RD-180, NPO Energomash, Khimki

For two decades, American national-security launches, including GPS satellites, flew on a Russian engine, the RD-180 of the Atlas V. The dependence, judged untenable after 2014, is dying out with the last Atlas Vs and ULA's shift to the Vulcan and its American BE-4 engine. A textbook case of an inherited strategic dependence that is unwound only over a decade.