Start with the largest aircraft ever built, with a wingspan longer than a football field and a split fuselage fitted with six Boeing 747 jet engines — enough thrust to get 1.3 million pounds off the ground, about 425,000 pounds more than a fully loaded 747. Sling a 120-foot, three-stage rocket below the aircraft, and when the plane reaches 30,000 feet, fire the rocket into space. Then the plane flies back to Earth.
Microsoft co-founder Paul Allen calls his newest venture Stratolaunch, a system designed to lift 13,500-pound payloads — satellites, science experiments, cargo and, eventually, humans — into low-Earth orbit, where the space shuttle used to fly and where the international space station still dwells. Construction of the aircraft is underway in California, with test flights planned for the end of 2016 and the first mission to occur in late 2017 or early 2018.