"The private sector can go out and make money doing something that only governments now do. You really are going to see an expansion of the industry," Discovery commander Mark Kelly said.
"I personally think it's great," he said, joining six other crew members at a news conference in Tokyo after last month's 14-day mission that set up Japan's first space laboratory.
Kelly's comments came hours after Virgin Galactic, owned by British tycoon Sir Richard Branson, unveiled in the California desert a futuristic aircraft dubbed WhiteKnightTwo that will ferry tourists into suborbital space.
"In the early part of the 20th century when airplanes first started to fly, there were initially some advancements but only when companies started doing it to make a profit did it really take off," Kelly said.
US and Japanese space agencies will "likely stay on the forefront of space exploration," he said. "But the other stuff like flying in Earth's orbit is going to take off with space tourism."
Virgin Galactic is hoping to send its first paying customers 110 kilometres (70 miles) above the Earth in 2010. The company has said more that more than 200 passengers have already signed up for the first flights, which will cost 200,000 dollars each.
"I think the company is going to be successful. I'm pretty excited about it," Discovery commander Kelly said.
But he said there "is certainly going to be a lot of risk involved for those passengers," in part because the missions would have less heating than US shuttles.
Kelly said that for now space flights would likely be limited to short travel involving shooting up and shooting back down to Earth.
Virgin Galactic mission would go five times the speed of sound, while Discovery travelled 25 times as fast, he said.
"There is a much greater technical challenge to go into orbit around the Earth. You've got to get going a lot faster," he said.