[rtkwe]

Because the difference between a rocket and an ICBM is basically non existent and being able to simulate the environment inside a rocket engine would help a lot with designing either. To do pretty much any job in aerospace you'll have to qualify under ITAR which means you'll have to be a U.S. citizen, lawful permanent resident of the U.S., protected individual as defined by 8 U.S.C. 1324b(a)(3), or eligible to obtain the required authorizations from the U.S. Department of State.

[devrandomguy]

So, why don't we have these restrictions in Canada, Japan or Europe? Many countries have advanced aerospace programs. The only reason that I can see for those export regulations to exist, is because eliminating them would require effort and PR risk on the part of politicians.

[rtkwe]

ITAR is a little old so it's a bit crufty from a different time. But also I'd be shocked if ESA, JAXA, and CSA were completely open.

[StreamBright]

True, however there are other countries that are considered allies of US at the extent that new technology is ok to be worked on (more specifically HPC).

https://fas.org/sgp/crs/natsec/RL31175.pdf