Aerion Corp. is preparing to start another round of test flights in the development of what would be the world’s first supersonic business jet (SBJ). A new test article is set to fly in the centerline position beneath one of NASA’s F-15B aircraft in either June or July.

The work is continuing as Aerion continues to pursue its goal of persuading an existing business aircraft manufacturer to join it in launching an SBJ development. The U.S.-based company believes it would take six years to get the aircraft into service following a full program launch.

The new section of aerostructure, which is a bi-convex airfoil specimen with a 40-inch vertical span and an 80-inch chord, has been built to incorporate findings from the last round of flight trials, held in the summer of 2010. These reached speeds of Mach 2.0 and used an instrumented flat plate to map the high-speed flow field under the F-15B and validate computer modeling by Aerion’s engineering team.

According to Aerion, the new test article will be more representative of the Aerion wing in order to evaluate supersonic boundary-layer transition properties. This will prepare the way for establishing manufacturing standards for surface quality and assembly tolerances. The flight trials will test the airfoil for waviness and surface with a view to maintaining laminar flow.

“There has not yet been any focus in the civil [aerospace] regime in transonic and supersonic speeds up to about Mach 2.0,” explained Aerion chief operating officer Doug Nichols. “We will be looking at allowable tolerances to ensure laminar flow from the perspective of manufacturing and operations, by looking at the allowable roughness. We think there is a fair amount of tolerance.”

Wing-body Configuration

Meanwhile, tests on the ground have focused on work to optimize the shape of the wing-body configuration and of the engine outlet nozzles. Aerion is also continuing to do external research and development work for business aircraft manufacturers wanting to optimize the aerodynamics of existing and future designs. This work is done through the U.S. company’s Aerion Technologies subsidiary with care being given to ensure that it doesn’t inadvertently transfer engineering know-how critical to the SBJ program. “There is a lot of interest from OEMs in moving aircraft up to the Mach 0.9 mark,” Nichols told AIN. “Mach 0.96 to 0.98 is entirely possible and we have done work to show this for several OEMs.”

According to Aerion vice chairman Brian Barents, discussions over a possible SBJ program launch are continuing confidentially with more than one OEM. “Our sweetspot is Mach 0.96 for long-range cruise and what we are aiming to do is achieve speed with a high degree of efficiency,” he said. “Some [other would-be SBJ developers] are offering more speed but with a loss of efficiency [in terms of fuel burn, and so forth]. There is uniform acceptance of the technology [proposed by Aerion] and the questions surrounding the technology are really more practical engineering questions over issues, such as permissible tolerances and manufacturing.”

Aerion established the baseline configuration for the SBJ in 2006 and had hoped to have the aircraft in service by 2014. The company holds approximately 50 letters of intent from prospective buyers, each of whom placed $250,000 refundable deposits. According to Nichols, the main purpose of collecting these LOIs was to demonstrate initial market acceptance of the SBJ concept to prospective OEM partners for an aircraft priced at $80 million in 2007 values.

Awaiting a Partner

So why is Aerion still waiting for a manufacturing partner to commit to the program? The obvious answer would seem to be the market-stultifying effect of the financial crisis. But Aerion’s management believes that OEMs have been more impacted by wider business conditions. “If the competition is not driving you there [toward launching an SBJ], then why go there yourself? And they may also be considering whether it would cannibalize their existing products,” said Nichols. “But some will make the first move.”

Nichols acknowledged that Aerion has had discussions with prospective OEM partners from outside the industry’s existing main players, such as aircraft manufacturers from new markets like Russia and Asia. He indicated that one of these companies might end up as part of the eventual joint venture partnership with a main OEM. Once launched, the SBJ may well take a brand name designated by Aerion’s main partner.

In the meantime, Aerion remains unconcerned that the delay in getting the SBJ to market may mean that the enabling technology becomes superseded by something better. “New technologies “such as, maybe, a lighter engine [as an alternative to the planned pair of Pratt & Whitney JT8D-200 turbofans] would simply strengthen us,” said Nichols.

Rivals have been looking at boom-attenuation technology using a spike at the front of the fuselage, but Aerion believes this will come with an unpalatable drag penalty. “We’re not faced with that challenge [of dealing with supersonic noise],” said Barents. “We can fly [efficiently] at Mach 0.99 and our dual sweetspot [Mach 0.96/0/97 and Mach 1.5] means that we don’t have to wait for that technology.”

Aerion’s SBJ is envisaged as an aircraft that would carry 8 to 12 passengers at high subsonic speeds (for instance, over land to avoid noise restrictions) and also at supersonic speeds of up to Mach 1.6 with an intercontinental range of more than 4,000 nm and with operating costs comparable to those of current large business jets. The 30-foot-long, 6-foot-2-inch-high cabin would have a full galley and lavatory to deliver comfort comparable to that provided by current midsized jets.