WASHINGTON — A formal bid protest filed April 28 by upstart rocket maker Space Exploration Technologies Corp. is targeting most, but not all, of a large block of national security launches the U.S. Air Force intends to award without competition to its incumbent provider, United Launch Alliance.

Hawthorne, California-based SpaceX has asked the U.S. Court of Federal Claims to bar the Air Force from buying 22 first-stage rocket cores on a sole-source basis from ULA. That number is a subset of the 36 cores the Air Force plans to buy from Denver-based ULA, some of which will be used for heavy-lift missions that require three cores strapped together in a side-by-side configuration.

SpaceX concedes that until its planned Falcon Heavy rocket is fully up and operating in fiscal year 2017 it cannot compete for these heavy missions, currently carried out by ULA’s Delta 4 Heavy rocket. But in the meantime, SpaceX is fighting for the right to bid on the missions it can launch with its proven Falcon 9 rocket.

In its complaint, SpaceX said that as far as it can tell, about 22 of the ULA cores would be used for Atlas 5 and Delta 4 rockets in a single-core launch configuration. These launches would take place from 2017-2019, SpaceX said.

“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.”

By filing the claim — one of several ways to protest a contract — SpaceX will now receive a judicial review of Air Force’s so-called block-buy plan. The court has the power to issue an injunction that would at least temporarily stop the purchase in its tracks.

In December, ULA and the Air Force reached contractual terms for the first batch of rockets under the block buy, which is a pillar of the service’s strategy for saving money on its overbudget satellite-launching program.

The other pillar is competition, and the Air Force, in parallel to the block buy, 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 Defense Department’s top acquisition official, 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.

In an April 28 response to SpacX’s claim, ULA said launch is one of the “most risk-intolerant and technologically advanced components” of national security.

“ULA is the only government certified launch provider that meets all of the unique … requirements that are critical to supporting our troops and keeping our country safe,” ULA spokeswoman Jessica Rye said. “That is the case today, when the acquisition process started in 2012 and at the time of the contract award in December 2013.”

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.