WASHINGTON — A temporary U.S. federal court order barring the U.S. Air Force and United Launch Alliance from buying additional Russian-made engines for the Atlas 5 rocket will not affect their supply in the short term, but it does raise new questions about the long-term availability of a key U.S. government workhorse launcher.

In an April 30 ruling, Judge Susan Braden of the U.S. Court of Federal Claims barred the Air Force and ULA “from making any purchases from or payment of money to NPO Energomash or any entity, whether governmental, corporate or individual, that is subject to the control of [Russian] Deputy Prime Minister [Dmitry] Rogozin,” court documents said.

The ruling followed a hearing on a complaint filed April 28 with the court by upstart rocket maker Space Exploraton Technologies Corp. SpaceX is seeking to prevent the Air Force from buying rockets from ULA on a sole-source basis.

The complaint suggested that Rogozin, who oversees Russia’s space industry and is one of 11 Russian individuals sanctioned by the U.S. government following Russia’s annexation of Crimea, might be benefiting financially from ULA purchases of RD-180 engines from Energomash, which is based near Moscow.

The Atlas 5, one of two main rockets operated by Denver-based ULA, is powered by the Energomash-built RD-180 engine and sold to ULA by RD-Amross, a joint venture between the Energomash and United Technologies Corp. of East Hartford, Connecticut. The rocket is used to launch national security as well as civil-government missions.

The injunction does not apply to RD-180 engines ordered prior to April 30. ULA says it currently has two-and-a-half years worth of Atlas 5 engine inventory at its factory in Decatur, Alabama, and is expected to receive five more engines in 2014 and six in 2015.

That means ULA has enough engines, either delivered or on order, to continue launching the Atlas 5 for about four years.

The injunction stands until the court receives input from the U.S. Treasury, State and Commerce departments on whether buying the engine contradicts White House sanctions, which were issued March 16.

In a Twitter statement, Rogozin quipped that those who think he personally benefits from sales of the RD-180 engine are “morons.”

While SpaceX did not specifically ask the court to bar RD-180 purchases, Braden cited rules of the court that allowed her to issue the ban, including consideration of the public interest.

The injunction is the latest development affecting the RD-180, the use of which has come under intense scrutiny following Russia’s moves in eastern Ukraine, including Crimea. The Pentagon is looking into the feasibility of developing a U.S. built alternative, while a key congressional panel has recommended allocating money next year for that purpose.

In a statement issued May 1 SpaceX called the injunction “a prudent step.”

ULA offered a different view. “ULA is deeply concerned with this ruling and we will work closely with the Department of Justice to resolve the injunction expeditiously,” Kevin MacCary, ULA’s general counsel, said in a May 1 email. “SpaceX’s attempt to disrupt a national security launch contract so long after the award ignores the potential implications to our National Security and our nation’s ability to put Americans on board the International Space Station.”

Two of three U.S. companies vying to launch U.S. astronauts to the space station starting in 2017 are developing spacecraft that would launch atop Atlas 5 rockets.

SpaceX filed its complaint April 28 in response to the Air Force’s December order of the first batch of rocket cores under a planned block buy of up to 36 cores from ULA, its incumbent launch service provider. The block buy, consisting of first-stage cores for ULA’s Atlas 5 and Delta 4 rockets, is part of the Air Force’s strategy to reduce costs on a per-rocket basis while stabilizing the U.S. rocket manufacturing base.

Hawthorne, California-based SpaceX specifically asked the court to bar the Air Force from buying 22 rocket cores on a sole-source basis from ULA. That number is based on SpaceX’s best guess of the number of missions for which it could compete with its flight-proven Falcon 9 rocket.

A portion of the cores the Air Force intends to buy will be used for the Delta 4 Heavy rocket, which uses three cores stages in a side-by-side configuration to launch the largest national security satellites. SpaceX concedes that it cannot compete with the Delta 4 Heavy until its own Falcon Heavy rocket is up and operating sometime in 2017.

“Due to the opaque nature of the Air Force’s arrangement with ULA, SpaceX cannot determine to which missions each Single Core Launch Vehicle configuration procured by the Air Force will ultimately be assigned or what their precise performance requirements may be,” SpaceX said. “Therefore, SpaceX herein challenges all procurements of Single Core Launch Vehicle configurations.”

In addition to the Delta 4 Heavy, there are a number of single-core Atlas 5 and Delta 4 configurations featuring solid-fuel strap-on boosters that are beyond the Falcon 9’s current capability, advertised or demonstrated.

SpaceX said in the suit that without relief from the court, the company “will lose the opportunity to compete for and win hundreds of millions of dollars of business.”

In parallel to the block buy with ULA, the Air Force had planned to put an additional 14 missions up for bid to give newcomers like SpaceX a crack at Pentagon business.

However, that number was later reduced to seven, at least initially, for reasons that included a slowdown in the procurement of satellites whose launches were targeted for competition.

In its complaint, SpaceX said it has identified seven planned missions for which it can compete: two for the U.S. National Reconnaissance Office, three next-generation GPS 3 navigation satellites, one missile warning satellite and one mission known as Air Force Space Command-4.

The company said it has not seen information from the Air Force that explains why SpaceX is “not qualified to compete for the other fifteen missions.”

SpaceX also accused the Air Force of making last-minute changes to the rules for certifying so-called new entrants to launch national security missions. The Air Force has certified one Falcon 9 mission to date and must certify two more before the vehicle becomes eligible, which is expected to happen this year.

In its complaint, the company pointed to a January 2013 memo from Frank Kendall, the Pentagon’s acquisition czar, that says the Air Force “will allow new entrants to compete for launch contract awards as soon as the new entrant delivers the data from their final certification launch.”

SpaceX said it turned over all of the required data March 22, presumably clearing the way for it to bid for Air Force business.

But on March 20, SpaceX said, the Air Force informed the company that it still needed to complete a risk assessment of various Falcon 9 systems, the claim says. That action contradicts Kendall’s memo, SpaceX said.

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.