Features selected for the fighter were: close coupled canard; blended wing/body; vortex strakes; Rockwell aerofoil; variable-camber wing; drag modulation; winglets; cambered fuselage; self-trimming wing; underfuselage intake; integrated propulsion and flight controls; digital fly-by-wire; active controls and relaxed static stability; composite structure; aeroelastic tailoring; stress-limiting controls; direct lift and sideforce; and high aspect ratio, two-dimensional (2D) nozzles.
Those which did not make it onto HiMAT include the blended wing/body, vortex strakes, cambered fuselage and the 2D nozzle. The blended wing/body and vortex strakes are already familiar features on the F-16. The highly swept, sharp-edged strakes generate vortices which sweep back over the wing, energising the air and maintaining lift to greater angles of attack. Blending the wing and body reduces interference drag at their junction and creates a forebody strake.
Windtunnel tests on the original HiMAT configuration—with strakes and blending—showed that the vortex lift created nonlinear pitching characteristics which could not be trimmed out without the jet flap created by the 2D nozzle. There was not enough time to incorporate the advanced nozzle in HiMAT so the blended wing/body and canard strakes were deleted. Canard sweep was increased to 63° to generate the vortices required to maintain wing lift...
...Several changes were made to the HiMAT wing-canard combination to achieve the desired induced drag. More vertical separation was required but was limited by the depth of fuselage. Instead, canard dihedral was increased, which also improved the direct sideforce capability of canard flaps and rudders. Increased dihedral meant more side area forward of the centre of gravity. To compensate, winglet chord was increased and the surfaces extended below the wing. This was a more efficient way of regaining directional stability, as winglets reduce induced drag by taking some of the sting out of vortices cast off by the wing.
BTW I'm currently working on updating my page about "these kind of things".)
