Howard Smith

Buckling control using embedded shape memory actuators and the utilisation of smart technology in future aerospace platforms

Abstract In this paper experimental tests are described and discussed which illustrate the feasibility of buckling control in composite structural elements using induced strain actuation in a smart technological manner. Compressive tests on simply supported square composite plates which utilise the shape memory effect for buckling control are shown to exhibit substantially reduced post-buckling deflections when under activated control in comparison to those experienced for the uncontrolled case. The alleviation of the post-buckling deflections is shown to result in reduced non-linear stress levels in the post-buckling range and thus it is intimated that the ultimate failure levels of the composite plates can be improved through the application of shape memory control. The influence of temperature, from ohmic heating of the actuated shape memory alloy wires, on the mechanical performance of the composite laminated plates is discussed and the analysis procedures for the determination of the resulting non-uniform stress profiles in the composite plates are duly outlined. It was found that temperature effects could be significant and that these in turn depended to a large extent on laminate lay-up configuration. Particular attention is paid in the paper to tests carried out to ascertain the characteristic behaviour of the Nickel–Titanium shape memory material employed for actuation purposes. The cyclic recovery force capabilities of the actuator wires utilised in the compressive plate tests is highlighted and a detailed account of the determination of the alloys characteristic transformation temperatures is given. The paper discusses, in some detail, the feasibility of the proposed smart structural concept and gives some thought to the implementation of smart advanced composite materials within the marketplace with particular reference to future aerospace applications.

A generic stability and control methodology for novel aircraft conceptual design

CONCEPTUAL DESIGN. The aerospace flight vehicle conceptual design phase is, in contrast to the succeeding preliminary and detail design phases, the most important step in the product development sequence due to its pre-defining function. However, this phase can be considered the least well understood part of the entire flight vehicle design process due to its high level of abstraction and associated risk, multidisciplinary design complexity, permanent shortage of design information available, and finally chronic time pressure to find solutions. Currently, the important primary AeroSpace vehicle design decisions (e.g. sizing of control effectors) at the conceptual design level are still made using extremely simple analyses and heuristics. A reason for this scenario is the difficulty in synthesizing the range of individual design-disciplines in a timely manner for both, classical and novel aerospace vehicle conceptual designs, in more than an ad-hoc fashion. The recent period has been filled with exceptionally interesting developments and advances leading to highperformance conventional and non-conventional aircraft shapes. Although those vehicles seem to comply well with specific mission performance requirements, one is still confronted with an apparent weakness to reliably stabilize and control. Although not always recognized as such, stability and control is the single most critical requirement for flight safety. Because the provision of satisfactory stability and control characteristics invariably compromises flight performance to some extent, it is essential to integrate performance-optimal stability and control design solutions into the initial flight vehicle concept as early as possible.

Airframe integration for an LH2 hybrid-electric propulsion system

Purpose – The purpose of this paper is to explore some of the challenges associated with the integration of an LH2-fuelled advanced hybrid-electric distributed propulsion system with the airframe. The airframe chosen as a case study is an ultra-high-capacity blended wing body configuration. It is designed to represent an A-380 class vehicle but in the 2025-2030 timeframe. The distributed propulsion system is a hybrid-electric concept that utilizes high-temperature superconducting technologies. The focus of the study is the application of LH2 as a fuel, with comment being given to kerosene and LCH4. Design/methodology/approach – The study consists of a conceptual design developed through the preliminary design phase and part way into the detailed design phase. Findings – The relationship between passenger capacity and fuel capacity is developed. Some remaining challenges are identified. Practical implications – The study supports further conceptual design studies and more detailed system studies. Social im...

A review of supersonic business jet design Issues

Key issues relating to the Supersonic Business Jet (SBJ) concept are reviewed with the intent to assess the readiness of enabling technologies and hence the concept itself. The multidisciplinary nature of aircraft design precludes an in-depth analysis of each specific aspect, which could individually be the subject of a separate discipline review, hence an overview is presented. The review looks at the market, environmental issues, with particular reference to the sonic boom phenomenon & solutions, technological issues, including prediction methods, flight testing, systems, certification and interested aerospace companies and design organisations. It is apparent that the need to reduce the sonic boom signature is vital if the vehicle is to be permitted to operate over land and hence be economically viable. It is clear that sonic boom acceptability requirements must be set if resources are to be effectively focused and designs are to converge. Despite this challenge, considerable investment is aimed at de-risking many of the enabling technologies and raising readiness levels. Many technologies are moving beyond theoretical and numerical analysis into the experimental and flight test domains. Collaboration between the civil and military sectors is increasing. Clearly, supersonic air travel is not an efficient means of personal conveyance; however, concerns for the environment are difficult to balance against the ‘value of time’ benefits offered by the SBJ concept. Air travel, of which this is a specialised form, is important to the global economy. Continued effort in the areas of human factors, customer demand and certification & requirements would be beneficial.

Modelling of solar irradiance and daylight duration for solar-powered UAV sizing

Solar energy from the sun is the largest available renewable energy that enhances the endurance of a solar powered unmanned aerial vehicle. However, harnessing this solar power is a great challenge. This is due to having solar module system’s power output efficiency of only about 15–30%. However, a solar powered unmanned aerial vehicle has the potential to outperform a battery only operated unmanned aerial vehicle, especially when task being a pseudo satellite which requires long operating hours. The atmospheric conditions and geological locations undoubtedly the main cause for poor performance of these solar modules. In spite of its prolific improvement in solar cell efficiency over the years, the overall solar module system barely converts half of sun’s power into electricity. Therefore, this situation makes the current system unattractive to be widely used for energy harvesting. Recent attention has been focused not only on type of solar cells but on its positioning system. However, there were lack of understanding and research on the solar irradiance intensity and daylight duration’s effect on the power output. Therefore, a comprehensive model was developed to study on how the sun movement affects the solar module system’s performance. This simulation model has identified the daylight duration is more important in comparison to the available solar irradiance. Moreover, the higher the solar irradiance and daylight duration, the solar module system gives the most power output. The daylight duration also depends on the latitude where the higher the latitude gets, the longer the daylight duration. Besides, the longitudinal coordinates and elevation have minor effect on the daylight duration estimation. In other words, in summer, the northern hemisphere has more advantage compared to the southern hemisphere locations and vice versa.

Modeling and Simulation of Solar Irradiance and Daylight Duration for a High-Power-Output Solar Module System

Solar energy is the largest available renewable energy for enhancing the endurance of a solar-powered unmanned aerial vehicle (UAV). However, harnessing solar energy is a great challenge because the power output efficiency of solar module systems is only 15% to 30%. A solar-powered UAV has the potential to outperform a battery-powered UAV, particularly in tasks involving a pseudo satellite that requires long operating hours. Atmospheric conditions and geographical location are the main causes of the poor performance of solar modules. Despite the improvements in solar cell efficiency over the years, solar module systems can still barely convert half of the sun’s power into electricity. This limitation hinders the use of current solar module systems for harvesting solar energy. Recent studies have focused not only on the type of solar cells but also on the positioning system. However, understanding and research on the solar irradiance intensity, as well as on the effect of daylight duration on the power output, remain lacking. A comprehensive model was developed to address this gap and investigate how the movement of the sun movement affects the performance of solar module systems. This simulation model found that daylight duration is more important than available solar irradiance. Higher solar irradiance and daylight duration corresponds to a higher power output of the solar module system. Daylight duration also depends on latitude where higher latitudes lead to longer daylight duration. On the other hand, longitudinal coordinates and elevation have minor effects on the estimation of daylight duration. Therefore, the northern hemisphere has more advantages than southern hemisphere during summer and vice versa.

The Development of a Small Solar Powered Electric Unmanned Aerial Vehicle Systems

Unmanned Aerial Vehicle (UAV) has an enormous role to both military and civilian missions. However, a short range endurance of current UAV system affects the life expediency, data monitoring, and output performance of a mission. This is due to having UAVs that are dependent on batteries. The weight of the battery and low temperature environment has undoubtedly been the main cause for the poor UAV performance. In spite of its prolific improvement in UAV system, the endurance permissible is between 45 minutes to 4 hours. Therefore, this situation makes battery no longer attractive to be widely used for UAV. Lately attention has been focused on the use of solar cell in UAV in replacement to battery as its power system. Nevertheless, current solar cells characteristic and efficiency is insufficient to sustain a long endurance flight. This is due to failure to identify an appropriate selection of material and parts in designing the UAVs solar augmented power module system. Therefore, comprehensive work on the solar power system and its integration is essential for an excellent UAV performance. Thus, a research work has been done to studies on the design of a solar and battery power system for an electric UAV. Subsequently, a small solar powered electric UAV has been developed. As a result, the UAVs specification, layout and systems description are presented extensively in this paper. This UAV has enabled an understanding how the solar augmented system has enhanced the endurance performance the electric UAV to almost 24 hours. Moreover, this UAV has 5 successfully flight up till date with useful data that predicted this UAV aerodynamic characteristic.

Multidisciplinary Optimisation Framework for Minimum Rotorcraft Fuel and Air Pollutants at Mission Level

Helicopters play a unique role in modern aviation providing a varied range of benefits to society and satisfying the need for fast mobility. However, environmental concerns associated with the operation of rotorcraft have increased due to envisaged growth of helicopter operations. New rotorcraft designs, innovative aero engines and all-electrical systems, which may take decades to be in service, are being developed in order to diminish rotorcraft footprint on environment. However, since there is a large number of polluting rotorcraft that are in use and will only gradually be replaced, in the nearterm, improvements to minimise air quality degradation may also be possible from better use of existing rotorcraft by focusing on mission profile management. A multidisciplinary framework, intended to generate outputs for estimating rotorcraft block fuel burn and emissions, was developed. Outcomes generated with this tool were, subsequently, the basis to carry out a parametric study for assessment of light single-engine rotorcraft environmental impact, in terms of fuel burn and emissions. Single and multi-objective optimisation for minimum fuel consumption and air pollutant emissions was part of this research as well. Case studies were carried out varying flight parameters at every segment of a baseline mission profile. Single and multi-objective optimisation proved that favourable reductions in fuel burn of about 2% may be attainable at the expense of a slight increase in NOX emissions during the entire mission. If reductions of more than 3% in block fuel burn are to be achievable in the short term for a single helicopter, savings for air transport companies are expected to be significant if mission profile management is considered for a whole fleet of helicopters.

The GENUS aircraft conceptual design environment

The design of aircraft has evolved over time from the classical design approach to the more modern computer-based design method utilizing multivariate design optimization. In recent years, aircraft concepts and configurations have become more diverse and complex thus pushing many synthesis packages beyond their capability. Furthermore, many examples of aircraft design software focus on the analysis of one particular concept thus requiring separate packages for each concept. This can lead to complications in comparing concepts and configurations as differences in performance may originate from different prediction toolsets being used. This paper presents the GENUS Aircraft Design Framework developed by Cranfield University’s Aircraft Design Group to address these issues. The paper reviews available aircraft design methodologies and describes the challenges faced in their development and application. Following this, the GENUS aircraft design environment is introduced, along with the theoretical background and practical reasoning behind the program architecture. Particular attention is given to the programming, choice of methodology, and optimization techniques involved. Subsequently, some applications of the developed methodology, implemented in the framework are presented to illustrate the diversity of the approach. Three special classes of aircraft design concept are presented briefly.

Supersonic business jet conceptual design in a multidisciplinary design analysis optimization environment

This paper introduces a multidisciplinary design analysis and optimization (MDAO) environment called GENUS, which has been developing in Cranfield University’s Aircraft Design Group. The GENUS aircraft design environment has the feature of modular, expandable, flexible, independent, sustainable, and performable. This paper discusses the application of this environment to supersonic business jets (SSBJs), which are regarded as the pioneer for the next generation of supersonic airliners. Methodologies appropriate to SSBJ are developed in the GENUS environment. Mach plane cross-sectional area is calculated based on the parametric geometry model. PANAIR is modified to do automated aerodynamic analysis. Drag coefficient is corrected by Harris wave drag calculation and form factor method. NASA EngineSim is integrated for engine modeling. Carlson simplified sonic boom prediction method has been used for sonic boom signature prediction. Results of the Cranfield E5 SSBJ are presented. Low-boom and low-drag SSBJ designs can be explored based on the framework.