Funding two ventures may raise development costs while also fostering competition and giving NASA an alternative if one vehicle encounters technical difficulties, said Marco Caceres, director of space studies with Teal Group, a Fairfax, Virginia-based consultant.

Congressional opposition to a similar arrangement for the crew contract has waned as the fraying U.S.-Russia relationship focuses attention on NASA's dependence on Soyuz rockets to put astronauts into orbit, Caceres said in a telephone interview.

"The Russians have done NASA a favor in terms of funding," Caceres said.

The problem is that the Space Launch System program lacks a clear mission, according to Marco Caceres, director of space studies at the Teal Group Corp., a defense industry think tank. “They’ve toyed with lassoing an asteroid and hauling it to the moon, or using it as a vehicle to take people back to the moon, but it’s not clear why” we’re funding SLS, Caceres said.

The political landscape may have changed, however, now that Russia has blocked sales of its Russian RD-180 rockets, which are used to launch U.S. defense satellites. Russia also has announced that it plans to end its operations on the ISS in 2020, effectively disabling the station. “There’s a good chance that SLS will be developed and built, mainly because politically it just looks bad to not be developing your own national launch vehicle and we have to rely on Russia to launch our astronauts,” Caceres said.

Marco Caceres, senior space analyst for the Fairfax, Virginia-based Teal Group, said there have been no public disclosures of any anomalies in the April 18 mission. Caceres, who follows the launch industry, said that even if there was a glitch with the mission, such as falling short of the intended orbit, it was a success because the SpaceX vehicle was able to dock with the space station. “Rockets don’t usually fall short in delivering their payloads to the intended orbit, but it happens on occasion,” he said. “It’s certainly legitimate for Rogers to ask.”

Two companies vying with SpaceX for a NASA commercial crew program – Boeing(BA:US) and Sparks, Nevada-based Sierra Nevada Corp. – - may also find themselves relying on Russian engines, because of their plans to use Atlas V rockets, said Marcia Smith, a former director of the space studies board at the National Research Council and now editor of Arlington, Virginia-based spacepolicyonline.com. Even so, mutual dependencies in space may make this one area that’s immune to disagreements on the ground. “The Russians are making money off these sales,” said Marco Caceres of the Fairfax, Virginia-based Teal Group. “It would make sense from a political standpoint to snub us, but from a financial standpoint, it’s not so good.”

If Russia did cut off supplies of the RD-180, it might be more symbolic than actually painful for the US, according to Marco Caceres, director of space studies with the Teal Group. “The Atlas V isn’t launching that much, so short-term impact would be minimal,” Caceres said. “The long-term impact would be that Atlas V would have to find another engine and that wouldn’t be easy.” The biggest impact might come not to US military launch, but to the corporate firms that provide it. Right now, military launch is provided either by ULA’s Atlas V or Delta IV. For years, the US has wanted to maintain two families of launch vehicles in case one failed. However, SpaceX looks poised for certification this year. The combination of having a third launch option, along with the lack of RD-180 parts, might lead to the end of the Atlas V. That may be all hypothetical, however, as Caceres doubts Russia would block sales of RD-180s, primarily because of the financial impact. “It’s not to the benefit of the Russians to do this. These are engines that bring in hard currency to Russia, the same way Russian oil and gas does,” he said. “Russia doesn’t really export much else of any consequence. ”