Soviet Solid Rocket ICBMs

Western literature tended to attribute the development of large solid rockets to Nadiradze, but more recent Russian literature allocates pride of place to Yangel. To the creation of solid-fuel rockets, Yangel approached cautiously, weighing every step. It would appear that Yangel took an early interest in solids, then his enteprise returned to the them some years later.

One of the new ballistic missiles was combined: the first stage worked on solid fuel, the second - on liquid. The solution was not the best, but in general the new missile had a number of valuable innovations and pioneer solutions. It was the first mobile missile system RT-20P. The main designer of the self-propelled launcher on the caterpillar track was the creator of the famous heavy tanks KV and IS, many self-propelled artillery mounts Josef Kotin.

The novelty of the rolling complex was the transport and launch container, directly from which the missile started. At the same time, the so-called "mortar launch" was used: the intercontinental rocket flew out of the container like a cork from a bottle of champagne, and its engines were launched already in flight. This complex anticipated the appearance of other mobile complexes, in particular railway. Despite the fact that the new rocket was proudly displayed on Red Square during the military parades, the series did not go into series.

The first solid rocket motor (SRM) designed by Yuzhnoye was a 15D15 main motor for the first stage of the 8K99 (SS-X-15) missile. The motor development started in 1963. The first firing of the 15D15 motor was conducted in April 1965. However, in October 1969, development of the 8K99 missile was stopped regardless of a series of completely successful launches. The experience in SRM development allowed working on new advanced approaches to the definition of the optimum configuration of future main solid rocket motors.

In 1969, Yuzhnoye started the development of the 15Zh43 ICBM and its first-stage motor, the 15D122. A number of breakthrough technologies were proposed for the motor design:

• Combined casing with a fiber-glass longitudinal-circumferential wound pipe and metal motor heads
• Case-bonded block of solid butyl-rubber propellant
• Central fixed nozzle partly submerged into the combustion chamber, with thrust vector control provided by injecting hot chamber gas into the submerged diverging section of the nozzle.

The 15D122 motor firing tests demonstrated the motor performance and characteristics of the thrust vector control system based on the hot-injection technique.

In this period, Yuzhnoye developed steering SRM for deployment of objects in space. The 15D161, 15D171, and 15D221 motors featured increased running time and control forces. The motors used end-burning charges made of metal-free propellant mixture with an original design of case bonding and a unique configuration of the seal in bearings of the rotating nozzles.

The next work Yuzhnoye performed in the SRM design was the development of the 3D65 main motor for the first stage of the 3M65 naval missile (designed by Makeyev design bureau). The motor design incorporated the most advanced engineering solutions:

• All-wound cocoon casing with a load-bearing shell made of high-strength organic fiber and embedded parts made of titanium alloy
• Case-bonded charge of high-energy butyl-rubber propellant
• Fixed nozzle with a three-axis thrust vector control system based on the hot-injection technique
• A number of engineering solutions determined by the specifics of using the motor in
• the naval missile (for both above-water and underwater launches).

In 1982, the 3D65 motor was accepted for series production.

In the mid-1970s, Yuzhnoye started developing main solid rocket motors for a silo-based 15Zh44 ICBM and a rail-mobile 15Zh52 ICBM: the 15D206 motor for the first stage and the 15D207 motor for the second stage. To reduce the scope and period of development tests, the 15D206 motor was designed as a complete analog of the 3D65 motor. The modifications included increased thrust/consumption performance, increased throat diameter, and increased chamber pressure. The following new technologies were used in the 15D207 motor:

• Fixed nozzle with an extendable high-altitude exit cone
• Carbon-carbon composite materials in the throat liner
• Formulation of propellants with higher energy characteristics
• Block of solid propellant with high chamber volumetric loading efficiency.

Ground tests of the motors started in 1979.

However, in 1983, it was decided to stop the development of the 15Zh44 and 15Zh52 missiles and use them as the basis for the 15Zh60 and 15Zh61 missiles with higher performance characteristics and better nuclear hardness.

A new motor, 15D290, was designed for the second stage of rail-mobile 15Zh61 missiles. Better performance of the motor was attained by using a new high-energy propellant mixture and making a number of design decisions to increase the motor’s nuclear hardness.

In the 15Zh60 missile, the first- and second-stage main motor requirements necessitated the development of a fundamentally new motor, 15D305, for the first stage and the upgrade of the 15D339 motor for the second stage. The 15D305 motor design was based on the following unique technologies:

• High-energy propellant based on cyclotetramethylene tetranitramine (octogene)
• Cocoon casing
• Central swiveling nozzle with a one-piece throat liner made of 3D reinforced carbon-carbon material.

For the 15D339 motor, a multifunctional coating to protect the casing against all nuclear effects was developed; mass efficiency of the motor and erosion resistance of the nozzle were improved. In 1986-1988, development tests of the 15D290, 15D305, and 15D339 motors were completed, and series production started.

In 1988, Yuzhnoye design office was tasked with developing the 15Zh65 ICBM first-stage propulsion system, the 15D365. The 15D365 motor design features include:

• Block of propellant with a swiveling control nozzle, following a circular motion pattern
• Organic plastic cocoon casing
• Case-bonded octogene-based propellant mixture.

Five firing tests were conducted, and the 15D365 motor was accepted for flight tests. However, due to collapse of the Soviet Union, all work on the 15D365 in Yuzhnoye was shut down.

Besides main and steering motors, Yuzhnoye developed 82 types of small motors, pressure accumulators, and gas generators, which were used for a broad range of applications:

• Missile ‘mortar’ launch
• Missile ‘mortar’ staging
• Missile ‘wag’ during a mortar launch
• Nose-cone inflatable tip geometry change
• Increase of a main motor nozzle altitude capability
• Separation and removal of various objects away from the missile trajectory
• Missile parts flight control
• Ejection of objects from the missile and support a specified velocity of their flight
• Spin stabilization.

Many years of successful operation have proven high reliability and high operating environment resistance of the developed SRM.