Will Europe's Spacelab be an orbiting 'white elephant'?

For 10 years, Western Europe has waited to prove itself in the supreme test of putting people into space. But when the American space shuttle takes Europe's Spacelab into orbit sometime later this year or next, many may wonder if it will be the space age's first white elephant.

Under a 1973 agreement, the 11-nation European Space Agency (ESA) has spent almost $1 billion building the hardware, which it turned over to the National Aeronautics and Space Administration (NASA). By way of exchange, ESA will pay nothing toward the launch costs of the first Spacelab mission, which should last for a week and take into orbit a series of 72 scientific experiments, contributed by scientists from Europe, the United States, and Japan.

Along with Spacelab (which fits into the space shuttle's cargo bay), the flight will carry Ulf Merbold, a West German physicist, as part of the crew of six. Merbold will be the first European in a manned US space mission.

After the seven-day flight is over, ESA, whose principal members are France, West Germany, Britain, and Italy, and which has an annual budget of around $800 million, will have to pay NASA the commercial rate for any more trips. This could work out to about $90 million per mission.

This expense, and the huge cost of developing Spacelab, does not unduly worry Europe's space planners. They accept it as the price to be paid for making the US take Europe seriously as a partner in space.

The problem with Spacelab is its size. Inside the 26-foot-long cylinder and on a series of racks, or pallets, which sit outside, there is room for 13 tons of experiments.

''Spacelab is so big,'' explained an ESA official. ''To make a mission economical, you have got to fill it up.''

On top of the launch fees that anyone using Spacelab must pay to NASA is the cost of developing the experiments, and integrating them with the complex electronics that control the shuttle itself. Then there is the cost of sending data back to earth via two satellites in geostationary orbit 22,300 miles above the equator.

West Germany, which has footed the bill for over half of ESA's spending on Spacelab, has booked its own national Spacelab flight, code-named ''D-1,'' and due to fly in 1985.

Yet West German officials were appalled when they worked out the total estimated cost of the seven-day mission - around $160 million. This means West German taxpayers will have to pay about $1 million for every hour the laboratory stays in space. They may be unimpressed by the purely scientific results, some of them verging on the abstruse, which the mission will achieve.

Not surprisingly, the West German government has said it will sanction no more Spacelab flights until the results of the first can be assessed. Officials at ESA will also make no commitment about funds for future flights.

NASA, however, is a little more enthusiastic. It plans to finance four further Spacelab missions through 1987 - which means a total of six are definitely on the drawing boards. After that the future is uncertain.

Scientists, who would be expected to benefit most from Spacelab, can no longer be counted on to keep the venture going. Many of those providing the experiments for the first flight have lost heart as a result of delays in the program.

Six years ago, Spacelab's first trip was scheduled for 1980. But it was postponed by three years, mainly because of technical problems experienced by the shuttle. Consequently, many of the researchers would have liked to substitute more up-to-date experiments for the ones flying on the mission. But the integrated set of instruments doesn't lend itself to quick changes with updated instruments.

Nevertheless, Europe's space planners are determined to take a sanguine view of the Spacelab saga. They are talking to NASA about participating in any plans the US dreams up over the next couple of years for a manned space station - a permanent presence in space to match the series of Salyut stations that the Soviet Union has launched with consummate ease over the past few years.

Parts of the Spacelab hardware - possibly the pressurized cylinders - could be used in the station which, if it goes ahead, would cost perhaps $3 billion and require 10 years of work in which Canada and Japan, besides the European nations, could also be involved.

At the same time, ESA is going ahead with the $200 million development of a ''mini'' Spacelab, a project much more in keeping with the financial stringencies of the 1980s. This is an unmanned space platform officially called EURECA (European Retrievable Carrier). A shuttle should take it on its first flight in 1987; the craft will jettison the platform, together with a batch of experiments, and return to collect it perhaps three months later.

Just to show they are not abandoning Spacelab altogether, ESA and NASA officials are talking about using the hardware from 1988 onward as part of an international microgravity laboratory. Experiments could be left in space for long periods and, other nations, particularly Japan, would be asked to help with the costs.