This film explains how cameras are positioned to record and later study blast effects (with smoke trails) and thermal fenomena (with ground dust lifted by heat). Quite techinical, with lots of footage directly from "Operation Tumbler-Snapper" of 1952 (avaiable also here on Archive.org).
You can stream OperationTumblerDoeVideo0800077 free and legally on OldReel, via the Internet Archive.
Yes — it is in the public domain and can be watched and shared freely.