|Function||Technology demonstration vehicle|
|Country of origin||India|
|Height||~16 m (52 ft) (Length: 6.5 m (21 ft) (Orbiter))|
|Diameter||1 m (3 ft 3 in)|
|Mass||12 tonnes (Orbiter 1.75 tonnes)|
|Launch sites||Satish Dhawan Space Centre|
|First flight||01:30 UTC, 23 May 2016 |
RLV-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.
The RLV-TD successfully completed its first atmospheric test flight on 23 May 2016, which lasted for 770 seconds and reached a maximum altitude of 65 kilometres (40 mi). It was designed to evaluate various technologies, and development of the final version is expected to take 10 to 15 years. Landing experiment (RLV-LEX) from a height of 4.5 kms was successfully completed on 2 April 2023. The fully developed RLV is expected to take off vertically like a rocket, deploy a satellite in orbit, return to Earth, and land on a runway.
RLV-TD was developed by ISRO under the RLV Technology Demonstration Programme. The Technology Demonstration Programme consists of development of hypersonic rocket with air-breathing engines and the reusable launch vehicle. The RLV-TD is being designed and built at the Vikram Sarabhai Space Centre. Its navigational equipment was supplied by the ISRO Inertial Systems Unit in Thiruvananthapuram and ISRO's Satellite Applications Centre in Ahmedabad. The RLV-TD's landing gear is supplied by Hindustan Aeronautics Limited.
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.
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 ₹95 crore (equivalent to ₹136 crore or US$17.0 million in 2023). 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.
Main article: Hypersonic Flight Experiment
The Hypersonic Flight Experiment (HEX), first of the five test flights was conducted on 23 May 2016. The Sub-orbital test flight was launched at 07:00 IST (01:30 GMT) from Satish Dhawan Space Centre in Sriharikota (80 kilometres (50 mi) north of Chennai). The test flight lasted for 773.6 seconds, reached maximum altitude of 65 kilometres (40 mi), atmospheric entry speed of Mach 5 and covered a distance of 450 kilometres (280 mi) Sriharikota, steered itself to an on-target splashdown to land (ditch) at a designated spot in the Bay of Bengal. Not designed to float, the vehicle disintegrated on impact with water and was not recovered.
RLV-TD was launched mounted on top of a single stage solid fuel booster (HS9 booster), derived from strap-on boosters flown on India's Polar Satellite Launch Vehicle. Once the booster consumed its solid propellant in 91 seconds, the RLV-TD separated and peaked to a sub-orbital altitude of about 65 kilometres (40 mi). The heat shield, guidance, navigation and control algorithms were tested by accurately steering the vehicle during the hypersonic speed descent phase. During this phase, the test vehicle was programmed to pitch its nose up, exposing silica tiles on its underside and reinforced carbon–carbon nose cap to the airflow into the thick lower layers of the atmosphere. The RLV-TD's thermal protection system enabled the vehicle to endure high temperatures of descent through the atmosphere.
All stages of the test flight were tracked by ground station at the launch site and a shipborne terminal. All the mission objectives were met and technologies like autonomous navigation, guidance and control, reusable thermal protection system and descent mission management were successfully validated.
Main article: RLV-LEX
On 2 April 2023, ISRO successfully conducted the Reusable Launch Vehicle Autonomous Landing Mission (RLV-LEX) at the Aeronautical Test Range (ATR), Chitradurga, Karnataka. The RLV took off at 07:10 IST by a Boeing CH-47 Chinook helicopter of the Indian Air Force as an underslung load and flew to an altitude of 4.5 km. Once the predetermined parameters were attained the RLV was released in mid-air at a down range of 4.6 km. The release of RLV was autonomous after which it performed approach and landing maneuvers using the Integrated Navigation Guidance & Control system and completed an autonomous landing on the ATR airstrip at 07:40 IST.
In other experiments, ISRO intends to carry out an orbital re-entry experiment (OREX) and a Scramjet Propulsion Experiment (SPEX) using a reusable carrier vehicle. ISRO Chief K. Sivan stated that the agency had many experiments planned for the RLV-TD, but would only focus on them from 2019, as it was occupied with other missions.
We have commenced the next phase of Reusable Launch Vehicle technology development towards an Orbital Recovery Experiment.