The Space Transportation System launched like a rocket, worked in orbit for up to two weeks as a laboratory and construction site, and glided home as an unpowered airplane. This episode traces the Space Shuttle from its origins in the post-Apollo budget squeeze, when Max Faget's vision of a fully reusable two-stage space plane collided with U.S. Air Force demands for a 60-foot payload bay and 29,000-kilogram lift capacity for spy satellites. We explain why eastward launches carry more than polar ones and how that compromise shaped a vehicle that could never be the cheap space taxi it was promised to be.

From there we get into the hardware: solid rocket boosters that could not be shut off, RS-25 engines running at 104 percent of their original rating, throttling down through Max-Q, 30,000 silica tiles that stayed cool enough to touch, and fi ...