by a nozzle that operates utilizing the gas from the fuel supply turbopump. Ground tests of the RSM-50 included 18 launches, while the 22 tests aboard submarines were staged over the period 1976-1978 (4 launches with a single warhead, 6 launches with 3 warheads, and 12 launches with 7 warheads).

The three-stage RSM-54 was built in 1979. The first- stage engine exhibits the highest level of performance, particularly where combustion chamber pressure is concerned. Morover, its containerized launch sequence is modified because the RSM-54 has a diameter larger than that of its predecessors. The third stage and the nosecone go to form a single assembly having common reservoirs. The missile can accommodate two different nosecones, armed with four or ten warheads.

The START treaties envision their continued operational status through the year 2003. Fifty-eight percent of the Russian nuclear strike force shall be based upon submarines, thereby representing 1,750 nuclear warheads of an overall total of 3,000. However, 1,200 warheads shall arm the large-scale RSM-52 solid-propellant missiles aboard TYPHOON submarines; the rest shall go to arm RSM-50 and RSM-54 missiles.

The first solid-propellant SLBM was developed by P.A. Tyurin, beginning in 1971. This was a medium-range RSM-45 employing a solid-fuel pressure converter for exiting its container, its engine igniting once it had cleared the water surface. Ground-based testing as well as testing aboard a submarine took place over the period 1976-1979. As early as 1980, 12 such models armed an experimental submarine. Tyurin ws then to propose a three-stage version with intercontinental range. But, the Makeyev Design Bureau, which had also been developing a solid-propellant SLBM since 1971, finally won the contract for the RSM-52. This latter has a first-stage engine rated at 52.8 T of thrust, built by the ISKRA Scientific Production Facility in Perm, and also installed aboard the SS-24 missile of the Yuzhnoe Scientific Production Facility. The third solid-propellant stage is situated within the nosecone housing 10 nuclear warheads, the guidance system, and the liquid-fuel engines for guiding the warheads to their targets. The RSM-52 has been in service aboard TYPHOON-class submarines since 1983. Normally, solid-propellant missiles were supposed to be more reliable than liquid-fuel missiles. And yet, it turned out that the sole accident caused by an SLBM was the explosion of a solid-propellant RSM-52 aboard a TYPHOON submarine on 27 September 1991. The solid-propellant had ignited within the missile container.

Hereinafter, the SLBMs from the Makeyev Design Bureau are intended to serve as space launch vehicles. Several submarine-launched suborbital flights have already been made. But, the most significant project is that of the RIKSHA space launch vehicle, from the KOMPOMASH consortium, which also makes use of "immersed engine" technology Cf. AIR & COSMOS, No. 1523. Equipped with new liquid oxygen and liquid methane engines from the Energomash Scientific Production Facility, it shall be capable of terrestrial launch, shipboard launch, or launch from a floating platform. KOMPOMASH expects to stage the maiden flight of this launch vehicle in 1999.