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Jet noise generated by turbofan engines which are designed for supersonic aircraft operation is expected to remain a challenge for the aerospace industry. For civil supersonic transport, low bypass ratio engines with internal mixing and external plugs are currently seen as promising exhaust architecture to meet aircraft mission and certification requirements. Measurements of the noise from a representative low-bypass ratio long duct mixed flow with external plug exhaust configuration were made, along with corresponding steady-RANS and LES analyses. The measured data showed excess high frequency noise across a wide range of operating conditions as compared to an equivalent single stream jet, or an equivalent uniform jet with internal plug. The absolute levels of the excess noise were relatively insensitive to forward flight, and the excess noise was most dominant when the primary and secondary streams had large velocity and temperature mismatch just upstream of the internal mixer. Preliminary indications from the LES analysis also indicated that significant pressure fluctuations, at the same frequencies which are insensitive to forward flight, develop inside the nozzle as the internal shear layer from the mixer grows and gets accelerated by the external plug. Parametric study test measurements on the fan and core operating conditions were performed, providing support for the hypothesis that the excess noise is generated as the internal shear layer, starting inside the nozzle, gets accelerated by the plug and passes through the weak shock at the nozzle exit where the flow accelerates more and turns over the external plug. [ABSTRACT FROM AUTHOR]

The abatement of sonic boom noise level is a decisive issue for supersonic transport of next generation. The low sonic boom optimization always make the configuration to a trend of higher swept and longer distribution of the wing along the fuselage，which is unfavorable to the trim and low speed characteristics. A civil supersonic transport is researched. A parametric geometry representation method based on class function/shape function transformation（CST）is developed to describe the wing body configuration. The effects of geometry parameters on sonic boom is analyzed by supersonic linearized theory. Based on the above work，the low sonic boom and pitch moment characteristics optimization are taken for the fuselage，wing planform and twists separately and the optimal result is validated by CFD. The numerical simulation results show that compared with the basic configuration，the drag decrease 19 cts（unit of drag coefficient）and the over pressure at near-field is abated obviously without the distinct increase of pitch moment，which bring 5.1 PLdB reduction of loudness on the ground.

In the present, work a modification of the multipole decomposition method is developed, which makes it possible to relate the overpressure distribution in the near-field of a supersonic transport (SST) with a far-field distribution, which is needed for the solution of sonic boom propagation problem from an SST. A generalization of the method for solving the integral equations arising from multipole decomposition is performed. An algorithm for multipole correction of near-field overpressure signatures obtained in numerical simulations has been developed and tested. [ABSTRACT FROM AUTHOR]

Landing of supersonic transport (SST) suffers from a large uncertainty due to its highly sensitive aerodynamic properties in the subsonic domain, as well as the wind gusts around runways. At the vehicle design stage, a landing trajectory optimization under wind uncertainty in a multi-objective solution space is desired to explore the possible trade-off in its key flight performance metrics. The proposed algorithm solves this robust constrained multi-objective optimal control problem by integrating non-intrusive polynomial chaos expansion into a constrained evolutionary algorithm. The computationally tractable optimization is made possible through the conversion of a probabilistic problem into an equivalent deterministic representation while maintaining a form of the multi-objective problem. The generated guidance trajectories achieve a significant reduction of the uncertainty in their terminal states with a marginal modification in the control history of the deterministic solutions, validating the importance of the consideration of robustness in trajectory optimization. [ABSTRACT FROM AUTHOR]

Supersonic biplanes can achieve low-boom and low-drag supersonic flights. In the present study, aerodynamic analysis of a two-dimensional stagger Bussmann biplane (staggered upper element by 0.5c) at zero degrees angle of attack with trailing edge flap was investigated with the help of computational fluid dynamics (CFD) tools. Due to the wave cancellation effect, the Busemann biplane delivers a positive drag reduction at design supersonic Mach values. However, when operating outside of its intended parameters, it performs worse, and the wave cancellation effect has no beneficial effects on reducing drag. Another issue with the Busemann biplane is flow chocking, which produces a potent bow shock wave in front of the aircraft. This paper attempts to address low aerodynamics efficiency problems during take-off through numerical simulation of a staggered Busemann biplane with trailing edge flaps at zero degrees angle of attack. It was confirmed that the staggered biplane airfoil with flap has better aerodynamic performance during take-off at lower subsonic free stream Mach numbers. In 2D wings, the effect of flow chocking and hysteresis as starting problems, which arise when the biplanes accelerate from low Mach numbers, is reduced by using the suitable dimension and angle of rotation of the flap, and the flap is effective in settling these issues.

An adaptive controller and a nonlinear rate limiter are presented in order to improve the flight safety of manually controlled reentry vehicles and supersonic transport (SST) aircraft. The adaptive controller is based on the principle of dynamic inversion. The calculation of the controller parameters corresponding to the aerodynamic coefficients of the vehicle was carried out by a proposed online identification procedure. The effectiveness of the adaptive controller was tested through a set of experiments performed using a ground-based simulator. The obtained results were used to estimate the probability of an accident due to pilot error for the basic Space Shuttle flight control system and for its improved version with the adaptive controller. It was found that using the adaptive controller causes high required rates of elevon deflection. Because of the actuator's rate limiting, this is a source of pilot-induced oscillations. To counteract these oscillations in the pilot-vehicle closed loop system, an adaptive nonlinear rate limiter is introduced. The effectiveness of using the adaptive prefilter for improving the flight safety and flying qualities of the Space Shuttle reentry vehicle and an SST was demonstrated in experiments involving a ground-based simulator. • Real time dynamics identification ensures fast adaptive control. • Flight safety is considerably improved using adaptive flight control. • A well designed adaptive prefilter eliminates PIOs arising in case of low actuator rate limiting. • Adaptive flight control systems provide a considerable improvement of pilot-vehicle system performance. [ABSTRACT FROM AUTHOR]

An analysis of the critical factors affecting the next generation supersonic transport flight safety, due to the features of the low sonic boom configuration, was carried out. A new concept of a hybrid airframe design of a supersonic passenger jet based on pro-bionic sections and sections of conventional structural layout was proposed. Pro-bionic sections were developed on the basis of composite lattice structures. Previously, this type of structural layouts has been successfully adapted in commercial space vehicles in Russia and the EU. Pro-bionic supersonic passenger jet airframe sections include a rigid composite frame of unidirectional ribs, elastic panels based on 3D reinforced woven skins. These sections are equipped with a built-in structural health monitoring system based on fiber optic sensors. New principles for ensuring pro-bionic structural strength and enhanced flight safety based on the positive synergetic interaction of the primary structural elements are proposed and validated. The weight efficiency of pro-bionic structures is estimated. • Pro-bionic structure for next generation supersonic transport inspired by space vehicle lattice structural layout. • Hybrid design approach for primary aircraft structures to comply with weight efficiency and flight safety requirements. • Enhanced protection system with structural health monitoring. [ABSTRACT FROM AUTHOR]

An evolutionary algorithm (EA) was applied in this study to optimize the landing flight path of a delta-winged supersonic transport (SST). However, it is difficult for a delta wing with a large sweepback angle to reduce the aerodynamic drag during supersonic cruising to gain sufficient lift force at low speeds, particularly during takeoff and landing. Besides, high-fidelity computational fluid dynamics is required to evaluate the flight path with a complex flowfield. This study performed an efficient flight simulation based on the Kriging model-assisted aerodynamic estimation to carry out global optimization. Then, the designs of the flight and control sequence were realized for time-series optimization of effective SST landing. To develop the EA, two design scenarios were considered; one involved only the elevator, which is an aerodynamic control surface that controls the aircraft, and the other involved introducing thrust control in addition to elevator control. In the scenario involving only elevator control, feasible solutions could not be obtained owing to the poor low-speed aerodynamic performance of the SST. This paper presents several feasible solutions enabling reasonable SST landing performance in the scenario involving the elevator and thrust controls along with descriptions regarding the optimum flight and control sequences. In addition, we analyzed the solutions by analyzing the variance to obtain qualitative information. Consequently, we determined that elevator control was considerably effective in cases with the microburst effect than in cases without the microburst effect. [ABSTRACT FROM AUTHOR]

Precooled engine is a highly expected solution to achieve supersonic transport. As the crucial component, heat exchangers protect other components from ultrahigh temperature. In traditional design methods, the nominal result is multiplied by a safety factor, whose selection entirely depends on experience, ensuring sufficient working margin to cope with fluctuation of parameters. For aero-engine, heat exchangers must work reliably with minimum weight. An advanced method of thermal optimization design with parameters' fluctuation is proposed and proved to be effective by experimental verification. The heat transfer area can be quantitatively linked with the design confidence level, considering the coupling effect of various parameters' fluctuation. The probability density distribution of heat transfer area has the characteristic of positive skewness distribution. With the increase of design confidence, the required heat transfer area is growing faster and faster. After optimization, the design of heat exchanger meets the requirements and the weight is effectively controlled. [ABSTRACT FROM AUTHOR]

Landing of supersonic transport (SST) suffers from a large uncertainty due to its highly sensitive aerodynamic properties in the subsonic domain, as well as the wind gusts around runways. At the vehicle design stage, a landing trajectory optimization under wind uncertainty in a multi-objective solution space is desired to explore the possible trade-off in its key flight performance metrics. The proposed algorithm solves this robust constrained multi-objective optimal control problem by integrating non-intrusive polynomial chaos expansion into a constrained evolutionary algorithm. The computationally tractable optimization is made possible through the conversion of a probabilistic problem into an equivalent deterministic representation while maintaining a form of the multi-objective problem. The generated guidance trajectories achieve a significant reduction of the uncertainty in their terminal states with a marginal modification in the control history of the deterministic solutions, validating the importance of the consideration of robustness in trajectory optimization.

Research on supersonic transport seeks to overcome two main challenges, to mitigate sonic boom and improve aero- dynamic performance, in order to become environmentally viable and economically practicable. To achieve these goals, this research proposes a waverider configuration to solve the challenge of designing commercial supersonic aircraft. The waverider is famous for providing a higher lift-to-drag ratio than that provided by other conventional designs for super- sonic and hypersonic flights. The study of three types of supersonic waveriders, cone-derived, power-law, and osculating-cone waverider, is introduced for low-supersonic designs. The flight condition includes a speed of Mach 1.5 at an altitude of 18,000 m. An unstructured grid with an inviscid Euler equation solver is used to calculate the flow field of the vehicle. The ground noise post-processing uses an augmented Burgers equation solver to assist in far-field signature evaluation. The result of a cone-derived waverider provided significant volume with low overpressure, while the power-law waverider showed the advantages of aerodynamic performance and ample design space. The osculating-cone waverider obtained the merits from both the cone-derived and power-law waveriders. The waverider is expected to have a quality that satisfies the design objectives of supersonic aircraft: high aerodynamic performance and sonic boom mitigation. [ABSTRACT FROM AUTHOR]

Reducing the sonic boom to a community-acceptable level is a fundamental challenge in the configuration design of the next-generation supersonic transport aircraft. This paper conducts a survey of recent progress in developing efficient low-boom design and optimization methods, and provides a perspective on the state-of-the-art and future directions. First, the low- and high-fidelity sonic boom prediction methods used in metric of low-boom design are briefly introduced. Second, efficient low-boom inverse design methods are reviewed, such as the classic Jones–Seebass–George–Darden (JSGD) method (and its variants), the high-fidelity near-field-overpressure-based method, and the mixed-fidelity method. Third, direct numerical optimization methods for low-boom designs, including the gradient-, surrogate-, and deep-learning-based optimization methods, are reviewed. Fourth, the applications of low-boom design and optimization methods to representative low-boom configurations are discussed, and the challenging demands for commercially viable supersonic transports are presented. In addition to providing a comprehensive summary of the existing research, the practicality and effectiveness of the developed methods are assessed. Finally, key challenges are identified, and further research directions such as full-carpet-low-boom-driven multidisciplinary design optimization considering mission requirements are recommended. [ABSTRACT FROM AUTHOR]

Review and discussion of substantive to revolutionary concepts to enable a commercially viable, societally acceptable supersonic transport. Issues addressed include economic viability, take off noise, sonic boom, emissions and frontier aircraft configurations. Solution spaces include an enabler for most of the issues, which is doubling the lift-to-drag ratio. Approaches in most cases require serious further research for application to and optimization of frontier aircraft configurations. [ABSTRACT FROM AUTHOR]

We here reflect on two important articles on stratospheric ozone depletion written by P. J. Crutzen (1974) and P. J. Crutzen and D. H. Ehhalt (1977) in the early 1970s. These articles provide a clear description of the stratosphere and the most important chemical reactions involved in stratospheric ozone depletion. They present modeling results and provide recommendations for future research on stratospheric ozone depletion caused by chloro-fluoro-carbons, supersonic transport, nitrous oxide, and nuclear explosions. These two articles represent the beginning of a scientific era, which led to discovery of the Antarctic ozone hole and political action in the form of the Montreal Protocol and its amendments. [ABSTRACT FROM AUTHOR]

The high-fidelity sonic-boom prediction is crucial for the design of low-boom supersonic transport aircraft. In this article, a far-field sonic-boom prediction method solving the augmented Burgers equation is studied, and a prediction code called " bBoom "is developed. First, the numerical method for solving augmented Burgers equation and a ray tracing method in propagation are studied. Some significant parameters of molecular relaxation processes and thermoviscous absorption in the Burgers equation are presented. Second, some benchmark cases from the 2 thAIAA Sonic Boom Prediction Workshop, including a simple axi-symmetric body, a NASA low-boom configuration, and LM1021 configuration, are employed to validate the code. The results show that the developed code is accurate and reliable for predicting the far-field waveforms . At last, far-field sonic boom waveforms propagated from different near-field pressure signals at different locations are compared, and the distinction of waveforms in different flight azimuthal angles with atmospheric winds is investigated. It is shown that, in order to improve the accuracy of predicting the sonic boom for configurations like a C25D model, the near-field signal should be extracted at a distance of three body lengths off the aircraft.It is also shown that atmospheric wind profiles have a significant impact on the sonic-boom waveform and sonic-boom carpet on the ground. [ABSTRACT FROM AUTHOR]

The reduction of sonic boom noise level is one of the most important problems that must be resolved to get the commercial success in the future. For the sonic boom noise prediction and control of supersonic flight vehicle，the sonic boom noise level prediction methods based on supersonic linear theory and waveform parameter method were developed. The prediction results agreed well with the experiment results of the lml021, thus the reliability of the prediction methods were validated. The low sonic boom configuration optimizations were researched. The sonic boom level of a basic configuration of supersonic business jet was computed，and the cause of sonic boom formation was analyzed. Based on the results and the analysis, the fuselage and wing planform were optimized separately to decrease the noise level of sonic boom. Compared with the basic configuration，the sonic boom level of optimized configuration decreased distinctively. The overpressure decreased 41%，and the A-weighted noise level decreased 7. 55 dB. The aerodynamic characteristics of optimized configuration were computed by computational fluid dynamics (CFD). Compared with the basic configuration, the drag decreased significantly at the cruise condition，while the moment almost unchanged. [ABSTRACT FROM AUTHOR]

This paper reviews the environmental issues and challenges appropriate to the design of supersonic business jets (SSBJs). There has been a renewed, worldwide interest in developing an environmentally friendly, economically viable and technologically feasible supersonic transport aircraft. A historical overview indicates that the SSBJ will be the pioneer for the next generation of supersonic airliners. As a high-end product itself, the SSBJ will likely take a market share in the future. The mission profile appropriate to this vehicle is explored considering the rigorous environmental constraints. Mitigation of the sonic boom and improvements aerodynamic efficiency in flight are the most challenging features of civil supersonic transport. Technical issues and challenges associated with this type of aircraft are identified, and methodologies for the SSBJ design are discussed. Due to the tightly coupled issues, a multidisciplinary design, analysis and optimization environment is regarded as the essential approach to the creation of a low-boom low-drag supersonic aircraft. Industrial and academic organizations have an interest in this type of vehicle are presented. Their investments in SSBJ design will hopefully get civil supersonic transport back soon. [ABSTRACT FROM AUTHOR]

This paper evaluates the reduction of airport noise that can be expected from an optimized LH2-fueled SST due to its shorter takeoff and landing performance compared to an equivalent kerosene-fueled SST. An initial comparison shows that flyover noise is reduced by 7.7EPNdB since the LH2-fueled SST has a steeper climb following a shorter takeoff roll. Although sideline and approach noises are increased, the total cumulative loudness is reduced by 6.5EPNdB. Then, the effect of reduced-thrust takeoff is evaluated for the LH2-fueled SST, which has a takeoff performance surplus. The result shows the sideline noise is reduced while flyover noise is increased. A parametric study is also conducted for further airport noise reduction potential. [ABSTRACT FROM AUTHOR]

Busemann biplanes and its modified versions are recently being reinvestigated for possible low boom supersonic transport. The Busemann biplane offers a very favorable drag reduction at design supersonic Mach numbers due to wave cancellation effect. However, at the off design speeds its performance deteriorates and the wave cancellation effect offer no favorable drag reductions. Another problem associated with the Busemann biplane is the chocking of the flow due to inability of the biplane to engulf the normal starting shock wave in front of the biplane. This paper attempts to address the chocking problem through the numerical simulation of Busemann biplane with staggered airfoil configurations. Lift and drag characteristics of a Busemann biplane with staggered tandem airfoil configurations are investigated at various Mach numbers between 0.5 and 2.5 using Computational Fluid Dynamics. The stagger increases the throat area thus reduces the flow chocking characteristics of the Busemann biplane without effecting the wave cancellation much. The results suggest that a significant reduction in wave drag can be realized even at off-design conditions, especially at low Mach numbers through staggering of the Busemann biplanes. [ABSTRACT FROM AUTHOR]

Optimal non-planar wing planform geometries for a Mach 2.2 45-seat supersonic transport are generated using Kriging-based Bayesian optimisation techniques on a 22-variable, 3-objective problem for two wing-loading conditions. Sonic boom loudness, drag, and root bending moment are simultaneously minimised at a fixed lift. A Python-based framework is developed for rapid evaluation of designs in a parallel computation environment, automating conceptual geometry generation, optimised mesh griding, Euler CFD evaluation, and thermoviscous atmospheric boom propagation. An empirical turbulent skin friction coefficient is used to correct the Euler drag and an estimate of wave drag is performed. Self-organising maps and polynomial chaos expansion Shapley effects are used to explore the design variables and their associated sensitivities with respect to the design objectives. A geometric centroid-based proxy for trim is used to filter the results; feasible extreme designs and a compromise design are compared and discussed. The results indicate a trade-off between each of the three objectives due to competing design requirements, however an improvement in two of the objective functions is possible by sacrificing the remaining objective. One possible compromise solution reduces the root bending moment coefficient by 25% and the sonic boom loudness by 24% at the cost of a 5% increase in drag. [ABSTRACT FROM AUTHOR]

At Mach 2, the supersonic Concorde reduced travel time from New York to London to 43% of today's subsonic aircraft. However, it was not commercially successful because of issues related to supersonic shock waves: high fuel consumption and the sonic boom. The unexplored phenomenon of aerodynamic tunneling has the potential of enabling efficient, quiet, zero-emissions supersonic transport. A vehicle is transported from terrestrial point A to B via a closed, ambient-pressure tube containing an atmosphere more aerodynamically favorable than air. A predicted speed limit of such a vehicle is Mach 2.8–3.0 in a hydrogen tube, without shock waves. We have commenced a multi-phase project to experimentally measure the power and energy of a 1:16-scale tunneling vehicle. For each of six experimental gases – methane–hydrogen (mixture), methane, carbon dioxide, air, oxygen, and argon – we will measure thrust, power, energy consumption, and propulsive efficiency. This paper concerns the completed first phase, engineering design of the experimental vehicle, a monorail, wheeled tube vehicle that balances with ailerons and uses propeller propulsion. [ABSTRACT FROM AUTHOR]