Vancouver's Expo 86 has begun accepting advance ticket orders for next summer's world's fair. And one of its main attractions, a 17-story geodesic dome called Expo Centre, will be open on May 2 -- exactly one year before the scheduled kickoff of the fair.

The optimistic Canadians seem to be undaunted by the fact that many similar fairs have ended in debt and a few recent ones have been embroiled in controversy. They place the primary blame for those past failures on lack of sufficient financing and point out they won't have that problem, since the fair is backed by the government. In fact, they're spending a billion and a half dollars to finance the show.

The theme of the full exposition -- which will run 12 hours a day and seven days a week from May 2 to Oct. 13, 1986 -- is "World in Motion -- World in Touch." More than 35 nations have agreed to participate (including the United States, the Soviet Union and the People's Republic of China -- the first time the three countries have jointly appeared at any North American world's fair), as well as two U.S. states (Washington and Oregon), five of Canada's 10 provinces and both the Yukon and Northwest Territories, and 15 corporations. Ten other nations, additional states and provinces, and 10 more corporations also are expected to take part.

Expo Centre is being opened a year early in the hope that it will draw tourists to this Pacific port city in British Columbia, Canada's third largest province in terms of population. Part of an aggressive marketing campaign to drum up interest in next year's fair, the structure is located at the eastern end of the 173-acre fair site.

A little over a mile away from the main site is the five-acre location for Canada Place, the Canadian Pavilion that will house the world's first 3-D IMAX theater and present a film, "Carrying Things," about transportation. (IMAX's non-3-D versions on different subjects can be seen at the Smithsonian's National Air and Space Museum, where it uses special high-resolution film projected on a five-story tall, seven-story-wide screen.)

Michael Bartlett, president and chief executive officer of the Expo 86 Corp., is a U.S. citizen who formerly was an operator and developer of theme parks in this country and Canada. He predicts Expo Centre will be "one of our best-selling attractions."

It will house restaurants, shops and three major exhibits: In a 500-seat Omnimax theater featuring the world's largest domed screen, an 18-minute film, "A Freedom to Move," will transport viewers from the North Pole to the Mojave Desert to the far reaches of space; in the 323-seat Futures Theatre, the first interactive theater in Canada, the audience can press buttons in the arms of their seats to vote on possible future scenarios in international transportation and communications, and then see the consequences; and in the Design 2000 exhibit, visitors will walk through a display about the future -- prototype vehicles and presentations relating to space, nature, city life.

Admission to this year's limited preview at Expo Centre will cost $4.50 for adults and $2.25 for those 65 or over and for children 6 to 12. All prices quoted here and below are in Canadian dollars ($1 U.S. is worth about $1.36 Canadian according to recent exchange rates), thus actual costs for U.S. visitors will be less.

When the fair opens, more than 80 pavilions and various plazas will focus on transportation and communications.

Off site, under joint sponsorship with the Royal Bank of Canada, Expo will offer "The World Festival," a celebration of theater, dance, music and opera featuring more than 300 performances in city concert halls. In addition, scholars, scientists, artists and inventors will join in a series of "think tank" symposiums on the theme subjects. On site, popular entertainers will appear and the Royal Mounted Police Musical Ride will lead a daily show at the Pacific Bowl, an open-air amphitheater. Vancouver also will be celebrating its 100th birthday (the actual anniversary is April 6) during the fair. The exposition site lies in the heart of the city, which is surrounded by coastal mountains. Major hotels, restaurants, shops and beaches are minutes away. A new rapid transit system, to be completed in January, will connect the main site with the host Canadian Pavilion 1.2 miles away on Burrard Inlet.

Visitors to the fair will walk along boulevards and also travel between pavilions via a monorail system, a People Mover system, a Japanese magnetic levitation train, two gondola systems operating on overhead cables and an intrasite ferry system linking various points of the main site plus another ferry link with Canada Place.

Bartlett says that Vancouver's situation bears no relation to problems at the 1982 World's Fair in Knoxville, Tenn., or the 1984 Louisiana World Exposition in New Orleans. Though the '82 fair surpassed its attendance goal of 11 million visitors, brought substantial benefits to Knoxville, and the show itself received generally good reviews, a disastrous reservations system combined with fast-buck landlords charging exorbitant rates hurt the city's image. The New Orleans fair, in contrast, drew a little more than 7 million visitors (instead of the predicted 12 million), and closed in a sea of red ink after filing for protection under the bankruptcy code -- though it, too, spurred redevelopment and was considered an artistic success.

Some critics suggested that the two cities' geographical closeness and the proximity of their fair dates were negative factors. Others have maintained that the era of world's fairs has ended. But that hasn't stopped Chicago from preliminary planning for its 1992 fair or Vancouver from eagerly anticipating next year's prospects.

Bartlett says the official estimate is that the fair will draw 13.75 million visitors, but a series of market studies now indicate the figure may go as high as 15 to 20 million.

"Our fair is almost 2 1/2 times as big as the two earlier American fairs in terms of acreage," Bartlett adds, indicating there will be much more to see. Sixty percent of the fairgoers are expected to come from Canada, 35 percent from the United States and 5 percent from overseas.

There are 18,000 hotel rooms in Vancouver and within a 50-mile radius. In addition, a bed-and-breakfast network is being organized. Six months ago the province set up a reservations system for a variety of accommodations, and Bartlett says, "This government would not stand for price gouging. British Columbia wants to send people home with a good taste in their mouths."

Canadian Tourist Minister Tom McMillan recently expressed concern about his country's sagging travel market, saying that selling Canada to visitors requires convincing them that the destination means more than "moose, Mounties and mountains." Bartlett says he thinks Expo 86 will be a major factor in changing the country's image. "No question -- we will be marketing all of North America, with an emphasis on the area west of the Mississippi. This is the best opportunity since Expo 67 and the Olympics to bring North Americans to Canada."

The fundamental difference between U.S. and Canadian fairs, Bartlett says, is that U.S. fairs are not underwritten by the government. In contrast, the Canadian federal and provincial governments provide enough money to produce a "first-class" world's fair. He says it is impossible financially for the private sector to mount a quality fair on a break-even basis. Canada is betting that its huge current travel deficit will turn into a surplus -- as was the case after Montreal's 1967 fair -- and the benefits to tourism and trade will continue to accrue for years.

Admission to the fair will include all transportation (monorail, magnetic train, cable skyways, ferries and the rapid transit line between the two sites); entrance to more than 80 pavilions; all displays, including "Ramses II and His Times," a collection of artifacts from Egypt; demonstrations of transportation technology at work (for example, during Marine Week -- July 21-31 -- vessels from various nations -- including the tall ships -- will dock and fairgoers will be able to go aboard); and most on-site entertainment. Tickets for amusement rides, the World Festival and other special entertainment concerts are extra.

Expo tickets are available in three forms: a season pass ($99 for adults, $49.50 for children and seniors 65 and over), a three-day pass ($29.95 adults, $14.95 children and seniors) and a one-day admission ($20 for everyone except children 5 years and under, who enter free). The single-day tickets will not be placed on sale until Oct. 14, and the price will not change. Advance orders can now be placed for the other tickets, but those prices are good only through Oct. 13, after which they will rise in three steps. (The adult season pass, for example, will be $119 beginning Oct. 14, go to $139 on Jan. 7, 1986, and reach $160 on opening day.) Reduced group rates are also offered.

Actual processing of orders will not begin until May 2. The exchange rate used for advance orders will be that in effect on the date a check is cashed or, in the case of credit card transactions, the date a charge is processed by the card company.

Tickets may be purchased now by phone (604-660-3976) with VISA, MasterCard and American Express; or by mail (using credit card, Canadian money order or your personal check -- with notation "in Canadian funds" next to the amount in numerals to give you the benefit of the favorable exchange rate) from: Expo 86, P.O. Box 1850, Station A, Vancouver V6C 3A9 (660-EXPO). Beginning May 2, they will be available at Expo Centre and other locations in Canada. For information about hotels, apartments, house rentals and B & B establishments, or to make reservations: ResWest, P.O. Box 1138, Station A, Vancouver, B.C., V6C 2T1, (604) 662-3300.