WASHINGTON — With the space shuttle fleet having retired in July, leaving NASA with no independent means to launch astronauts to the international space station, human spaceflight will be the primary focus of the agency’s 2012 procurement activity.

NASA intends to select one or two companies this year to finalize designs for commercially operated vehicles to ferry crews to and from the station starting around 2017. The agency also intends to competitively award contracts for risk reduction studies for the Space Launch System (SLS), a congressionally mandated heavy-lift rocket that in combination with the Orion Multi-Purpose Crew Vehicle will support manned missions beyond low Earth orbit starting as soon as 2021.

The next phase of the Commercial Crew Program, which was to feature fixed-price contract awards, will now be administered under a Space Act Agreement structure. A request for proposals is expected in late February, with plans to award Space Act Agreements to at least two aspiring providers by August.

The object of the 21-month Space Act Agreements is to get competing crew taxis ready for production. The follow-on contracts, whose award date has not been announced, will be aimed at getting the vehicles up and flying to the international space station by 2017.

Ed Mango, NASA’s manager for the effort, said in December that most of the $406 million Congress appropriated for the agency’s commercial spaceflight activities in 2012 will not be used for the third round of the Commercial Crew Program but will instead support the second round, which is set to wrap up in July. NASA requested $850 million for the activities this year, and the smaller amount approved by Congress was the rationale for pursuing  Space Act Agreements for the upcoming round. Fixed-priced contracts, NASA reasoned, would be more costly to manage, and given the congressional appropriation the agency would have been able to support only a single provider.

Five companies have received NASA funds in the first two phases of the Commercial Crew Program: Blue Origin, Kent, Wash.; Boeing Space Exploration Systems, Houston; Sierra Nevada Space Systems, Louisville, Colo.; Space Exploration Technologies Corp., Hawthorne, Calif.; and United Launch Alliance, Denver.

Developing the next generation of government-owned human spaceflight hardware, meanwhile, involves less competition than its commercially operated counterpart. Marshall Space Flight Center in Huntsville, Ala., will lead development of SLS, and some of its main support contractors have already been chosen.

But NASA is preparing to spend money on SLS risk-reduction studies, including one that could shape the agency’s thinking on what sort of advanced main-stage booster system will power the rocket’s deep-space exploration missions starting next decade.

Marshall will decide this year which companies will share $200 million for risk reduction studies of the main-stage propulsion system. A NASA Research Announcement, in which the agency will describe its objectives and invite industry responses, will be released Feb. 9, NASA said.

In a presolicitation synopsis, NASA said it wants to award multiple contracts to explore liquid- or solid-propulsion systems that would replace the shuttle-derived solid-rocket motors built by ATK that will power the first two SLS flights in 2017 and 2021.

Similarly, Marshall is soon expected to issue a NASA Research Announcement for broader SLS risk- and cost-reduction studies. In addition to propulsion, these studies could cover advanced manufacturing techniques, and avionics and software development.

The announcement is expected “early in calendar year 2012,” according to NASA procurement documents posted online. An industry day at Marshall is scheduled for mid-February.

Up for grabs at the Johnson Space Center in Houston, meanwhile, is a $50 million Program Integration Services contract to support the Lockheed Martin-built Orion deep-space crew capsule to be launched atop the SLS. A request for proposals is expected June 1, with an award anticipated Nov. 15, according to the center’s procurement website.

Johnson is also preparing to award a contract for a two-way communications system for vehicles visiting the international space station. The final request for proposals is due Feb. 6, and an award is anticipated June 25.

Also in support of the international space station, Johnson intends to issue a final competitive solicitation for  Russian Language and Logistics Services Jan. 31. Proposals are due March 1, with an award to follow June 29.

While some NASA centers are gearing up to build or manage the next government-owned crew launching system, the agency’s Kennedy Space Center in Florida is preparing to upgrade the infrastructure needed to get it off the ground.

Kennedy this year will award the massive Test and Operations Support Contract, which covers many of the services formerly provided by United Space Alliance of Houston under the Space Program Operations Contract. Proposals for the new contract are due Feb. 21. The winning bidder will modernize Kennedy’s ground and launch-support infrastructure in preparation for the SLS/Orion missions.

United Space Alliance, whose primary job of operating the space shuttle has gone by the wayside, will not be picking up this contract. The joint venture’s parent companies, Lockheed Martin of Bethesda, Md., and Chicago-based Boeing Co., in December instructed the group not to bid on any new business, and in fact Boeing has said it intends to pursue the work.

Dan Leone is a SpaceNews staff writer, covering NASA, NOAA and a growing number of entrepreneurial space companies. He earned a bachelor’s degree in public communications from the American University in Washington.