Aerodynamic Design of a Mach 2.2 Supersonic Cruise Aircraft

The McDonnell Douglas Corporation has conducted numerous Mach 2.2 supersonic aircraft design and in- tegration studies in support of the NASA Supersonic Cruise Aircraft Research (SCAR) program. This program traces the evolution of a baseline study configuration and an improved performance configuration through several aerodynamic design and trade study cycles. The impact of real-world constraints on configuration design is discussed. Previous studies have not addressed the Mach 2.2 cruise design condition and this work has resulted in a structurally feasible configuration capable of achieving £/D's in excess of 9 at this cruise Mach number. The purpose of this paper is to present the resulting design and wind-tunnel test results for two configurations. The wind-tunnel test results are compared to the analysis methods. N 1972, interest was renewed both at NASA and in the industry in conducting technology assessment studies on supersonic cruise aircraft. The NASA Supersonic Cruise Aircraft Research (SCAR) program emerged late in 1972, charged with the task of identifying, through aircraft design studies, key technologies whose pursuit would lead to im- proved aerodynamic efficiency, reduced operating costs, and environmental compatibility for typical next-generation supersonic cruise configurations. McDonnell Douglas (MDC) reassessed the entire spectrum of supersonic travel beginning with a market analysis and a review of technology available at various design Mach numbers. Results of these preliminary design studies indicated that a 273-passenger, Mach 2.2 aircraft offered the best mix of low operating costs, productivity, near-term technology materials, and reduced program risk for typical supersonic transport con- figurations. 1 Using this as a starting point, McDonnell Douglas conducted numerous aerodynamic studies, trade studies, and sizing studies in support of the SCAR program.2'3 A baseline study configuration, shown in Fig. 1, emerged, which was a structurally feasible arrow-wing configuration promising good cruise L/D's. Subsequent studies indicated that improved performance was available through wings optimized to reduce configuration trim drag. In 1975, a cooperative MDC-NASA wind-tunnel test program was conducted in which the performance of the study baseline configuration and an improved-perf ormance configuration was substantiated, and the analytical techniques used in their design were validated. Methods of Analysis The primary analytical tools used in the aerodynamic design and analysis of the McDonnell Douglas advanced supersonic cruise aircraft configuration have been the Woodward program4 and the Douglas Arbitrary Body Wave Drag Program.5 The McDonnell Douglas version of the Woodward program has been extensively modified to im- prove its versatility. In the SCAR studies it was used in both the inverse (optimization) and direct (analysis) modes. Wings were designed by optimizing the wing camber distributions for minimum drag due to lift at specified CL's, with and without specified pitching moments. Wings were primarily optimized as wings alone extended to the fuselage centerline, but some optimizations were done in the presence of the fuselage. Drag due to lift and wing-body pitching moments were computed by direct analysis of wing-body combinations including wing thickness effects. Wing panels were spaced equally spanwise and chordwise on both wings alone and wings exterior to the fuselage. All wings were represented by 9 spanwise and 12 chordwise panels, which is sufficient for converged solutions. Biquadratic interpolation was used to determine exterior wing camber distributions from wing-alone optimizations, and vice versa. A typical Woodward wing-body paneling scheme is shown in Fig. 2. Although not depicted on Fig. 2, the Woodward program was used in the full configuration mode to calculate wing-body pitching moments, including the ef- fects of forebody lift. Configuration zero-lift wave drag was calculated using the McDonnell Douglas-developed Arbitrary Body Wave Drag Program which calculates, based on the area rule theory,6'7 the wave drag of completely arbitrary configurations. All analyses were performed on full wing-body and wing-body- nacelle configurations at their cruise attitudes. While the program can accept cambered fuselages with exact cross sections, it has been determined that cambered fuselages with