From Slashdot:

NASA Sticking To Imperial Units For Shuttle Replacement: JerryQ sends in a story at New Scientist about the criticism NASA is taking for deciding to use Imperial units in the development of the Constellation program, their project to replace the space shuttle. ‘The sticking point is that Ares is a shuttle-derived design — it uses solid rocket boosters whose dimensions and technology are based on those currently strapped to either side of the shuttle’s giant liquid fuel tank. And the shuttle’s 30-year-old specifications, design drawings and software are rooted in pounds and feet rather than newtons and meters. … NASA recently calculated that converting the relevant drawings, software and documentation to the “International System” of units (SI) would cost a total of $370 million — almost half the cost of a 2009 shuttle launch, which costs a total of $759 million. “We found the cost of converting to SI would exceed what we can afford,” says [NASA spokesman Grey Hautaluoma].'”

Maybe they should take a look at SI Calc, the iPhone SI Unit calculator that I wrote 🙂