Performance and Control
Although ramjets have been run from as low as 45 m/s (162 km/h) upwards, below about Mach 0.5, they give little thrust and are highly inefficient due to their low pressure ratios.
Above this speed, given sufficient initial flight velocity, a ramjet will be self-sustaining. Indeed, unless the vehicle drag is extremely high, the engine/airframe combination will tend to accelerate to higher and higher flight speeds, substantially increasing the air intake temperature. As this could have a detrimental effect on the integrity of the engine and/or airframe, the fuel control system must reduce engine fuel flow to stabilize the flight Mach number and, thereby, air intake temperature to reasonable levels.
Due to the stoichiometric combustion temperature, efficiency is usually good at high speeds (Mach 2-3), whereas at low speeds the relatively poor pressure ratio means the ramjets are outperformed by turbojets, or even rockets.
Read more about this topic: Ramjet
Famous quotes containing the words performance and/or control:
“The honor my country shall never be stained by an apology from me for the statement of truth and the performance of duty; nor can I give any explanation of my official acts except such as is due to integrity and justice and consistent with the principles on which our institutions have been framed.”
—Andrew Jackson (1767–1845)
“Surrealism, n. Pure psychic automatism, by which it is intended to express, whether verbally or in writing, or in any other way, the real process of thought. Thought’s dictation, free from any control by the reason, independent of any aesthetic or moral preoccupation.”
—André Breton (1896–1966)