WASHINGTON — A key issue in the lawsuit filed by rocket maker Space Exploration Technologies Corp. challenging a U.S. Air Force contract with rival United Launch Alliance appears to be whether money associated with the contract winds up in the hands of a high-ranking Russian government official who has been hit with U.S. sanctions.

The lawsuit, originally filed April 28 in the U.S. Court of Federal Claims, took an unexpected turn April 30 when the judge handling the case issued an injunction temporarily barring ULA and the Air Force from buying the Russian-built engines that power the company’s Atlas 5 rocket. The plaintiff did not request the injunction, but Judge Susan Braden cited sanctions against Russian Deputy Prime Minister Dmitry Rogozin, who oversees that country’s space industry, in issuing the ban.

The Atlas 5 is powered by the RD-180 engine, which is built by NPO Energomash of Russia and sold to ULA by RD-Amross, a joint venture between Energomash and United Technologies Corp. SpaceX Chief Executive Elon Musk has suggested that Rogozin is financially benefiting from the arrangement, something the Russian official has denied.

Rogozin was one of 11 Russian government officials sanctioned by the U.S. government following Russia’s annexation of Crimea and continued meddling elsewhere in Ukraine. The sanctions bar defense and other high technology trade with entities associated with these officials.

In a filing with the court May 2, lawyers from the Justice Department, which is representing the government in the case, requested a clarification out of concern that the injunction could be interpreted so broadly as to apply to all contractual dealings between ULA and the Air Force. Such an interpretation would put the Air Force’s existing contracts with ULA at risk, the Justice Department lawyers said.

In a response later that same day, Braden’s clerk said the injunction directs that the Air Force and ULA “place no orders and send no money to NPO Energomash or to any other entity (as defined in the Preliminary Injunction) subject to the control of” Rogozin.

SpaceX countered with its own filing May 4, saying the burden is on the Air Force and ULA to prove their assertion that some of the money used to purchase RD-180s does not ultimately wind up in Rogozin’s hands. If the court chose to clarify its injunction at all, SpaceX said, it should stress that neither the Air Force nor ULA can make direct or indirect purchases from NPO Emergomash.

“SpaceX opportunistically seeks to expand the scope of this Court’s injunction far beyond its plain language in order to prohibit all payments by the United States Air Force to” ULA, the Denver-based launch company wrote in a motion May 5. “SpaceX’s response is rife with speculation about the manner in which [United Launch Alliance] acquires the RD-180 engines and how money is transferred from the United States to [ULA] to RD AMROSS to NPO Energomash.”

Mike Gruss covers military space issues, including the U.S. Air Force and Missile Defense Agency, for SpaceNews. He is a graduate of Miami University in Oxford, Ohio.