By Emelie Rutherford

NASA is moving forward with its controversial plans to help develop a commercial space transportation industry, awarding more than $250 million in contracts to four firms to continue developing space systems to carry astronauts to the International Space Station.

NASA announced late Monday it awarded four Space Act Agreements to companies as part of the second round of its Commercial Crew Development (CCDev) effort, or CCDev2. The firms are charged with advancing concepts for commercial crew space transportation systems, and with maturing the design and development of launch vehicles and spacecraft for carrying up to seven people.

The space agency’s CCDev2 effort is intended to help U.S. commercial companies develop transportation systems for carrying crew to low-Earth orbit destinations like the space station, as NASA grapples with tight budgets and the retirement of its space shuttle this year. The companies with the CCDev2 agreements also are using their own funds to develop their systems, and are free to sell them to commercial customers as well.

“The next American-flagged vehicle to carry our astronauts into space is going to be a U.S. commercial provider,” NASA Commercial Crew Program Manager Ed Mango said in a statement. After the shuttle retires, NASA is planning on using Russian vessels to carry astronauts to the space station, until the U.S. commercial systems are ready.

Congress and President Barack Obama agreed last year to dismantle much of former President George W. Bush’s Constellation manned-spaceflight program, which was intended to build systems to carry astronauts to the moon, yet was underfunded. In its place, NASA is helping launch a commercial space transportation industry, while working on systems such as a new heavy-lift rocket for future deep-space exploration. NASA awarded the first round of CCDev contracts, worth $50 million, last year.

NASA Administrator Charles Bolden dubbed the new CCDev2 agreements “significant milestones in NASA’s plans to take advantage of American ingenuity to get to low-Earth orbit.”

“We’re committed to safely transporting U.S. astronauts on American-made spacecraft and ending the outsourcing of this work to foreign governments,” Bolden said in a statement.

The contracts will run through mid-2012, after which the space agency is expected to launch another contest for building a flight system.

The largest of the four CCDev2 contracts was awarded to Boeing [BA], which snagged a $92.3 million, 14-month deal to continue work on the system design of its Crew Space Transportation (CST)-100 spacecraft.

John Elbon, the vice president and program manager of Boeing Commercial Crew Programs, said the company is “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” as it works to fly the CST-100 in 2015.

The CST-1000 completed a System Definition Review (SDR) last October, and under the new contact NASA intends to bring it to a Preliminary Design Review (PDR), a step in NASA development efforts that ensures the system designs meet all requirements.

Aside from Boeing, the other three companies awarded contracts on Monday for the CCDev second round are Sierra Nevada Corp. of Louisville, Colo., SpaceX of Hawthorne, Calif., and Blue Origin of Kent, Wash.

Sierra Nevada, which received a $80 million contract, is developing the Dream Chaser shuttle. SpaceX is developing a Dragon spacecraft and received $75 million in CCDev2 funds. Blue Origin, which snagged a $22 million contract, is developing a capsule as part of its Crew Transportation System.

The four companies were picked from a group of 22 contenders, Philip McAlister, acting director of commercial spaceflight development at NASA, reportedly told journalists on Monday.

Companies that did not receive CCDev2 contracts include ATK [ATK], United Space Alliance, and Orbital Sciences Corp. [ORB]. United Space Aliiance is a joint venture between Lockheed Martin [LMT] and Boeing.