This is the first time that a winged body has been released mid-air by a helicopter and carried out an autonomous landing

The realisation of an Indian Reusable Launch Vehicle is a step closer to becoming a reality as the Reusable Launch Vehicle Autonomous Landing Mission (RLV-LEX) has been successfully accomplished by the Indian Space Research Organisation (ISRO). At the Aeronautical Test Range in Chitradurga, Karnataka, the trial involved a winged body lifted to an altitude of 4.5 km by an Indian Air Force Chinook helicopter, subsequently freed to execute an independent landing on a runway.

This is the first time that a winged body has been released mid-air by a helicopter and carried out an autonomous landing. The RLV-LEX is essentially a space plane with a low lift-to-drag ratio requiring an approach at high glide angles that necessitated a landing at high velocities of 350 kmph.

Under conditions similar to those of a space re-entry vehicle landing, the autonomous landing was executed, achieving landing parameters such as precise body rates, the sink rate of landing gears, and ground relative velocity. To accomplish the Reusable Launch Vehicle Autonomous Landing Mission (RLV-LEX), several cutting-edge technologies were necessary, including accurate navigation hardware and software, a Pseudolite system, a Ka-band Radar Altimeter, a NavIC receiver, an indigenous landing gear, Aerofoil honeycomb fins, and a brake parachute system.

ISRO designed localised navigation systems using pseudolite systems, instrumentation, and sensor systems. The Ka-band Radar Altimeter provided precise altitude information with the aid of a Digital Elevation Model (DEM) of the landing site. Aerodynamic characterization of RLV was made possible prior to the flight through extensive wind tunnel tests and CFD simulations.

With an autonomous, high-speed (350 kmph) landing, the LEX mission accomplished the final approach phase along the re-entry return flight path. The Integrated Navigation test took place in 2019, succeeded by multiple Engineering Model Trials and Captive Phase tests in subsequent years.

The Indian Air Force, Centre for Military Airworthiness and Certification (CEMILAC), Aeronautical Development Establishment (ADE), and Aerial Delivery Research and Development Establishment (ADRDE) collaborated with ISRO to conduct the test. Multiple sorties were carried out to perfect the release conditions, with Secretary in the Department of Space and ISRO Chairman S Somanath among those who witnessed the test.

The successful RLV-LEX test demonstrates that the adaptation of contemporary technologies developed for RLV-LEX can make other operational launch vehicles of ISRO more cost-effective. This success comes after ISRO's demonstration of the re-entry of its winged vehicle RLV-TD in the HEX mission in May 2016, which marked a major accomplishment in developing Reusable Launch Vehicles.