"I don't see how Orbital, given all the negative publicity around Russian engines, could go with another Russian engine," says Marco Caceres, space industry analyst for aerospace and defense consultancy Teal Group. "How could the CEO explain another accident to shareholders? I think you have to go with a red, white, and blue company."

But finding that company could prove daunting. Aerojet Rocketdyne's existing production line produces powerful engines for the Delta IV and NASA's new super-heavy-lifting Space Launch System—likely too much engine for Orbital's medium-sized Antares rocket, Caceres says. 

This is not the first time the Russian-made AJ26 engines have caused problems, Marco Caceres, an analyst at Teal Group Corp., wrote in an Oct. 31 note. In 2007, the Sea Launch Zenit 3SL exploded because of an engine clogging and SpaceX failed to launch its Falcon 1 in March 2006 due to engine failure, he wrote.

If the engine proves to have been at fault in the latest explosion, it would be easier for Orbital to replace them rather than to attempt a repair, Caceres said in a phone interview today. "Their confidence in the engine was never high," he said.

NASA is "looking for cheaper access to space," said Marco A. Caceres, a space analyst at the Teal Group, a consulting firm in Virginia. The trouble, he said, is that reliability and price are often tied together.

"It may be unreasonable to expect to pay under a certain amount to get a reliable vehicle," Mr. Caceres said. "That comes at a cost."

Each mission is expected to take about a month; it takes about five days for the Cygnus to make it to the station, it will stay there for anywhere from two weeks to two months, and it will take another day or two for the spacecraft to disintegrate on reentry. "The idea of now relying on private industry and let[ting] them lead the way has already been decided," said Marco A. Caceres, director of space studies at the Teal Group. "The question is: Can industry do it without too many failures?" He said Orbital's success, along with that of SpaceX, which has already made it to the space station, would provide the needed competition and potentially open the door to more companies. "There's a lot at stake here because you're really talking about the future of human spaceflight. It's not going to be NASA that does it," said Caceres. "It's these companies ... that are supposedly going to be colonizing the moon and maybe even Mars."