In the early 1970s, a classical theoretical model of molecular collision processes provided important information to designers of advanced chemical lasers. The model was developed by H.K. Shin of the University of Nevada with AFOSR support, and described energy-transfer processes involving excited cited hydrogen hy halides (hydrogen fluoride and deuterium fluoride). e). The model used classical theories to predict temperature effects on vibrational energy relaxation rates using assumptions mptions of ideal dipoles, rigid rotator molecules, and strong attractive tractive interaction forces. The theory was in agreement with experimental results obtained by AFWL and other ther AFOSR researchers.48
Free Electron Laser (1970-present) -present) In 1970, Dr. John Madey, then a graduate student at California Technical Institute (Caltech) proposed what he called the Free Electron Laser (FEL). Shortly thereafter, AFOSR funded Madey’s work at Stanford University with the goal of developing trated in 1975. the first operational FEL, which was demonstrated FELs are fundamentally different from other lasers and more ly gain. They can be tuned to any like microwave amplifiers in that they use beams of electrons to supply e capable of extremely wavelength, from hard X-rays to microwaves, by changing the beam energy. They are teristics high power and, because the beam energy can be recovered, very high efficiency. These characteristics make the FEL important for a wide range of research, industrial, and defense applications; it was studied extensively for possible employment by the Strategic Defense Initiative program in the 1980s. The FEL is used today in a variety of medical applications. (See “Medical Free Electron Laser,” p. 53.)49
Fracture Mechanics Methodology (1970-1975) With AFOSR funding, the development of a fracture mechanics methodology has resulted in the accurate prediction of crack growth rates in metallic structures. It has been a key technology for extending aircraft life under the Air Force’s aircraft structural integrity program. Knowledge of crack growth rates is a key determinant in establishing the appropriate inspection intervals for airframes, resulting in preventive maintenance and best use of maintenance personnel.50
AFOSR and Superplastic Forming: A Revolution in Aerospace Material Science (1976-1982) AFOSR has sponsored an active research portfolio concerning “aircraft structures and materials” from the day it was first chartered. One program initiative was the superplastic forming (SPF) of aluminum, titanium, and nickel alloys for aircraft structure components. The superplastic process allows the production of larger complex shapes with a minimum of tooling and machining. The SPF program was due in large measure to AFOSR Program
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1970s
Model of Chemical Laser Processes (1970-1972)