KENNETH Gatland who died on December 11, aged 73, was a leading space flight theorist of the post-war years. His paper, Minimum Satellite Vehicles, written with A M Kunesch and A E Dixon, was credited with convincing the US armed forces that artificial satellites could be launched using existing technology. It was published in September 1951, at the inaugural Congress of the International Astronautical Federation, along with an equally definitive paper by T R F Nonweiler on returning spacecraft to earth; both were reprinted in L J Carter's comprehensive book, Realities of Space Travel, in 1957.

Gatland was born in 1924 and educated at Surbiton Secondary School. At 17 he joined the design staff of Hawker Aircraft Limited in Kingston, and worked during the war on development of Hurricane, Typhoon, and Tempest fighters. He became a council member of the British Interplanetary Society at its post-war rebirth, and served as vice-president and president before leaving it in the 1970s to return to a staff post with British Aerospace.

A quiet man, he will chiefly be remembered for his contributions to the literature of spaceflight. His first book, The Development of the Guided Missile, (1952) was immediately translated into Russian, and was followed by Space Travel (with Kunesch, 1953), Astronautics in the Sixties (1962), the four-volume Encyclopaedia of Spaceflight (1967-75), and Encyclopedia of Space Technology (1981), each in turn a standard reference for its decade. In 1958 he caught the imagination of the press with Project Migrant, a proposal for a soft-landing lunar probe. Unfortunately there was only one volume (1964) of Spacecraft and Boosters, intended to be an ongoing series analysing space launches year by year.

In 1959 he joined the staff of the Aeroplane as editor, missiles and astronautics, and in the same year took over the British Interplanetary Society's magazine, Spaceflight, from its founding editor, Patrick Moore. He made the magazine a monthly and introduced its regular ''New Frontiers'' issues, on speculative topics such as interstellar travel and the search of extra-terrestrial intelligence. In that category he published my first non-fiction article to appear outside university, and his help and advice at that early stage of my career was much appreciated. He was also a regular broadcaster and columnist on space affairs for the Daily and Sunday Telegraph and many other outlets.

He is survived by his wife, Doreen, whom he married in 1952.