Researchers at the Indian Institute of Technology (IIT) Madras have made significant strides in the field of vertical take-off and landing (VTOL) aircraft and unmanned aerial vehicles (UAVs) by developing hybrid rocket thrusters. This innovative approach was demonstrated through an advanced experiment that combined real-time hybrid rocket propulsion with virtual simulations, enabling the achievement of the required velocity for a “soft landing”—an essential capability for various aerospace applications.
The touchdown velocity is a critical factor that ensures the safety of vertical landings, whether for crewed or uncrewed exploration modules on other planets or for terrestrial VTOL aircraft. This research evaluated the potential of hybrid rocket motors, which are simpler and safer than traditional liquid engines, for use in vertical landing platforms. The increasing popularity of hybrid rocket systems can be attributed to their safety features, throttling capabilities, and the benefits derived from both liquid and solid rocket engines.
The study, published in the peer-reviewed International Journal of Aeronautical and Space Sciences, introduced the concept of a hybrid rocket thruster-powered platform aimed at developing an effective propulsion system for achieving VTOL capabilities in aircraft and UAVs. According to Prof. PA Ramakrishna from the Department of Aerospace Engineering at IIT Madras, “VTOL will allow aircraft to take off and land vertically, removing the necessity for extensive infrastructure like long runways. This capability will facilitate access to remote and rugged regions where constructing large airports is impractical. Currently, helicopters serve these areas but are limited in terms of speed, range, and efficiency compared to fixed-wing aircraft.”
Prof. Ramakrishna further emphasized that once the VTOL system reaches the appropriate Technology Readiness Level (TRL) for commercial use, it could revolutionize both civil and military aviation by decentralizing air transportation to multiple sites instead of relying on a single large airport or airbase. This decentralization offers notable strategic and operational benefits, marking this study as a preliminary step toward developing a proof-of-concept for a hybrid rocket-powered VTOL platform.
Another noteworthy advancement from this research is the creation of a hybrid rocket fuel that utilizes only compressed air as an oxidizer. This innovation simplifies the integration of VTOL systems with aerospace vehicles, especially in scenarios where compressed air is readily accessible.
Additionally, Dr. Joel George Manathara, an Associate Professor in the Department of Aerospace Engineering at IIT Madras, highlighted the unique Hardware-in-the-Loop Simulation (HILS) framework developed by their team. This framework merges physical hardware testing with simulations, offering a cost-efficient method for rapidly developing complex systems. Unlike typical HILS setups, which usually incorporate a servo motor or microcontroller, this project integrated a real, live-firing hybrid rocket motor directly into the simulation loop. The successful implementation of this setup resulted in a soft landing with a touchdown velocity of less than 1 m/s.
