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Back in 2009 there was some traction for conversion to SI units completely.

According to this article,

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.

This seems like a very bloated figure. I am sure NASA is literally working on "Rocket Science" and its not going to be easy. How was this figure calculated and how accurate is it?

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    Given this site's penchant for references, this is a comment rather than an answer. Going metric involves a whole lot more than merely converting, for example, changing the size of a hole cut in a piece of metal from 1.05 inches to 2.67 cm. The reason for that 1.05 inch hole is that it needs to accommodate a 1 inch diameter bolt. You won't find a 2.54 cm diameter bolt. You'll find instead a metric bold that is 2.5 cm in diameter. A 2.67 cm diameter hole means that that metric bolt will move around too much. Now the question is will that 2.5 cm bolt be strong enough? ... – David Hammen Dec 6 '16 at 12:31
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    This happens over and over. There's a whole lot more to "going metric" than just changing units. BTW, this is coming from someone who works for NASA and consistently uses the metric system. Then again, I'm not bending metal. It's bending metal (or drilling holes in metal) that makes "going metric" hard. – David Hammen Dec 6 '16 at 12:34
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    It's also worth noting that NASA is partly metric already. And the mixture of metric and imperial measurements has already proven quite expensive. – Jack B Dec 6 '16 at 14:30
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    @DavidHammen if the measurements of the 1 inch diameter bolt are also converted, then you suddenly have your missing metric bolt :) converting to metric doesnt mean you have to actually find new bolts, just how the bolts already in use are referred to... – Moo Dec 6 '16 at 15:00
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    One notable exception is American-made automobiles, which are almost all metric. Economics has forced the U.S. automotive industry to go metric. The U.S. cannot export its rockets. There is no economic incentive to go metric with regard to building rockets. It's the other way around. SpaceX wanted to be fully metric. Even though SpaceX started with a blank slate, they found that economics forced them to go customary. Poke inside a SpaceX rocket and you'll find metal bent per specs in customary units, attached with customary fasteners, and wired with customary wiring. – David Hammen Dec 6 '16 at 18:03

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