Should The Air Force Bring Back the Adaptive Engine Program for F-35?

By Logan Williams, Warrior Editorial Fellow

In the middle of Summer 2023, the United States Air Force inexplicably cancelled a Pentagon-funded research program designed to create a cutting-edge, new turbofan jet engine for the F-35 Lightning fifth-generation fighter jet. This new jet engine was truly revolutionary — it was exactly the sort of technological frontier that the Pentagon’s financing should enable our defense industrial base to cross.

Yet, after nearly ten years of research, and billions of dollars, the Air Force decided that it was time to quit.

First, to understand the true brilliance of this new jet engine, it is necessary to understand how turbofan engine technology works.

Jet engines operate in four basic stages. First, air enters the intake towards the front of the engine; some of this air enters the core of the engine, and the rest is shifted to a duct which runs just outside the engine core. The air in this duct runs around the engine, providing cooling before escaping out the rear.

The air that enters the engine core undergoes the rest of the multi-stage process. First, it is forced into a combustion chamber by a number of compressor fans, which compress the air to up to 12-times its original density. Inside the combustion chamber, fuel is injected into the pressurized, high-temp air, and then the combination is ignited, causing an exponential increase in temperature – and therefore, in pressure – as well as the release of additional gasses. This air is then forced through the exhaust system, which is much smaller than the intake, and then expelled from the engine. It is the expulsion of this air which provides the forward thrust for a jet to fly.

Why does this matter? The amount of air which enters the combustion chamber, and thus, the amount of air which is directed through the bypass duct, determines the way in which an engine functions.

A jet engine which limits the bypass of air, such as those used for fighter jets, must use more fuel to increase the heat and temperature of the air in the engine core, to cause greater air compression, and therefore, greater thrust upon exhaust. These low-bypass engines are optimal for supersonic flight.