Explanation:

Thrust is the force which moves any aircraft through the air. Thrust is generated by the propulsion system of the aircraft. Different propulsion systems develop thrust in different ways, but all thrust is generated through some application of Newton's third law of motion.
For every action there is an equal and opposite reaction. In any propulsion system, a working fluid is accelerated by the system and the reaction to this acceleration produces a force on the system.
The combustion that produces thrust in the ramjet occurs at a subsonic speed in the combustor.

In both propulsion systems of ramjets and rockets, a rocket is used to bring the ramjet up to speed before it produces thrust. Because the ramjet uses external air for combustion, it is a more efficient propulsion system for flight within the atmosphere than a rocket, which must carry all of its oxygen.
Aakash missile is powered by Ramjet-rocket propulsion system (RRPS) which renders thrust for the missile to intercept the target at supersonic speed without any retardation. A ramjet engine is most suitable for high speed flights within the atmosphere.