Category NEW DESIGN CONCEPTS FOR HIGH SPEED AIR TRANSPORT

The current trends in air traffic are well known [9|. Growth has been positive for most of the past twenty-five years. International travel is growing faster than developed countries’ domestic trav­el. leisure travel is growing faster than business travel, and Asia-Pacific traffic has the largest regional growth rate. Air travel has become a commodity in the following sense: 404 of the trav­el is discount coach travel; the remaining 60** of the travel is comprised of 204 coach. ЗОЧ business class and 104 first class. One would be wrong to conclude, however, that full-fare pas­sengers comprise 604 of travel; пилі of this travel is also discounted. Because of frequent flyer upgrades and business and other traveller discounts, less than 304 of the passengers on interna­tional routes pay "full" fare. In 1995. 954 of the revenue passenger miles in the U. S.were sold at a discount. In the first seven months of 1996. the discount averaged 684.

Two airline systems have now developed. One is the airline system that dominates most markets and provides air service to both the economy and business passengers, subsidiz –

mg economy travel by higher fares for the business traveller. The other provides a true commod­ity service: no advanced scat assignments, no meals, and sometimes no baggage connection to other airlines. The latter airlines have enlarged the market for commodity travel For any new aircraft to succeed in the commercial aircraft market, it must compete either in convenience / comfort, or in fare, or some combination of the two.

In 1968 nearly eight million international passengers arrived at or departed from Kennedy International Airport, with 97 thousand arrival» and departures In 1982 over eleven million passengers arrived at or departed from Kennedy. Because of the introduction of wtde – body aircraft, this travel was accommodated with under 55 thousand arrivals and departures In 1993 fifteen million international passengers used Kennedy, requiring 92 thousand arrivals and departures. Once again aircraft arrivals and departures there arc close to the airport’s capacity.

Expected growth in air traffic cannot he accommodated for long with the world’s cur­rent airports and aircraft. In developed countries there are few airports dial can be added Thus, it is presumed that some of the increased traffic will be accommodated by larger aircraft. One SST configuration, a w ing with passengers inside, flying obliquely, must be large and responds to both the SST and the large aircraft market. This Oblique Flying Wing is discussed in two chapters in this book.

The U. S. SST program begun in June, 1963 when President Kennedy, in a commencement speech at the Air Force Academy, said. "As a testament to our strong faith in the future of air power… I am announcing today that the United States will commit itself to an important new program in civil aviation… a plane that will move ahead at a speed faster than Mach 2. more than twice the speed of sound, to all comers of the globe ~ The day before this speech the president of Pan American World Airlines had made the announcement that Pan Am was taking options on six Concordes. Prior to thai Air France and British Airways had ordered eight Concordes each.

A few days later President Kennedy followed up his commencement address with a message to Congress in which he said, "In no event will the government investment be permitted to exceed $750 million” [81 Development costs were then estimated to be approximately $1 billion.

This program soon became one with two competitive aircraft designs, one by Lock­heed and the other by Boeing, and two competitive engine designs, one by General Electric and the other by Pratt & Whitney. Boeing and General Electric were the eventual w inners of this competition with the Boeing 2707-100, a swing wing. M * 2.7. 200-300 passenger aircraft with a presumed range of 3500 nautical miles, weighing 750.000 pounds, an aircraft that was not then – and perhaps is not now. technically realizable. The swing wing provided both airport noise reductions and improved aerodynamic performance at lower speeds The weight of the mechanism used to pivot the wings resulted in unacceptably low range, or km payload, or both. The Boeing design evolved to a fixed wing, titanium aircraft, not unlike that proposed by Lock­heed The government’s investment in the SST program was to be repaid by royalties on aircraft sales. The government’s investments, including interest, would be recovered with the delivery of the 300th aircraft.

The two principal issues of concern with SSTs in the late 1960s were their economic viability because of a likely restriction to subsonic operation over populated areas and airport noise levels upon takeoff. There was limited concern before 1970 about the effects of such air­craft on the stratosphere.

The U. S. program died in the Senate in May 1971. in part from concerns about noise in the airport environs, in part from concerns about its impact on the stratospliCTe. in part due to politics, and in pan because its economic success seemed far less than certain. Today, twenty – five years later, these remain legitimate concerns

On November 5. 1956. the British had their first meeting of the Supersonic Transport Aircraft Committee, or STAC. The members had concluded that the U S. Boeing 707 and Douglas DC – 8 would capture so much of the subsonic market for commercial aircraft that the only options available to them were to go above the speed of sound or to give up the market J4|. It may have been better strategy to remain with subsonic aircraft, although die Concorde program did much to bring Britain into the Luropean community.

In March 1959 STAC urged the controller of aircraft in the Ministry of Supply to con­sider the development of a supersonic transport, estimating a market of 125-175 aircraft. The British then approached the French about a joint program, with one goal being their eventual admission to the European Common Market, then dominated by France. Later there were repeated attempts by Britain to cancel the Concorde Then President de Gaulle stood by the simple, irrevocable, two page treaty between the United Kingdom and the French Republic, entered intoon November 29. 1963 |4). |5).

Commercial flight operations began twenty years ago in January, 1976. with Bnush

Airways alien BOAC) flying between London and Bahrain, and Air France operating between Pans and Rio de Janeiro |6|. In a carefully considered (and in retrospect, enormously wise) decision. Secretary of Transportation William T. Coleman, on February 4. 1976. permitted lim­ited scheduled flights of the Concorde into the United States, initially for a trial penod of 16 months (SJ. Two flights per day for each carrier were to be allowed into Kennedy, and one flight per day for each earner was to be allowed into Dulles. Because the FAA operated Dulles, there was no difficulty in obtaining permission to operate there, and commercial service began at Dulles on May 24. 1976. The New York Port Authority banned such flights in March 1976. but this ban was overturned in court and commercial operations began there on November 27. 1977.

To my knowledge there have been no lasting complaints of concern about Concorde operations in selected U S. airports. But one must presume that for an economically successful SST. the fleet зілс will not be small, and with this increased SST traffic, it may be necessary to adhere to the latest airport noise level regulations for subsonic aircraft. Perhaps some modest deviations for SSTs will be allowed.

Perhaps the golden age of the Concorde was in 1987 and 1988 when over 60,000 pas­sengers were transported by each airline, more than 40.000 of those in a destination market w ith load factors just over 60*T. In January’. 1993. Air and Cosnun/Avtation Magazine wrote. "Since 1989-1990 the situation has declined to the point of Air France not even reaching 40.000 total passengers last year. And the results for the first trimester of 1993 do not indicate a substantial increase….*’ (3].

Important national goals were achieved by the Concorde program Perhaps the most important was the development of a successful European community aircraft consortium. It is unknown, and not knowable. whether the joint Bntish-Frcnch venture to develop the Concorde was the best or the only route to this end. It was achieved, however, and this must be attributed, at least in part, to this joint venture The French also gamed a considerable technological advance in their aircraft. Together, they proved the reliability and safely of public transport at supersonic speeds. The program s cost, through March 1976. was put at between 1.5 and 2.1 bil­lion in 1976 pounds sterling, or between 3.6 and 5.1 billion in 1977 U S. dollars (yearly weighted exchange rates) (7).

A. R. Scebass

University of Colorado, Boulder, CO, L’SA

1.1 Introduction

This chapter on the prospects for commercial transport at supersonic speeds must begin by de­ciding what we will call the genetic prospective aircraft Since the first generation aircraft were called Supersonic Transports, or SSTs for short, this practice is continued here Today, in the United States. NASA’s nomenclature is High Speed Civil Transports or HSCTs. while in Europe and Japan it is Supersonic Commercial Transports or SCTs

The title of this introductory chapter may seem ill-advised. Commercial transport at supersonic speeds has been a reality since 1976 Indeed, it has been a great technical success. The Concorde fleet has flown over 300.000 hours, most of them at supersonic speeds, and it has done so with over 93‘3t – reliability These aircraft will be in service for many years to come (1)1 can go to my local travel agent and buy a ticket to fly from Kennedy International Airport out­side of New York City to Heathrow Airport outside of London on British Airways, or to Charles de Gaulle Airptxi outside of Paris on Air France, and back The round-trip fare for the summer season. 1996, was 57,574 for London and S6.5I6 for Paris The corresponding first-class, busi­ness, and full coach fares are $6,752. $4,496. and $2,274 for London, and $5,700. $3,220 and $2,042 for Paris, the discount coach fares are $586 for London and S838 for Pans The cost of halving my flight time between New York and London or Pans is. averaging the two trips, about 113** that for first-class. 1835fr that for business class. 425Я that for coach and nearly 10 times that for discount coach During the previous winter season, the discount coach fares were about 509f less, making Concorde travel over 15 limes more expensive than discount coach then. The

discount fare to London during the 1996-97 winter season was less than 1/30 of the Concorde’s $7995 fare there.

We can probably assume that this fare is covering the direct operating cost of the Con­corde. exclusive of the depreciation or amortization of the aircraft itself. At these lares the mar­ket for supersonic travel is very limited.

Current scheduled Concorde flights include London • New York. Paris – New York in the summer, and London – Barbados (weekly). Recent reports on the Concorde indicate that the dozen now in service are under utilized (2). (3J. Excursion flights arc a small but growing part of the Concorde operations While service to and from Dulles Airport to dc Gaulle and to Hea­throw was provided by both airlines for many years, this (from Dulles to Heathrow> was discon­tinued in November 1994.

The first SST to fly was the Tupolev-144. with its maiden flight on December ЗІ. 196H. a year before the Concorde’s first flight. Tu-144 mail serv ice began on December 26. 1975. Pas­senger service commenced on November 1, 1977. but was discontinued 7 months later. While this aircraft was not an operational success, the Concorde has been an operational success for the two airlines that operate this small fleet. Commercial transport at supersonic speed is a real­ity. Docs a second generation SST make sense? This chapter reviews the Concorde and U. S. SST programs, and provides die author’s own conclusion regarding the prospects for a second generation SST The readers should develop their own conclusions; this book will help them to do so.

At a time when the increase in global traffic suggests a need for innovative solutions, this book offers a collection of contributions to the design of methodologies for a new generation of high speed transport aircraft, and of supersonic craft in particular.

The contributors come from university aerospace departments, the aircraft industry, and an aerospace research institution: the University of Colorado and Pennsylvania State University in the United States of America. Daimler Benz Aerospace and the DLR German Aerospace Research Establishment in Germany. They have been selected to provide a balance between the practical requirements for development and the tools and concepts for achieving design goals.

The book consists of twenty chapters arranged in three parts:

The first six chapters, after exploring the market outlook, present the challenge of developing the technologies needed to create solutions to high speed air transport within the framework of a variety of economic, environmental, and other practical constraints. Chapter 1 discusses the prospects for the development of a supersonic transport, including unconventional solutions. Chapter 2 provides a method for predicting future aircraft pricing. Chapter 3, outlines a multidisciplinary approach to the development of new aircraft, while Chapter 4 presents the problem as a multipoint design challenge. Chapter 5 lists the technologies needed. The final challenge, certification of a new supersonic aircraft, is examined in Chapter 6.

A collection of design tools follows, with theoretical models of the aerodynamics supporting generic aircraft shape definition, for use in systematic optimization strategies. While aerodynamics clearly dominates in the contents of this book, structural and thermal loads arc treated as well in Chapters 7 through 15, stressing a careful selection of design parameters based on mathematical modeling, and reviewing recent techniques for optimization. Chapter 7 introduces phenomcna-bascd tool development, illustrating the value of a detailed understanding of flow phenomena in the transonic flight regime. Chapter 8 then provides mathematically defined supersonic configurations. Both phenomena and configuration models sene as the basis for the geometry’ preprocessor software development in Chapter 9. The inverse aerodynamic problem formulation of Chapter 10 is compared with other strategics for optimization in Chapter 11. A combination of these techniques is reported in Chapter 12. Thermal problems are discussed in Chapter 13, and structural problems in Chapter 14, applying inverse and optimization strategies. Finally, a global approach to multidisciplinary inverse design and optimization in a parallel computing environment is treated in Chapter 15.

In the last five chapters various knowledge bases arc used for special and innovative aircraft concepts. Comparison of optimum conventional and novel configurations resulting from systematic design approaches stimulates the designer’s creativity, so that he can improve on his own methods. Certain aspects of the initial challenge are encountered in some case studies in Chapter 16. The industrial use of optimization tools is illustrated in Chapter 17. Chapter 18 discusses the possibility of improving aircraft performance by establishing laminar flow on aircraft components. The concluding chapters are devoted to an unconventional configuration, the oblique flying wing: Chapter 19 investigates a case study, with the application of industrial methods, while Chapter 20 discusses other studies of this unusual aircraft and some of its aerodynamic characteristics.

The collaboration between authors R. Scebass and H. Sobieczky was funded by the Alexander von Humboldt Stiftung with a Max Planck grant which helped to make possible the results outlined in Chapters 7, 8. 9 and 20. and substantially supported the editor in his idea of organizing the lecture series “New Design Concepts for High Speed Air Transport” held at CISM in June 1995. The encouragement of W. Schneider of Vienna is also gratefully acknowledged.

Many thanks go to Michael Klein and Stephanie Alberti of the DLR Institute for Fluid Mechanics in Gottingen, who put all the manuscript data into book form, and to the DLR for providing the computer equipment to make this possible.

H. Sobieczky