This paper looks at how the aerospace industry can achieve the Acare goal of greener manufacturing, maintenance and disposal. It looks further than merely reducing waste and eliminating hazardous materials and processes and suggests that the organisational structure of the industry will play an important role in facilitating a move towards such a goal. Greater co-operation or integration within the industry at all stages of the product life cycle chain is a fundamental requirement as individual companies run a risk of increasing the total environmental burdens if they concentrate solely on reducing their own impacts without considering the effect a change they make may have on other companies. The use of comprehensive environmental supply chain management systems and end of life plans can smooth the implementation of extended product responsibility and accelerate the benefits of greener manufacturing, maintenance and disposal.

This paper looks back on the designs and ambitions of ARA in resolving a long term acoustic noise problem which threatened ARA with closure. This paper today briefly looks back to the original issues but deals more fully with the later phases of a two phase project implementation and construction. ARA is now a truly ‘silent site’, where closure was once threatened, ARA has achieved the implementation of a bespoke noise reduction enclosure where 24-hour running has proved to be a reality. This paper looks at the design and construction phases, the ‘before and after’ noise footprints and at some of the financial benefits ARA has achieved.

The ARA transonic wind tunnel is sited on an industrial estate on the north west perimeter of Bedford. When it was first built it was on an original farm site with no appreciable residential houses in close proximity. Since the early 1950s there has been considerable residential development around the ARA site resulting in the local householders complaining about the wind tunnel acoustic noise. In early 1999 ARA was obliged to consider several options for noise reduction measures to reduce the noise to within UK government statutory requirements.

This paper deals briefly with the original noise nuisance characteristics and footprint, the noise reduction design and method that ARA selected and shows the construction phases, the further noise treatment ARA had to do on other major ancillary equipment to make ARA a truly quiet industrial site.

The paper shows how ARA has utilised the resulting benefits of these investments to increase productivity and reduce costs, and the influence it has had on ARA’s financial health.

This paper presents a simulation study of ion thruster plume effects on formation flying spacecraft. Two formation flight applications using micro-ion propulsion are considered: an L2-Halo orbit interferometer formation and a LEO micro-satellite formation. Worst case scenarios in both missions have been investigated. We focus our study on thruster configurations resulting in possible indirect plume impingement on satellites outside of the direct impingement zone. Indirect impingement which cannot be predicted except through plasma simulation or in-flight measurements might expose critical spacecraft elements such as optical sensors to a harsh contamination environment. A high-fidelity electrostatic plasma simulation code for parallel computing platforms was used in the study.

In our study, we found that using miniature scale ion propulsion in both formation missions creates a very low charge-exchange plasma environment which results in tolerable contamination environment for other spacecraft in the formation.

Commercial transport aircraft developed today are defined to balance all requirements foreseen for the short or medium term. Best engineering knowledge as much as minimum business risks consistently lead to the so-called ‘classic’ aircraft configuration. This balanced approach is efficient but can also inhibit innovative practices.

Ensuring a sustainable growth in the aviation sector may require radical changes in the way we design and operate aircraft. Started in April 2005, NACRE is a four-year European research and technology integrated project, partly funded by the European Community under the Sixth Framework Programme, which aims at integrating and validating technologies that will enable the potential of new aircraft concepts to be assessed.

In order to explore the most relevant capabilities and meet the widest range of challenges, the NACRE R&T project has identified a set of concepts tailored to address specific subsets of design drivers:

• • The Pro-Green aircraft concepts putting a major emphasis on the reduction of environmental impact of air travel;

• • The Passenger-driven Aircraft concepts aiming at optimised payload and appreciable quality of future aircraft for the end users;

• • The Simple Flying Bus, which puts the biggest emphasis on low manufacturing costs and minimum cost of ownership.

Irrespective of what final future product configurations might ever look like, the NACRE aircraft concepts act as basic vectors, encompassing all the expected capability developments. The general project objectives are thus to use these concepts in order to:

• • Explore alternative routes for the major aircraft components (fuselage, wing, engine integration) better suited to their specific targets and which would have been rejected in a balanced approach;

• • Provide better answers to the full range of requirements by developing and, in some cases, validating the associated envelope of innovative component designs and associated technologies.

NACRE is by essence a focused multidisciplinary approach. It does not concentrate on one specific aircraft concept, but it is aimed at developing solutions at a generic aircraft component level, which will enable the results to be applicable for a range of new aircraft concepts. For each of the major aircraft components, the multidisciplinary investigations will require an exploration of the different associated aspects of aerodynamics, materials, structure, engines and systems with the goal of setting the standards in future aircraft design, thus ensuring improved quality and affordability, whilst meeting the strengthening environmental constraints (emissions and noise), with a vision towards improving significantly the global efficiency of the air transport system.

As civil aviation expands, environmental aspects and fuel savings are becoming increasingly important. Amongst technologies proposed for more efficient flight, air-to-air refuelling (AAR), ‘hopping’ and flying in close formation (drag reduction), all have significant possibilities. It will be interesting to know also how these technologies may co-exist e.g. AAR and formation flying.

In military use, AAR is virtually indispensable. Its benefits are real and largely proven in hostile and demanding scenarios. We present a case for applying AAR in a civil context to show that substantial reductions in fuel burn for long-range missions are achievable. Overall savings, including the fuel used during the tanker missions, would be of the order of 30-40% fuel and 35-40% financial. These are very significant in terms of the impact on aviation’s contribution to reducing atmospheric pollution.

AAR allows smaller, efficient (greener) aircraft optimised for about 3,000nm range to fulfil long-range route requirements. This implies greater usage of smaller airports, relieving congestion and ATC demands on Hub airports. Problems due to shed vortices and wakes at airports are reduced. Smaller engines will be needed.

Integrated (accepted) AAR could lead to further benefits. Aircraft could take-off ‘light’, with minimum fuel and reserves and a planned AAR a few minutes into the flight. The ‘light’ aircraft would not require over-rating of the engines during take-off and would therefore be less noisy during take-off and climb-out, permitting more acceptable night operations.

The availability of civil AAR will enable opportunities for hitherto borderline technologies to be utilised in future aircraft. Laminar flow will provide fuel savings and increased efficiency in its own right but could be significantly enhanced within a civil AAR environment. Similarly, supersonic transport may become an acceptable economic option.

AAR affords the possibility of a complete widening of the design space and this should appeal to the imagination of current and future designers.

In an effort to reduce the negative impact of civil aviation on the human environment, trajectory optimisation techniques have been used to minimise the single event impact of noise and gaseous emissions of departures on communities in the vicinity of airports. For this purpose, the earlier developed trajectory optimisation tool NOISHHH has been adapted to design departure trajectories optimised for environmental criteria, based on area navigation. The new version of NOISHHH combines a noise model, an emissions inventory model, a geographic information system and a dynamic trajectory optimisation algorithm to generate flight paths with minimised environmental impact. Operational constraints have been introduced to ensure that the resulting flight paths are fully compliant with the guidelines and regulations that apply to the design of standard instrument departures and the use of area navigation. To illustrate the capabilities of the new version of NOISHHH, two numerical examples are presented, which are both redesigns of standard instrument departures currently in use at Amsterdam Airport Schiphol.

Commercially-driven air traffic management (ATM) innovations typically aim to increase air space capacity and/or reduce delays. Here, their potential application for environmental mitigation is discussed. Both carbon dioxide (CO2) and non-CO2 climate impacts are considered, as are noise and air quality issues. We outline the technological, scientific and political barriers to an integrated approach to applying ATM technologies to environmental mitigation. These issues highlight the need to improve comparison and prioritisation of the emissions and effects of aviation.

Aviation emissions have an impact on the global climate, and this is consequently an active area of research worldwide. By adapting replicable and transparent systematic review methods from the field of evidence-based medicine, we aim to synthesise available data on the effects of aviation emissions on climate. From these data, we aim to calculate lower and upper bounds for estimates of the effect of aviation on climate in an objective manner.

For the systematic review an appropriate protocol was developed and applied by two independent reviewers, to identify research that met the inclusion criteria. These included all aviation types, original research studies, climate models with aviation as a specific component, with outcomes for emissions, radiative forcing, global warming potential and/or surface temperature changes. These studies were prioritised and data extracted using a standard process. The 35 studies reviewed here reported radiative forcing, global warming potential and/or temperature changes as outcomes, allowing direct comparisons to be made.

Tabulated results and a narrative commentary were provided for overall effects on climate, and the individual effects of carbon dioxide, water, contrails, cirrus clouds, ozone, nitrogen oxides, methane, soot and sulphur oxides. Lower and upper bounds for these effects, and their relative contributions compared to overall radiative forcing and surface temperature changes, have been described.

This review shows that the most recent estimates for the contribution of aviation to global climate are highly dependent on the level of scientific understanding and modelling, and predicted scenarios for social and economic growth. Estimates for the future contribution of aviation to global radiative forcing in 2015 range from 5·31% to 8·04%. For 2050 the estimates have a wider spread, from 2·12% to 17·33%, the latter being for the most extreme technology and growth scenario. These global estimates should be considered within the context of uncertainties in accounting for the direct and indirect effects of different contributions. Variations between lower and upper bounds for estimates of radiative forcing are relatively low for carbon dioxide, around 131% to 800% for cirrus clouds effects, and 1,044% for soot. Advances in climate research, particularly in the area of contrail and cloud effects, has led to some revision of the 1999 IPCC estimates(1), and demonstrates that the research community is actively working to further understand the underlying science.

The approaches assumptions, limitations and future work were discussed in detail. We have demonstrated how the systematic review methodology can be applied to climate science, in a replicable and transparent manner.

We set a target for a ‘Silent’ aircraft to be imperceptible outside the airfield perimeter in an urban environment, and then address conceptual designs to meet this requirement. Avoiding some traditional aircraft noise sources requires a radical rethink about the configuration. An all-lifting design has many benefits, enabling a closer integration of airframe and engine than the traditional ‘tube and wing’. Low-noise design includes taking advantage of shielding of engine noise by the airframe; low-noise engines with large, low speed jets; an order of magnitude increase in absorption by liners; and operations for low-noise informing the design. Progress to date on the Silent Aircraft Initiative is presented, along with some conceptual aircraft and engine designs. The further work needed to develop these into viable future aircraft is discussed.

Consideration of the environmental impact of aircraft has become critical in commercial aviation. The continued growth of air traffic has caused increasing demands to reduce aircraft emissions, imposing new constraints on the design and development of future airplane concepts. In this paper, an aircraft design optimisation framework is used to design aircraft that minimise specific environmental metrics. Multidisciplinary design optimisation is used to optimise aircraft by simultaneously considering airframe, engine and mission. The environmental metrics considered in this investigation are CO2 emissions — which are proportional to fuel burn — and landing-takeoff NOx emissions. The results are compared to those of an aircraft with minimum direct operating cost. The design variables considered in the optimisation problems include aircraft geometry, engine parameters, and cruise settings. An augmented Lagrangian particle swarm optimiser and a genetic algorithm are used to solve the single objective and multi-objective optimisation problems, respectively.

Boundary-layer noise produced by rough surfaces is a potential contributor to airframe noise. In this paper, an attempt is made to assess the surface roughness noise for a conceptual Silent Aircraft design SAX-40 using a prediction model described in previous theoretical work (Liu and Dowling(12)). Estimates of three idealised test cases show that surface roughness could produce a relatively high noise level and enhance the trailing-edge noise somewhat. Roughness height and roughness density are two significant parameters which affect surface roughness noise, with roughness height having the more dominant effect. The distribution of roughness noise sources decreases in the streamwise direction on the SAX-40 surface. Two candidate rough surfaces are selected for SAX-40 to keep surface roughness noise at a negligible level and to meet an aggressive noise target.

An integrated parametric model involving the design of propulsion system, airframe and flight mission is presented. Based hereon, the carbon dioxide (CO2) emission characteristics of advanced direct-drive turbofan and open rotor powered aircraft are analysed against pertinent aircraft and propulsion system design parameters. In addition, initial concept-specific trend statements on nitrogen oxides (NOx) as well as propulsor noise emission characteristics are derived. The obtained results contribute to a better understanding of more appropriate aircraft design attributes for advanced system architectures.

This paper presents the results of a study conducted at the Laboratoire de recherche en commande active, avionique et aéroservoélasticité, École de technologie supérieure, regarding the costs in fuel burn and pollutant emissions corresponding to a flight profile determined by a missed approach procedure. The evaluated missed approach flight profile starts at the point where the missed approach decision is made and ends at the same point, after the aircraft completes the missed approach procedure.

This study uses the fuel burn and pollutant emissions data for a Boeing 737-400 aircraft (chosen at random for this study), published by the European Environment Agency, and the standard flying cycle model elaborated by Group 08 of the Task Force on Emissions Inventories and Projections – a task force created by the United Nations Economic Commission for Europe (UN ECE)/the co-operative program for the monitoring and evaluation of the long-range transmission of air pollutants in the Europe (EMEP). The missed approach fight profile is based on the Area Navigation/Required Navigation Performance procedure for runway 13R of the King County International Airport/Boeing Field (BFI) in Seattle.

Four study cases are considered for the missed approach flight evaluation. These cases correspond to four navigation profiles – a combination of two lateral navigation profiles, one with a 20 nautical miles holding pattern and the other without, and two vertical navigation profiles. The results obtained for the missed approach flight profiles, in terms of fuel burn and emissions, are compared with the fuel burn and emissions reference data corresponding to a standard approach procedure and complete flights (from taxi out to taxi in).

Modern gas turbine combustor design is a complex task which includes both experimental and empirical knowledge. Numerous parameters have to be considered for combustor designs which include combustor size, combustion efficiency, emissions and so on. Several empirical correlations and experienced approaches have been developed and summarised in literature for designing conventional combustors. A large number of advanced technologies have been successfully employed to reduce emissions significantly in the last few decades. There is no literature in the public domain for providing detailed design methodologies of triple annular combustors.

The objective of this study is to provide a detailed method designing a triple annular dry low emission industrial combustor and evaluate its performance, based on the operating conditions of an industrial engine. The design methodology employs semi-empirical and empirical models for designing different components of gas turbine combustors. Meanwhile, advanced DLE methods such as lean fuel combustion, premixed methods, staged combustion, triple annular, multi-passage diffusers, machined cooling rings, DACRS and heat shields are employed to cut down emissions. The design process is shown step by step for design and performance evaluation of the combustor.

The performance of this combustor is predicted, it shows that NOx emissions could be reduced by 60%-90% as compared with conventional single annular combustors.

Space debris represents a significant risk to satellite operations, due to the possibility of damaging or catastrophic collisions. Consequently, many satellite operators screen the orbiting population for close approaches with their on-orbit assets and a public conjunction assessment service, Satellite Orbital Conjunction Reports Assessing Threatening Encounters in Space (SOCRATES), generates close approach predictions on a daily basis for all satellite payloads in the catalogue. These screening capabilities are used to inform operational decisions relating to risk mitigation but it is anticipated that the demands placed on these services will increase as debris becomes more prolific. This hypothesis is explored in a preliminary analysis of conjunction data for the years 2004 to 2009 and a new ‘Business as usual’ study using the Debris Analysis and Monitoring Architecture for the Geosynchronous Environment (DAMAGE) model. The results suggest a 50% increase in the number of close approaches reported by SOCRATES (or its equivalent) within the next ten years. By 2059, daily conjunction reports could contain over 50,000 close approaches below 5km, affecting the demands placed on tracking facilities and satellite resources.

This paper contributes to the prediction of aircraft noise. The framework of our study is based on a comprehensive analysis, which includes sub-models for airframe, propulsion and propeller noise. The sources models are complemented by various accounts of interference phenomena, including fuselage scattering, propeller shielding, wing and flap effects. The propagation of the acoustic pressures from the noise sources is done through a number of additional sub-models, which include spherical spreading, Doppler effects, ground reflection, shear winds and temperature gradients through the atmosphere. We present some fly-over noise data. The data include measurements by 13 microphones at community locations, meteorological data, and flight recorder data packs, which provide the complete state of the aircraft along the noise trajectory. Examples of verification are shown for the turboprop airplane Dash8-Q400, both on approach and departure. A sensitivity analysis is carried out to investigate the importance of the uncertainty effects, which are split between internal (aircraft and propulsion), external (atmospheric environment), and aircraft position.