The Indian Space Research Organisation (ISRO) has made impressive strides in space technology, helping India become a key player in the global space scene. One of ISRO’s notable projects is the development of the Reusable Launch Vehicle (RLV). This project aims to make space missions cheaper and more sustainable by creating vehicles that can be used multiple times, much like airplanes. The Pushpak vehicle, part of this initiative, has gone through several important tests in the RLV Landing Experiment (LEX) series. The missions RLV LEX-01, LEX-02, and LEX-03 showcase ISRO’s progress in developing autonomous landing technology and reusable vehicle design.

 RLV LEX-01 Mission: The First Autonomous Landing Test

The journey of the Pushpak vehicle started with the RLV LEX-01 mission on April 2, 2023, at the Aeronautical Test Range (ATR) in Chitradurga, Karnataka. This mission was a big milestone for ISRO as it demonstrated the vehicle’s ability to land on its own, simulating conditions experienced during space re-entry.

 Mission Execution

In the LEX-01 mission, the Pushpak vehicle was lifted to a height of 4.5 kilometers by an Indian Air Force Chinook helicopter. Once the required conditions were met, the vehicle was released at a distance of 4.6 kilometers from the runway. It then performed various maneuvers on its own to approach the runway and landed at a high speed of 350 km/h.

 Technological Innovations

Several advanced technologies were used in the LEX-01 mission:

Navigation Systems: The vehicle was equipped with systems like the Pseudolite system, Ka-band Radar Altimeter, and NavIC receiver for precise navigation.

Structural Design: The Pushpak had special landing gear, aerofoil honeycomb fins, and a brake parachute to ensure safe landing.

Wind Tunnel Testing and Simulations: Extensive testing and simulations helped understand the vehicle’s aerodynamic behavior.

 Significance

This mission was a first of its kind, where a winged body was carried to such an altitude by a helicopter and landed on a runway autonomously. It validated crucial technologies needed for future reusable launch vehicles, moving ISRO closer to achieving cost-effective space missions.

 RLV LEX-02 Mission: Revalidating Autonomous Capabilities

The RLV LEX-02 mission, conducted on March 22, 2024, at the same location, aimed to improve and revalidate the autonomous landing capabilities of the Pushpak vehicle under tougher conditions.

Mission Execution

Similar to the first mission, Pushpak was lifted to 4.5 kilometers by a Chinook helicopter and released at a distance of 4 kilometers from the runway. The vehicle then corrected its path on its own and landed using its brake parachute and landing gear brakes. The nose wheel steering system and rudder ensured a stable ground roll.

 Technological Enhancements

The LEX-02 mission introduced some improvements:

Structural Reinforcements: The airframe and landing gear were strengthened to handle higher landing loads.

Reusability: The same winged body and systems from LEX-01 were reused without any modifications, proving their durability.

 Significance

This mission successfully simulated the landing conditions of a space-returning vehicle, proving ISRO’s skills in navigation and control systems essential for high-speed autonomous landings. The repeated success showcased ISRO’s ability to master critical technologies for future orbital re-entry missions.

 RLV LEX-03 Mission: Advanced Testing and Validation

The RLV LEX-03 mission, conducted on June 23, 2024, was the third and final test in the series. It further tested the Pushpak vehicle’s capabilities under more challenging conditions.

 Mission Execution

In this mission, the Pushpak vehicle was lifted to 4.5 kilometers and released with stricter parameters, such as a cross-range deviation of 500 meters. The vehicle executed complex maneuvers to correct its path and landed at a high speed of over 320 km/h, slowing down to around 100 km/h using its brake parachute and landing gear brakes.

 Technological Achievements

The LEX-03 mission demonstrated several critical advancements:

Multisensor Fusion: Various sensors, including inertial sensors and radar altimeters, guided the vehicle for a controlled landing.

Advanced Guidance Algorithms: The mission validated algorithms necessary for future Orbital Re-entry Missions.

Reuse Capability: The winged body and systems from LEX-02 were reused without any modifications, proving their robustness.

 Significance

The LEX-03 mission simulated the approach and landing conditions for a vehicle returning from space, validating ISRO’s advanced guidance systems. It marked a significant step towards developing a fully reusable launch vehicle, paving the way for more cost-effective space missions.

 Collaborative Efforts and Future Prospects

The success of the RLV LEX missions was made possible through the collaboration of multiple ISRO centers and various organizations:

ISRO Centers:The Vikram Sarabhai Space Centre (VSSC), Liquid Propulsion System Centre (LPSC), and ISRO Inertial Systems Unit (IISU) played crucial roles in these missions.

Collaborating Agencies: The Indian Air Force (IAF), Aeronautical Development Establishment (ADE), Aerial Delivery Research and Development Establishment (ADRDE), and Centre for Military Airworthiness and Certification (CEMILAC) provided essential support.

Academic and Industrial Partners: Contributions from institutions like the Indian Institute of Technology, Kanpur, and various aerospace partners were vital to the missions’ success.

 Conclusion

The RLV LEX series has demonstrated ISRO’s commitment to developing reusable launch vehicle technology, a crucial step towards reducing the cost of access to space. The Pushpak vehicle, through its autonomous landing capabilities and robust design, has shown that reusable space vehicles are within reach for India. The successful execution of the RLV LEX-01, LEX-02, and LEX-03 missions has validated key technologies and set the stage for future orbital re-entry missions. As ISRO continues to innovate and push the boundaries of space technology, the Pushpak vehicle stands as a testament to India’s growing prowess in the global space arena.