NASA provides a quick look at its current and future human spaceflight activities.

By Alan Boyle

NASA is closing out one chapter in the multibillion-dollar effort to create new fleets of spaceships, and getting ready to open the next one. Sometime in the next month or two, the space agency will pick up to three teams of companies to receive hundreds of millions of dollars worth of funding for their spaceship development efforts. That's a lot of money but it's important to keep all those expenditures in perspective.

As an accompaniment to this week's series of commentaries about the commercial space race, here's a guide to what's gone on before and what's coming up:

Cargo transportsNASA's push to commercialize transportation services to low Earth orbit began in 2006, a couple of years after the White House decided that the space shuttle fleet had to be retired, when SpaceX and Rocketplane Kistler were awarded almost half a billion dollars to support the development of robotic cargo spacecraft capable of resupplying the space station in the post-shuttle era. "If it doesn't work, I've frankly made the wrong bet," said Mike Griffin, who was NASA's administrator at the time.

In Rocketplane Kistler's case, the bet didn't pay off. NASA paid the company $32.1 million, but Rocketplane failed to win enough private backing to keep going. The company lost its NASA funding and ended up declaring bankruptcy. Orbital Sciences Corp. was selected as a replacement.

With May's successful demonstration flight of the Dragon cargo capsule, SpaceX has virtually completed all its objectives for the Commercial Orbital Transportation Services program, or COTS. It should soon get the last of the $396 million in COTS money that NASA has set aside for the company. Orbital Sciences, meanwhile, is gearing up for key flight tests of its Antares rocket and Cygnus capsule, and at last report has received $266.5 million of its $288 million in COTS money.

Even as the development program nears its end, SpaceX and Orbital are getting ready to begin routine cargo flights to the space station under a follow-on program known as Commercial Resupply Services, or CRS. SpaceX is due to get $1.6 billion for 12 flights scheduled through 2015, while Orbital gets $1.9 billion for eight flights. Citing NASA figures, NBC News' Jay Barbree says SpaceX and Orbital have each received $337.6 million in preparation for the CRS flights.

May 31: SpaceX's Dragon cargo craft returns to Earth from the International Space Station.

Space taxis So far, we've been talking about unmanned flights to the space station, but NASA also needs U.S. spaceships capable of carrying astronauts to and from the station. Because these "space taxis" will be carrying people rather than mere stuff, the safety standards will have to be higher than they are for cargo craft. In 2010, NASA started setting aside funds to support the development of such spacecraft by private-sector partners. In the first phase of the program, NASA awarded $50 million to five companies for work on future spaceships or safety systems: $3.7 million to Blue Origin, $18 million to the Boeing Co., $1.4 million to Paragon Space Development Corp., $20 million to Sierra Nevada Corp., and $6.7 million to United Launch Alliance.

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NASA's costly space race