○○○ hypersonic ⪢⪢
U.S. officials now believe the objects are mostly likely not secret U.S. technology but they worry they could be
advanced systems by another country, potentially Russia or China, both known to test hypersonic systems.
http://qindex.info/i.php?x=15561
○○○ DARPA ⪢⪢
Defence
Advanced Research Projects Agency, abbreviated DARPA or the Office of
Advanced Research Projects of the United States Department of Defence was established in 1958, almost immediately after the launch of the USSR's Sputnik-1.
http://qindex.info/i.php?x=1057