United Launch Alliance, a joint venture of Lockheed Martin Corp (LMT.N) and Boeing Co (BA.N), on Wednesday said it had ordered 20 more RD-180 rocket engines from Russia, on top of 29 engines ordered before Russia’s invasion of the Crimea region of Ukraine last year. ULA said it would use the Russian engines on its Atlas 5 rockets to serve existing and potential civil and commercial launch customers until a new U.S.-built engine was developed and certified.