GUY NORRIS / RENO
Northrop Gumman and Raytheon Aircraft have chosen the "join wing" configuration
Northrop Grumman and principal team member Raytheon Aircraft have unveiled their preferred "dual relevant" concept for the next phase of the US Defense Advanced Research Projects Agency (DARPA) Quiet Supersonic Platform (QSP) programme.
The distinctive "joined-wing" or "strut-braced wing" configuration emerged as the winning design from 12 concepts studied since early 2001. "We came up with a dual relevant approach as we did not want to look at dual use because this would have over-penalised the design. The result is something we think can be evolved into a strike aircraft or a business jet," says Northrop Grumman QSP chief engineer Steve Komadina.
QSP targets include a low sonic boom signature of 0.14 millibar (0.3lb/ft2), a range of 11,100km (6,000nm), and a maximum cruise speed of Mach 2.4. The vehicle, weighing around 45,400kg (100,000lb), would also have a payload of around 9,080kg, and 7.5 thrust-to-weight ratio engines with a thrust specific fuel consumption (TSFC)of 1.05. Target cruise lift/ drag ratio was 11.
Although Komadina says the design falls short of some QSP goals such as lift/drag and TSFC, he says it meets the "strict constraints imposed by the sonic boom requirements". To comply with the dual-relevant targets, the aircraft is aimed at a slightly lower M2.2 cruise speed and a balanced field length take-off run of 2,140m (7,000ft) roughly mid-way between the 2,440m military strike requirement and the 1,980m needs of business jets.
The dual relevant approach means the design can accommodate either two side-by-side, 8.3m (27.3ft) long weapons bays, or a 6.9m long passenger cabin. To ensure good lift distribution over the slender, almost 51.9m long vehicle, the team adopted a joined-wing planform. The main wing is a highly swept cranked arrow design with a straight trailing edge. Inboard leading edge sweep is 84º, extending to 35% span outboard, while the leading edge sweep reduces to 71.5º outboard of the planform break.
The main wing incorporates 10º dihedral, while the aft wing is set at 23º dihedral. The resulting out-of-plane arrangement structurally stabilises the slender structures. Overall span is 17.6m with the wing joint at 60% span. The aft wing is swept forward at 18.5º.
A single vertical tail extends above the dual General Electric GE449 engine nacelles nested at the rear of the aircraft.
No details of the strike aircraft design are being revealed, though it is expected to resemble the dual relevant configuration.
Source: Flight International