HOUSTON - NASA is engaged in a new space race.

The agency says a decision on which company will build its next-generation vehicle to put astronauts in space is imminent. A $4 billion contract is at stake, and that's made for some intense competition.

Boeing is one of three companies competing to build the successor to the space shuttle. It hopes its CST-100 capsule will be chosen to ferry Americans to the International Space Station.

Three companies are competing for the contract to build the new craft that will ferry astronauts to the International Space Station. CBS News

John Mulholland heads Boeing's program. He knows there's a lot on the line, but he's confident.

"We've got an incredible team. Human space flight has been at our core since day one, all the way back to Mercury, Gemini, Apollo, the shuttle, the station - all Boeing products developed in partnership with NASA," he said

"It's provided a lot of benefit for us to have that experience to bring to this design," Mulholland said.

A competing design looks a lot like the space shuttle. It's called the Dream Chaser and it's built by Sierra Nevada. The company has made parts for probes and satellites, but Mark Sirangelo told us this is his company's first manned spacecraft.

"It's hard to define what a win like this would be. How do you win a gold medal in the Olympics when you started in a small town and you've never been able to get any notice and all of a sudden you're on that Olympic stage? I think that's how we feel," he said.

Elon Musk's Space X already flies unmanned cargo missions to the space station. CBS News

But the front-runner may be billionaire Elon Musk's SpaceX and its Dragon 2. SpaceX already flies unmanned cargo missions to the space station.

NASA now pays the Russians $80 million a pop to get American astronauts there. NASA has already spent more than $1 billion on this competition.

Is it going to be worth the money in the long run?

"The price NASA is going to pay will be significantly less. And just having that alternate mechanism to take people back and forth provides a level of redundancy that's important to the long-term viability of the space station," Mulholland said.

The first flight to the space station is scheduled for 2017.