Almost 71 years to the day after Gen. Charles “Chuck” Yeager broke the sound barrier for the first time, the unveiling of General Electric’s Affinity engine for Aerion’s AS2 here at NBAA is the strongest signal yet that the era of supersonic business aviation is finally getting under way.

It is also 15 years since the Anglo-French Concorde Mach 2 airliner retired, and while several civil supersonic projects have been proposed, none have emerged with viable 21st-century engines – until now. The development of an environmentally compliant engine is therefore seen as a pivotal first step toward the return of faster-than-sound travel.

“The announcement by GE is a huge step forward in realizing this aircraft. Without an engine, you don’t have an airplane and it is the enabler for this whole enterprise. It’s the thing that makes this go,” says Dave Richardson, the director for air vehicle designs and technologies at Lockheed Martin Skunk Works.

Lockheed has been working with Aerion and GE on a definition of the AS2 and, as with all supersonic programs, propulsion has always been the pacing item of the entire development. Speaking earlier this year Richardson commented that the scarcity of viable suitable engines with low overall pressure ratio compressor designs remains the “big one” for all new supersonic projects.

According to Richardson, technology development of engines from the 1950s and 1960s – such as General Electric’s J79, YJ93 and GE4; Pratt & Whitney’s J58; and the Rolls-Royce Olympus – ended “when we started looking at more efficiencies.” Although subsequent advances have been made in materials that enable cores to run a lot hotter, the cycles are not optimized for long-endurance supersonic running.

However, with GE’s new Affinity – a medium-bypass engine combining a fighter-like low-pressure system with the well-known core of the F101/CFM56 – now in hand, Richardson says “there are no showstoppers. No technologies have to be invented to enable us to get us to where we need to be to make this airplane happen – that’s significant. There’s nothing ahead from the technical side that would hold us back.”

For instance, the Mach 1.4-to-1.6 maximum speed range of the AS2 means that no variable-geometry inlet is required. “That’s why this is in the sweet spot, because you can go fast but you don’t have the penalties of all that weight. It’s a fixed-geometry inlet, and the variable-area nozzle has a cone that moves back and forth,” says Richardson. “It’s pretty ingenious and it was used before in the 1960s, so we are just borrowing from the past,” he adds.

While further details are scant, the variable-nozzle design is believed to be centered on an external-expanding, or plug, nozzle which consists of a central axi-symmetric plug that translates fore and aft, depending on the phase of flight. The plug sits in the freely expanding supersonic jet and replaces more usual designs, such as convergent-divergent nozzle, as a means of containing the expansion.

From GE’s perspective, the business case for the Affinity extends beyond the 1,500 potential engines it could supply to Aerion if it sells all 500 AS2 trijets in its long-term forecast. “It represents the first of a family. We don’t view this as one application. It’s a class of engines. We are building a technology suite so we can add additional engines,” says Brad Mottier, GE vice president and general manager for business and general aviation and integrated services. He envisions that future evolutions of Affinity could power further generations of Aerion supersonic jets.

Outlining the growth plan, Aerion CEO Tom Vice says, “The key to this is sustainable supersonics. We build on the AS2 and build on the technology to look at new engine types and how will we meet the environmental targets. We want to start a renaissance that’s sustainable versus the development of one aircraft. We learned a lot from the Concorde as an industry,” he adds.

“We start with the AS2, and the revenue return and cash generated from that helps us fuel development of the AS3, AS4 and AS5. We have long-term plans to do those. We have had discussions with GE on both where we are today with this engine and on a long-term road map,” says Vice.

The future civil supersonic market could include hybrid developments that build on business jets to provide commercial high-speed service. “We think there is a variant of an airliner that carries a first-class cabin, for example, that’s how we think of AS3 and AS4. There’s also derivatives inside of that plan and what those could be, but we have a very clear sightline of what our first airliner looks like, and it’s probably very different to the way other people have talked about it. We are looking forward to that press conference, and we are not going to do that today, but we have that program plan in place,” he concludes.