An unmanned Atlas 5 rocket blasted off from Cape Canaveral Air Force Station in Florida today with a classified satellite for the US National Reconnaissance Office.

Five minutes after the launch, rocket manufacturer United Launch Alliance (ULA), a partnership of Lockheed Martin and Boeing, shut down its live webcast under a prearranged news blackout ordered by the military.

While the mission unfolds under a veil of secrecy, the future of the Atlas 5 launcher is getting wide public view. Potential rival Space Exploration Technologies (SpaceX) filed a lawsuit last month to attempt to end ULA's exclusive right to sell launch services to the U.S. military.

In its lawsuit, SpaceX also questioned whether the Atlas rocket's Russian-made RD-180 engine violated economic sanctions that the United States imposed to punish Russia for its annexation of Ukraine's Crimea peninsula. A U.S. federal judge slapped a temporary injunction on the engine sales but then lifted it a few days later after US Treasury and State Department officials said no specific sanctions appeared to have been violated.

The reprieve lasted less than a week. Russia, stung by US export bans, countered with a ban of its own on sales of rocket engines that would be used to launch US military satellites.

So far, the United States has received no official word that the engine sales will stop, General William Shelton, who heads the Air Force Space Command, told reporters at a Space Foundation conference in Colorado Springs, Colo., this week.

For now, ties between the Russian company that builds the rocket engines and ULA were proceeding as "business as usual," Shelton said on Tuesday.

A new Air Force report on the RD-180 issue determined that an export ban would have significant impact on the U.S. military launch program, sources briefed on the report told Reuters.

Options to mitigate a loss of the engines are limited through 2017, the report said. It recommended the Air Force increase funding to develop a replacement engine that would be manufactured domestically.

Shelton, who declined to comment on the report, said developing a new engine likely would cost more than $1 billion and take five years to complete.

In its lawsuit, filed in the U.S. Federal Court of Claims, SpaceX offered another option - buying its U.S.-made Falcon 9 rockets.

"Domestic competition using American rocket engines is available," the lawsuit states.

ULA has said it has two years' of RD-180 engines available in its inventory.