In the next test, HSTDV will fly without upper stage fairings | Part-3

Bengaluru: While the success of India’s recent flight-test of the Hypersonic Technology Demonstrator Vehicle (HSTDV) using the indigenously developed scramjet propulsion system is being hailed as a major technological breakthrough, scientists who are a part of the mission say that there are several challenging milestones that will be achieved in the days ahead.

In this final part of the Onmanorama series ‘HSTDV Story’, we look at some of the coming stages for this mission, the future of hypersonic research and the roles of academic institutions in providing support for the mission so far.

Missile scientists say that the immediate stage will be to launch HSTDV without upper stage fairings, exposing the cruise vehicle (CV) to the atmosphere.

DRDO scientists are now working on a new rocket motor that will reduce aerodynamic forces and lower kinetic heating. This will enable the CV to withstand the thermal and structural loads during launch.

“We are aiming to achieve this, and it will be another milestone for DRDO and the nation,” said a scientist who is in the HSTDV mission.

sAs things stand now, India is poised to test an indigenously developed hypersonic missile by the end of 2024.

A hypersonic mission is a different ball game altogether as it is an air-breathing system which operates at very high velocity, which is over five times the speed of sound.

Normally in jet engines and other piston engines, combustion takes place at low subsonic speeds, giving sufficient time for the fuel and air to mix, ignite, evaporate and combust. The scramjet engine doesn’t have more than 1.0–1.5 milliseconds for the fuel to mix with air and ultimately produce thrust.

“There are several intake non-start incidents worldwide in hypersonic missions as intake functions at a very specific window of flight conditions. HSTDV has done it at the very first attempt and crowned our indigenous efforts,” said the scientist.

Hypersonic research

A scientist, who has been a part of the HSTDV mission for the past several years told Onmanorama that there are several areas of futuristic hypersonic research that must be taken up by young scientists.

“The world of hypersonics is extremely fascinating, and there are several challenging areas that youngsters must dive into to make India self-reliant,” the scientist said.

Among the key areas offering challenges in the research space are: the effect of shockwave boundary layer interaction on the hypersonic regime, experimental studies on scramjet intake with wide range of entry Mach numbers, endothermic fuel development, ignition delay prediction, active cooling designs for scramjet engine, non-intrusive sensors, multi-disciplinary optimization techniques and material technologies.

Over the years, DRDO has made several modifications to the existing facilities to undertake work linked to the HSTDV mission.

“A few hypersonic test facilities like hypersonic wind tunnel and shock tunnel are available in India. Academic institutions (IIT Madras, IISc Bengaluru) and DRDL Hyderabad have wind tunnels and shock tunnels for R&D. HSTDV cruise vehicle and launch vehicle testing were carried out at these institutions,” said a scientist.

DRDO has recently developed a hypersonic wind tunnel facility in Hyderabad which will be used for future hypersonic missions.

The Rail Track Rocket Sled facility at Terminal Ballistics Research Laboratory (TBRL) Chandigarh has helped in demonstrating the panel separation at dynamic conditions.

“The scramjet connect pipe test facility provided the opportunity to carry out ground tests of the scramjet combustor. Thermo-structural facilities were upgraded to carry out thermo-structural test of sections,” the scientist added.

Role of Academic Institutions

The HSTDV mission involves almost every branch of engineering as it requires fundamental studies of different fields of science — physics, chemistry and mathematics. Subsequently it needs different technologies to convert fundamental studies into applied research and make it into the product.

“A very complex mission that needs engineers from aerospace, mechanical, computer science, electronics, communication, electrical and material science streams. In addition, we also had huge support from thermal, propulsion and structural engineering wings,” the scientist added.

Several academic institutions played a part in paving the way for the successful HSTDV mission. The Aerospace Department of IISc Bengaluru did the panel separation and scramjet related studies, IIT Bombay did the heat transfer and computational studies for the HSTDV fore body, IIT Madras undertook propulsion studies and shock tunnel experiments, IIT Kharagpur did the risk assessment studies and National Aerospace Laboratories (NAL) Bengaluru did the upper stage carbon epoxy nose cone design and development.

The HSTDV team also fondly remembers the role played by Missile Man Dr A P J Abdul Kalam, who inspired several missile scientists to take up next-gen technologies within India.

“During a conference at Hyderabad in 2007, Dr Kalam had said that by 2020 India’s technological capabilities will overpower the world. His words became true and we had the successful flight of HSTDV in September 2020,” recalled a scientist.

In short, the HSTDV is a successful mission so far, though there are several boxes to be ticked ahead of the actual hypersonic missile’s flight in 2024.

Scientists are of the opinion that the recent success of the HSTDV mission is a big milestone in India’s quest to develop a homegrown hypersonic missile.

They say the future wars will be dictated by hypersonic missiles. And, the project is slowly and steadily moving into a full-fledged hypersonic cruise missile flagship programme.

(The writer is an independent aerospace and defence journalist, who blogs at Tarmak007 and tweets @writetake.)