Hammack was associated with the design of the space capsule used in Project Mercury, NASA's first manned space program. He later had similar duties in the Gemini, Apollo, Skylab and shuttle projects.
"Jerry was one of seven people who are considered to be the inventors of the Mercury capsule," said Milt Heflin, associate director of the space center. "He also was a key figure in putting together the team that dealt with recovery — finding the astronauts after they landed in the water, and how we were going to retrieve them."
Astronaut Jim Lovell, commander on the Apollo 13 space mission in 1970 that returned to Earth after a service module oxygen tank ruptured, recalled how gently Hammack broke the news to Lovell's wife, Marilyn, that a life-threatening problem had occurred.
"He was very helpful in the recovery and in taking care of my family," Lovell said. "Jerry had a productive life. He can be proud of what he did."
Miguel Hernandez of Hernandez Engineering Inc., which Hammack joined after retiring from NASA in 1987 as chief of its safety division, described Hammack as "a very simple, amiable person and at the same time very bright.
"He could explain in simple terms the most complicated things," Hernandez said. "He was known and loved by the astronauts, especially the early ones. He was a gentleman's gentleman."
Born on May 2, 1922, in Randolph County in southwest Georgia, Hammack grew up on the farm of his parents, William D. and Gussie Beauchamp Hammack. As a boy, he built model airplanes from scratch and became fascinated with the science of flying, said his son, Charles "Chuck" Hammack.
In 1943, Jerry Hammack received a degree in aeronautical engineering from the Georgia Institute of Technology. He joined the Douglas Aircraft Co., but soon was drafted into the Army Air Corps and assigned to the National Advisory Committee for Aeronautics as an aeronautical research engineer at Langley Field, Va.
In 1958, the NACA became the National Aeronautics and Space Administration. Hammack was among the cadre of 35 people who came to Houston in the early 1960s to establish what became the Johnson Space Center.