Next Generation Adaptive Propulsion engines given a boost
January 29, 2025
Since the NGAP is a US Air Force program to develop new engines for the planned (but currently stalled) NGAD (Next Gen Air Dominance) 6th generation fighter programme, it may hint at pending good news for NGAD.
The new NGAD (Next Generation Air Dominance) manned fighter looks set to be a large, long range fighter with prodigious range, unprecedented internal weapons carriage and formidable sensor capabilities. New engine technologies are being developed for it under the Next Generation Adaptive Propulsion (NGAP) programme, and these will provide the basis of the powerplant for the new fighter.
The contract modification for General Electric is described as covering: “technology maturation and risk reduction services for the execution of the prototype phase of the Next Generation Adaptive Propulsion programme,” while that for Pratt and Whitney also covers: “technology maturation and risk reduction services,” but goes on to say that the work includes design, analysis, rig-testing, prototype engine build and testing, and weapon system integration. The contract modification is for the execution of the prototype phase of the Next Generation Adaptive Propulsion program and is focused on delivering a state-of-the-art propulsion system with a flexible architecture that can be tailored for future combat aircraft operating across various mission threads; and digitally transforming the propulsion industrial base.”
In simpler times, a fighter’s propulsion system was all about burning fuel to produce thrust. That is still the primary task of a jet fighter engine, although today it will have to provide a robust source of power and fuel efficiency, advanced survivability, electrical power (at unprecedented levels) and solve the thermal management issues of the platform.
A bit of history
The Next Gen Adaptive Propulsion (NGAP) programme can trace its roots back to work on finding a solution to the F-35’s propulsion system shortcomings, which included significant thermal management issues, inadequate cooling capacity and poor fuel economy.
The F136, a promising alternative engine for the F-35 from Rolls Royce, partnered with GE Aviation, was cancelled, and instead the Adaptive Versatile Engine Technology (ADVENT) project (which had been intended to develope an efficient adaptive cycle, or variable cycle engine for next generation military aircraft) successively became the 2012 Adaptive Engine Technology Demonstrator (AETD) programme, and then in 2016 the Adaptive Engine Transition Program (AETP), which focused on developing (and testing) a 45,000 lb st thrust class adaptive cycle engine for potential F-35 re-engining. The General Electric design became the XA100 Adaptive Cycle Engine and Pratt & Whitney’s competitor the XA101.
In the end, the F-35 JPO opted for Pratt & Whitney’s F135 Engine Core Upgrade (ECU) which, it was insisted, offered the durability and performance needed to enable Block 4 capabilities. Easily retrofittable to all F-35 variants, including the STOVL F-35B, the Engine Core Upgrade provided additional power and thermal management capacity, though some fear not by enough!
Work then turned to the Next Generation Adaptive Propulsion (NGAP) programme, which aimed to develop a 35,000–40,000 lb st class engine to power the Next Generation Air Dominance core manned fighter aircraft. The competing designs for NGAP are the General Electric XA102 and the Pratt & Whitney XA103.
Both are what are known as ‘Adaptive engines’, which can operate in a high-thrust mode for maximum power and a high-efficiency mode for long endurance or long range. They leverage advanced additive manufacturing methods and use state of the art, lightweight, durable materials which together allows the engine to operate beyond previous-generation engine temperature limits. Both candidate engines are believed to offer a ‘third stream’, giving an extra source of cooled air. This improves propulsion and fuel efficiency, but crucially gives a step change in thermal management capability.
John Sneden, Air Force Propulsion Directorate Director, was quoted in a Defense News article after last year’s Life Cycle Industry Days that the Adaptive Engine Transition Program (AETP) has had an important role in informing the technologies that are being used in the NGAP programme, and that some are being directly ported across.
