The HSTDV is an unmanned scramjet demonstration aircraft for hypersonic speed flight. It is being developed as a carrier vehicle for hypersonic and long-range cruise missiles, and will have multiple civilian applications including the launching of small satellites at low cost. The HSTDV program is being run by the Defence Research and Development Organisation (DRDO).
Introduction
India is pushing ahead with the development of ground and flight test hardware as part of an ambitious plan for a hypersonic cruise missile.
The Defence Research and Development Laboratory's Hypersonic Technology Demonstrator Vehicle (HSTDV) is intended to attain autonomous scramjet flight for 20 seconds, using a solid rocket launch booster. The research will also inform India's interest in reusable launch vehicles. The eventual target is to reach Mach 6 at an altitude of 32.5 km (20 miles).
Initial flight testing is aimed at validating the aerodynamics of the air vehicle, as well as its thermal properties and scramjet engine performance. A mock-up of the HSTDV was shown at the Aero India exhibition in Bengaluru in February (see photo), and S. Panneerselvam, the DRDO's project director, says engineers aim to begin flight testing a full-scale air-breathing model powered by a 1,300-lb.-thrust scramjet engine in near future.
Design and development
The design for airframe attachment with the engine was completed in the year 2004.
In May 2008, Dr. Saraswat said:
Israel has provided some assistance on the HSTDV program, including wind tunnel testing, as has Cranfield University of the U.K. An unnamed third country is helping as well. According to a report, Russia has provided critical help in the project. India's main defence-industrial partner is Russia, which has carried out considerable research into hypersonic propulsion.
The 1-metric-ton, air vehicle under construction features a flattened octagonal cross section with mid-body stub-wings and raked tail fins and a 3.7-meter rectangular section air intake. The scramjet engine is located under the mid-body, with the aftbody serving as part of the exhaust nozzle. Development work on the engine is also in progress.
Two parallel fences in the forebody are meant to reduce spillage and increase thrust. Part span flaps are provided at the trailing edge of the wings for roll control. A deflectable nozzle cowl at the combustor end can deflect up to 25° to ensure satisfactory performance during power-off and power-on phases.
Surfaces of the airframe's bottom, wings and tail are made of titanium alloy, while aluminum alloy comprises the top surface. The inner surface of the double-wall engine is niobium alloy and the outer surface is nimonic alloy.
Due to technology denial of material for the scramjet engine, a new program was initiated and the materials were developed in-house. This led to self-sufficiency in the area and the scramjet engine was ground tested successfully for 20s instead of the initial 3s.
In the 12 June 2019 test, the cruise vehicle was mounted on an Agni-I solid rocket motor to take it to the required altitude. After the required altitude was reached and the Mach was achieved, the cruise vehicle was ejected out of the launch vehicle. Mid-air the scramjet engine was auto-ignited, and propelled the cruise vehicle at Mach 6. DRDO spent $30 million during design and development phase while $4.5 million was spent on HSTDV prototype development.
Testing
Wind tunnel testing
A 1:16 scale model of the vehicle was tested at a hypersonic wind tunnel operated by Israel Aerospace Industries. The isolated intake has been tested at a trisonic wind tunnel at India's National Aerospace Laboratory (NAL) in Bangalore. During the lab testing the scramjet engine was tested twice for 20s. A total of five to six tests are required before the test flight. The test flight was expected to take place by the end of 2010.
In November 2010, DRDO officials told press that they were in the process of opening four state-of-the-art facilities inside as well as in the vicinity of Hyderabad at a cost of more than over the next five years. Reportedly, they will invest 3 to 4 billion (US$66 to 88 million) for setting up a much-needed hypersonic wind tunnel at Hyderabad's Missile Complex. The advanced Hypersonic Wind Tunnel (HWT) test facility was finally commissioned at Dr APJ Abdul Kalam Missile Complex on 20 December 2020.
The facility facilitate testing of various parameters of the Hypersonic Technology Development Vehicle (HSTDV), including engine performance.