I'm almost positive that Lockheed is required to build in English units because 'murica. And while NASA tries to use SI, vast swaths of their infrastructure are English. http://www.airspacemag.com/flight-today/commentary-metric-mayhem-1929361/?no-istThe problem is that while Lockheed Martin’s space division operates entirely in metric, its manufacturing side and many of its contractors use Imperial Units because rebuilding sophisticated hardware in metric would be wildly expensive, says Edward Euler, the company’s program manager of the ill-fated Mars mission. For similar reasons, NASA requested proposals for its next generation of space shuttles in inches, feet, and pounds even while most of the agency’s own scientists use metric. “You really have two NASAs—one English and one metric,” says Euler, who adds that Lockheed Martin has the same problem. “We can’t buy our nuts and bolts to the metric standard—that’s the place, on the commercial and manufacturing side, where there’s really resistance.”