Maybe a study for the A-X or A/F-X program?
Relatively large wings and control surfaces ("carrier approach friendly"), subsonic or low supersonic I'd say, short and quite large canopy so maybe side by side seating?
I'll look for my copy of Tony's excellent book, Flying Wings and Radical Things" later this evening since my wife has been on a boxing spree ahead of our upcoming move. I'm definitely seeing quite a bit of Scaled Composites influence.
Pure speculation, but could this possibly be a Tacit Blue follow-on of some sort, designed for higher altitudes and perhaps a different customer/requirements set (such as AEW as SteveO mentioned}? The inlets are....odd, but otherwise this strongly resembles a "Son of BSAX" if such a thing ever existed.
More speculation - Although Hughes was the contractor for Tacit Blue's phased array radar, Grumman was responsible for the AN/APY-7 in the E-8 Joint STARS. As Paul mentioned, the 773 would seem to date from just before the merger with Northrop, so perhaps this was a last ditch effort to develop and pitch a "survivable", loitering battlefield surveillance and targeting platform using a version of the radar that they developed?