The HSTDV is an unmanned scramjet demonstration aircraft for hypersonic speed flight. The HSTDV program is run by the Indian Defence Research and Development Organisation

India Wednesday carried out its maiden test of the indigenously developed Hypersonic Technology Demonstrator Vehicle (HSTDV) off Odisha Coast but there was no clarity on whether the test met all parameters.

While the Defence Research and Development Organisation (DRDO) claimed it was a success, defence sources said that the Agni-I ballistic carrier vehicle on which the HSTDV was to receive its altitude boost didn’t complete the mission. This is likely due to the weight issue, sources said, adding that this is just first of the many tests that are planned. The vehicle was test launched using the Agni 1 missile platform that was to take it up to a predetermined altitude where scramjet technology—the ability to fly at speeds in excess of Mach 6 while using atmospheric oxygen as oxidiser—had to be validated with separation of the platform and a short flight at high altitude. While the missile on which the platform was mounted successfully took off from the range, the test could not be completed to demonstrate the vehicle at hypersonic speed as the Agni 1 did not reach the desired altitude for the test. Scientists are looking at the technical reasons behind this and are studying all available data.

However, the DRDO issued a short and vague statement saying the test was indeed successful. “The DRDO today launched a Technology Demonstrator Vehicle to prove a number of critical technologies for futuristic missions from Dr Abdul Kalam Island off the coast of Odisha. The missile was successfully launched at 11.27 hours,” a DRDO statement said.

What Is HSTDV?

HSTDV Cruise vehicle will be mounted on a solid rocket motor which is covered by fairings will take it to the required altitude and once required altitude and Mach numbers are achieved cruise vehicles will be ejected out of the launch vehicle and later Scramjet engine will be auto-ignited mid-air thus taking over to propel cruise vehicle for next 20 seconds at Mach 6.

This is dual-use technology Project which will have multiple civilian applications. It can be used for launching satellites at low cost. It will also be available for long-range cruise missiles of the future.

According to a News18 report the significance of the HSTDV is enormous on both security and technological grounds. Security-wise, a hypersonic cruise missile can be key in taking out hostile airborne attacks, giving the Air Force an edge in terms of launching offences of their own. It is also a technological feat that can be incorporated into other areas such as sweeping surveillance tasks, all the while being energy efficient in operation.

This is where the technology comes in. The HSTDV is an unmanned scramjet, designed to eventually reach production target of Mach 6.5 (2,229.5 metres per second) speeds at an altitude of 32,500 metres. This would give the cruise missile a total flight impact distance of nearly 45 km, within impact time of just 20 seconds. The key areas of technological emphasis in this project include hypersonic propulsion, wind transmission with minimal drag loss, enhancing aerodynamics, and refining the scramjet engine.

The HSTDV uses a solid rocket launch booster for initial propulsion, following which combustion takes place in the anterior scramjet engine. The engine takes in an inflow of air particles, and compresses them inside a combustion chamber without slowing them down, thereby producing thrust that is further helped along by the side fins that aerodynamically amplify the thrust. It is this mechanism that is deemed imperative in giving the cruise missile hypersonic speeds. The double-wall engine is built using a Niobium alloy, which has a high thermal latency, and can therefore withstand the high combustion temperature and pressures inside the engine chamber.

While this is only the prototype design, DRDO engineers have stated before that they intend to test the HSTDV at up to Mach 12. Assuming that impact range remains constant, the HSTDV will increase its impact range by 1.8x, if such speeds can be achieved. This will be a new straw in the hat for India and its quest for equipping its offensive and defensive arsenal with ballistic cruise missiles. A weapon to the tune of the HSTDV can be lethal even in non-warfare cases, and the technology itself can be path-breaking.

If the combustion model is harnessed, it may, in fact, lead up to commercial usage designs, which in turn can aid areas such as reusable spaceflight and more efficient commercial cargo transmission. The first test has been claimed to have been a success by DRDO officials, as per radar data, marking a successful start to the quest for hypersonic engineering that began nearly two decades ago.

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. India’s main defence-industrial partner is Russia, which has carried out considerable research into hypersonic propulsion.

The aim of planned flight test of the project is to demonstrate autonomous flight of Hypersonic scramjet integrated vehicle using hydrocarbon fuel and also measure aerodynamics of the air vehicle, its thermal properties and scramjet engine performance. HSTDV will have a flight duration of 20 seconds at an altitude of 31 km which is also cruising altitude of Boeing 747 but at Mach 6.

Scramjet combustor under development is of 520 kg thrust engine which has cleared 4 static test for the 20-second duration at ground test facilities at simulated speed entry condition of Mach 2.25.

Performance evaluation testing of scramjet combustor was carried out on the last leg off ground-based trials last year in June which was declared successful and scramjet combustor engine was cleared for the first flight.

HSTDV’s hydrocarbon fuel in 20 seconds flight will be in the gaseous stage but in future long-duration flight, it will be in a liquid state. HSTDV in its 20-second flight will be travelling roughly for 31 km before plunging into the ocean. DRDO plans to conduct further longer duration flight which could ultimately lead to the development of re-usable nuclear/conventional weapons delivery platforms to perform precision strikes at targets guarded by Anti-ballistic layered air defences systems.

HSTDV is a very different vehicle with different set of configurations. HSTDV will fly up to Mach 6.5 whereas BrahMos-2 has lesser RCS and will fly up to Mach-9 and beyond. And this new heat-resistant material hasn’t been developed with Russian assistance.

It took us almost 5 years to develop this new material and everything was done at IISc-Bangalore with 100% indigenous in-house research. IISc-Bangalore had signed an MoU with BrahMos Aerospace Ltd in 2011, under which the Indians were supposed to make the thermal heat-resistant material nd guidance systems whereas the Russians were supposed to design the propulsion system of the missile.

The Russians will now develop the propulsion system of BrahMos-2. Being a defence journalist, I stumbled upon this project while doing a story on hypersonic missile propulsion in early 2016. At that time the material was still in development and a team of 20 scientists and engineers were working on it. I was requested by the IISc researchers and scientists to maintain silence on it citing secrecy and national security reasons.

But now this material has been fully developed and is ready for wind-tunnel testing. That’s today’s update. And it is just a mere coincidence that the Russians have parallel hypersonic missile propulsion projects which r seeing the light of the day simultaneously. And yes, now coming again to DRDO’s HSTDV..the first 2 prototypes are already ready for flight testing since last year. The govt is reluctant to give the go ahead for the maiden test flight of HSTDV as it may have geopolitical ramifications. It may be test flown after the Prime Minister’s Office (PMO) decides on it.

A hypersonic missile with a scramjet engine at Mach 20 plus is so indefensible .And it has tremendous range extension utility. For instance an Agni-5 with a hypersonic last stage will extend its range well beyond intercontinental distances.

Pentagon has described hypersonic flight ‘the new stealth’ for its promise of evading and outrunning the enemy fire. The effort to develop hypersonic engines is necessary because they can propel vehicles at a velocity that cannot be achieved from traditional turbine-powered jet engines.

Reference Sources: Wikipedia, Tarmak007, DefenceUpdate & Indian Defence Review