By Graham Warwick in Washington DC
Designer encouraged by progress and plans partner talks
Supersonic business jet (SBJ) designer Aerion’s private backers, led by billionaire investor Robert Bass, were due to say this week at the European Business Aviation Convention and Exhibition (EBACE) in Geneva that they have agreed to continue funding the programme until an industrial consortium can be assembled to launch development and production of the aircraft.
Vice-chairman Bryan Barents says work completed so far has given the Reno, Nevada-based company “the confidence to enter into discussions” with airframe manufacturers and first-tier suppliers that could become consortium partners. Certification of the Mach 1.6 SBJ is expected to take five years from launch.
The commitment to fund Aerion through to programme launch includes plans to conduct a rocket-sled test of a half-wing model to validate the drag-reducing natural laminar flow design that is key the SBJ’s ability to cruise efficiently at subsonic as well as supersonic speed to avoid sonic booms when flying over land.
Planned for June/July at Sandia National Laboratories near Albuquerque, New Mexico, the sled test is intended to demonstrate supersonic laminar flow at Reynolds numbers approximating those on a full-size wing. Reynolds number is used to scale aerodynamic effects such as boundary-layer transition and skin-friction drag.
Software used by Aerion to predict the transition from low-drag laminar to high-drag turbulent flow – crucial to calculating aircraft performance – was validated by a small-scale supersonic test article flown on a NASA Boeing F-15, but a near full-scale test is needed to give potential partners confidence the SBJ will meet its predictions.
The wing model, with root chord of 1.37m (4.5ft) and 1.22m span, will achieve more than 90% of the chord Reynolds number experienced by the full-size aircraft, Aerion says. Sandia’s rocket sled will get the model to M1.5 for about 1.7s. If successful, it would avoid the need for specialised flight or windtunnel tests, but carries risks.
Rocket noise, sled vibration and shock reflections could cause transition to occur sooner than in flight, says Aerion, while the rapid acceleration and short duration could prevent infrared cameras detecting the all-important transition by observing the different heating rates of the laminar and turbulent boundary layers.
Based on work so far, Aerion believes its eight- to 12-passenger SBJ will exceed 7,400km (4,000nm) range whether flying at M1.6 over water or overland at M0.99 to avoid sonic boom.
The aircraft’s straight wing will provide a 120kt (220km/h) approach speed, and allow operation from 1,800m runways, the company says.