At first, it seemed unreal.

Relaxed in the blue-upholstered contour seat, the bright morning sun pouring through the plastic canopy overhead, this passenger had the fleeting thought that this was how astronaut Alan B. Shepard must have felt the moment before being hurled into space.

But this was Detroit, not Cape Canaveral.

Ahead lay not the limitless space, but only the broad expanse of Detroit's expressway's.

The Firebird III, General Motor's experimental "space age car," nosed gently down the Mt. Elliot ramp of the Ford Expressway and picked up speed as if anxious to achieve its ultimate destiny.

Once on the ribbon of concrete, the Firebird responded with effortless ease. There was no sensation of acceleration, only one of tremendous horsepower straining mightily to be unleashed.

Conklin, through almost imperceptible motions of his hand, demonstrated how the car could be accelerated or braked, all by means of the one control stick.

"The average person, particularly who has had some flying experience, could learn to operate this car with 15 minutes instruction," Conklin, GM Research test supervisor, assured his dubious passenger, still not accustomed to the absence of the inevitable steering wheel.

The Firebird III had scores of motorists gaping by this time as Sgt. Moore and Patrolmen Williams Saunders and Donald Morkin herded them to the side of the highway.

As the car surged effortlessly up the incline at the Ford-Lodge expressway interchange, Detroit's skyline came into view over the pearlescent white hood.

Looking to the rear, the General Motors and Fisher building could be seen, framed by the towering fins and tail of the Firebird III.

Conklin stepped up the pace. The Forest-Warren exit from the Lodge Expressway flashed by.

Operation of the vehicle looked too easy to be true.

"Wait until they install automatic guidance systems in the expressways," said Conklin, 8625 Chicago, Warren. "When that day comes, you'll simply have to touch a couple of buttons and steering and speed will be controlled automatically by the electronic system in Firebird III."

The end of our ride into the future came at the Grand River exit.

As the power-operated door swung open and the canopy swung up, it was with regrets we said goodby.

Conklin must have sensed our feelings.

"Don't worry," he said, "the day when cars like Firebird become commonplace is not as far away as you might think."

We had the feeling there was more truth than prophecy in his statement.

At the wheel was Emmett Conklin, 54, of 8265 Chicago, Warren, test supervisor of the gas turbine department at the center. Alongside was Cecil Thompson, 18, of 8864 Longacre, who will appear in the movie, to be shown in high schools throughout the nation next fall.

The car has a dual engine system by which a 10 horsepower gasoline engine drives all accessories and the 225 horsepower engine drives the rear wheels only.

Capable of speeds in excess of 100 miles per hour (although it has never been pushed that far), the Firebird III has no steering wheel, accelerator, or brake pedal.

Steering, braking, acceleration and transmission selection are combined in a single control stick located between the two passengers. It is also equipped with an automatic guidance system which would be supplied by electrical impulses from a wire imbedded in the pavement.

The product of the combined skills of more than 500 GM engineers, stylists, and other specialists, Firebird III was introduced publicly three years ago.

Until yesterday, however, it had appeared only in shows and on test tracks.

The early morning test runs started at Mt. Elliot and on the Ford Expressway and ended at the Grand River exit of the Lodge Expressway. The car was later taken to Cobo Hall, where it drew a crowd of more than 200 spectators despite the early hour.