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In Nazi Germany, von Braun and his colleagues which would then go on to work in the US, surely worked with metric units.

Coming to the US, I can imagine they would have had to adjust to the imperial unit system.

Is there any record of how he and his German colleagues managed to do that? Reports of problems or other complications? Were they maybe still designing everything in metric and aides would then convert it all to imperial units?

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Side note: The US does not use imperial units. There are subtle differences between imperial and US customary units.

I have seen multiple claims that von Braun despised US customary units. But he pretty much had to live with those US customary units, at least as far as hardware was concerned. The same pressures that made von Braun hate but be stuck with US customary units exist to this very day. Elon Musk also apparently despises US customary units. Despite this dislike, there are some aspects of the rocketry at SpaceX that still use US customary units.

For example, from the 1930s through the 1960s, there were very few, if any, US suppliers of space qualified metric fasteners. The European suppliers had been bombed out of existence by World War II. To this day, hardware developers, especially those who deal with "bending metal", fasteners, plumbing, structures, physical support systems, ..., tend to lean strongly toward US customary units. This has turned out to be a very tough nut to crack (pun intended). On the other hand, software developers, especially those who deal with physics-based software such as the on-board guidance, navigation, and control software and ground-based simulation software, tend to lean strongly toward the metric system.

Those on the physics side of things have tried to get NASA to finally go fully metric. This has not been not easy. Metric fasteners and customary fasteners, and the tools used for them, do not mix and match. The efforts to get NASA to go fully metric has resulted in blowback from the hardware developers, so much so that they tried to force the software developers to switch to US customary units. The end result is a detente.

This mishmash of units can lead to disasters such as the Mars Climate Orbiter and can lead to statements such as this from NASA's Space Launch System fact sheet:

Initial 70-metric-ton Rocket Development
The 70-metric-ton SLS will stand 321 feet tall, provide 8.4 million pounds of thrust at liftoff, weigh 5.5 million pounds and carry 154,000 pounds of payload.

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  • $\begingroup$ One nice thing about US customary units is that it's easy to tell that a rocket that can "provide 8.4 million pounds (force) of thrust at liftoff, weigh 5.5 million pounds (mass) and carry 154,000 pounds (mass) of payload" will be able to lift off because 8.4 > 5.5. The German rocket scientists in who built the German V2 rockets used a now-deprecated metric unit, the kilogram-force (aka kilopond), that had the same relationship with kilograms that the pound force and pound mass have with one another. $\endgroup$
    – David Hammen
    Aug 4, 2021 at 7:12
  • $\begingroup$ David, converting between kilograms-force and Newtons is easy, and you already demonstrated the understanding necessary to make the conversion second-nature. Kilograms are a unit of mass and Newtons are a unit of force, so the missing unit is gravity. All you need to do is divide or multiply by 9.8. $\endgroup$
    – rspeed
    Jan 1, 2023 at 5:18

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