NASA Engineer George Mueller, who was known as the "father of the space shuttle" and a leader in the U.S. space agency's spaceflight efforts through the historic moon landing in the 1960s, died on Monday, Oct. 12, after a short bout with illness. He was 97.

During his term as NASA's Associate Administrator for Manned Space Flight from 1963 to 1969, Mueller introduced an approach to testing that made it possible for humans to land on the moon by 1969.

He also played a critical role in designing the first space station of the United States and called for a reusable space transportation system that eventually became known as the Space Shuttle.

Mueller realized in 1963 that the Saturn V launch vehicle test plans would make it impossible for the Apollo program to land on the moon at the end of the decade, President John F. Kennedy's deadline for the lunar mission, so he overhauled the management system and instituted the controversial "all-up" test approach that involved flying full vehicles instead of certifying individual stages of the rocket.

"It didn't make much sense to fly the first stage and then fly it with the second stage, or fly the second stage separately, which was also proposed," Mueller said in a 1998 interview. "If you lost a vehicle, you were likely to lose it at any stage so you might as well go as far as you can and find out where the problems are."

Mueller's proposal sounded reckless at the time but his calculated risk eventually proved crucial in making it possible for man to land on the moon by the end of the decade.

"In retrospect it is clear that without all-up testing the first manned lunar landing could not have taken place as early as 1969," NASA acknowledged of Mueller's crucial role in the manned moon mission.

Mueller, who was born in St. Louis, Missouri on July 16, 1918, continued to help NASA even after stepping down from his leadership role by advocating for the Skylab and the Space Shuttle.

Mueller died at his home in Irvine, California. A family spokesman said that the cause of death was congestive heart failure.

The "father of the space shuttle" is survived by his wife of 37 years, Darla; three daughters, Karen Hyvonen, Jean Porter and Wendy Schwartzman; son, Bill Schwartzman; 13 grandchildren and 13 great grandchildren.