Cruise Range in Formation Flight

Optical window systems protect sensor systems from the aerodynamic and atmospheric environments. The aerodynamic heating on an optical window located about 1 foot downstream from the spherical nose tip is analyzed. The vehicle flies at a constant Mach number and at a constant altitude. The Mach numbers range from 1.5 to 5 and the altitudes from 10 to 30 km. The mechanical responses are calculated for yttria and lanthana-doped yttria, infrared window materials currently being developed for the 3 to 5 im applications. The results show that the yttria window temperature is about 1000 K at Mach 5 and 10 km altitude for an emissivity of 0.04 at 5 μm Steady state and constant altitude flight are assumed.

The method of high-accuracy and high-speed calculation of flight performance data is the key point of air traffic automation and simulations. The Base of Aircraft Data (BADA) performance model provided by the Euro-control Experiment Centre (EEC) has been widely used by international research organizations to calculate the aircraft performance data. The mode can calculate the fixed mach number cruise data, but it cannot calculate the long range cruise mode (LRC) flight data as is mostly adopted by the airlines in order to save fuel or flight cost. Based on the BADA model and related parameters, this paper studies the methods used to calculate the LRC cruise mach number, and also calculates the data for the B737-800 aircraft. The results are compared with calculations obtained by INFLT in the same conditions, which shows that the accuracy and calculating speed can be accepted by the research of ATC automation and simulations. The flight modes between fixed cruise mach number and LRC are also compared in the end, which shows that the LRC cruise mode can decrease the operation cost for airlines by saving cruise fuel consumption.

Limited available data suggest a substantial impact of Mach number on the heat transfer from an array of jets impinging on a surface at fixed Reynolds number. Many jet array heat transfer correlations currently in use are based on tests in which the jet Reynolds number was varied by varying the jet Mach number. Hence, this data may be inaccurate for high Mach numbers. Results from the present study are new and innovative because they separate the effects of jet Reynolds number and jet Mach number for the purposes of validating and improving correlations that are currently in use. The present study provides new data on the separate effects of Reynolds number and Mach number for an array of impinging jets in the form of discharge coefficients, local and spatially averaged Nusselt numbers, and local and spatially averaged recovery factors. The data are unique because data are given for impingement jet Mach numbers as high as 0.60 and impingement jet Reynolds numbers as high as 60,000, and because the effects of Reynolds number and Mach number are separated by providing data at constant Reynolds number because the Mach number is varied, and data at constant Mach number because the Reynolds number is varied. As such, the present data are given for experimental conditions not previously examined, which are outside the range of applicability of current correlations.

An experimental investigation was made to determine the variation of shock shape and extent of subsonic region behind the shock wave with angle of attack for a 70° cone at various Mach numbers. The main interest was centered on those Mach numbers which produced detached shock waves or for which the possibility of detachment at angle of attack existed. The tests were conducted in the GALCIT 2.5 Supersonic Wind Tunnel at angles of attack of 0°, 3°, 6°, 9°, 12°, and 15° and Mach numbers of 1.438, 1.544, 1.584, 1.857, 1.986, and 3.01. It was found that, with increasing angle of attack and constant Mach number, the subsonic region behind the shock wave increased in the lower portion and decreased in the upper portion. With increasing Mach number the subsonic region decreased for all angles of attack. Interaction between the upper and lower portions of the shock wave affects the subsonic region behind the wave, suppressing its appearance on the upper surface, retarding its disappearance from the lower surface.

The problem of finding an optimal aircraft trajectory in close to real time is considered. Using multiple models for different parts of the trajectory, where each model is tailored for the particular conditions, an efficient method has been developed which solves the trajectory optimization problem in a few seconds making interactive use feasible. The different models are used in order to accurately model flight at different conditions such as constant Mach number, constant calibrated airspeed, or constant altitude, using a minimum number of state variables and state equations for each condition. The modeling used and the numerical implementation is described in some detail. A user interface for computing optimal aircraft trajectories using a standard web-browser over the Internet has also been developed. To further illustrate the interactiveness of the developed computational procedures, a mobile Internet implementation has been developed where a cellular phone supporting the Wireless Application Protocol can be used to compute an optimal aircraft trajectory. Copyright

Birds fly in formation to benefit from the upwash wake vortices created by their peer leader. Similar strategies can be employed on aircraft for fuel saving or for range extension. However, further understanding of wake vortices in the near field and mid field is needed for close formation flight (< 10 wingspans). This paper introduces a new method for wake vortex detection using small UAV formation. A NonLinear Dynamic Inversion (NLDI) based formation control law is adapted to the WVU Phastball UAV platform. The designed controller showed good tracking performance during close formation flight (5-10 wingspans) with typical errors of less than 3 meters during straight legs. Then, multiple sensor measurements from leader-follower UAV formation flights were used for the wake vortex detection, including angle of attack, angle of sideslip, accelerometers, and gyros. The collected flight data showed the feasibility of using UAV formation for the wake encounter detection.

SummaryAn integral part of the study of supersonic combustion is the investigation of supersonic turbulent mixing of dissimilar fluids. Experimental results obtained in the course of investigating the turbulent mixing zone between supersonic streams of CO3 and air are presented. Good correlation between observation and available theories has been obtained in terms of the parameter ξ=σy/x. The correlating parameter σ defines the spreading rate of the mixing zone. The available theories, though not developed for these specific conditions, are shown to be applicable to the turbulent mixing of supersonic streams.The correlating parameter σ was determined for three different combinations of internal and external flow Mach numbers. The values found for σ were 18, 16·3, 15·3 for constant external Mach number 1·62 and internal Mach number 1·62, 1·53, 1·47 respectively. The magnitudes of σ showed the expected trend, that is the higher value implies the least divergence of the mixing boundaries.The reasonable agreement with experiment and the simplicity of application of the momentum integral form of solution would appear to favour the use of this approach for the theoretical prediction of the mixing conditions.

Avian formation flight has always inspired technology protagonists to mimic and harness associated benefits for the aviation industry. This paper discusses the performance benefits of similar and hybrid jet airliners flying in formation. The aerodynamic forces are modelled through potential flow theory. The lateral and vertical spacing is varied to estimate advantages in range. For simplicity, only cruise performance is analysed. By employing formation flying in wide-body aircrafts, an increase in range up to 65% is observed relative to standard flight. In addition to that, an optimal switching point during cruise flight is evaluated to give equal benefits to both aircrafts flying in formation. The study proposes a new concept of shared airspace where different aircrafts cooperate on long routes for fuel savings. However, the findings reported in this paper are of theoretical nature and high-fidelity models and experimentation is considered necessary to further evaluate the benefits of formation flying. Moreover, existing distancing restrictions between two aircrafts, imposed by regulatory authorities, are also a potential limitation in successful realisation of commercial formation flight.

Drift-free solar sail formations in elliptical Sun-synchronous orbits

This paper deals with a behavioural decentralized approach for UAV formation flight to carry out a waypoint-passing mission. The objective of the proposed approach is to make each UAV in the formation fly through predefined waypoints while maintaining the distance from other UAVs. To apply the behavioural decentralized controller based on the coupled dynamics, a feedback linearization technique with a diffeomorphic transfer map is derived for a three-dimensional UAV kinematics model. The behavioural approach in which the control input is decided by the relative weight of each UAV's desired behaviour is considered so that each UAV can promptly react on various situations. Optimization techniques of the gain matrices are also performed to improve the performance of the formation flight using eigen-structure analysis and Cholesky decomposition. To verify the performance of the proposed controller, numerical simulation is performed for a waypoint-passing mission of multiple UAVs.

Solovev’s approach of finding equilibrium solutions was found to be extremely useful for generating a library of linear-superposable equilibria for the purpose of shaping studies. This set of solutions was subsequently expanded to include the vacuum solutions of Zheng, Wootton and Solano, resulting in a set of functions {SOLOVEV_ZWS} that were usually used for all toroidally symmetric plasmas, commonly recognized as being able to accommodate any desired plasma shapes (complete-shaping capability). The possibility of extending the Solovev approach to toroidal equilibria with a general plasma flow is examined theoretically. We found that the only meaningful extension is to plasmas with a pure toroidal rotation and with a constant Mach number. We also show that the simplification ansatz made to the current profiles, which was the basis of the Solovev approach, should be applied more systematically to include an internal boundary condition at the magnetic axis; resulting in a modified and more useful set {SOLOVEV_ZWSm}. Explicit expressions of functions in this set are given for equilibria with a quasi-constant current density profile, with a toroidal flow at a constant Mach number and with specific heat capacity 1. The properties of {SOLOVEV_ZWSm} are studied analytically. Numerical examples of achievable equilibria are demonstrated. Although the shaping capability of the set {SOLOVE_ZWSm} is quite extensive, it nevertheless still does not have complete shaping capability, particularly for plasmas with negative curvature points on the plasma boundary such as the doublets or indented bean shaped tokamaks.

Slender wing vortex flows at subsonic, transonic, and supersonic speeds were investigated in a 6 x 6 ft wind tunnel. Test data obtained include off-body and surface flow visualizations, wing upper surface static pressure distributions, and six-component forces and moments. The results reveal the transition from the low-speed classical vortex regime to the transonic regime, beginning at a freestream Mach number of 0.60, where vortices coexist with shock waves. It is shown that the onset of core breakdown and the progression of core breakdown with the angle of attack were sensitive to the Mach number, and that the shock effects at transonic speeds were reduced by the interaction of the wing and the lead-edge extension (LEX) vortices. The vortex strengths and direct interaction of the wing and LEX cores (cores wrapping around each other) were found to diminish at transonic and supersonic speeds.

The development of aircraft in civil aviation has led to higher cruise flight altitudes and Mach numbers. At the same time, economical and ecological requirements as well as passenger comfort demands have been increased. In particular the high fuel costs force the airframers to discuss new aircraft concepts and to change the aircraft architecture design. Especially the bleedless architecture of the more electrical aircraft promises further optimization potential. However, in the current aircraft architecture bleed air is used to get compressed and fresh air for the cabin air conditioning, in the more electrical aircraft architecture the lack of bleed air has to be compensated by additionally inducted air. Taking into account that the conventional centralized hydraulic system shall also be replaced by electrical actuators or local hydraulic units, more additional cooling air from the outside atmosphere has to be inducted to fulfill the new cooling requirements of the components. This means all in all that the required fresh and cooling air has to be provided by either additional air intakes or up-scaled existing air intakes. Since the drag of air intakes can’t be neglected, the air intake type, design and the placement will have a crucial impact on the overall eciency of the aircraft. This has to be taken into account even in the early design phase of the aircraft. Only with a sophisticated evaluation methodology it is possible to realize an optimal air intake integration and to obtain an eciency benefit in comparison to conventional aircraft architecture. Therefore, the main objective of the presented research work has been to develop an evaluation methodology which allows for comparing the impact of dierent air intake designs and integrations on the overall aircraft performance. A main part of the work is to couple a one-dimensional air intake design method with results of a three-dimensional CFD calculation of the targeted aircraft application to get realistic conditions as input parameters for the design study. Only this approach allows for a reliable evaluation of dierent intake types. In the presented work essential aspects of air intake designs will be discussed, constraints which lead to a decision for a certain intake type and a suitable placement will be considered, and, finally, a methodology for the evaluation of dierent air intakes in regard to the global aircraft performance will be discussed.

: In this research the close formation flight control problem is addressed. The formation consists of a lead and wing aircraft, where the wing flies in close formation with the lead, such that the lead's vortices produce aerodynamic coupling effects, and a reduction in the formation's drag is achieved. A controller, i.e., a formation-hold autopilot for the wing aircraft, is designed such that the formation's geometry is maintained in the face of lead aircraft maneuvers. In the formation flight control system, the wing and lead aircraft dynamics are coupled due to kinematic effects, and, in the case of close formations, additional aerodynamic coupling effects are introduced. In the research these additional aerodynamic coupling effects are properly modeled. The most significant aerodynamic coupling effect introduced by close formation flight entails the coupling of the lateral/directional channel into the altitude-hold autopilot channel. It is shown that formation hold autopilots designed ignoring the aerodynamic coupling effects, yield satisfactory performance in close formation flight.

Renewed interest in supersonic air travel has prompted researchers to consider where next-generation civil supersonic aircraft will operate. These aircraft are expected to fly lower and slower than Concorde, meaning that prevailing winds will have a greater impact on flight duration and fuel consumption. However, nonstandard atmospheric conditions have not always been considered in recent supersonic design studies. This paper therefore quantifies the influence of the jet stream on next-generation supersonic operations between London and New York and investigates the potential benefits of wind-optimal transatlantic routing. Four notional supersonic aircraft with performance characteristics representative of concepts found in the literature are used to assess the effect of wind at different cruise Mach numbers and altitudes. For great circle routes, the assumption of standard atmospheric conditions leads to average time and fuel burn underestimates of 4–7% and 3–6%, respectively, for westbound winter flights. If aircraft deviate from the great circle to seek favorable wind conditions, statistically significant reductions in average flight time and fuel burn are possible, but this is not the case for all cruise altitudes, Mach numbers, or flight directions. Nevertheless, wind-optimal routing is presented as one strategy to help reduce the environmental impact of future supersonic aircraft.