Start-up supersonic airliner developer Boom Technology has completed the preliminary design review (PDR) for the XB-1 “Baby Boom” demonstrator, clearing a key hurdle on the path to flight tests of the Mach 2-plus aircraft late next year.

Boom, which may announce news of additional airline interest at the Paris Air Show, plans to use the XB-1 as a pathfinder for the 55-seat supersonic trijet planned for service entry around 2023. The full-scale aircraft will cruise at Mach 2.2 and is targeted at over-water routes around 4,000 nm.

“When you do a PDR you always find things to improve, but overall, we have a clean bill of health,” says Boom CEO Blake Scholl. Speaking to Aviation Week on the sidelines of the AIAA Aviation 2017 conference in Denver, Scholl adds that “we have some development testing and risk reduction still to do. We are going to do one more validation wind-tunnel test and then we are going to look at late next year for wind under the wheels.”

The tests will be conducted at the 3 x 4-ft. subsonic facility at Wichita State University’s National Institute for Aviation Research.  “The high-speed stuff you basically don’t need to go into a wind tunnel for because the simulations are really good. The weakest part of the simulation, which people find counterintuitive, is the low speed. Anytime you have flow separation or complex vortices such as takeoff and landing is when you want to make sure you are absolutely dialed in on.”

The subscale demonstrator will prove many of the basic aerodynamic, structural and control principles of the larger production version says Scholl. To achieve the higher Mach speeds of the proposed airliner, Boom has moved to General Electric J85-21 non-afterburning engines with variable-geometry inlets and nozzles. Although the original concept was sketched around the J85’s civil derivative engine, the CJ610 turbojet, the military version was selected for its additional power. “The J85-21 has got one more compressor stage which has about 20% more thrust, and you want margins for more thrust,” he adds.

As with the Concorde, the only previous successful large supersonic transport, the Mach cruise number is limited by materials choice. However, while the Concorde was limited to just above Mach 2 by metallic materials, Boom is banking on almost 50 years of progress in lightweight composites for a structural breakthrough. Boom has teamed with Netherlands-based TenCate Advanced Composites, which, among other programs, provides high-temperature-resistant materials to SpaceX for the Falcon 9 rocket.

Negotiations with prospective engine makers remain at an early stage, although Concorde engine provider Rolls-Royce has openly discussed renewed interest in the reviving commercial supersonic market.