Nor does the Pentagon really want a fast-tracked rocket engine, says Marco Caceres, senior analyst and director of space studies at aerospace consultancy Teal Group. "The engine is the core of your rocket, and the majority of things that go wrong in a rocket have to do with the engines," he says, "You really don't want to rush this."

Moreover, the Pentagon plan intends to spread the cost of technology development out via public-private partnerships, each of which would require roughly a dozen private sector space launches each year to remain viable. That launch demand doesn't yet exist, nor does a spike in demand appear on the horizon.

All that places SpaceX in a particularly good position to take on a lot, if not all, of the military's space launches toward the end of this decade, at least until other launch technologies can be adequately matured. Barring a change in Congress's stance on RD-180 imports or some kind of mishap that jeopardizes its certification, SpaceX might not just break ULA's military launch monopoly—it may become the monopoly.

"Overall, SpaceX is starting to look very all-American and very attractive, and ULA looks weak without its Delta IV," Caceres says. "All along ULA has had its eggs in one basket, but that only works as long as you've got a monopoly."

Marco Caceres, an analyst with the Teal Group, says there is a strong business case for ULA to retire the Delta IV, as the cost for keeping two redundant lines is significant. But he also acknowledged that there is a smart political angle at work. "If they were to cancel the Delta IV medium and all they have is the Atlas V, then there is a better argument to be made for preserving the RD-180 shipments," Caceres said. "No question about that. Have they thought about it? I'm sure people at ULA have considered it as a good strategic move."

But, Caceres said, there are many practical reasons for ULA to move away from the Delta IV, a largely redundant and expensive capacity. He notes that part of the reason Bruno was brought in to lead ULA last summer was to streamline the company in the face of SpaceX's competition. "If the Air Force wants ULA to be more competitive on price, it has to become leaner, and it can't do that with two redundant systems," Caceres said.

Additive manufacturing could save substantial time and money in engine development, but the technology is still unproven, said Marco Caceres, senior analyst and director of space studies at the Teal Group consulting firm. "Right now, what the Air Force needs with regard to a new engine is precisely that, to save a lot of time and money," he said.

And the RD-180 has its supporters. "There's nothing out there that's better in terms of weight-to-power ratio than the RD-180," said Marco Caceres, an analyst with the Virginia-based Teal Group. "I don't know if you can come up with an engine as powerful as the RD-180 in a short time from scratch. "It's really more about developing the least expensive engine that will make the Atlas V much cheaper commercially."

It's believed that ULA has enough RD-180s to continue to launch Atlas V's for the next two years, however if it is to continue to do so in the long-term it would need to develop a replacement engine, which Marco Caceres, director of Space Studies at the Teal Corporation, a US research agency, tells IBTimes UK could cost the military up to $1bn. "The real winner in all of this is SpaceX," says Caceres, who explains that the US airforce will now be encouraged to look at alternative options to the Atlas V, including SpaceX's Falcon 9 rocket. He continues: "From a business standpoint it's a silly move as they make money from the sale of the engine. On the other hand, from a pride standpoint, it doesn't surprise me that Putin would stop selling the engine altogether, in a way saying to the US: 'see how you like that'."