India tested the Hypersonic Technology Demonstration Vehicle (HSTDV) today (January 27) from Kalaam Island off the coast of Odisha.

In 2019, the Defense Research and Development Organisation conducted the first tests of the HSTDV. It is a pilotless aircraft designed for hypersonic flight (five times greater than that of sound).

The HSTDV project’s goal, as stated in 2008 by then-DRDO chief V K Saraswat, was to show the “performance of a scram-jet engine at an altitude of 15 km to 20 km.” The HSTDV’s scram-jet engine allows it to reach speeds of Mach 6 (7408.8 km/h).

The goal of the research, he explained at the time, was to create a hypersonic vehicle propelled by a scram-jet engine.
Supersonic combustion ramjet engines, or scramjets, are capable of operating at hypersonic speeds.

The fuel for a scramjet is stored on board the aircraft, but the oxidizer is drawn from the surrounding air. The engine’s high speed then compresses the air before being injected into the combustion chamber.

In contrast to a ramjet, which slows the air down to subsonic velocities (speeds below that of sound) before combustion, a scramjet maintains a constant supersonic airflow.

As a result, the engine won’t fire up until the car reaches a predetermined speed. The speed is attained using alternative propulsion sources, such as a rocket engine.

Unlike a rocket engine, which carries the fuel and the oxidizer with itself, the scramjet only carries fuel. So it can only operate in the suborbital atmosphere when oxygen is sufficiently present.

India will be able to build hypersonic missiles in the future because of the technologies proven by the HSTDV test.