Engines from GE Aerospace and RTX’s Pratt & Whitney have cleared the Air Force’s “Detailed Design Reviews” for the Next-Generation Adaptive Propulsion program, paving the way for the engine-makers to build prototype ground demonstrators, the two companies announced separately.
The plan is for the winner of the NGAP program to power the Air Force’s Next-Generation Air Dominance NGAD fighter.
Detailed design is the fourth of six phases the Air Force has set for NGAP, after initial design, preliminary design, and adaptive prototyping planning, but before engine fabrication and engine assessments.
The completion of design review “marks a significant step toward delivering revolutionary propulsion technology for the Air Force’s future fleet,” GE said in a press release. Its NGAP engine is called the XA102, while Pratt’s is the XA103.
Both companies touted the use of modeling and simulation, as well as other digital tools, in the design of their engine.
GE said the XA102 is the first in company history to be developed using a model-based systems engineering approach, and in its design presentation to the Air Force, the company showcased “the comprehensive digital engine model and [validated] its readiness for the next stage of development.”
Steve Russell, vice president and general manager of GE’s “Edison Works” technology incubator unit, said MBSE “has been instrumental in the success” of the XA102 design.
“As we transition into the procurement and build phase, we will continue to incorporate this innovative approach while working closely with our supply chain partners to advance the engine toward a full-scale demonstration,” he said.
Pratt said it made its design presentation to the Air Force “directly from its collaborative digital environment, providing reviewers with immediate access to all the data and material to satisfy the stringent criteria. Passing this fully digital evaluation allows the team to begin procuring hardware for the construction of its XA103 prototype ground demonstrator, which is expected to test in the late 2020s.”
Jill Albertelli, president of Pratt’s military engines business, said digital processes—which are required in the NGAP program—“will be at the foundation of our technology maturation for our future next-gen solutions.”
Pratt said its NGAP engine’s adaptive architecture enables its components to adjust for “optimized fuel efficiency, survivability, and power and thermal management, surpassing the capabilities of fourth- and fifth-generation engines. This step change in engine capability will help ensure the U.S. Air Force maintains air superiority and deters pacing challenges.”
GE similarly said adaptive engine cycles are “critical to ensure U.S. combat aircraft maintain their superiority by providing greater range and significantly more thermal management capability compared to today’s most advanced combat engine.”
Both engines derive from the work the companies did on the Adaptive Engine Transition Program, which yielded powerplants intended to fit in the F-35 fighter and provide that aircraft with significantly more thrust, range, loiter time, and cooling capability than the aircraft’s original equipment, Pratt’s F135 engine.
However, the bypass characteristics of the two AETP engines made them incompatible with the F-35B and C models without extensive re-engineering. The Pentagon decided not to pursue an all-new engine for only the Air Force F-35A variant, and instead chose to pursue the F135 Engine Core Upgrade, now in development by Pratt, which will be applicable to all F-35 variants. Remaining monies in the AETP program were shifted to NGAP in the fiscal 2025 defense budget.
The NGAP program is largely classified, and all that Air Force officials have said about it is that the engine will be a different size from the engines built for AETP.
Despite the green light to proceed to fabrication, the future of NGAP is uncertain. The Air Force put a pause on the NGAD program last summer, with then-Air Force Secretary Frank Kendall saying it was under review to see if its capabilities still matched the anticipated threat. The aircraft’s projected cost of hundreds of millions of dollars was also a factor.
Near the end of his tenure, Kendall punted a decision on the future of NGAD to the incoming Trump administration, saying it should make further decisions in the project because it will “own” the next steps in development.
With the program’s future uncertain, the unnamed contractors working on NGAD received Technology Maturation and Risk Reduction contracts to tide them over until the next steps are decided. The options include selecting a contractor to enter engineering and manufacturing development as planned; change requirements for the existing competitors; or cancel the program and take a different approach to future air superiority.
Deciding what to do about NGAD is likely one of the first decisions facing Air Force Secretary nominee Troy Meink, should he be confirmed. Presidential advisor Elon Musk, whose Department of Government Efficiency commission is eyeing potential Pentagon budget cuts, has derided the F-35 and all human-crewed fighters as technological relics unworthy of further investment.
The Air Force was not immediately able to offer comment on the design review or contracts for the next stages of NGAP.