According to unverified sources, DRDO is currently engaged in the development of Endothermic fuels for hypersonic Vehicles, specifically for utilization in Scramjet and Hypersonic Glide Vehicle technologies. The incorporation of Endothermic fuel represents a viable approach to achieving active cooling in Scramjet systems.
The fundamental concept entails employing a heat exchanger to facilitate the transfer of thermal energy from the components requiring cooling to a hydrocarbon fluid, which initially possesses a low temperature. When the fuel is utilized in this manner, it progressively increases in temperature, eventually reaching a point that triggers endothermic chemical reactions such as dehydrogenation and cracking. These reactions cause the hydrocarbon molecules to break down into simpler units.
At this stage, the fuel continues to serve as a heat sink, effectively dissipating thermal energy, while its temperature ceases to rise further. Instead, the absorbed heat initiates a chemical conversion process within the initial compound, leading to the formation of alternative hydrocarbon products that exhibit a simpler molecular structure. These transformed products can then be utilized as fuel for propulsion. In a similar vein, when energy is transferred to liquid water, its temperature rises until it reaches the boiling point. Subsequently, the water is capable of absorbing additional energy at the boiling temperature, but this input of energy does not cause a further increase in temperature; rather, it drives the process of evaporation.
Hypersonic Technology Demonstration Vehicle (HSTDV)
On September 7, 2020, the DRDO conducted a successful flight test of the hypersonic air-breathing scramjet technology with the Hypersonic Technology Demonstration Vehicle (HSTDV).
The hypersonic cruise vehicle was propelled into motion by a proven solid rocket motor, propelling it to an altitude of 30 km. At this altitude, the aerodynamic heat shields were separated at a hypersonic Mach number. Subsequently, the cruise vehicle disengaged from the launch vehicle, and the air intake opened as planned. The hypersonic combustion process sustained, allowing the cruise vehicle to maintain its intended flight trajectory at a velocity six times the speed of sound, equivalent to nearly 2 km/s, for a duration exceeding 20 seconds. During this time, critical events such as fuel injection and auto-ignition of the scramjet engine were successfully demonstrated, showcasing the technological maturity of the system. The performance of the scramjet engine exhibited a textbook-like execution.
To ensure comprehensive monitoring of the launch and cruise vehicle parameters, including the scramjet engine, a multitude of tracking radars, electro-optical systems, and Telemetry Stations were employed. The scramjet engine operated under high dynamic pressure and at extremely elevated temperatures. Additionally, a ship was deployed in the Bay of Bengal to effectively monitor the performance of the hypersonic vehicle during the cruise phase.
The overall performance parameters of the mission indicated a resounding success, further solidifying the significance of DRDO’s accomplishment in the field of hypersonic air-breathing scramjet technology.