The Indian Space Research Organisation (ISRO) successfully conducted the 'Reusable Launch Vehicle Autonomous Landing Mission' (RLV LEX) on Sunday morning. The test was conducted at the Aeronautical Test Range (ATR) at Chitradurga, Karnataka in the early hours of April 2.
The RLV took off at 7:10 am IST by a Chinook Helicopter of the Indian Air Force as an underslung load and flew to a height of 4.5 km. Once the predetermined pillbox parameters were attained, based on the RV's Mission Management Computer command, the RV was released in mid-air, at a down range of 4.6 km.
Release conditions included 10 parameters covering position, velocity, altitude and body rates, etc. The release of RLY was autonomous. RLY then performed approach and landing manoeuvres using the Integrated Navigation, Guidance & control system and completed an autonomous landing on the AlK at the strip at 7:40 AM IST. With that, ISRO successfully achieved the autonomous landing of a space vehicle.
How landing was carried out?
The autonomous landing was carried out under the exact conditions of a Space re-entry vehicle's landing high-speed, unmanned, precise landing from the same
return path as it the vehicle arrives from space.
Landing parameters such as Ground relative velocity, the sink rate of Landing Gears, and precise body rates, as might be experienced by an orbital re-entry space vehicle in its return path, were achieved.
The RL LEX demanded several state-of-the-art technologies including accurate Navigation hardware and software, Pseudolite system, Ka-band Rada:
Altimeter, NavIC receiver, indigenous Landing Gear, Aerofoil honey-comb fins and brake parachute system.
Winged body carried by helicopter
In a first in the world, a winged body has been carried to an altitude of 4.5 km by 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.
LEX utilize several indigenous systems. Localized Navigation systems based on pseudolite systems, instrumentation, and sensor systems, etc. were developed by ISRO.
Digital Elevation Model (DEM) of the landing site with a Ka-band Radar Altimeter provided accurate altitude information. Extensive wind tunnel tests and CFD
simulations enabled aerodynamic characterization of RL prior to the flight Adaptation of contemporary technologies developed for RV LEX turns other operational launch vehicles ofISRO more cost-effective.
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 : major accomplishment in developing Reusable Launch Vehicles.
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LEX mission achieves final approach phase
In HEX, the vehicle landed on a hypothetical runway over the Bay of Bengal. Precise landing or 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.
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 te perfect the achievement of release conditions. Dr. S Unnikrishnan Nair, Director, VSSC, and Shri Shyam Mohan N, Programme Director, A TSP guided the teams.
Dr. Jayakumar M, Project Director, RV was the Mission Director, and Shri Muthupandian J, Associate Project Director, RL was the Vehicle Director for the mission. Meanwhile, Ramakrishna, Director, ISTRAC was also present on the occasion.
Chairman, ISRO/Secretary, DOS Shri S Somanath witnessed the test and congratulated the team. With LEX, the dream of an Indian Reusable Launch Vehicle comes one step closer.