Stretched, trijet 50-seat configuration to be tested by subscale supersonic demonstrator

Guy Norris Los Angeles

Boom Time

More than half a century after development of the Concorde was launched, progress toward economically viable supersonic airliners has proved elusive. But now a Silicon Valley-backed startup says the ingredients for a successful, small, faster-than-sound airliner are in place, thanks to a new wave of enabling technology and a market primed with the need for speed.

Since first unveiling plans earlier this year for a 40-seat, twin-engine, supersonic transport, Denver-based Boom Technology has revised and fine-tuned the design that will cruise at Mach 2.2 for the same ticket price as subsonic business class. The aircraft has since been stretched to seat up to 50 and is now reconfigured as a trijet to permit immediate use on long overwater routes.

Scholl’s Supersonic Plan

Designed for up to 50 passengers, Mach 2.2 cruise and 4,000 nm range

Original twinjet design changed to trijet for ETOPS routes

Two engine cores, one military, one commercial, under evaluation for propulsion

Subsonic tests planned for Colorado, supersonic tests for California

“Moving from a twinjet to a trijet is a better answer,” says Boom Technology CEO Blake Scholl. “A twinjet is more challenging to certify for early ETOPS [extended twin operations], while a trijet will enable unrestricted travel on routes with up to 180 min. diversion time with an engine out.” The aircraft length has also been extended to “around” 155 ft. to accommodate 10 extra seats. “It is not too terribly different” from the original version, says Scholl, who adds that wingspan has also marginally increased.

Unlike a new generation of supersonic business jets and a NASA X-plane in development, the small airliner is neither a low-boom nor lower Mach number design. Instead the delta-winged Boom design is intended to rely on a speed slightly higher than that of the long-retired Anglo-French Concorde to achieve higher utilization and shorter sector times on 4,000 nm overwater routes.

Although Boom is not disclosing additional design changes, the aircraft’s delta wing now appears to have more dihedral (upsweep) at the tips and an extended chine where the wing root blends with the forward fuselage. The aircraft’s single fin is slightly reduced in area and, although still swept, is configured with a conventional leading edge rather than the crescent profile of the earlier configuration. Air inlets have also been added to either side of the aft fuselage to feed the new tail-mounted engine, which is buried, fighter-style, in the tail cone section.

The company is reviewing engine options, and Scholl says “at least two off-the-shelf cores are a good fit; one commercial and one military, the latter with good exportability.” The propulsion system, designed to supercruise and power the aircraft for takeoff without the need for afterburning, will require a new low-pressure spool. “It’s essentially a refan project,” says Scholl, who adds that “making the whole flight profile possible without afterburner is crucial to making it viable.”

As engine selection is the pacing item for the entire project, Boom intends to downselect to the appropriate core in 2017-18 to enable entry into service by 2023. The target speed of Mach 2.2 “can be done with a propulsion system that will make it [noise] compliant for takeoff and be efficient in cruise, without having to get into the complexities of fancy variable cycle engines,” he adds. The design will be capable of meeting Chapter 14 noise limits, though Scholl acknowledges this will only be achieved with compromises and “with pain, for sure.”

Boom is developing a one-third-scale prototype dubbed XB-1 at its Centennial Airport facility in Denver, which will be used to verify key elements of the design and aerodynamics. The demonstrator, which will be powered by three General Electric CJ610 turbojet engines, will be used to expand the subsonic flight envelope in Colorado starting in late 2017. Flight tests will then transfer to California, where supersonic flight tests will be conducted in the restricted airspace around Edwards AFB.

Virgin Galactic’s Mojave, California-based subsidiary, The Spaceship Co. (TSC), is providing engineering, design and manufacturing services and will be involved in flight test and operations support. Virgin Galactic itself has taken options on the first 10 aircraft (AW&ST March 28-April 10, p. 34).

“The whole idea is to gain real-life experience with the configuration we intend to fly with passengers [onboard],” says Scholl. “The demonstrator is being built in-house, and Virgin is assisting in flight testing but not production,” he adds. “It would be a real mistake to outsource that early

For full-scale manufacturing, Boom is “open to different strategies,” says Scholl. “Plan A is to team up with Tier 1 suppliers like the Spirit AeroSystems of this world. We would not be able to do the whole thing in-house,” he adds. The company says “we take a lot of inspiration from the SpaceX story. Clearly those guys achieved things on a smaller budget that everyone else thought was impossible. Where it makes sense, we are following that lead,” he says.

Key off-the-shelf structural and design technologies are available that make the small supersonic airliner project feasible, says Scholl. Large-scale primary structural composites pioneered by Boeing and high-temperature composites developed by SpaceX for the Falcon 9 launch vehicle are cited as examples. “Composites can carry more thermal load when coupled with the right resin system. These are capable of dealing with even the highest temperatures from the leading edge to the nose, where we expect to see about 307F at the stagnation point,” he adds.

Scholl acknowledges, however, that no amount of technological initiatives will bring the Boom project to life without the support of investors and the airlines. “There is no passenger that does not want to go faster, and we can do it in a package that makes sense,” he says. Given an estimated market of at least 1,000 aircraft and a sales price of $200 million, Scholl says “every side of the equation will want to be there.”

Results shown exclusively to Aviation Week of an independent study into market prospects for the supersonic transport by forecaster Boyd Group International suggests as many as 1,300 aircraft worth $260 billion will be needed over a 10-year period.

The biggest potential market sector is predicted to be North America, with an estimated requirement for 377 aircraft, while European carriers would be the second-biggest user group with a requirement for more than 360. The Middle East and Africa region could be the third-biggest customer group with about 250 aircraft, while the Asia-Pacific and China sectors could potentially take up to 128 and about 100, respectively.

The report says the “ability of the aircraft to slash flight times for the important premium passenger could result in it becoming a necessary part of global airline fleets in order to remain competitive.” It also states that “while the projected costs of the Boom airliner indicate full ability to accommodate fares charged on current-generation airliners, the enormous advantage of reduced travel time could allow carriers to charge a premium over service on conventional airliners.” The report also highlights the potential benefits of lower block times on asset utilization.

The Boyd report argues that, just as the regional jet created a new category of demand by delivering new mission capabilities, the Boom airliner could do the same for the supersonic niche. “This is the future for the Boom airliner. It is not a further evolution of existing aircraft. Instead, it offers an entirely new set of air travel metrics and a new product offering for major international airlines,” it says.

Image credit & Article via: Aviation Week & Space Technology