RLV Technology Demonstration Programme
Introduction '''Reusable Launch Vehicle–Technology Demonstration Programme''' is a series of technology demonstration missions that has been conceived by the Indian Space Research Organisation (ISRO) as a first step towards realising a Two Stage To Orbit (TSTO) re-usable launch vehicle, in which the second stage is a spaceplane.For this purpose, a winged reusable launch vehicle technology demonstrator (RLV-TD) has been configured. The RLV-TD acted as a flying test bed to evaluate various technologies like powered cruise flight, hypersonic flight, and autonomous landing using air-breathing propulsion. Application of these technologies would bring down the launch cost by a factor of 10.This project has no connection with the Avatar spaceplane concept by India's Defence Research and Development Organisation.
History In 2006  the Indian Space Research Organisation performed a series of ground tests to demonstrate stable supersonic combustion for nearly 7 seconds with an inlet Mach number of 6.In March 2010, ISRO conducted the flight testing of its new sounding rocket: Advanced Technology Vehicle (ATV-D01), weighing 3 tonnes at lift-off, a diameter of , and a length of ~. It carried a passive scramjet engine combustor module as a test-bed for demonstration of air-breathing propulsion technology.In January 2012, ISRO announced that a scaled prototype, called '''Reusable Launch Vehicle-Technology Demonstrator''' ('''RLV-TD'''), was approved to be built and tested. The aerodynamics characterization on the RLV-TD prototype was done by National Aerospace Laboratories in India. The RLV-TD is in the last stages of construction by a Hyderabad-based private company called CIM Technologies.By May 2015, engineers at the Vikram Sarabhai Space Centre (VSSC) in Thumba Equatorial Rocket Launching Station were installing thermal tiles on the outer surface of the RLV-TD to protect it against the intense heat during atmospheric reentry. This prototype weighs around 1.5 tonnes and flew to an altitude of 65 km mounted on top of an expendable solid booster HS9.On August 28, 2016, ISRO successfully tested its scramjet engine on second developmental flight of its Advanced Technology Vehicle ATV-D02 from the Satish Dhawan Space Centre for 28 August 2016.The scramjet engine will be integrated to the RLV at a later stage of development.
RLV-TD leftRLV-TD or Reusable Launch Vehicle Technology Demonstrator is India's first uncrewed flying testbed developed for the Indian Space Research Organisation (ISRO)'s RLV Technology Demonstration Programme started in 2012.It is a scaled down prototype of an eventual two-stage-to-orbit (TSTO) reusable launch vehicle.In January 2012, the design of ISRO's reusable launch vehicle was approved by the "National Review Committee" and clearance was granted to build the vehicle. The vehicle was named "Reusable Launch Vehicle-Technology Demonstrator" (RLV-TD). ISRO aims to bring down the cost of payload delivery to low Earth orbit by 80% from existing $20,000/kg to $4,000/kg.The RLV-TD was developed with an objective to test various aspects such as hypersonic flight, autoland, powered cruise flight, hypersonic flight using the air-breathing engine propulsion and "Hypersonic Experiment". A series of four RLV-TD test flights are planned by ISRO: HEX (Hypersonic Flight Experiment), LEX (Landing Experiment), REX (Return Flight Experiment), and SPEX (Scramjet Propulsion Experiment).A team of 750 engineers at Vikram Sarabhai Space Centre, National Aeronautical Laboratory, and Indian Institute of Science worked on the design and development of RLV-TD and the associated rocket. RLV-TD underwent 120 hours of wind tunnel, 5,000 hours of computational fluid dynamics and 1,100 runs of flight simulation tests. RLV-TD has mass of 1.75 tonnes, wingspan of 3.6 meters and overall length of 6.5 meters (excluding the rocket). The vehicle had 600 heat-resistant tiles on its undercarriage and it features delta wings and angled tail fins. Total cost of the project was . Future planned developments include testing an air-breathing propulsion system, which aims to capitalise on the oxygen in the atmosphere instead of liquefied oxygen while in flight.===Engines===In January 2006, ISRO completed the design, development and tests of Scramjet (supersonic ramjet) at its Vikram Sarabhai Space Centre in Thiruvananthapuram. During the ground tests, stable supersonic combustion with an inlet Mach number 6 was demonstrated for 7 seconds.On 3 March 2010, ISRO successfully conducted the flight test of its new sounding rocket ATV-D01 from Satish Dhawan Space Centre in Sriharikota. ATV-D01 weighed 3 tonnes at lift-off and was the heaviest sounding rocket ever developed by ISRO at the time. It was mounted with a passive Scramjet engine. The rocket flew for 7 seconds, achieved Mach number 6 + 0.5 and dynamic pressure 80 + 35 kPa.
RLV TD Experiments === Hypersonic Flight Experiment ===The Reusable Launch Vehicle Hypersonic Flight Experiment or '''RLV HEX''' was the first test flight in the RLV Technology Demonstration Programme. HEX was successfully conducted on 23 May 2016.RLV-TD consists of a fuselage (body), a nose cap, double delta wings and twin vertical rudders. It has active control surfaces called Elevons and Rudders. Apart from the twin rudders it is similar in shape and operation to a small Space Shuttle Orbiter. TDV uses 600 or so heat resistant silica tiles and Flexible External Insulation, nose-cap is made out Carbon-Carbon composite with SiC coating. The leading edges of twin rudders are Inconel-718, wing leading edges of 15CDV6.HEX was the first test flight of a reusable launch vehicle developed by India. The test flight objectives included:* Validating the aerodynamic design characteristics during hypersonic flight* Characterize induced loads during the hypersonic descent through the atmosphere* Assess the performance of the carbon fibre used in construction of the nose of the vehicle* Demonstrate first stage separation sequencingThe vehicle was tracked during its flight from ground stations at Sriharikota and a shipborne terminal. The total flight duration from launch to splashdown lasted about 773.6 seconds. The unit was not planned to be recovered. ISRO plans to construct an airstrip greater than 4km long in Sriharikota island in the "near future". Critical technologies such as autonomous navigation, guidance & control, reusable thermal protection system, and descent mission management were validated in this flight.===Landing Experiment===The Reusable Launch Vehicle Landing Experiment was the second test flight in the RLV Technology Demonstration Programme following the Hypersonic Flight Experiment. The demonstration trials will pave the way for the two-stage-to-orbit (TSTO) fully reusable launch vehicle. LEX was successfully conducted on 2 April 2023 at the Chitradurga Aeronautical Test Range.LEX was the second test flight of the reusable launch vehicle which was developed by India. The test flight objectives included:* Simulating the exact conditions of a Space Re-entry vehicle's landing - high speed, unmanned, autonomous, precise landing from the same return path* Validating the landing parameters such as the ground relative velocity, the sinking rate of landing gears and precise body rates as might be experienced by an orbital re-entry space vehicle on its return pathAfter the successful completion of the mission, S. Somanath, chairman of ISRO, said to the media that they are currently planning to conduct more such landing tests to check the readiness of software and hardware under different conditions.=== Future ===Two more experiments are planned by ISRO: '''OREX''' (Orbital Return Flight Experiment) and '''SPEX''' (Scramjet Propulsion Experiment). The OREX will launch on a GSLV mk.II rocket and renter the earth's atmosphere for a landing to demonstrate the viability of the project.
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See also * Avatar, an unrelated spaceplane concept by India's DRDO * Space Rider a planned robotic spaceplane by ESA
References
External links *  Home page for RLV-TD at ISRO *  RLV-TD test flight animation at YouTube