WASHINGTON (AP) _ The secret ''Star Wars'' experiment conducted last week provided information that one day will make it possible for small interceptor rockets based in space to hunt down nuclear missiles, the program's director said Thursday.

Lt. Gen. James A. Abrahamson, lifting the veil of official secrecy surrounding the $150 million experiment, said last Friday's trial was an unqualified success that proved America's technological acumen and demonstrated that President Reagan's dream of an anti-missile defense was closer to reality than most believe.

The experiment's success ''will lead, just inexorably, to the kinds of capability that we are all trying to move to in this research program as quickly as possible,'' Abrahamson said.

''I personally believe from the data I've seen that our job's going to be a lot easier than we thought,'' added Lt. Col. Mike Rendine, the Air Force officer who served as the project manager.

The three-star Air Force general said the main objective of the experiment had been to obtain data on what rocket plumes look like in space beyond the earth's atmosphere. That information is essential, he explained, for the development of sensors and guidance systems for small rockets that could be launched from ''garages in space'' to shoot down enemy missiles.

Without the pressure of the earth's atmosphere to keep a rocket plume streaming in a straight line from the bottom of a missile, the plume expands and even envelopes a missile flying through space, the general said. It thus becomes critical to develop sensors that can guide a rocket to impact against a missile body without being confused by the ball of hot exhaust gases, he said.

Although Abrahamson said the information on rocket plumes was classified and could not be discussed, he assured reporters it was sufficient to allow research on actual weaponry to proceed.

The broad outlines of the experiment, which began with the successful launch of a NASA Delta rocket from Cape Canaveral, Fla., had been disclosed previously by officials speaking anonymously.

For roughly 2 1/2 hours after launch, the second and third stages of the Delta danced and pirouetted around each other in orbits about 138 miles above the earth's surface. In the process, they collected data on what solid-fuel as well as liquid-fuel boosters looked like - silhouetted against the backgrounds of both space and the Earth. One of them detected and tracked from a distance of 200 miles another rocket launched from the White Sands Missile Range in New Mexico.

To buttress his claims of success, Abrahamson offered new details of the work Thursday and also released pictures of portions of the experiment, including footage of its spectacular end when the two Delta stages were sent into a deliberate collision.

Among Thursday's disclosures, as outlined by Abrahamson and Rendine:

-From start to finish, the equipment needed for the experiment was designed and fabricated within 14 months - almost matching Abrahamson's goal of one year. The scheduled was ''hurried,'' Abrahamson said, because the research program could not proceed without the data on ''rocket plume signatures.''

-The second stage of the Delta was carrying ''the world's first space-based laser radar,'' Rendine said. The device was described as low-powered, incapable of use as a weapon, but providing extremely accurate range data. The laser radar was used to point and steer the other sensors on the second stage.

-Many of the sensors employed during the experiment were derivatives of existing guidance systems. The second stage carried an infrared TV tracking system from the Maverick air-to-ground missile, while the third stage carried the radar guidance system used aboard the Phoenix air-to-air missile.

The third stage of the Delta was a brand new liquid-fueled vehicle, built from scratch. The sensors on each stage collected data on the rocket plumes streaming from the other.

-More than 1 million lines of new computer software, or programming instructions, had to be written for the mission. The computer instructions worked flawlessly, Abrahamson said, offering a rebuttal to scientific critics who maintain it is impossible to develop a computerized control system for a large-scale Star Wars system that would function with confidence.

-The experiment was the most complex ever attempted by the United States from the standpoint of communications and coordination, Rendine said. It involved 38 radars on the earth's surface, six aircraft flying at high altitude in various parts of the world to receive information beamed down by the spacecraft, and 31 different satellite communication links tying the monitoring system together.