The Indian Space Research Organisation (ISRO) has achieved a third consecutive success in the Reusable Launch Vehicle (RLV) Landing EXperiment (LEX) on June 23.

The third and final test in the series of Landing Experiments (LEX-03) was conducted at the Aeronautical Test Range (ATR) in Chitradurga, Karnataka.

How was the experiment conducted? 

• RLV LEX-03 which stands for Reusable Launch Vehicle Landing Experiment-3, re-demonstrated the autonomous landing capability under more severe wind conditions.

• The RLV was made to undertake more difficult maneuvers with dispersions, correct both cross-range and downrange and land on the runway in a fully autonomous mode.

• The winged vehicle, named ‘Pushpak’, was released from an Indian Air Force Chinook Helicopter at an altitude of 4.5 km from a release point 4.5 km away from the runway. 

• Pushpak autonomously executed cross-range correction manoeuvres, approached the runway and performed a precise horizontal landing at the runway centreline.

• Pushpak approached the runway with a speed of 320 kmph as against 280 kmph of a typical fighter aircraft due to the low lift-to-drag ratio aerodynamic configuration. 

• After the touchdown, Pushpak’s velocity was reduced to nearly 100 kmph using its brake parachute. After which the landing gear brakes were employed for deceleration and stop on the runway. 

• Pushpak utilised its rudder and nose wheel steering system to autonomously maintain a stable and precise ground roll along the runway. 

Reusable Launch Vehicle

• RLV is essentially a space plane with a low lift to drag ratio requiring an approach at high glide angles that necessitates a landing at high velocities of 350 kmph. 

• It utilises several indigenous systems. Localised 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 characterisation of RLV prior to the flight. 

• Adaptation of contemporary technologies developed for RLV-LEX makes  other operational launch vehicles of ISRO more cost-effective.

• With this second mission, ISRO has re-validated the indigenously developed technologies in the areas of navigation, control systems, landing gear and deceleration systems essential for performing a high-speed autonomous landing of a space-returning vehicle.

• The winged body and all flight systems used in RLV-LEX-01 were reused in the RLV-LEX-02 mission after due certification/clearances. 

• Hence, reuse capability of flight hardware and flight systems is also demonstrated in this mission.

• Based on the observation from RLV-LEX-01, the airframe structure and landing gear were strengthened to tolerate higher landing loads.

• The mission was accomplished by Vikram Sarabhai Space Centre (VSSC) along with the Liquid Propulsion System Centre (LPSC) and the ISRO Inertial Systems Unit (IISU). 

• ISRO has been working on reusable technology for reducing the cost of access to space, including the development of a winged body unmanned reusable launch vehicle for launching payloads into Low Earth Orbits.

• In May 2016, ISRO had demonstrated the re-entry of its winged vehicle Reusable Launch Vehicle–Technology Demonstrator (RLV-TD) in the HEX mission.

(The author is a trainer for Civil Services aspirants.)