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.

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.

In the June 12, 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.

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.