In 1960’s a lot of advancements in Liquid propulsion (LP) engine made it most suitable for rocket applications. Solid propelled engines had a long way to go. Composite propulsion was at its infancy. Gas turbines were beyond practicality in India those times. Ram-jet engines along with liquid propelled engine had found uses in missile applications, around the world.
With this background, the Special Weapons Development Team (SWDT), Delhi, later merged with Defence Research and Development Laboratory (DRDL), Hyderabad, plunged into creating a host of missile development related including rocket motor development.
Some work on propulsion had been carried out by DRDL on the Anti Tank Missile project of 1960’s, with success.
In 1964, Flying Officer Gopalaswamy from IAF joined DRDL due to his interest in liquid propulsion. A dedicated scientist V Gopalan joined him in the pursuit.
100 Pound Engine
Their first experimental engine was a small LOX – Kerosene motor with a 100 pound thrust. In process they created a host of infrastructure for development and testing liquid engines.
In early 1970’s DRDL developed first liquid propulsion engine of about 900 kg thrust. Another sophisticated 3 – tonne liquid propelled engine was successfully designed and flight tested in a period on 1971 to 1976. This engine had 150 seconds flight duration.
The experiences gained proved invaluable when a project eventually came up for the development of a 30000 kg thrust engine under “Project Valiant.”
A project to develop a multistage vehicle with intercontinental ranges came up. Having converged on a liquid propulsion system from system preliminary consideration, it appeared that a 30 – tonne Valiant engine will be for staging needs. The engine would have tubular wall engine chamber with turbine feed. The engine would be powered by Nitrogen tetraoxide and UDMH propellant combination, though the later was not available in India.
The Valiant engine tasks were taken on a project basis. A large “Vertical Engine Test” (VTF) facility was created by M/s Engineering India Limited. In 1974, the first Valiant Engine was tested in the facility to prove the entire infrastructure.
Project Devil was first serious attempt to make a Surface to Air missile. The sustainer engine was propelled by a liquid engine. This was a sophisticated piece of engineering during its time as it was regeneratively cooled by the propellant. The propellant was fed into combustion chamber by power driven turbine pumps. This turbo pump itself was driven by a separate monopropellant gas generator. The construction of the engine was entirely by stainless steel corresponding to AISI 304.
In 1960’s Unsymmetrical dimethylhydrazine (UDMH) propellant developments in Germany attracted attention interest of Dr. B Venkatramani at DSL. At that point of time none of the LP engines used UDMH. After grand success of Valiant engine test firings, even Indian Space Research Organisation (ISRO) approached DRDL for the UDMH. Andhra Sugar Tanuku produces UDMH for DRDL and ISRO today.
All these achievements helped India to develop various missiles under Integrated Guided Missile Development Program (IGMDP).