To fly farther, to fly higher, and to fly faster, have been the aims ever urging the aircraft designer on to further progress. Of all, the lust for high speed is the most compelling. While the past few years have seen spectacular increases in the World's High Speed Record (see Fig. 1) still higher performance in the supersonic region will be commonplace in the near future. To attain these speeds, largely made possible by the increased power and light weight of the turbo-jet unit, the designer must seek out means still further to reduce aerodynamic drag.