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26th March, 2024 Science and Technology


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ISRO successfully conducts ‘Pushpak’ Reusable Landing Vehicle landing experiment.


Background on RLV-TD

  • The Reusable Launch Vehicle–Technology Demonstration Programme (RLV-TD) initiated by the Indian Space Research Organisation (ISRO) aims to develop and demonstrate technologies for a Two Stage To Orbit (TSTO) reusable launch vehicle, with the second stage envisioned as a spaceplane.

Ground Tests and Sounding Rocket Demonstrations:

  • Supersonic Combustion Tests (2006): ISRO conducted ground tests to demonstrate stable supersonic combustion for approximately 7 seconds, achieving an inlet Mach number of 6. This laid the foundation for air-breathing propulsion technology.
  • Advanced Technology Vehicle (ATV-D01) Flight Testing (March 2010): ISRO conducted flight testing of the ATV-D01 sounding rocket, weighing 3 tonnes at lift-off. It carried a passive scramjet engine combustor module to demonstrate air-breathing propulsion technology.

Development of RLV-TD Prototype:

  • Approval of Reusable Launch Vehicle-Technology Demonstrator (January 2012): ISRO announced the approval for the development and testing of a scaled prototype known as the RLV-TD. The aerodynamics characterization of the prototype was carried out by the National Aerospace Laboratories in India.
  • Construction and Assembly (Ongoing): The RLV-TD prototype is being constructed, with the final stages of assembly being undertaken by CIM Technologies, a Hyderabad-based private company. The prototype is designed to evaluate various technologies including powered cruise flight, hypersonic flight, and autonomous landing using air-breathing propulsion.
  • Thermal Protection System (May 2015): Engineers at the Vikram Sarabhai Space Centre (VSSC) installed thermal tiles on the outer surface of the RLV-TD to protect it from intense heat during atmospheric reentry. This is crucial for ensuring the vehicle's survivability during reentry.

Scramjet Engine Testing:

  • Scramjet Engine Test (August 28, 2016): ISRO successfully tested its scramjet engine during the second developmental flight of the Advanced Technology Vehicle (ATV-D02) from the Satish Dhawan Space Centre. The scramjet engine, integral to air-breathing propulsion, is intended to be integrated into the RLV-TD at a later stage of development.

About Pushpak

  • The Pushpak, also known as RLV-TD (Reusable Launch Vehicle Technology Demonstrator), serves as India's first uncrewed flying testbed developed for the Indian Space Research Organisation's (ISRO) RLV Technology Demonstration Programme, which began in 2012.
  • Project Cost: The total cost of the Pushpak (RLV-TD) project was approximately ₹95 crore.

Development and Objectives:

  • The primary objective is to create a two-stage-to-orbit (TSTO) reusable launch vehicle, ultimately aiming to reduce the cost of payload delivery to low Earth orbit by 80%.
  • Testing Objectives: The Pushpak (RLV-TD) was developed to test various aspects critical to the success of reusable launch vehicles. These include hypersonic flight, autonomous landing, powered cruise flight, and the use of air-breathing engine propulsion.

Test Flight Series:

  • HEX (Hypersonic Flight Experiment): The first in a series of four planned test flights, focusing on demonstrating hypersonic flight capabilities.
  • LEX (Landing Experiment): Intended to validate autonomous landing technologies for the reusable vehicle.
  • REX (Return Flight Experiment): Testing the vehicle's ability to safely return from space after completing its mission.
  • SPEX (Scramjet Propulsion Experiment): A planned experiment to test a scramjet propulsion system, utilizing oxygen from the atmosphere during flight.

Development Efforts:

  • Engineering Teams: A collaborative effort involving 750 engineers from the Vikram Sarabhai Space Centre, National Aeronautical Laboratory, and Indian Institute of Science worked on the design and development of the Pushpak (RLV-TD) and associated rocket.
  • Technical Specifications: The Pushpak (RLV-TD) has a mass of 1.75 tonnes, a wingspan of 3.6 meters, and an overall length of 6.5 meters (excluding the rocket). It features delta wings and angled tail fins for aerodynamic stability.
  • Thermal Protection: The vehicle is equipped with 600 heat-resistant tiles on its undercarriage to withstand the intense heat during atmospheric reentry.

Engine Development:

  • Scramjet Technology: ISRO completed the design, development, and testing of a scramjet (supersonic ramjet) engine at the Vikram Sarabhai Space Centre in Thiruvananthapuram in January 2006.
  • Flight Test: The new sounding rocket ATV-D01, carrying a passive scramjet engine, was successfully flight-tested on March 3, 2010, achieving supersonic speeds and demonstrating stable supersonic combustion.

Cost and Future Plans:

  1. Project Cost: The total cost of the Pushpak (RLV-TD) project was approximately ₹95 crore.
  2. Future Developments: ISRO aims to continue testing and development, including the implementation of an air-breathing propulsion system, leveraging atmospheric oxygen during flight.

Key Experiments under RLV-TD

Hypersonic Flight Experiment (HEX):

  • Objective: The first test flight conducted on 23 May 2016 aimed to validate various aspects of the vehicle's design during hypersonic flight, including aerodynamic characteristics, induced loads, and the performance of structural materials.
  • Technological Focus: Tested the aerodynamic design characteristics and induced loads during hypersonic descent, assessed the performance of carbon fiber construction in the nose section, and demonstrated first-stage separation sequencing.
  • Outcome: The vehicle was tracked throughout the flight from ground stations and a shipborne terminal. Critical technologies such as autonomous navigation, guidance & control, and reusable thermal protection system were validated.

Landing Experiment (LEX):


  • Objective: Conducted on 2 April 2023, this experiment simulated the conditions of a space re-entry vehicle's landing to validate landing parameters and precision landing capabilities.
  • Execution: The vehicle was released mid-air from a downrange distance of 4.6 km and successfully landed at the Chitradurga Aeronautical Test Range.
  • Outcome: Successfully validated landing parameters including ground relative velocity, sinking rate of landing gears, and precise body rates.


  • Objective: Conducted on 22 March 2024, this experiment focused on autonomous precision landing after release from an off-nominal position.
  • Execution: The vehicle was released from an altitude of 4.5 km and had to correct cross-range and down-range deviations before autonomously landing on the runway.
  • Outcome: Demonstrated the capability of the vehicle to autonomously correct deviations and execute a precise landing using its nosewheel steering system, landing gear brakes, and drogue parachute.

Future Experiments:

  • OREX (Orbital Return Flight Experiment): Planned experiment involves launching on a GSLV mk.II rocket, re-entering the Earth's atmosphere, and performing a controlled landing to demonstrate the feasibility of orbital return.
  • SPEX (Scramjet Propulsion Experiment): Planned experiment to test a scramjet propulsion system, leveraging atmospheric oxygen during flight, which is crucial for enhancing the vehicle's performance.

Pushpak in mythology

Mythical Origins:

  • According to the Ramayana, Pushpak Viman was initially a gift from Brahma to the god of wealth, Kuber.
  • However, Ravana, the demon king of Lanka, seized this magnificent aircraft from Kuber’s possession.
  • It is in this chariot that Ravana famously abducted Sita from Panchavati and transported her to Lanka, setting the stage for the epic clash between good and evil.
  • Following Ravana’s demise, the virtuous Vibhishana assumed control of the Pushpak Viman, eventually returning it to Kuber. The cycle continued when Kuber bestowed this celestial wonder upon Lord Rama after his triumphant victory over Lanka.
  • Using the Pushpak Viman, Lord Rama, along with his companions Sita, Lakshmana, and the devoted Hanuman, journeyed back to Ayodhya in grandeur.

A Glimpse into Technological Marvels:

  • Valmiki Ramayana describes it as a peacock-shaped aircraft, powered by the synergistic forces of fire and air.
  • The Viman’s interior was a marvel to behold, boasting golden pillars, gem-encrusted doors, and sapphire seats.
  • It was an all-weather, air-conditioned marvel that could expand or contract in size at will.
  • The Pushpak Viman wasn’t limited to earthly journeys; it possessed interplanetary capabilities, resembling a spacecraft.


Q.  The Pushpak Viman is a testament to the ingenuity of ancient Indian civilization. Comment. (150 Words)