In a significant milestone for the Indian Space Research Organisation (ISRO), the Reusable Launch Vehicle (RLV) successfully completed an autonomous landing mission (LEX) on April 2, 2023. The test, conducted at the Aeronautical Test Range in Chitradurga, Karnataka, saw the RLV take off at 7:10 am IST by a Chinook helicopter of the Indian Air Force and fly to a height of 4.5 km (above MSL).
Once the predetermined pillbox parameters were attained, the RLV was released mid-air, at a down range of 4.6 km, with release conditions covering position, velocity, altitude, and body rates. The release was autonomous, and the RLV then performed approach and landing maneuvers using the Integrated Navigation, Guidance & control system and completed an autonomous landing on the ATR air strip at 7:40 AM IST.
The autonomous landing was carried out under the exact conditions of a space re-entry vehicle's landing, including high speed, unmanned, precise landing from the same return path as if the vehicle arrives from space. Landing parameters such as ground relative velocity, the sink rate of landing gears, and precise body rates were achieved. The RLV LEX demanded several state-of-the-art technologies, including accurate navigation hardware and software, pseudolite system, Ka-band radar altimeter, NavIC receiver, indigenous landing gear, Aerofoil honey-comb fins, and brake parachute system.
In a first in the world, a winged body has been carried to an altitude of 4.5 km by a helicopter and released for carrying out an autonomous landing on a runway. RLV 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.
ISRO had demonstrated the re-entry of its winged vehicle RLV-TD in the HEX mission in May 2016. The re-entry of a hypersonic sub-orbital vehicle marked a major accomplishment in developing reusable launch vehicles. In HEX, the vehicle landed on a hypothetical runway over the Bay of Bengal. Precise landing on a runway was an aspect not included in the HEX mission. The LEX mission achieved the final approach phase that coincided with the re-entry return flight path exhibiting an autonomous, high speed (350 kmph) landing. The LEX began with an Integrated Navigation test in 2019 and followed multiple Engineering Model Trials and Captive Phase tests in subsequent years.
With LEX, the dream of an Indian Reusable Launch Vehicle arrives one step closer to reality. Along with ISRO, IAF, CEMILAC, ADE, and ADRDE contributed to this test. The IAF team hand in hand with the Project team and multiple sorties were conducted to perfect the achievement of release conditions. The test was witnessed by Chairman, ISRO/Secretary, DOS Shri S Somanath, who congratulated the team on the historic achievement.
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