Blackstar: the US space conspiracy that never was?

Two-stage ultrasecret vehicle wows the crowds

Those among you who like their skies filled with black helicopters, or indeed secret space launch vehicles, might have already caught a quite remarkable March report in Aviation Week & Space Technology which claims that the US has successfully developed and tested a "two-stage-to-orbit system that could place a small military spaceplane in orbit" (see AWST pic, right).
The spook system, deliciously dubbed "Blackstar", allegedly comprises a carrier vehicle (codename "SR-3" according to AWST), to which is docked a reusable spacecraft (XOV or "experimental orbital vehicle"). On 4 October, 1998, claims AWST, eyewitness James Petty of Salt Lake City saw "a small, highly swept-winged vehicle nestled under the belly of the XB-70-like aircraft. The vehicle appeared to be climbing slowly on a west-southwest heading. The sky was clear enough to see both vehicles' leading edges, which Petty described as a dark gray or black color".
The orbiter apparently lands in a conventional manner, a la Space Shuttle, and reported sightings encompass Hurlburt AFB, Florida, Kadena AB, Okinawa, and Holloman AFB, New Mexico.
Provocative stuff. Of course, nobody in the US military has ever heard of Blackstar. ASWT says "top military space commanders apparently have never been 'briefed-in'," concluding that "most likely user is an intelligence agency" with eyes on the deployment of surveillance equipment comprising "an advanced imaging suite that features 1-metre-aperture adaptive optics with an integral sodium-ion-sensing laser".
So what's the solid evidence supporting AWST's story? As noted above, the SR-3 carrier vehicle resembles the XB-70 Valkyrie - legendary in both its technical ambitions and sheer cost.

The Ride of the Valkyrie

The XB-70 programme, initiated in 1955 by manufacturer North American, was designed to provide a very fast, long-range replacement for the B-52.