Perspectives on the Past, Prospects for the Future

Unfortunately for the immediate future of civilian supersonic flight, the successful LaNCETS project coincided almost exactly with the spread of the global financial crisis and the start of a severe recession. These negative economic developments hit almost all major industries, not the least being air carriers and aircraft manufacturers. The impact on those recently thriving companies making business jets was aggravated even more by populist and political backlash at executives of troubled corporations, some now being subsidized by the Federal Government, for continuing to fly in corporate jets. Lamenting this unsought nega­tive publicity, Aviation Week and Space Technology examined the plight

of the small-jet manufacturers in a story with following subheading: "As if the economy were not enough, business aviation becomes a scape­goat for executive excess.”[541] Nevertheless, NASA was continuing to invest in supersonic technologies and sonic boom research, and the air­craft industry was not ready to abandon the ultimate goal of supersonic civilian flight. For example, Boeing—under a Supersonics Project con­tract—was studying low-boom modifications for one of NASA’s F-16XL aircraft as one way to seek the holy grail for practical supersonic com­mercial flight: acceptance by the public. This relatively low-cost idea for a shaped sonic boom demonstrator had been one of the options being considered during NASA’s short-lived Sonic Boom Mitigation Project in 2005. Since then, findings from the Quiet Spike and LaNCETS exper­iments, along with continued progress in computational fluid dynam­ics, were helping to confirm and refine the aerodynamic and propulsion attributes needed to mitigate the strength of sonic booms.

In the case of the F-16XL, the modifications proposed by Boeing included an extended nose glove (reminiscent of the SSBD), lateral chines that blend into the wings (as with the SR-71), a sharpened V-shaped front canopy (like those of the F-106 and SR-71), an expanded nozzle for its jet engine (similar to those of F-15B No. 837), and a dorsal extension (called a "stinger”) to lengthen the rear of the airplane. Although such add-ons would preclude the low-drag characteristics also desired in a demonstra­tor, Boeing felt that its "initial design studies have been encouraging with respect to shock mitigation of the forebody, canopy, inlet, wing leading edge, and aft lift/volume distribution features.” Positive results from more detailed designs and successful wind tunnel testing would be the next requirements for continuing consideration of the proposed modifications.[542]

It was clear that NASA’s discoveries about sonic booms and how to control them were beginning to pay dividends. Whatever the fate of Boeing’s idea or any other proposals yet to come, NASA was commit­ted to finding the best way to demonstrate fully shaped sonic booms. As another encouraging sign, the FAA was working with NASA on a roadmap for studying community reactions to sonic booms, one that would soon be presented to the ICAO.[543]

As shown in this study, past expectations for a quiet civilian super­sonic transport had repeatedly run up against scientific, technical, eco­nomic, and political hurdles too high to overcome. That is why such an airplane has yet to fly. Yet the knowledge gained and lessons learned from each attempt attest to the value of persistence in pursuing both basic and applied research. Recent progress in shaping sonic booms builds upon the work of dedicated NASA civil servants over more than half a century, the data and documentation preserved through NASA’s scientific and techni­cal information program, the special facilities and test resources main­tained and operated by NASA’s research Centers, and NASA’s support of and partnership with contractors and universities.

Since the dawn of civilization, conquering the twin tyrannies of time and distance has been a powerful human aspiration, one that has served as a catalyst for many technological innovations. It seems reasonable to assume that this need for speed will eventually break down the barriers in the way of practical supersonic transportation, to include solving the prob­lem of the sonic boom. When that time finally does come, it will have been made possible by NASA’s many years of meticulous research, careful test­ing, and inventive experimentation on ways to soften the sonic footprint.