Days after the devastating Challenger disaster in 1986, US President Ronald Reagan shocked the country in his State of the Union Address by announcing plans to build a single-stage-to-orbit aircraft, an elusive concept that had been revisited several times as far back as the 1950s. Along with a baseline design initially developed by millionaire Tony DuPont, engineers from five government agencies joined forces to dust off this holy grail of aerospace engineering. The air-breathing aircraft would take off