After the first manned Moon landings, NASA had a vision that did not include a Space Shuttle. Unfortunately, Congress and President Richard Nixon had a vision for the agency that did not include four percent of what was then known as the Gross National Product. The long term development of the Hubble Telescope and a reusable manned Space Shuttle designed around the telescopes dimensions won out. Nine years later Apollo 16 veteran John Young and Bob Crippen few Columbia around the world. Another eight years would pass, and in 1989 what proved to be a myopic HST was deployed. Both were originally promised for the 1976 Bicentennial.
By 1986, though the cost of each Space Shuttle mission already exceeded the production costs of a single Saturn V (in 1970 dollars), NASA continued to pressure it's logistics network to fulfill the long-overdue promise of an admittedly remarkable vehicle. The result was the Challenger disaster, and the deaths of seven extraordinarily skilled and courageous astronauts.
It would take nearly twenty-two years after its initial launch and the distruction of Columbia in February 2003 to prove, as innovative as the Space Shuttle had become and remained thirty years after its conception (and usurpation of Apollo) that the vehicle would never be more than an highly experimental and inherently dangerous low-earth orbital spacecraft.
As to the Road untaken in 1972, an examination of the European Space Agency's ATV immediately calls to mind a similarly multipurpose Space Tug, envisioned as integral to the upper stage of the Saturn boosters just as the ATV is now designed to be integral to the Arianne V launched from Kourou.
Also included in those pre-Shuttle notions was a pressurized crew vehicle much like the concept cabin, combined with the versital MIT-NASA-Naval Research Laboratory Chariot chassis.
Nearly thirty years after putting all it's heaviest cargoes of eggs in the Space Shuttle basket, NASA is retracing it steps and returning to the fork in the road Congress abandoned with the end of Apollo, taking the best of what's been learned from a decades-long experiment with the Shuttle imprisonment.
Hopefully, this time Congress will hold steady to the course.