John Houbolt: Engineer whose efforts ensured that US astronauts landed on the moon using a lunar-orbit rendezvous

John Houbolt was an engineer whose contributions to the US space programme were vital to the moon landing in 1969. He was the catalyst in securing US commitment to the science and engineering theory that eventually carried the Apollo crew to the moon and back safely.

His efforts are largely credited with convincing Nasa to focus on the launch of a module carrying a crew from lunar orbit, rather than a rocket from Earth or a spacecraft while orbiting the planet. He argued that a lunar-orbit rendezvous, or LOR, would not only be less mechanically and financially demanding than building a huge rocket to take man to the moon or launching a craft while orbiting the Earth, but it also was the only option to meet President Kennedy's challenge for an American to be on the moon before the end of the 1960s.

On its website Nasa describes "the bold step of skipping proper channels" that Houbolt took by pushing the issue in a private letter in 1961 to an incoming administrator. "Do we want to go to the moon or not?" the letter asked "Why is a much less grandiose scheme involving rendezvous ostracized or put on the defensive? I fully realize that contacting you in this manner is somewhat unorthodox, but the issues at stake are crucial enough to us all that an unusual course is warranted."

Houbolt had begun his career with Nasa's predecessor, the National Advisory Committee for Aeronautics, in 1942, served in the Army Corps of Engineers and worked in an aeronautical research and for a consulting firm before returning to Nasa in 1976 as chief aeronautical scientist. He retired in 1985 but continued consulting work.

John Cornelius Houbolt, aerospace engineer: born Altoona, Iowa 10 April 1919; died Scarborough, Maine 15 April 2014.