Venture capitalist Alan Walton has trekked to the North Pole, climbed Mount Kilimanjaro and skydived over Mount Everest. A hop into space to enjoy a few minutes of weightlessness would have been the ultimate adventure.
After waiting seven years to fly aboard Sir Richard Branson's Virgin Galactic spaceline, Walton gave up on the dream and asked for a $200,000 ticket refund on his 75th birthday this past spring.
Walton, who was among the first 100 customers to sign up, is not as spry as he used to be, and he's concerned about the project delays.
"This was a decision I wish I didn't have to make," he said recently. But "it was time."
Promises of space travel for the masses reached a euphoric pitch in 2004 when the experimental SpaceShipOne air-launched over the Mojave Desert and became the first privately financed, manned spacecraft to dash into space. It won the $10 million Ansari X Prize on Oct. 4, 2004, for accomplishing the feat twice in two weeks.
The flights were hailed by space enthusiasts as a leap toward opening the final frontier to civilians.
Virgin Galactic, which licensed the SpaceShipOne technology, began taking reservations before a commercial version was even built. Branson predicted back then that the maiden passenger flight would take off in 2007.
Other private rocketeers hunkered down in their hangars and sketched out designs to compete with Virgin Galactic. Soon a cottage industry rose. While there's been progress made - most are in the testing stage - there's still no launch date.
"It's tough," said Erika Wagner of the X Prize Foundation, which sponsored the 2004 contest. "We've seen slower progress than a lot of people would have liked."
Human spaceflight so far has been restricted to governments and a handful of wealthy thrill-seekers who have plunked down millions of dollars to hitch rides aboard Russian rockets to the International Space Station, which circles the Earth 250 miles high.
Instead of flying all the way to orbit, current space tourism efforts are focused on suborbital trips using vehicles designed to rocket up to the edge of space then immediately descend rather than circle the Earth. Virgin Galactic promises flights to altitudes of at least 62 miles with a few minutes of weightlessness. Cost per head ranges from $100,000 to $200,000 - far cheaper than the trips to orbit but still pricey.
Besides Virgin Galactic, other players include XCOR Aerospace headed by rocketeer Jeff Greason; Armadillo Aerospace founded by computer game programmer John Carmack; and Blue Origin headed by Amazon.com chief executive Jeff Bezos.
The companies are privately held and do not answer to shareholders. As a result, details about progress are hard to come by. Scaled Composites, which designed SpaceShipOne and is building a passenger version for Virgin Galactic, is publicity-shy, but posts results of test flights on its website.
Blue Origin is the most tight-lipped. The company didn't disclose a recent accident until a week after it happened. Even now, details about what failed during the test flight are sketchy.
Except for Blue Origin, the space tourism players are separate from those vying to build space taxis to the International Space Station under a NASA contract.
John Gedmark, executive director of the Commercial Spaceflight Federation, a trade group that represents suborbital and orbital space companies, is pleased with the testing despite the longer-than-expected time frame to get off the ground.
"Everything in aerospace always takes longer that you originally think," he said.
Scaled Composites, considered by many in the industry as the front-runner, has been conducting glide tests in the Mojave Desert since last year. The project suffered a setback in 2007 after a deadly explosion during testing to develop the propellant flow system for the hybrid rocket motor.
Virgin Galactic chief executive George Whitesides said he expected powered test flights to begin sometime next year. Commercial service will start up after the company gets a license from the Federal Aviation Administration, he said.
About 450 ticket-holders are in line to fly with Virgin Galactic. A small number of people - fewer than 10 - dropped out due to medical and other reasons, Whitesides said.
"Folks are tremendously loyal and excited," he said. "They want us to do it safely. They want us to take our time and make sure we got it right."
Even if space tourism takes off, it's unclear whether there's a strong market for joy rides to view the curvature of the Earth, said space policy expert John Logsdon of George Washington University.
"In the current economic climate, how many people have that level of discretionary money?" he said.
Space Tourism Society founder John Spencer said the industry has matured in recent years with some branching out beyond passenger flights and inking deals with universities and NASA to take scientists and experiments to space.
Later this month, Virgin Galactic executives and selected customers will gather at Spaceport America in New Mexico for a dedication ceremony. The company plans to launch from the spaceport once construction is complete.
One space tourist who will not be present is Walton, the British-born venture capitalist who lives in Connecticut. Walton booked with Virgin Galactic in 2004 and became a "founder" - a title given to the first 100 customers who paid in full. He got a refund earlier this year.
Walton is coping with the reality that he will never fly like an astronaut but believes he made the right decision.
He has moved on his latest adventure - investing in genome-mapping pioneer J. Craig Venter's quest to create artificial life.
Explore further: Space tourism craft reaches glide-test milestone (Update)