Interesting. First I'd heard of Lockheed's self-funded scale model of a TSTO. I'm convinced that TSTO technology with a reusable 1st stage flyback is the way to reduce orbital socts. R&D is expensive though, and scale model real flight hardware is a great approach to find many unknown unknowns.

Were I Lockheed or anyone, I'd try to build a simpler ballistic/glide transcontinental two stage flyback version first. There's an unadressed market for one hour transcontinental delivery. The delta V is less than the 5 miles/sec orbital, which reduces the launch mass considerably and the re-entry heating is a bit less. Incremental steps.