Erik Bergaust, 52, author of more than 50 books on aviation, space sciences and nuclear energy, as well as the offical biographer of Dr. Wernher von Braun, died of cancer Wednesday at his home in McLean.

Mr. Bergaust was born in Oslo, Norway, and served as aviation editor of Aftenposten, a Norweigian daily newspaper, before coming to this country in 1949.

He worked here as a freelance writer of aviation articles and wrote books for children on such subjects as helicopters, rocketry and histories of various branches by our armed forces, and nuclear energy. Over the years he lectured on scientific topics at a number of schools in the Washington area.

Mr. Bergaust was the author of two biographies of Dr. von Braun. The first was "Reaching for the Stars," published in 1960, and the second was "Werhner von Braun, " published by the National Space Institute here in 1976.

He also was the author of "Murder of Pad 34," published in 1968. This was a critical examination of the causes of the accident that took the lives of three astronauts, Virgil I. Grissom, Edward H. White and Roger B. Chaffee, on Jan. 27, 1967. He used the specific accident as a springboard for an examination of safety procedures and performance of the National Aeronautics and Space Administration.

He also worked for a number of trade and specialized journals. He was editor of Aero Digest from 1955 to 1956 and of American Aviation, then worked on the staff of the NATO Journal from 1960 to 1962.

He was the founder and first editor of Missiles and Rockets, the first American trade magazine devoted exclusively to rocketry and space flight.

Mr. Bergaust served as consultant to a number of aerospace companies, including Lear-Siegler and Fairchild Industries, as well as a consultant to NASA.

He was a member of the Information Advisory Group to the Presidnt's Committee on Scientists and Engineers in 1957.

Mr. Bergaust was a founder and first president of the National Space Club of Washington and a past president of the national capital section of the American Rocket Society. He was a director of the Aviation and Space Writers Association and a member of the National Press Club.

He is survived by his wife, Jean, two sons, Erik R. and Paul, and a daughter, Jane, all of the home; another daughter, Christine, of Memphis, Tenn, and a brother, Ragnar, and his mother, Tullik Bergaust, both of Oslo.

The family suggest s that expressions of sympathy be in the form of contributions to the Stuart Trust Cancer Fund at Washington Hospital Center.