WASHINGTON — NASA on April 18 awarded a combined $269 million to four companies designing spacecraft capable of ferrying passengers to and from low Earth orbit on a commercial basis, but snubbed industry proposals to develop rockets that could launch the spacecraft.

A follow-on to last year’s Commercial Crew Development (CCDev) awards, which doled out $50 million in NASA Space Act Agreements to seed technology development in support of commercial crew transportation, NASA’s second round of CCDev awards is supposed to accelerate work on elements of those systems. Of the 22 CCDev 2 bids submitted, NASA selected concepts offered by Boeing, which garnered the biggest award at $92.3 million; Sierra Nevada Space Systems, which will receive $80 million; Space Exploration Technologies Corp. (SpaceX), $75 million; and Blue Origin, $22 million.

Phil McAlister, NASA’s commercial crew planning lead and the selection authority for CCDev 2, said the decision to favor crew-carring vehicles over rockets in making the awards was a matter of applying resources where they are needed the most.

“Within the U.S. industrial base, there is considerable launch vehicle development expertise and experience, as many companies have successfully developed new launch vehicles over the last few decades,” McAlister wrote in an April 4 source selection document that was briefly posted on a NASA website April 18. “In contrast, no U.S. company has successfully developed a crew-carrying spacecraft in over thirty years.”

NASA’s space shuttle program, which for the past three decades has been the sole U.S. means of launching astronauts into space, is slated to end this year. Work on a follow-on effort dubbed Constellation was begun more than six years ago, but U.S. President Barack Obama halted key elements of that effort, which relied heavily on shuttle-derived hardware, in favor of commercially developed systems to ferry astronauts to and from the international space station. Until the commercial vehicles come on line, possibly by mid-decade, NASA will rely on international partners to deliver crew and cargo to the orbiting outpost.

“We’re committed to safely transporting U.S. astronauts on American-made spacecraft and ending the outsourcing of this work to foreign governments,” NASA Administrator Charles Bolden said April 18 in a prepared statement accompanying the CCDev 2 award announcement. “These agreements are significant milestones in NASA’s plans to take advantage of American ingenuity to get to low-Earth orbit, so we can concentrate our resources on deep space exploration.”

Among the CCDev 2 proposals that did not make the cut was Alliant Techsystems’ (ATK) bid to leverage hardware developed for Constellation’s now-canceled Ares 1 crew launch vehicle. Minneapolis-based ATK on Feb. 8 announced a partnership with Astrium Space Transportation of France to build a crew launcher dubbed Liberty that would combine Ares 1’s solid-rocket first stage with a second stage based on the Astrium-built cyrogenic main stage for the Ariane 5 launcher. According to ATK, Liberty is designed to launch all U.S. crew vehicles currently in development and could make a first test flight in 2013, with operational capability targeted for two years later.

But NASA disqualified the Liberty proposal in part because ATK and Astrium had no commitments by crew vehicles developers to launch atop the rocket. ”This was a significant concern on my part as NASA could fund the Liberty all the way through the development phase and there would be the possibility that no spacecraft developer would select that launch vehicle as part of its [Crew Transportation Systems] design,” the source-selection document states.

Yet McAlister was equally unmoved by Denver-based United Launch Alliance’s multiple teaming arrangements with commercial spacecraft providers vying for CCDev 2 funding. The Boeing-Lockheed Martin joint venture won $6.7 million under the first round of CCDev awards last year to develop an Emergency Detection System for its Atlas 5 and Delta 4 launch vehicles. The system would prompt operators to abort a mission in the event of a problem with the launch vehicle.

In addition to partnering with a number of CCDev 2 hopefuls, United Launch Alliance pitched a stand-alone proposal that sought $40 million for work needed to certify the Atlas 5 and Delta 4 to launch astronauts and for continued work on the Emergency Detection System, according to industry sources.

McAlister praised the adaptability of Emergency Detection System design, which can be used with different launchers and spacecraft. But the source selection document said the “work content on their existing launch vehicles was not on the critical path” — despite the fact that Atlas 5 and Delta 4 are seen as likely candidates to launch crew vehicles being designed under the CCDev program.

Of the companies that submitted CCDev 2 proposals in December, three did so in partnership with United Launch Alliance: Chicago-based Boeing, which is refining the design of its seven-person CST-100 crew capsule; Sparks, Nev.-based Sierra Nevada, which will advance work on its Dream Chaser lifting-body spacecraft; and Dulles, Va.-based Orbital Sciences Corp., which proposed a lifting-body spacecraft design that McAlister rejected in part for not being as mature as Sierra Nevada’s concept.

Industry sources said Blue Origin of Kent, Wash., a secretive startup, initially plans to use an Atlas 5 rocket to launch its proposed New Shepard crew capsule. But these sources said United Launch Alliance was not a part of Blue Origins’ CCDev 2 proposal. According to an April 18 press release issued by the Commercial Spaceflight Federation, a Washington-based trade group, Blue Origin will use its $22 million in CCDev 2 funds for design work on a crew escape system and for engine testing.

With the exception of SpaceX, all of the CCDev 2 awardees received NASA funding under the first round of CCDev awards, made in 2010. But SpaceX is under contract to develop and provide a commercial logistics service for the space station and will use the CCDev 2 funds to design a launch aboard system for the Dragon cargo capsule that the company hopes to adapt for crewed missions.

Mark Sirangelo, executive vice president of Sierra Nevada and head of the company’s space business, said United Launch Alliance was embedded in the company’s CCDev 2 proposal, putting them on the critical path for launching the company’s Dream Chaser vehicle.

“I don’t know the details of their proposal, but we are still continuing to work with [United Launch Alliance] as our partner and they are a big part of our continuing proposal,” Sirangelo said in an April 20 interview. “We expect they’ll stay highly engaged with the commercial spaceflight business.”

In a press release, Boeing said it would use the CCDev 2 funding to reduce risk on its Crew Space Transportation (CST) -100 capsule.

“We are combining lessons learned and best practices from commercial airplanes, satellites and launch systems with those from human spaceflight programs such as the space shuttle and the International Space Station to design, deliver and fly the CST-100 in 2015,” John Elbon, vice president and program manager of Boeing Commercial Crew Programs, said April 18 in a prepared statement.

Boeing expects in May to choose a rocket on which to launch test articles and conduct early missions of CST-100, which is being designed to launch atop a variety of rockets, including Atlas 5, Delta 4, SpaceX’s Falcon 9 and Liberty, among others.

The only U.S. rockets operating today that are capable of lifting the CST-100 and Dream Chaser spacecraft are Atlas 5 and Delta 4.