iÂ·deÂ·a. n. 1. Something, such as a thought or conception, that is the product of mental activity. 2. An opinion, conviction, or principle: has some strange political ideas. 3. A plan, purpose, or goal: She started school with the idea of becoming a doctor. 4.
The direction of the thrust is normally along the longitudinal axis of the rocket through the rocket center of gravity. But on some rockets, the exhaust nozzle and the thrust direction can be rotated, or gimbaled. The rocket can then be maneuvered by using the torque about the center of gravity. The magnitude of the thrust can be determined by the general thrust equation.
Because the exit velocity is greater than the free stream velocity, thrust is created as described by the general thrust equation. For ramjet and scramjet engines, the exit mass flow is nearly equal to the free stream mass flow, since very little fuel is added to the stream. The thrust equation for ramjets and scramjets contain three terms: gross thrust, ram drag, and a pressure correction.