"The Shuttle and US segments of the ISS were built using the English system of measurements," says NASA spokesman Grey Hautaluoma. "And much of the Ares launch vehicle and Kennedy Space Center ground systems are legacy hardware built in the English system, too."It's too costly to join the rest of the world:
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 Hautaluoma.That's even though there have been two spacecraft disasters due to a mix-up of metric and imperial units (the Mars Climate Orbiter Probe in 1999 and the DART spacecraft in 2006.
Can you imagine having to ever again calculate something in foot-pounds?