It was designed to do a RTLS abort after the SRB's discontinued firing, which is a little over 2 minutes into the flight. Up to T plus 4 minutes, the maneuver was still possible.
The idea is to design a RTLS for the first stage of a reusable rocket. The second stage continues with the payload to orbit.
On return, the wings can support the much lighter craft. My original thought was to have the tanks in the wings, but that means more weight supported by the wings, which is a non starter. That appears to be the stumbling block. Perhaps the wings can support the engines? The fuel would stay in the "fuselage".