Two years ago when Seattle travel agent T.C. Swartz ran low on new, exotic places to lead expeditions, he saw no where to go but up.

As a result, an adventure lover today can plunk down $50,000 - plus a $2,000 training fee and $200 for registration - for an eight to 12-hour flight in space as part of a seven-day travel package.It is all part of Swartz's newest venture, Space Expeditions Inc.

Reservations are being taken now, but don't expect a firm departure date. The spaceship that will take tourists into low orbit hasn't been built yet.

After announcing the plan in 1985, Swartz logged nearly 200 people wanting to take his latest jaunt. The January 1986 explosion of the Challenger space shuttle, which killed seven people, stopped the program.

But a growing public interest at the promise of a shuttle lift-off in 1988 has renewed hopes within the organization and Space Expeditions is again pushing its product, with departure expected by 1995, said Lori Hunter, public relations spokeswoman.

The company has proposed construction of a manned space ship that could take off and land without assistance. Travelers each would have a window seat, and various experts on board would answer questions.

So far, however, the idea hasn't gone past the planning stages.

If the vehicle is built, it will need two years of testing, Hunter said.

Not everyone believes the project will get off the ground.

Deke Slayton, a former National Aeronautics and Space Administration astronaut and head of Space Services Inc., believes the proposal is more smoke than reality.

"I don't think they have or are likely to have a space vehicle to ride on," Slayton said in a telephone interview. His company is developing unmanned rockets to boost satellites and other payloads into space. It already has several contracts for payloads but doesn't expect its first full launch for another 18 months.

Bryon K. Lichtenberg, a payload specialist for a 1983 space shuttle launch and president of Payload Systems Wellesley, Mass., is one of several advisers to Space Expeditions, although he admits no one has asked for advice yet.

"I am not in it deep enough to assess it," Lichtenberg said. But he added it sounds like a "neat idea. That's my personal feeling. I am willing to look at anything that looks reasonable . . . I certainly think the basic idea is good."

Swartz is no stranger to traveling to remote destinations. For 13 years he owned and operated Society Expeditions, an expedition cruise company that specialized in tours to such out-of-the-way places as Antarctica, the Amazon River, Tibet and the North and South Poles. He sold the company earlier this year.

The seven-day space trip would include five to eight orbits around the Earth and special training programs at a resort where participants can relax in style between sessions.

Space enthusiasts too impatient to wait until the mid-1990s to see if the dream becomes reality can take advantage of the company's Project Space on Earth. For $1,790, plus airfare, a person can tour a series of space facilities including Space Camp in Huntsville, Ala., a replica of NASA's astronaut training center and the Johnson Space Center in Houston.