ISRO's Revolutionary Reusable Launch Vehicle Autonomous Landing Mission (RLV LEX)

India's space agency, the Indian Space Research Organisation (ISRO), achieved a groundbreaking milestone with the successful completion of the Reusable Launch Vehicle Autonomous Landing Mission (RLV LEX). This remarkable feat took place at the Aeronautical Test Range (ATR) in Chitradurga, Karnataka, on April 2, 2023. The RLV LEX mission demonstrated ISRO's ability to autonomously land a space vehicle, opening doors to new possibilities in the realm of space exploration and transportation. This article delves into the mission's key details, technological advancements, and the collaborative efforts that made this achievement possible.

Autonomous Landing in Space Re-entry Conditions
The RLV LEX mission perfectly replicated the conditions experienced by a space re-entry vehicle during landing. Autonomous landing was carried out with precision, mirroring the high-speed, unmanned nature of a space vehicle's return path. The landing parameters, including ground relative velocity, sink rate of landing gears, and precise body rates, were meticulously achieved. This feat required the integration of several state-of-the-art technologies, such as accurate navigation hardware and software, a pseudolite system, Ka-band radar altimeter, NavIC receiver, indigenous landing gear, aerofoil honeycomb fins, and a brake parachute system.

RLV's autonomous approach and landing pic.twitter.com/D4tDmk5VN5

— ISRO (@isro) April 2, 2023

The Unprecedented Winged Body Approach
A notable aspect of the RLV LEX mission was the unique approach of carrying a winged body to a height of 4.5 km using a Chinook helicopter of the Indian Air Force. This approach allowed for the release of the RLV in mid-air, enabling it to execute autonomous landing maneuvers on a runway. The RLV, essentially a space plane, required an approach at high glide angles and landing at high velocities of 350 kmph. This unprecedented method of transportation and landing showcased India's ingenuity in the field of aerospace engineering.

Indigenous Systems and Technologies
ISRO's RLV LEX mission showcased the development and utilization of several indigenous systems and technologies. The mission incorporated localized navigation systems based on pseudolite systems, instrumentation, and sensor systems developed by ISRO. Accurate altitude information was provided by a digital elevation model (DEM) of the landing site, equipped with a Ka-band radar altimeter. Extensive wind tunnel tests and computational fluid dynamics (CFD) simulations were conducted to characterize the RLV's aerodynamics prior to the flight. The adaptation of these contemporary technologies for the RLV LEX mission also contributes to the cost-effectiveness of other operational launch vehicles developed by ISRO.

Building Upon Previous Achievements
The RLV LEX mission builds upon ISRO's earlier accomplishments in reusable launch vehicle development. In May 2016, ISRO demonstrated the re-entry of its winged vehicle, RLV-TD, in the HEX mission. This hypersonic sub-orbital vehicle successfully landed on a hypothetical runway over the Bay of Bengal. However, the precise landing on a runway was not included in the HEX mission. The RLV LEX mission, on the other hand, achieved the final approach phase that aligns with the re-entry return flight path, culminating in an autonomous, high-speed landing at 350 kmph. The RLV LEX mission represents a significant leap forward in the development of reusable launch vehicles.

Collaborative Efforts and Key Contributors
The success of the RLV LEX mission was the result of collaborative efforts between ISRO, the Indian Air Force (IAF), and multiple research and development organizations. The IAF team worked closely with the project team to ensure the achievement of release conditions. The mission was guided by Dr. S Unnikrishnan Nair, Director of the Vikram Sarabhai Space Centre (VSSC), and Shri Shyam Mohan N, Programme Director of the Aeronautical Test Range (ATSP). Dr. Jayakumar M, Project Director of RLV, served as the Mission Director, while Shri Muthupandian J, Associate Project Director of RLV, played the crucial role of Vehicle Director. Shri Ramakrishna, Director of the Indian Space Tracking Centre (ISTRAC), was also present during the momentous event. The Chairman of ISRO and Secretary of the Department of Space, Shri S Somanath, witnessed the test and congratulated the entire team for their remarkable achievement.

Conclusion
With the successful completion of the RLV LEX mission, ISRO has brought the dream of an Indian Reusable Launch Vehicle one step closer to reality. This revolutionary achievement demonstrates India's prowess in space technology and highlights the significant advancements made in autonomous landing systems. The RLV LEX mission serves as a testament to the collaborative efforts of ISRO, the Indian Air Force, and various research organizations. As India continues to push the boundaries of space exploration, the RLV LEX mission sets the stage for future developments in reusable launch vehicles and paves the way for exciting new possibilities in space travel and beyond.