Another Milestone Achieved! ISRO Conducts First-Ever Autonomous Landing Of Its Reusable Launch Vehicle Prototype

For a few days, the Indian Space Research Organisation (ISRO) has been in the headlines ahead of its new technologies. The ISRO has successfully conducted the Reusable Launch Vehicle Autonomous Landing Mission (RLV LEX) today i.e. on Sunday.

Official Statements

According to the statements issued by the national agency headquarter, the test was conducted at the Aeronautical Test Range (ATR), Chitradurga in Karnataka.

“With that, ISRO successfully achieved the autonomous landing of a space vehicle”, it said in a statement.

“With LEX, the dream of an Indian Reusable Launch Vehicle arrives one step closer to reality,” ISRO said.

It is the world’s first winged body that 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.

Details of the launch

Taking notes from the launch, the RLV took off at 7:10 am IST by a Chinook Helicopter of the Indian Air Force (IAF) as an underslung load and flew to a height of 4.5 km (above Mean Sea Level).

Once the predetermined pillbox parameters were attained, based on the RLV’s Mission Management Computer command, the RLV was released in mid-air, at a down range of 4.6 km.

Release conditions included 10 parameters covering position, velocity, altitude, body rates, etc. The release of RLV was autonomous. RLV then performed approach and landing manoeuvres using the Integrated Navigation, Guidance & control system and completed an autonomous landing on the ATR airstrip at 7:40 AM IST.

Autonomous landing

The autonomous landing was carried out under the exact conditions of a Space Re-entry vehicle’s landing. It was a 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, as might be experienced by an orbital re-entry space vehicle in its return path, were achieved.

The RLV LEX demanded several state-of-the-art technologies including accurate Navigation hardware and software, a Pseudolite system, Ka-band Radar Altimeter, a NavIC receiver, indigenous Landing Gear, Aerofoil honey-comb fins and a brake parachute system.

Use of indigenous systems

LEX utilized several indigenous systems. Localized Navigation systems based on pseudolite systems, instrumentation, 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 RLV before the flight.

“Adaptation of contemporary technologies developed for RLV LEX turns other operational launch vehicles of ISRO more cost-effective”, the statement said.

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HEX mission

ISRO 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, coinciding 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, Centre for Military Airworthiness and Certification (CEMILAC), Aeronautical Development Establishment (ADE), and Aerial Delivery Research and Development Establishment (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.

Secretary in the Department of Space and ISRO Chairman S Somanath was among who witnessed the test.