Explanation:

Other facts:
•    The Scramjet engine designed by ISRO uses Hydrogen as fuel and the Oxygen from the atmospheric air as the oxidiser.
•    A scramjet engine in flight is an important milestone in ISRO’s endeavour towards its future space transportation system.
•    The scramjet engine is used only during the atmospheric phase of the rocket’s flight.
•    Scramjet engines will help bringing down launch cost by reducing the amount of oxidiser to be carried along with the fuel.
•    The test-flight is maiden short duration experimental test of ISRO’s scramjet engine with a hypersonic flight at Mach 6 (six times the speed of sound).
•    Two scramjet engines were “hugging” the rocket on its sides and when the rocket reaches a height of 11 km the scramjet engines would start breathing air.
•    The ATV rocket weighed 3,277 kg during lift-off.
Challenges: Some of the technological challenges handled by ISRO during the development of Scramjet engine include the design and development of Hypersonic engine air intake, the supersonic combustor, development of materials withstanding very high temperatures, computational tools to simulate hypersonic flow, ensuring performance and operability of the engine across a wide range of flight speeds, proper thermal management and ground testing of the engines.