I've talked about the short life and death of the Spiral program and the Mig-105, but in a surprising turn of events, the story did not end in on dusty airstrip outside Moscow in 1978!
NASA had done quite a bit of their own lifting-body research in between the mid-60s to mid-70s, and in the late 80s, they dusted off some of the old research - but oddly enough, when it came time to make the vehicle geometry decision in 1989, they picked the Mig-105 shape as their baseline, rather than something based on NASA's own HL-10 or X-24. Langley began large scale work in late 1989, and built the full-scale mockup HL-20 (pictured above) over the summer of 1990. Evaluations of the concept continued through 1992.