J.D. Hunley, known to his friends as Dill, was chief historian for NASA Dryden Flight Research Center before his retirement in 2001. A Ramsey Fellow at the Smithsonian National Air and Space Museum in 2001-2002, he has written widely about German history, the life and thought of Friedrich Engels, and aerospace history. Among other prizes, he was the winner of the 2006 History Manuscript Award from the American Institute of Aeronautics and Astronautics for what became "The Development of Propulsion Technology for U.S. Space-Launch Vehicles, 1926-1991," published by Texas A&M University Press and now available as an e-book at http://books.google.com/ebooks?as_brr=5&q=J.+D.+Hunley&as_sub=. He received the American Institute of Aeronautics and Astronautics 2010 Gardner-Lasser Aerospace History Literature Award for his two volume set: "Preludes To U.S. Space-Launch Vehicle Technology: Goddard Rockets to Minutemen III" and "U. S. Space-Launch Vehicle Technology: Viking to Space Shuttle," published by the University Press of Florida.These three books about missiles and rockets not only explain the development of the technologies used in space-launch vehicles and missiles but also contain numerous anecdotes and sketches about the engineers who created the technologies and about the processes they used. For example, in developing the huge F-1 engine for the Saturn space-launch vehicle, with its 1.522 million pounds of thrust, engineers encountered major problems with what was called combustion instability (oscillations in the combustion chamber that could and did destroy the engine). Some 50 engineers and technicians from engine contractor Rocketdyne, NASA, universities, and the Air Force were assigned to a team to solve the problem. They included, among other experts, Rocketdyne's Dan Klute, who "had a special talent for the half-science, half-art of combustion chamber design." They knew from earlier rocket engines that the cause of the problem lay in the injectors for the propellants (kerosene and liquid oxygen), which had to mix precisely for smooth combustion. They tried perhaps 40 or 50 modifications of the design before they found a combination of features that worked, but they were never certain that the problem would not recur. Nevertheless, they went ahead with development, solving other problems as they occurred. The five F-1s in the Saturn first stage performed admirably in the July 16 to July 24, 1969, Apollo 11 mission that placed the first two astronauts on the Moon, a feat that had seemed impossible less than 10 years before that.