Why in News?

ISRO completed the third Reusable Launch Vehicle (RLV) Landing Experiment (LEX) of its winged vehicle ‘Pushpak’, at the Aeronautical Test Range (ATR) in Chitradurga, Karnataka.

What’s in Today’s Article?

• What is a RLV and How is it Different from Other Launch Vehicles?
• What is the Significance of RLVs?
• What is the History of ISRO’s RLV Missions?
• What are the RLV LEX Missions?

What is a RLV and How is it Different from Other Launch Vehicles?

• Primarily, launch vehicles comprise three or four stages apart from the payload, which needs to be launched into a polar or a geosynchronous orbit, depending on a mission’s requirements.
• In ISRO’s 3-stage rockets,
  • The first/ lowermost stage has solid fuel/ up to 4 liquid strap-on boosters in the GSLV;
  • The second stage has the Vikas engine powered by liquid fuel; and
  • The third and uppermost stage has a cryogenic engine, which uses liquid oxygen and liquid hydrogen.
• In the 4-stage PSLV,
  • The first stage has a motor using solid fuel augmentable with up to six solid-fuel strap-on boosters,
  • The second stage has a Vikas engine,
  • The third stage again has a solid-fuel motor, and
  • The fourth stage has two liquid engines.
• The RLV that ISRO is building has only two stages to propel the vehicle into orbit.
  • Once the fuel in the first stage has been expended, the vehicle will shed it and carry on with the second stage.
  • The first stage will re-enter the atmosphere and land in an autonomous fashion at a predetermined location.
  • After some maintenance, it will be available for reuse.

What is the Significance of RLVs?

• Low lift-to-drag (L/D) ratio: In aerodynamics, the L/D ratio is the lift generated by an aircraft, divided by the aerodynamic drag caused by moving through air.
• Cost-effective: The use of two staged RLVs can reduce the cost of a launch by nearly 80% of the current cost.
• Foundation for advanced technologies: It has the potential to serve as the foundation for advanced technologies such as
  • Hypersonic flight,
  • Autonomous landing,
  • Return flight experimentation,
  • Powered cruise flight, and
  • Air-breathing propulsion systems.
• Scientific, strategic and commercial advantages for India: The building of RLVs will ensure that the country does not lag in important scientific and strategic areas and will also commercially help ISRO.

What is the History of ISRO’s RLV Missions?

• In 2010, ISRO began developing a winged reusable rocket, taking the first step towards realising a two-stage-to-orbit (TSTO) launch vehicle that could be fully reusable.
• In 2016, the winged vehicle successfully flew at hypersonic speed and touched down at a predetermined site 425 km east of Sriharikota, in the Bay of Bengal.
• While several other related technologies have been tested through the years, ISRO’s RLV’s autonomous landing was only tested successfully in 2023.
• Currently, ISRO is working on the ‘Orbital Reentry Experiment’ (ORE), which will be taken to orbit by a modified launch vehicle comprising existing GSLV and PSLV stages.
  • The vehicle will stay in orbit for a stipulated period, re-enter, and finally land autonomously on a runway, with landing gear.

 What are the RLV LEX Missions?

• 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).
• This is the third and final test in the series of LEX (03), following the success of the RLV LEX-01 and LEX-02 missions.
• The third and final test re-demonstrated the autonomous landing capability of the RLV under more challenging release conditions.
• The mission simulated high-speed landing conditions for a vehicle returning from space, reaffirming ISRO’s expertise in acquiring the most critical technologies required for the development of a RLV.