NASA plans to spread $1.1 billion in seed money among Boeing, SpaceX and Sierra Nevada to continue the development of commercial spacecraft to launch crews to the International Space Station as early as 2017.

The three companies, all chosen to negotiate Space Act Agreements (SAAs) for the Commercial Crew Integrated Capability (CCiCap) seed-money effort, have very different approaches to the task of transporting up to seven astronauts to and from orbit. Boeing’s relatively simple, battery-powered CST-100 capsule would launch on an Atlas V — which still must be human-rated for the task — and return for a ground landing slowed by parachutes and cushioned by airbags. SpaceX is developing a human-rated version of its Dragon capsule, which already visited the station for an unmanned cargo delivery demonstration earlier this year, boosted by the company’s Falcon 9 rocket, and returned for an ocean splashdown.

Sierra Nevada has the most ambitious concept — a lifting body spaceplane that also would be boosted on an Atlas V, but would return for a runway landing.

Congress has been somewhat leery of the Obama administration’s push to cede responsibility for low-Earth-orbit (LEO) transportation to industry rather than develop a government-led space shuttle successor, while NASA focuses its efforts on the Orion multipurpose crew vehicle and Space Launch System heavy-lift rocket for deep-space missions. This has resulted in a cautious, “two-and-a-half” funding formula for CCiCap worked out with lawmakers worried about schedule slips and cost growth.

The two companies receiving full support under this scheme — enough to carry their concepts to critical design review (CDR) — are Boeing, with $460 million, and SpaceX, with $440 million. Sierra Nevada is the “half,” receiving only $212.5 million, which will not get its Dream Chaser concept as far as CDR but will allow for significant further development to take place.

Funding will be doled out over the 21-month base period of the SAA as the teams complete specific milestones, but each team is also contributing its own funds to the development. The expectation is for demonstration missions to occur by the middle of the decade, with NASA purchasing commercial orbital transportation services by 2017. But that schedule is dependent on whether an already skittish Congress fully backs the program.

William Gerstenmaier, associate administrator for the Human Exploration and Operations Mission Directorate, says NASA hopes to carry at least two providers all the way through to operational service contracts, although that will depend on congressional funding and the performance of the teams.

The commercial crew program has been planning for a fiscal 2013 appropriation of $525 million, although it could survive a continuing resolution in Congress — which would limit funding to prior-year levels — for a certain period of time without losing schedule. However, to fund all three teams, the program must get new appropriations for fiscal 2014.

Following a captive-carry test earlier this year, Sierra Nevada is now eyeing the final milestone of its previous CCDev-2 contract: an autonomous drop test of a full-size Dream Chaser prototype at Edwards AFB, Calif., set for the fourth quarter of this year. If all of the companies CCICap milestones, including optional milestones, are funded, Sierra Nevada could conduct both manned and unmanned orbital demonstration missions in 2016, according to Mark Sirangelo, head of the company’s Space Systems division.

Sierra Nevada has wider commercial ambitions for the vehicle, Sirangelo tells Aviation Week. One potential market is servicing other spacecraft in LEO, “very similar to how the shuttle repaired the Hubble telescope,” he says. Another would be long-duration, autonomous orbital stays of months or years that would allow for the testing and return of delicate scientific experiments or hardware. “Because our vehicle comes home and lands on a runway, unlike capsules we have a very soft, very low-g reentry,” he says.

The three CCiCap companies have received Space Act funding under two previous rounds of competition, as have others that did not receive CCiCap monies. Among the serious contenders in previous rounds were the Blue Origin startup endowed by Amazon.com founder Jeff Bezos, the ATK/Astrium joint venture that has received technical help but no funding for its Liberty Launch Vehicle concept, and Houston-based Excalibur Almaz, which is getting technical help from NASA for its plan to recycle Russian military-space hardware into crew transport vehicles and space habitats. ATK applied for CCiCap but did not make the cut.

At an Aug. 3 press conference at Kennedy Space Center in Florida, NASA Administrator Charles Bolden said, “The ultimate goal of our commercial crew space program is to bring human spaceflight launches right back here to American soil, and end the outsourcing of these important jobs,” referring to the current U.S. reliance on Russian Soyuz vehicles for crew transport to and from orbit. Sustaining multiple providers also will ensure NASA is not dependent on any one single provider of crew transport going forward, Bolden said.