|Above: A unique experimental vehicle employing the first stage largely borrowed from the RT-1 missile and two upper stages intended for the RT-2 ICBM.|
Origin of the program
As often was the case during the Cold War, American progress in the replacement of liquid propellants with solid fuels in long-range ballistic missiles prompted the USSR to act. With fast reaction being a key in the doomsday scenarios of a potential nuclear war, solid propellants promised to greatly extend the operational readiness of missiles and shorten the pre-launch process. Since solid propellants could be stored inside missiles much more easily than liquid ones, the mobility of new-generation systems could be dramatically improved.
By the end of the 1950s, Soviet engineers made their first attempts to build a large ballistic missile burning solid propellant. However, lack of progress in the development of highly effective combinations of solid fuel mixtures made this task very difficult. To tackle the problem, Soviet engineers had to adopt a stepped process, during which smaller solid-propellant motors would be clustered together to test progressively larger upper stage boosters. These engines burned essentially same powder fuel which had propelled the famous 1930s-vintage Katyusha rockets. (177)
The original Soviet project to build an experimental solid-propellant missile was designated RT-1 (8K95) from Russian "Raketa Tverdotoplivnaya" (solid-propellant rocket). Work on the project officially started on Nov. 20, 1959, at a special division of Sergei Korolev's OKB-1 led by Igor Sadovsky.
According to a government decree authorizing the project, RT-1 was to be a nuclear-tipped, three-stage missile with a range of 2,500 kilometers and burning Neilon-B solid fuel. Two types of flight control system had to be tried: a fully autonomous one and a hybrid (requiring ground stations). Either one had to be limited to a mass of 150 kilograms, while the autonomous system had to provide an accuracy comparable to that of the latest R-12 liquid-propellant missile. The rocket and its silo or a surface pad had to be designed to remain in battlefield readiness for no less than three years and to be able to fire in no more than 15 minutes after launch command. Also, the decree required that the preliminary design of the RT-1 rocket and its operational launch bases had to be submitted to the Ministry of Defense by May 1960. The beginning of flight testing was scheduled for the 4th quarter of 1960 with the hybrid flight control system, while launches with the fully autonomous flight control had to start in the fourth quarter of 1961. (473)
At the beginning of the RT-1 development, the largest diameter of solid propellant charges available in USSR was 800 millimeters. It became the basis for the missile design. The nozzles of main motors would be fixed, however smaller steering thrusters on the 1st and 3rd stage featured driving mechanisms, which could swivel the nozzles to an angle of 45 degrees. The 2nd stage was to be controlled with aerodynamic stabilizers which would be deployed after liftoff. The first two stages would keep firing until they had consumed all their propellant. However, the third stage had to be shut down as soon as the rocket reached the desired flight range.
Unlike liquid-fueled missiles, where the engine cutoff can be achieved by closing the flow of propellant into the combustion chamber, solid motor serve as the combustion chamber itself. To resolve the problem, engineers proposed to shut off the solid motor by blowing off with a pyrotechnic charge special covers on the top end of the rocket. The opening would create the exhaust jet with its thrust opposite to the direction of flight. In order to maintain the necessary accuracy of the missile, the engine shutdown would be "smoothed" by a two-phase sequence. Two out of four covers would be opened first, gently slowing down the missile, and the two remaining covers would go off next. (This method of solid-motor shutdown became classic for several generations of Soviet missiles.)
The missile's 800-kilogram warhead would then separate from the third stage for a free fall to the target. To minimize the mass of the third stage and thus increase its range somewhat, it would shed its tail skirt which was used to connect it to the second stage.
All stages were connected by a lattice structure which would allow the second and third stage to ignite before separation from the stage below. As soon as the engine develops the necessary thrust, an acceleration sensor would send a command to separate the spent stage.
Development and testing
The RT-1's extensive development program required between 30 and 40 live test-firings of each motor. Fully assembled stages were then test-fired three times at a special facility in the town of Krasnoarmeisk, near Moscow. There were also thermal tests of solid motors, trials of reentry protection materials and aerodynamic validation of the missile's design. Tests of the separation of the warhead, flight control checks and other work dragged on.
The missile finally reached the launch pad in Kapustin Yar considerably behind schedule. Test missions targeting impact areas near Lake Balkhash in Kazakhstan were conducted between April 28, 1962, and June 1963. The first of three successful flights was achieved on March 18, 1963, with six other missions failing. Most problems were related to the flight dynamics of the 2nd stage, whose aerodynamic surfaces were not able to keep the vehicle on course during the separation process. (84)
Although the RT-1 gave Soviet engineers critical experience in the development and testing of large solid propellant missiles, original plans to turn it into an operational weapon had to be shelved.
To take another step toward a workable solid-propellant ICBM, OKB-1 developed a new experimental missile designated RT-1-1963 (8K95-1963). It would carry a prototype of the new third stage intended for the RT-2 missile. The single solid motor of the third stage featured four nozzles.
To increase accuracy, the new autonomous flight control system of the new missile was capable of adjusting the pitch angle of the vehicle's trajectory based on live data coming from sensors measuring the actual distance in flight.
Between September and November 1965, the RT-1-1963, flew three missions, aiming to cover up to 1,950 kilometers, however only one was successful. (52)
A missing link
After the declassification of Soviet rocket systems in the 1990s, it was believed that the RT-1-1963 rocket led directly to the development of the RT-2, the first Soviet true ICBM using solid propellants. In fact, yet another intermediate-step vehicle apparently had to be built before the RT-2 could become reality. This experimental rocket still featured a cluster of solid motors forming the first stage as had been done on the RT-1, however the second and third stages were already comprised of the single motors intended for RT-2. Although the first stage of the rocket was made of a traditional aluminum alloy, the second and third stages used lighter fiber-composite bodies.
Most importantly, in the second and third stages, Soviet engineers reportedly for the first time used solid fuel prepared from a special liquid solution which would be poured and solidified right in the casing of the missile. This progressive technology, apparently gleaned by Soviet intelligence from US sources, helped significantly boost the capabilities of Soviet solid motors. Previously, individual rocket stages of the RT-1 missile had to be made of multiple solid-propellant charges, which then had to be loaded into the engine casing.
Only a few copies of the aluminum first stage were manufactured and they were later used for multiple live-firing tests.
Known specifications of the RT-1 missile:
RT-1 development team:
Chronology of the RT-1 rocket development:
1958 July: OKB-1 adopts a plan envisioning a large experimental solid-propellant missile.
1959 June 27: The State Committee for Defense Technology adopted a decree to create a branch of Korolev's OKB-1 based at TsNII58 research institute for the development of a solid-propellant rocket with a range of 2,500 kilometers. (52)
1959 August: Igor Sadovsky is appointed deputy to Sergei Korolev for the development of the solid-propellant missiles. (62)
1959 Nov. 20: The Central Committee of the Soviet Communist Party (TsK KPSS) and the Soviet of Ministers adopt decree No. 1291-570 "On the creation of an article RT-1 and the conduct of work on the subject of RT-2." (473)
1962 April: Flight tests of the RT-1 missile start in Kapustin Yar.
1963 March 18: The RT-1 achieves its first successful flight.
Next chapter: The RT-2 ICBM
Page author: Anatoly Zak; Last update: May 20, 2011
Page editor: Alain Chabot; Last edit: May 20, 2011
Copyright © 2011 RussianSpaceWeb.com
Test launches of the RT-1 missile. Credit: RKK Energia
Test launch of an RT-1-1963 missile, carrying the prototype of the third stage of the follow-on RT-2 ICBM. Credit: RKK Energia
A hybrid of RT-1 and RT-2 vehicles was designed for experimental purposes. Copyright © 2011 Anatoly Zak
The 15D24P1 solid-propellant engine for the second stage of the RT-2P rocket. Credit: KB Arsenal