On Board Future Flights

The Future of Aerospace Engineering

Syed Ali Noor Haider

Eilaf Media Services

On Board Future Flights

The Future of Aerospace Engineering

First published 2015by Eilaf Media Services

113 London RoadMorden

Surrey SM4 5HP

Printed in the United Kingdom

2015 Syed Ali Noor Haider

All rights reserved. No part of this book may be reprinted or reproduced or utilized in any form or by any electronic , mechanical ,or other means,

now known or hereafter invented including photocopying and recording, or any information storage or received system

without permission in writing from the publisher.

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To all those daring people who imagine heights of excellence,float ideas no matter they fly or fall and make inventions by

questioning the conventions.

And to those

Who enjoy science by treating it as an integral part of every day life and not an alien from skies.

And to those

Who believe in sharing knowledge of science in simple words understood by everyone.

· Introduction 1

· Why New Designs 6

· All On Board For A Better Future 13

· Concept Future Planes 32

· Hypersonic or Hallucination 36

· Determining the Direction 49

· Bibliography 52

Contents

Acknowledgments

I am truly grateful to following for providing me an opportunity of interview and giving me insight into the future of aerospace engineering :

Dr Guy Gratton, Head of FAAM, Facility for Airborne Atmospheric Measurements, Cranfield University.

Dr Mark Jabbal , Lecturer in Aerospace Engineering, Brunel University London.

Dr Oliver Buxton, Lecturer in Aeronautical Engineering at Imperial College London.

Dr Paul Bruce Lecturer in Compressible Aerodynamics at Imperial College London.

Mr Micheal Roberts , Research Supervisor , Ashcroft Technology Academy. London.

My very special thanks to Dr Guy Gratton for providing me an opportunity to observe systems of an aircraft at FAAM.

Thanks to library staff of Imperial College London to allow me access to books and journals.

And my very deep gratitude to my father Syed Shakeel Haider and my mother Syeda Sultana Rizvi who provided me an opportunity to travel extensively and always encouraged my curiosity about air planes.

Introduction

0“Welcome aboard flight Hs - Uav - Eco – Ul- 360 View. Ladies and gentleman this is a Hs - hypersonic flight, so cruising at a speed five times that of sound our flying time from London to New York will be just 90 minutes. This is an UAV- an unmanned aerial vehicle – so there are no pilots to fly this plane, however our bionic crew will be at your service during the entire duration of flight. Being an environmentally friendly aircraft, it is operated completely by solar and wind energy with no noise and Carbon emissions. To give you a unique opportunity

0of 360 view – looking out from all sides of plane- it is made up of Ul- ultralight transparent material, so don't forget to look down from the floor of plane, when we fly over the Statue of Liberty on our descend to New York. If you are uncomfortable with heights, you can block your view by pushing a button on your left side to turn your surroundings opaque. Your flexible seats are madeup of fusion of plant material with self-cleaning, biodegradable non- flammable plastics that could be adjusted according to your body shape. …………..”

Time is not far when you might be hearing this kind of announcements from the computer generated voice of bionic crew while boarding a hypersonic passenger plane or while attaching your personal travel capsule to a big flying machine. You may experience some or all of these features at your flight in near future. There may be possibilities of even more fascinating and dramatic features in the future that might put these features to shame. Thanks to the ever innovative aerospace engineering and technology that is turning dreams after dreams to reality at a superfast rate.

The prophetic vision of Thunderbirds- a British television series of 1960s about the hypersonic (flying at least 5 times faster than speed of sound) vehicles in the setting of 2065 might come true even earlier if aerospace researchers and manufacturers continue to overcome technological constraints by taking bold steps. Mankind, after experiencing supersonic travel with the advent of Concorde, though not operational at the moment, is waiting to enter an era of hypersonic travel. Daring experiments and huge investments are helping the new

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ideas fly with greater thrust to break away constraints. Aerospace technology is constantly spinning upwards to hit new frontiers, on the way picking up innovation in other fields and integrating the best practices to achieve heights of excellence.

After fulfilling the centuries old dream of mankind to fly, aviation industry is pursuing new dreams of making flying machines faster, safer, comfortable and economical and less damaging to natural environment. In these pursuits it is taking advantage from research and development in other disciplines which are not only traditionally allied to this area like physics and mathematics but also from fields of chemistry, biology and material sciences, information technology and many other from a diverse range of disciplines .

Developments in one field of science open doors for another one. Who knows a breakthrough in mechanics or an invention in material sciences may bring a quantum leap and shrink the journey of decades to matter of years for launching aircraft with hitherto unseen features. You may be travelling in a plane covered with a skin full of cooling gases in its capillaries to offset heat generated by flying on high speed. An aircraft wrapped up in artificially produced fish scales won't be surprising and so would be the possibility of systems attached to the aircraft, that could convert heat created by friction to energy required for operating different systems of an aircraft.

Air and space travel have remained fascinating for people of all ages and all age groups. All of us wish to be seated on a window seat to enjoy view from the top and feel happy to see the vast ness of sky. This has been made possible by the man- made flying machines. These fascinating flying machines require immense thought and ingenuity, to be designed, developed, manufactured and maintained.

In today's world air travel is most desired and compatible mean of transportation to keep abreast with the fast pace of life. Air travel not only enables quick connectivity in the globalized world it is also considered one of the safest means of transport with your chances of getting involved in accident 1 in 11 million.

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The transport of freight is also becoming important in the context of present day dynamics of global economy, which is heavily dependent on trade. Fighter jets and reconnaissance planes are important for security and defence as much as the space ships for exploring the universe and scientific research. Nowadays, we are hearing of space tourism also emerging as new class of travel with Virgin Galactic carrying out test flights to send tourists in space with in coming few years.

Flying machines have evolved at a faster pace and within little over hundred years since Wright brothers first experienced powered flight in 1903 and commercial air boat operated in 1914, both air and space ships and airline industries have seen marvellous achievements. Its not only the centuries old dream of flying on wings that has been realized, creativity and innovation has led to opening up of hitherto un -imagined frontiers of air and space travel.

The fast growth in air travel has led to expansion of air fleets but it is not devoid of negative impact on natural environment. Negative environmental impact from air travel is caused by Carbon emissions, and contrail formations. Contrails are frozen droplets of vapours emitted by planes flying on high altitudes which become frozen due to low temperature and remain suspended in upper atmosphere. These frozen particles obstruct heat from earth to escape thus add to rise in temperature. The environmental impact caused by air travel has raised concerns among people and world regulatory bodies. Targets have been set by various world bodies to reduce environmental impact from air transportation.

Aviation industry due to its commercial nature aspires for greater profits through the airplanes that are faster, safer, comfortable and economical - consume less and inexpensive fuel. These objectives can be achieved through better efficiency and performance of aircrafts. Aerospace engineering and technology faces a task of introducing changes in the designs of aircraft aimed to decrease carbon emissions and contrail formation as well as increase efficiency and performance of the aircraft to gain greater profits.

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A need to further increase speed of aircraft and decrease negative environmental impact have emerged as highly influential among other factors regarding the future course of aerospace engineering and technology. Researchers and manufacturers are now taking benefit from other fields of knowledge. They are aiming to improve engines, wings, and materials besides tapping sources of alternative fuel that is less expensive and yields less carbon emissions. Developments in the fields of chemistry, biology, information technology and environmental technology , hand in hand, with disciplines traditionally used in aircraft manufacturing like physics, mathematics and engineering , are making it possible to the aerospace industry to break the frontiers.

Interestingly inspirations are being drawn from the nature to design aircraft with an objective to protecting the nature. The aerospace industry has come on the forefront to protect environmental impact. It will not be wrong to assume that the future of aerospace technology is tied up with synthesising developments in other fields of science and technology, with a view to develop aircraft designs that will fulfil the requirements of profitability as well as environmental protection.

Like any other child, I was always carried away by the flying objects in the early years of my life. While growing up with a chance of travelling overseas, my observations about the aircrafts and flying added to my curiosity about flying machines. While studying at A levels I carried out research on the future of Aerospace Technology. Taking advantage of living in London I managed to get access to material in the library of Imperial College London and interviewed professors of Imperial College and Brunel University. I also had an opportunity to board a modified aircraft at the Facility for Airborne Atmospheric Measurements (FAAM) at Cranfield University when I visited to interview Dr Guy Gratton, the head of facility.

The astonishing developments in air travels made my research an enjoyable experience to me and I was able to achieve an A* in my extended research project on the topic 'Influence of Environment on the Future of aeronautical Technology' an area of research, which many people would think as a highly technical one. But I think many complex

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and technical ideas can be explained in a very simple way. As we grow up we want to know about many things that either interest us or effect our lives but are shy to read or ask about them presuming they would be too technical.

While travelling by air many of us want to know about air crafts and how they are designed and function and what kind of developments are on the way for aircraft in future .This realization encouraged me to share knowledge I have gathered about the future of aerospace technology with people who may or may not have studied engineering and technology and would like to know about the future developments in this field in simple words. In this book I have tried to look at the future of aerospace engineering and technology through the lens of considerations such as economic and environmental factor that influence the design and specifications of aircraft. Though the focus of this book remains on the civil aviation and future of passenger planes I have touched upon developments in military and space ships where they are relevant, because generally speaking developments in flying machines for defence and space often lead ways to improvements in civil aircraft.

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Why New Designs

New designs for flying machines are sometimes motivated by intellectual curiosity of engineers and researchers but most of the times they emerge to fulfil different needs like defence and security, scientific research, and most commonly fast transportation of people and goods. The improvements n designs are more often driven by the demands of buyers and to overcome challenges posed by the current designs.

In this part we will first have a bird's eye view of current scenario and challenges in the realm of civil aviation and then cruise through the importance of design in performance and efficiency of aircraft and the direction in which the aerospace engineering is heading to achieve objectives of new designs in the given context.

Current Scenario and Challenges

An ever increasing demand of air travel has generated greater interest in the future of aerospace engineering and manufacturing. It has become

stthe most prevalent form of transport in the 21 century and continuing to experience the fastest growth among all modes of transport. The number of aircraft in use is consistently rising to accommodate an ever growing number of passengers and amount of freight. The world population will have nearly doubled by 2050 and annual reports of International Air Transport Association (IATA) reveal that with an average growth of 5% per year roughly 9 billion people will need and want to travel by air.

Today, over 1,000 commercial airlines operate more than 26,000 airliners, carrying 3.1bn people and 51.7m tonnes of freight every year.

Whilst buying a new pair of shoes you always think about the criteria to match your requirements. Whether it be for the job, sports, parties, casual walking or simply aesthetics, no matter what the usage be, there are always a few things that are always given consideration such as price and comfort. Designers develop new products keeping in mind what the consumers’ desire.

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Aircraft operators and manufacturers expect that the current fleet in service will be replaced and 17000 additional aircraft will be added by 2025. Focusing on the 2014-2033 time frame the Global Market Forecast (GMF) by Airbus industry reconfirms the continued upward trend in the aviation market and forecasts a need for over 31,000 new passenger and freighter aircraft in this time period.

With air travel increasing at an enormously high rate the negative environmental impact doesn't remain hidden from any one. Among various goals and targets set by the European and American regulatory bodies, one is 50% reduction in CO emission by the year 2020. Dr Paul 2

Bruce, senior lecturer and researcher in high speed aircraft, at the Imperial College London stated in personal communication “The future of aeronautical technology is about having a step change quite soon. If we need to achieve emission targets set by EU and American agencies changes need to be carried out soon. Some radical changes need to be made in a decade or two. The conventional aircraft shapes and the way of operating has to be changed” and “There is a tag line to meet these targets,” he added.

Increase in air travel is associated directly with the environmental impact due to carbon emissions and contrail formation caused by flying current forms of aircraft. Contrails are frozen droplets of vapours which are formed due to aircraft flying at high altitudes where temperatures are significantly low. The costs of flying aeroplanes, both in economic and environmental terms, are huge due to the dependency on fossil fuels, which is not only expensive but also adds heavily to carbon emissions.

The challenges for the aviation industry are therefore improving the performance and efficiency of aircraft to achieve sizeable reduction in Carbon foot print and also to manage air traffic in a way as to reduce contrails which remain suspended in upper atmosphere for days and block the escape of heat from the earth's atmosphere, thus adding to global warming.

In this context environmental considerations have started to have a greater influence on the future aircraft design as it is becoming an

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important issue in the wake of targets set by world bodies. These challenges and targets nudged the aeronautical industry to bring a clean, safe and highly efficient system through good design, new technology and innovative business.

In the wake of environmental impact becoming an important factor a future aircraft will need to be much more efficient with radical approaches to engines, airframes and avionics,. The future economic and environmental forces are likely to become strongly aligned in favour of minimizing energy liberated to revenue work ratio (ETWR) which among other factors depends upon the amount of fuel burned to carry a given payload to a given distance.

What Determines Design

The design of aircraft and spaceships is central to aerospace engineering and manufacturing. Developments and modifications in design are required to meet newly emerging demands and overcoming challenges. Design revolves around intellectual engineering process of creating on paper or on a computer screen, a flying machine to meet certain specifications or to pioneer innovative new ideas and technology. Designs of most of the commercial airliners as well as cargo and military aircraft evolve in response to specifications required by the operators. In order to guarantee the successful sales of an aircraft the marketing departments of all major aircraft manufacturers produce yearly reports about the demands.

Aerospace technology is connected with profit driven aviation industry via manufacturers. Aircraft manufacturers spend huge sums of money to develop designs aimed at meeting demands of the aviation industry, mainly, enhancing aircraft performance and efficiency (which may be called eco-efficiency due to environmental considerations) by increasing cruising speed, passenger/load capacity, aircraft endurance (range) and reducing fuel consumption because all aircraft operators desire to increase efficiency, cost-effectiveness, environmental compatibility and safety.One big consideration, therefore, in the design of any aircraft is the fuel consumption because the physical structure of an aircraft affects the

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fuel consumption, similarly engines determine the kind and quantity of fuel to be used. To reduce environmental impact, fuel efficiency of an aircraft plays an important role and it can be achieved through many ways including, improving engines, aerodynamics through shape and configuration of body and wings, using light material for aircraft manufacturing and addressing operational aspects of optimal payload.

In recent years environmental concerns have compelled aeronautical technology to develop environment friendly aircraft in order to reduce the negative environmental impact caused by air travel. Eco-efficiency has been proposed as one of the main tools to promote sustainability of air travel. It is based on the concept of creating more goods and services while using fewer resources and creating less waste and pollution. Manufacturers and academic researchers are collaborating to achieve these goals.

Performance and Efficiency

You must have watched birds and insects flying. The beautiful quick movements of colourful wings of butterfly in a garden can make people feel happy but a quick dive of a seagull snatching away chips from the plate just bought from a kiosk at Brighton Marina may leave you angry and frustrated. It can also trigger a thought about smart moves of an apparently innocent bird, which are achieved through accuracy and manoeuvrability of its flight which involves not only the sharp vision of bird but more importantly the precision of moves and control over wings. It is precisely this capability of control over speed and manoeuvrability of movements that is about performance of a flight. In man-made flying machines performance and efficiency play a very big role with regard to purpose of aircraft. When we talk about civil aviation, profits take a central place as airlines look to maximise profits through better performance and efficiency of an aircraft. Whereas aviation authorities and regulatory bodies emphasize efficiency in order to protect the environment along with other factors such as safety.

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Performance and efficiency or eco-efficiency of an air craft are affected by its weight and drag. Drag is the resistance experienced by an air craft when it flies in air. The fuselage of an aircraft and its weight are two main factors for the drag. Wings on the other hand keep the aircraft floating in the air push it forward with the help of power from engines. Greater the drag on an air craft harder it is to move forward leading to more fuel consumption. New designs of aircraft are therefore concerned with minimising drag through different measures: including different sizes and configurations of wings and fuselage as well as use of new lighter materials for manufacturing of aircraft.

On the side of eco –efficiency alternative fuels like hydrogen, solar energy; advancement in engines to gain maximum fuel efficiency; and flight management to maximize eco-efficiency of aircraft in operations are being emphasized currently as well as for the future flights. Dr Oliver Buxton, senior lecturer of Aeronautical Engineering at the Imperial College London stated in a personal communication “The economics dictate that reducing fuel consumption and operating costs is paramount to modern aircraft designers.” Performance and efficiency are pivotal to air operations but eco- efficiency is much more relevant to environmental impact.

Performance is a statement of capabilities of an aircraft which are selected according to specifications for various categories such as transport, military and passenger aircraft. Several performance factors feature in every such selection. From technical point of view, at the design stage performance features serve as design criteria and as desirable objectives for the designers and engineers. In terms of marketing, sales staff quote the performance features as the basis for commercial strength of the emerging aircraft. Design of an aircraft is centred on a statement of performance according well renowned researcher M E Eshelby in his book ' Performance : Theory and Practice'.

Performance is stated in terms of quantities such as the direct operating cost (DOC); maximum range of pay load and fuel load; cruising speed; airport requirements for landing and take-off and the aircraft design which involves an integration of several different technologies and may

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often be improved by changes in

- aerodynamics- structures- materials- power plants- Systems, etc.

Efficiency of an aircraft relates to operating costs and environmental impact. Fuel efficiency of an aircraft relates directly to the distance it can fly, the amount of payload it can carry and more importantly better environmental performance which means less carbon emissions. Eco-efficiency has been proposed as one of the main tools to promote sustainability of air travel. It is based on the concept of creating more goods and services while using fewer resources and creating less waste and pollution.Fuel consumption can be reduced by reducing drag and weight of an aircraft by improving aerodynamics and using lighter materials. In order to minimize drag aircraft designers ensure that the aircraft is as streamlined as possible. Technologies such as wing tip devices and creating wings with a high aspect ratio are being used to achieve these objectives. In terms of reducing weight lighter metal alloys and more recently composite materials can help in reducing environmental impact. It can also be said that by reducing the drag on an aircraft less energy is needed to push the aircraft through the air, therefore requiring less fuel and less powerful, lighter engines.

Aircraft engines play significant role in determining an aircraft's fuel efficiency according to Beginners' Guide to Aviation Efficiency. There is a constant drive to design new engines with an improved efficiency. The introduction of the turboprop engine in the 1940s was seen as a major step-change in terms of power output, efficiency and reliability over older piston engines.

Although the turboprop technology was overtaken by the new turbofan technology an interest in them has resurfaced in recent years largely due to their economic and environmental benefits. A modern turboprop engine can consume 25-40% less fuel than an equivalent turbofan

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engine on short haul flights. Despite the advantages of turboprop engines they are only limited to short haul flights meaning that turbofan engines currently are and will be dominant as a means of aircraft propulsion.

Research and improvements in turbofan engines are on-going and their efficiency has been significantly enhanced through technologies like high-bass ratio engines. In the view of Dr Bruce, “Engines are important and more than half of the efficiency gains came from engines over the past few decades.” Another feature that can provide 10-15% reduction in energy liberated to work ration (ETWR) is use of open-rotor propulsion that can also help reducing environmental impact. This scenario requires much more change in the aircraft designs to enhance performance and eco- efficiency of the future aircraft.

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All on Board For A Better Future

You may or may not be aware of the fact, that despite rising fuel prices costs of operating air transport have come down in past 40 years. This was made possible due to more efficient engines and wing designs and better management of flight operations. But the consequent reduction in emissions have been offset by increase in air transport, giving rise to meet new challenges for air travel in future.

In response to ever increasing environmental concerns, the aeronautical industry is responding by improving the features of aircraft in order to make them more cost effective and environmentally friendly besides getting faster and safer. In the last 40 years some major advancement have taken place in aeronautical technologies aiming at reducing operation costs, optimizing performance and increasing eco-efficiency, which, as indicated by Annual Airbus Consumers Reports, resulted in an estimated 70% reduction in aircraft fuel burn and emissions and a 75% reduction in noise. Despite these major reductions, environmental impact due to CO emissions and contrails persist because of the growth 2

in air transport.

Developments in aircraft designs serve as an evidence that to meet the challenge of reducing CO emissions through fuel efficiency, research 2

in aeronautical engineering and technology has taken a turn towards introducing step changes in aircraft designs. This notion is supported by projections made by Joseph Lee in his M.Eng dissertation for MIT (2000), where he asserts that if the demand for air travel continues to grow by 5% it will surpass the current capability of emissions reductions through improvements in technology, this necessitates drastic technological improvements and step changes in a very short term to stabilize or reduce aviation emissions by 2050.

Aeronautical engineering and technology is taking a direction to improve performance and eco-efficiency of future aircraft with a view to make them more eco-efficient thus more environmentally friendly. Aeronautical industry is moving fast to introduce changes by using lighter materials, alternate fuels, revival of older designs; blended

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wings; new wing technologies advanced engines and making use of developments in other sciences.

Use of Alternative Fuels

In future you may find yourself boarding an aircraft that would fly on solar energy absorbed and stored by ultralight solar cells. You may find wind turbines attached to the body of an aircraft converting high velocity wind experienced by air craft to supply power for full operation or partially substitute the power needs. At present aircraft use huge amounts of Kerosene oil, a non- renewable fossil fuel which emits CO 2

upon combustion. Aviation industry is being tuned around to cut down on the use of fuel through better designed aircraft which are more efficient and also to utilize alternative sources of energy.

A need for alternative fuels has brought chemistry and environmental sciences much more closer to aerospace engineering. As research and development is taking place to make hydrogen, solar power and biofuels compatible to jet engines, at the same time aircraft designs are being modified to enable use of alternative fuels that are not only sustainable from environmental point of view but also economically viable. Airbus claims to be one of the first companies in the aviation that saw a need for action in the development of alternate fuels.

Sustainable aviation fuels produced from renewable resources can reduce CO emissions by up to 80% per tonne of fuel. Finding 2

sustainable fuels that can be produced in commercial quantities (without competing with food crops and water supplies) is considered as medium-term alternative to fossil fuels in order to power large commercial jetliners in the future. Alternative fuels have powered around 1,500 commercial flights till 2014. It is believed that up to a third of aviation fuel could come from alternative sources by 2030.

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Solar power

A completely solar-powered Swiss airplane Solar Impulse 2 (SI2) had completed a 26 hour flight running 100% on solar power in 2013. It has embarked on round-the-world journey in early March 2015. The plane

thcompleted first leg of its journey on 9 March 2015 without any other kind of fuel. The carbon fiber single-seater Solar Impulse 2 aircraft has a 72-meter wingspan, which is longer than the wingspan of a Boeing 747, and weighs about as much as a car. There are 17,000 solar cells built into the wings to harness the sun's energy, allowing it to fly through the night.

The Si2 a brainchild of two Swiss scientists, Bertrand Piccard and Andre Borschberg took 12 years to build. Bertrand Piccard who also made the first non-stop circumnavigation of the globe in a balloon in 1999, told Reuters news agency in January 2015 "Miracles can be achieved with renewables such as solar power, we want to show we can fly day and night in an aircraft without a drop of fuel.'' The aircraft's route includes stops in Oman, India, Mandalay, Myanmar and China. After crossing the Pacific Ocean via Hawaii, the plane will also make up to three stops in the U.S., touching down in Phoenix, Arizona and New York City, and possibly another location depending on weather.

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At the moment even best possible solar cells are about 50% efficient and due to the extremely large area of solar cells required to provide power, research is needed to develop light weight and more efficient solar panels and batteries. Despite this solar technology in its current form can be used to power unmanned and light military reconnaissance planes. The future planes will be taking greater advantage from solar energy once more efficient cells are developed.

Fuel Cells

Hydrogen has a huge advantage over use of kerosene as the emissions of a hydrogen engine are only water. However the current problem with hydrogen is that it is too space consuming and requires a lot of energy to produce. To solve this problem fuel cells are being developed. A fuel cell transforms chemical energy from a fuel, such as hydrogen, into electricity through a chemical reaction with oxygen, or another oxidizing agent. The only waste is water, heat and oxygen-depleted air, which would contribute to reductions in emissions and noise when applied aboard an airliner.

Water produced from this process also can be used by the aircraft's water and waste systems, so reducing the amount of water an aircraft

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needs on board which in turn also decrease fuel consumption and emissions. In 2008, Airbus, DLR and Michelin performed flight evaluations of a fuel cell emergency power system on a test bed A320. The fuel cell was installed on a cargo pallet and produced 25 kW of electrical power – operating the electric motor pump for the aircraft's back-up hydraulic circuit, and controlling the spoilers, ailerons and elevator actuator.

Biofuels

Advancements in biofuels are being picked up by air transport industry as with an openness in approach it utilizes developments from the other fields of sciences for its own strengthening. Sustainable aviation fuels produced from renewable resources can reduce CO emissions by up to 2

80% per tonne of fuel. Annual Airbus Consumers Reports reveal alternative fuels have powered around 1,500 commercial flights by 2014. It is likely that a third of aviation fuel could come from alternative sources by 2030.

As with all other aspects of aviation, safety is the first priority when identifying replacements to conventional jet fuel. This is ensured by adhering to a strict set of fuel specifications that are required for conventional and emerging fuels alike. The process for approving new fuels is slow because of number of tests required to pass for any new fuel.

At present three different types of biojet fuels have been approved, the most recent in June 2014, and several more are in the pipeline according to International Civil Aviation Organization (ICAO). Another sustainable alternative jet fuel pathway referred to as Synthesized Iso-Paraffinic (SIP) fuel was approved in 2014 for blends up to 10%. The ICAO reports predict that 2015 may see approval of additional pathways currently in the technical certification process.

With the prospect of additional supply options, regular supply and use by an airline, and increasing policy momentum from States, 2015 is being seen as having a potential to be a significant year in the evolution of alternative jet fuel use in aviation. By 2014 some 21 airlines had used

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alternative fuel for a commercial flight which is an encouraging figure as just 5 or 6 years ago the entire concept was labelled as hypothetical.

In 2014 Brazilian Company GOL was active in use of alternate fuel. KLM with supplier Sky NRG continued to pursue their efforts to deploy alternative fuel with a new series of 20 weekly intercontinental flights from Amsterdam to Aruba, while Air France have initiated a one-year series of weekly flights between Toulouse and Paris.

Cathay Pacific signed a one billion USD 10 year off-take agreement with Fulcrum Bioenergy. United Airlines will be using an amount of sustainable aviation fuel from Los Angeles Airport as part of their regular operations from quarter one, 2015 At a State level Indonesia announced a 2% alternative jet fuel mandate to commence in 2016 and has begun to implement and action plan including the establishment of the “Aviation Biofuels and Renewable Energy Task Force (ABRETF)”.

While cost remains a significant barrier to large-scale commercial production of aviation biofuels, there are a growing number of success stories, demonstrating that there is a spirit of collaboration between policy makers, suppliers and airlines. Despite this progress, continued research and support is needed to help increase the competitiveness at scale for this industry. Use of biofuels along with other best practices to reduce the air transport sector's environmental footprint has brought in the concept of perfect flight. A combination of using sustainable aviation fuels, streamlined Air Traffic Management (ATM) procedures and optimised operations has been used by Airbus' fuel-efficient modern aircraft for perfect flights.

The first North American 'Perfect Flight' took place during June 2012 in a joint effort between Airbus and Air Canada. This activity utilised an A319 flying from Toronto to Mexico City, with the aircraft powered by a 50% sustainable aviation fuel blend made with used cooking oil. Further enhancements to this flight's eco-efficiency included streamlined Air Traffic Management (ATM) procedures, use of Continuous Descent Approach (CDA) into the destination area, single-engine taxiing on the ground and external cleaning for improved aerodynamics. In August 2013, Airbus and Air Canada received

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aeronautical publication Air Transport World's Eco-partnership Award in honour of their successful 'Perfect Flight' collaboration.

Composite Materials

All of us are familiar with shiny Aluminium frames of aircraft. Aluminium is used for being light weight and strong to bear the impact of air flying on high speed. Another advantage of this material is less friction as compared to other metals. Ever increasing quest of aerospace industry to increase efficiency and performance of aircraft and to reduce both economic and environmental costs has led to research in using even lighter materials. Developments in material sciences have proved beneficial to the aerospace industry in this regard. Now the aircraft manufacturers have already started switching over to lighter materials.

Lighter materials such as composite materials have been developed and are being used in aircraft and their use is expected to rise in the future aircrafts. Composites are innovative new materials for building aircraft that can enhance strength while remaining lightweight. Carbon-fiber composites are predominantly used in the aerospace industry to enable significant reduction in weight leading to lower fuel consumption and reduced emissions. An extensive use of carbon fibre composite can reduce Energy Liberated To Work Ratio (ETRW) by 8-15%.

Composite materials remain the choice for future aircraft. Dr Guy Gratton, head Facility for Airborne Atmospheric Measurements (FAAM) stated in an interview “Composite materials have many advantages over the current aluminium alloys including weight reduction by up to 20% and better strength. Furthermore, due to their chemical properties composite materials can by be formed into more complex shapes which can provide better aerodynamic performance, composite materials are also resistant to corrosion meaning they require very little or no servicing.

The use of new materials is becoming more common in new aircraft. The structure of the new Boeing787 Dreamliner consists 80% of composite materials, much lighter in weight as compared to

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Aluminium. Airbus A-380 is constructed out of 25% composite materials and Airbus aims to further use composite materials in its upcoming A-350 series aircraft. This innovation has been seen as a “major revolutionary element” by the researchers in aeronautical engineering.

Keeping in view requirements of lighter materials for future aircrafts, Rolls-Royce has announced to set up, a centre of advanced fan system composite technology development at Bristol UK. The centre will focus on developing the next generation of fan blades and fan cases, made of carbon-fibre composite materials, for Rolls-Royce's future aero-engines. The Rolls-Royce CTi (carbon/titanium) blades are a key feature of the new advance engine design, unveiled in 2014, which will offer at least 20% less fuel burn and CO emissions than the first 2

generation of the Trent aero-engine.

A set of the CTi fan blades, incorporated into a Trent 1000 'donor' engine, successfully completed a full flight test programme on a Rolls-Royce 747 flying test bed at Tucson, USA in December 2014. A rigorous testing programme of the complete fan set will continue to take place. NASA is also committed to transforming aviation through cutting edge research and development. NASA has established a public-private partnership with five organizations to advance knowledge about composite materials that could improve the performance of future aircraft.

Image 2 . Source : Beginners guide to aviation (2010)

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Blended wing design

You must have noticed the span of wings of aircraft and their movements during a flight. Drag is caused by fuselage and wings help an aircraft fly. As we know that greater drag means greater fuel consumption, meaning higher costs of operations and negative impact on natural environment due to CO emissions. To overcome these 2

challenges embed in current aircraft designs a lot of research has been carried out on making aircraft that have greater area of wings and less fuselage called blended wings. These aircraft will be radically different in terms of design compared to conventional aircraft. Blended wing planes are not a new idea and first came to surface in 1940s in Horten sailplanes. Despite earlier constraints which discontinued the use of this configuration, the interest in only wing airplanes rests on the advantages that by deleting the non-lifting components from the conventional aircraft such as the fuselage and tail would increase speeds and lengthen range by lessening drag and reducing weight. They are also very aerodynamic meaning that a great deal of lift can be generated with little propulsion If the whole plane were simply one big wing [blended wing], the maximum aerodynamic efficiency could be achieved. Presently Boeing is conducting trails on its X-48 blended wing aircraft. Dr Mark Jabbal Lecturer in Aeronautical Engineering and an expert on green planes, at Brunel University London, speculates to see the first passenger blended wing plane around 2050.

Image 3 shows a blended wing aircraft (www.nasa.gov)

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New wing technologies

With the current environmental concerns in mind, over the years there has been a major improvement in the wings of the aircraft itself, features like wing-tips and high aspect ratios have been used to minimise drag and therefore reduced fuel burn. The Wright brothers before their successful flight in 1903, observed mechanisms of flight in birds and determined they needed to adjust the angle at the end of their wings for control, mimicking the way birds bend their outer feathers. In order to achieve angle adjustment, the Wright brothers used a mechanical wing warping method. Through a series of wires and pulleys, they were able to control their airplane. As aviation progressed, ailerons, rudders, and elevators replaced the Wright brothers' method of pulling wires.

In recent years several wing-tip devices have been used in an attempt to reduce drag, especially on aircraft that fly long distances where the drag reduction would have a considerable impact on the range and fuel efficiency of the aircraft. In the future we will still see the use of wing-tips, as they can significantly reduce fuel burn without the need for increasing the wing span, along with new technologies that are currently under development like laminar wings which can reduce drag by up to ten times.

Active flow control can not only benefit the efficiency of an aircraft but can drastically improve performance. A problem with high aspect ratio wings is that it increases the weight of an aircraft, due to extra toughing needed in the airframe to support them, and also make an aircraft difficult to park and manoeuvre on the ground however wing-tips allow the same drag reduction without a compromise in wing span.

Image 4 shows different wingtip devices,(Beginners guide to aviation (2010)

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Before their first successful flight in 1903, the Wright brothers spent lots of time observing birds for inspiration. Now scientists at NASA and many other research facilities and manufacturers are trying to unlock the secrets of animal wings for the next generation of aircraft. Scientists are again beginning to base much of their research in airplane wing design on the shapes of bird's wings, having an amazing amount of manoeuvrability when flying.

Over the past hundred years, airplanes have employed ailerons, rudders, and elevators on fixed wing aircraft. These controls change the plane's direction by mechanically moving a small portion of the body. Heavy hydraulic systems currently provide the mechanical power for the control systems. In aerospace engineering reducing weight and drag remain biggest challenges for increasing performance and efficiency.

In response to these challenges morphing materials are being considered to provide a lightweight solution for replacing ailerons. Instead of lifting or lowering a flap to change the wing's aerodynamics, the shape of the air foil will change, creating a new aerodynamically appropriate airfoil. This technique was used by the Wright brothers by pulling wires attached to cloth rather than applying voltage to morphing materials. Possible types of morphing materials include piezoelectric, macro fiber composites, shape memory alloys, and smart materials.

Morphing wings are another modification to standard airplanes which promises impressive future improvement in aircraft design. Traditional wings make use of numerous control surfaces to maneuver successfully. These control surfaces, however, are actually quite inefficient when it comes to the amount of drag they produce and, in military applications, the fact that they reduce the stealth of an aircraft. A morphing wing could change its shape without use of flaps, ailerons, or other standard control surfaces. The United States Defense Advanced Research Projects Agency (Darpa) is currently funding research into several "smart materials" which might be used to morph an aircraft.

These candidate materials include piezoelectric materials which

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change shape when an electric charge is applied, shape-memory alloys which respond to changes in temperature, and magnetostrictive materials which are controlled using magnetic fields. The focus of research being on designs for morphing wings to control manoeuvrability and lift however in the future they hope to incorporate morphing materials into the entire airplane's fuselage so, for example, the intake for engines could be optimized for flight at different speeds, or the fuselage could shrink as fuel is burned.

The primary obstacle faced in the integration of these smart materials into airplane wings is the amount of stress that the materials must be able to withstand. Consider, for example, the wings of an F-16 which under normal flight must support 25,000 pounds (110,000 N) of force. If, however, an F-16 performs a 9-G turn, the force on the wings grows to a whopping 250,000 pounds (1,000,000 N).

In the past, wings that were created to flexible and strong have ended up being too heavy for practical use. To solve this problem Sridhar Kota, president of FlexSys Inc, is working in conjunction Lockheed Martin and the Air Force to create a morphing wing using a technology known as compliant systems (FlexSys). Compliant systems are designed by a computer program which takes inputted requirements for the object and the calculates the shape, number of interconnection, and thickness of components yielding a compliant system to perform the task.

Compliant systems are milled out of a single piece of solid material, be it plastic or titanium, and take advantage of the elastic strain of these materials to perform work. FlexSys has used compliant systems to design a very unique prototype of a morphing wing. The shape of the wing's leading and trailing edges can changed by as much as 20° and at rates fast enough to be useful as control surfaces (FlexSys).

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Inspirations from Nature

Knowing that birds and animals enjoy far better performance and efficiency in their movements scientists hope to discover some of these secrets and apply similar techniques to future aircraft designs. Research is going on the shapes of wings in nature in an attempt to find the most efficient wing shape although it is constrained by the lack of ability to make models of the complex shapes for testing in wind tunnels.

While working as a fluid aerodynamicist for NASA, Barry Lazos has been studying birds' flight for years. For example, a common seagull flaps it's wings to make shaper turns, but during steady flight it uses almost imperceptible movements in its wing tips to change direction. In addition, a seagull makes no use of its tail as a rudder during steady flight.

Some of the wings have been developed based on inspirations from nature and some as hybrids between various animals and airplane wings. Among the models tested by Lazos are seagull wings, shark fins, and a hybrid known as the hyper elliptic and found that a wing with the hyper elliptic shape has a 15% improvement in its lift to drag ratio as compared with a normal airplane wing. So far these nature inspired designs are too complex for current computer simulations of fluid dynamics.

Another division of NASA is looking at the way birds use their feathers to control the flow of air over their wings. Unlike airplane wings which are designed to be as smooth as possible, a bird's wings are covered with feathers which create "flow unsteadiness" over the wing. To achieve flow unsteadiness similar to that caused by feathers, NASA developed micro jets which are tiny flaps of metal that when activated beat up and down, creating tiny air swirls. If several hundred or thousand of these micro jets are attached to airplane wings then they could theoretically be used to improve the aerodynamics of the wing.

Wing aerodynamics are crucial because by reducing the drag by 3 percent, amount of thrust needed can be reduced by 49 percent. Looking even further researchers envision having thousands of

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individually controlled micro jets as well as shape changing bumps or blisters which would dynamically change the shape of the wing to manage airflow and increase lift regardless of the airplane's speed. For this it is must to design a system of controlling these blisters first.

A Small Unmanned Aerial Vehicle Lab was developed by Mark Motter, at NASA to test different methods by which a computer system could analyze data from sensors on board an airplane to optimize its manoeuvrability. He experimented with a small unmanned aircraft whose ailerons have been divided into ten segments, each of which collect force data and can be adjusted individually. Though ten segments may seem like small amount of data for a computer to analyze , the adjustments to the ailerons segments based on this data must be made very quickly in order for the segmentation to improve the wing's aerodynamics.

If his systems are successful, they will eventually be responsible for collecting data from tens of thousands of blisters and pulse jets covering an airplane and using that data to make the minor shape adjustments necessary for optimum aerodynamic efficiency, just as a bird feels the wind flow over its wings and adjusts its feathers to fly efficiently.The Wright brothers' first flier didn't have ailerons or flaps. Instead the Wright brothers used a design which more closely resembles a bird's flight controls. To turn, the pilot would shift in a harness which would twist or warp one of the wings, turning the craft. However, as airplanes evolved most engineers began viewing a wing's flexibility as a weakness.

NASA and Boeing Phantom Works project on active aeroelastic wing (AAW) is another step forward to reduce drag in future flight. They began with one of the original "overly flexible" F-18 wings and modified it so that the outer and inner portions of the leading edge flaps and ailerons could be moved separately. The flaps on the tail can also be disabled in flight to prove that the plane can be successfully maneuvered using only control surfaces on its wings

While in flight the on board computers have been programed to use the outside leading edge flaps to create forces which twist the wings

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opposite the direction normal wings naturally twisting during a turn. Twisting the wings in the opposite direction allows the ailerons to work more effectively while still maintaining a manageable amount of stress on the wings. Because AAW wings don't have to be engineered to be super-stiff they can be lighter, reducing the gross weight of fighter jets by 7 to 10 percent while maintaining flight performance.

While these airplane concepts are still in their infancy, as far as design and research goes, the future benefits that they might yield are enormous. According to the researchers, most of these technologies won't even show up in military applications until after another 20 to 30 years of research and development. However, once the next generation of morphing airplanes begins to appear it will be fascinating to see whether our testing has resulted in an aircraft that can swoop like a bird, or simply another generation of "clumsy" fighter planes.

Texas A&M University researchers have discovered that a single formula of movement applies to insects, birds, fish and mammals alike. The study found that animals all flex their fins, tails or wings within a range of 30 to 60 degrees and their movements are most energy efficient. For now human-engineered vehicles cannot replicate this flexibility. Researchers at NASA hope to unlock some of the secrets that allow birds to fly with such efficiency and manoeuvrability and

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Focus on Fluid Dynamics for Better Aerodynamics

Most aircraft designers haven't attempted to research more natural wing shapes because they haven't had the ability to make models of the complex shapes for testing in wind tunnels. Unfortunately, these nature inspired designs are too complex for current computer simulations of fluid dynamics.

Computational simulation of fluid flow, often referred to as Computational Fluid Dynamics (CFD), plays a vital role in the aerodynamic design of aircraft; allowing engineers to understand complex flow patterns without ever flying a real aircraft, or firing-up a wind tunnel. It is becoming apparent, however, that current generation CFD software does not meet industrial needs – put simply, for complex flow problems the software takes too long to obtain a solution, and if it does eventually reach a solution, it is often wrong. A new generation of CFD software is required.

Dr Peter Vincent, at Imperial College London, is working with a team of PhD students to develop a new generation of CFD software. Their software is designed to harness the power of new 'many-core' computing platforms, such as Nvidia Tesla GPUs, the latest generation of which have over 2,500 compute cores (compare this with the 2-4 cores found in a modern laptop). In fact, the software is even able to run on clusters of hundreds of these GPUs, such as Emerald, the UK's largest GPU supercomputer. The ability to run on many-core technology means results can be obtained more quickly – valuable flow solutions in hours, potentially, instead of weeks.

Another idea that is being looked at is formation flight which is essentially mimicry of a flock of birds, research has shown that if many aircraft fly closely together in a formation the net drag is reduced which results in less fuel consumption by each aircraft. Wings of birds, their body structures, swimming of fish and their skins, fluid dynamics in human body are also being studied for their applications on aircraft design.

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Advanced Engines

To meet the demands of growing environmental concerns along with economic aspects, aeronautical technology is taking into account improvements in engines to maximize fuel efficiency. Advancements in aircraft engines have proved to be a major efficiency enhancing method. The high-bypass ratio engine technology has continued to evolve since its introduction in the 1960s and according to the Beginners guide to aviation it is estimated that their efficiency increases by about 1% every year meaning that in the next decade engines are likely to be 10% more efficient.

On the contrary Dr Jabbal thinks that “we are reaching a point where we cannot improve the efficiency of current conventional aircraft [engine] designs” and new technologies need to be introduced. One such technology is the open rotor or un-ducted fan engine design which was first trialled in the 1980s, the reason that it has reappeared again is due to the fact that an open rotor engine would burn 25-30% less fuel, compared to an equivalent turbofan, and most importantly it would emit 40% less CO2. Currently Easy jet seem to be keenly interested in the engine design as they have devised their own concept plane called the Easy jet Eco jet which is powered by open rotor engines, Airbus has also revealed an open rotor engine aircraft called the A30X which looks strikingly like the Eco jet.

In the view of Aviation journalist Mark Bursa “Airbus plans to flight-test a UDF engine … within the next couple of years as part of a €1.6bn European research project into green aviation technology called Clean Sky”.. There is much speculation that the first open rotor engine passenger aircraft would be in service during the middle of the next decade. In the Airbus concept plane Engines will be more reliable, quieter and fuel-efficient. The positioning of the engines, at the rear and semi-embedded, fully optimises the aircraft for lower fuel burn. The engine placement also boosts cabin comfort through decreased noise levels. The engines can be incorporated into the aircraft body because technological advances will have reached such a level that superior engine reliability will diminish the need for immediate access to its components.

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Image 5 shows an open rotor engine. (Source Bursa (2013))

British company Reaction Engines is working on a new type of engine called SABRE that would allow for the development of an unmanned spaceplane (not a spy plane) that could take off and land like a conventional aircraft. It would initially use air-breathing engines to take off and fly at Mach 5.5 before switching to a rocket engine at high altitude to ascend into the Earth's orbit, where it could travel at a speed of Mach 25 -25 times the speed of sound.

SABRE and Skylon were invented by Alan Bond and his team of engineers at the Abingdon, SABRE burns hydrogen and oxygen. It acts like a jet engine in Earth's thick lower atmosphere, taking in oxygen to combust with onboard liquid hydrogen. When SABRE reaches an altitude of 16 miles (26 kilometers) and five times the speed of sound.(Mach 5), however, it switches over to Skylon's onboard liquid

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oxygen tank to reach orbit. (Hypersonic flight is generally defined as anything that reaches at least Mach 5.)

As environmental impact together with economic aspects are asserting influence in designs of aircraft, in an endeavour to minimize drag on aircraft older designs are being revisited to make high performance aircraft in the future. By revisiting the designs of early military aircraft civil aviation can also benefit with more efficient designs. An example of this is the 2005 study by the American Defence Advanced Research Projects Agency (DARPA) on Hybrid Ultra-Large Aircraft (HULA), these lighter than air aircraft would rely on aerodynamic lift that will be produced by air flowing around the hull, to carry cargo over long distances, however due to congressional scepticism the program was cancelled in March 2006. But such designs are not far from being reintroduced. Dr Guy Gratton believes airships do certain things particularly well for instance scientific research and defence purposes.”

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Concept Future Planes

The two biggest competitors of the aircraft market; Airbus and Boeing, are working extensively to ensure that future aircraft are safe and comfortable as well as sustainable and eco-efficient. Airbus Consumer Report(2010) states “we need huge step changes in aircraft design, operations and energy management to keep air travel comfortable, affordable and eco-efficient” a similar view is shared by Boeing who have mentioned in their Environment report (2013) that “Boeing is researching and developing new technologies that will help define the next generation of cleaner, quieter and more fuel-efficient airplanes”, thus a realization of shift in technology to create environmentally friendly aircraft.

Airbus and Boeing have made some important advancements aeronautical technology; they are supported by academic institutions in research and development. The major areas of progress to make aircraft more eco-efficient and environment friendly are aircraft materials, aerodynamics, cabins and engines.

Airbus engineers have come up with the design that is an “engineer's dream”, to meet the expectations of the passengers of the future and also the goals of reducing carbon emissions. Its Concept plane illustrates what air transport could look like in 2050, even 2030 if advancements in existing technologies continue on fast pace. Some of the features of Airbus's Concept plane include ultra-long and slim wings, semi-embedded engines, a U shaped tail and lightweight intelligent body.

These entire features are aimed at improving environmental performance and eco-efficiency. The result: lower fuel burn, a significant cut in emissions, less noise and greater comfort. Boeing has also come up with two concept planes, the phantom eye and the X-48. The phantom eye is fuelled by hydrogen and is unmanned. Boeing aims to expand its knowledge on hydrogen fuel and its potential use in aircraft. The X-48C is a blended wing aircraft which is currently being tested to determine the increases in fuel efficiency and reduction in noise due to the blended wing design

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Inspired by nature - and designed to protect it Future aircraft could be built using a bionic structure that mimics the bone structure of birds. Bone is both light and strong, because its porous interior carries tension only where necessary, leaving space elsewhere. By using bionic structures, the fuselage has the strength it needs, but can also make the most of extra space where required. This not only reduces the aircraft's weight and fuel burn, but also makes it possible to add features like oversized doors for easier boarding, as well as panoramic windows.

Image 7 shows the Boeing concept plane.

Image 6 shows the Airbus concept plane

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My concept plane is influenced by environmental factors. It is an only wing plane with structure mainly built by composite material to reduce weight and drag. In addition transparent materials will be used on sides to make up for lack of windows in such designs. On the fuel side it will be hybrid of bio fuel and wind energy. During its flight it will rely on wind energy created by travelling on high speed and captured through tunnels at the back of wind turbines. Whereas for take-off and landing it will use bio fuels. Besides cutting down carbon emissions my conceptual plane will also tackle the problem of contrails formation, which is not being addressed by any other concept planes proposed so far. I will work on finding the paths of vapours and develop a capturing devise to channel these vapours to refuse tanks of the aircraft.

Biomimicry

Biomimicry or biologically inspired engineering, is helping solve human challenges by study and imitation of nature's best ideas. A growing number of aeronautical innovations have been inspired by an array of natural structures, organs and materials – and these tried and tested patterns of the natural world will continue to be a powerful source of inspiration in the future.

Another idea that is being looked at is formation flight which is essentially mimicry of a flock of birds, research has shown that if many aircraft fly closely together in a formation the net drag is reduced which results in less fuel consumption by each aircraft. Wings of birds, their body structures, swimming of fish and their skins, fluid dynamics in human body are also being studied for their applications on aircraft design.

Inspired by nature - and designed to protect it the future aircraft could be built using a bionic structure that mimics the bone structure of birds. Bone is both light and strong, because its porous interior carries tension only where necessary, leaving space elsewhere. Airbus has revealed the use of bionic structures in its future planes with the view that by using bionic structures, the fuselage has the strength it needs, but can also make the most of extra space where required. This not only reduces the aircraft's weight and fuel burn, but also makes it possible to add features

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like oversized doors for easier boarding, as well as panoramic windows.The aircraft cabin's bionic structure will be coated with a biopolymer membrane, which controls the amount of natural light, humidity and temperature, providing opacity or transparency on command and eliminating the need for windows. Future materials may be very different to the materials we see and use today. In the future materials may not even take a solid state, but could be a composition of fluid and gas, for example.

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Hypersonic or Hallucination

Imagine you are a businessman in London with a crucial meeting in China. Even with time difference of nearly eight hours you can expect to reach within two hours by boarding a Hypersonic flight meaning flying at a speed five times that of sound or nearly 4000 miles per hour. The speed of a flying machine can be defined in Mach numbers. Mach 1 is speed of sound or 768 MPH whereas Mach 5 is five times the speed of sound, which would be 6,200km per hour at sea level. Subsonic aircraft flies at Mach less than 0.8 or 609 miles an hour; Transonic between Mach 0.8 to 1.2 or 609- 914 MPH; Supersonic between Mach 1.2- 5.0 915-3,806 MPH and Hypersonic between Mach 5.0 to 10 or 3,806–7,612 MPH

The talk of flying at this speed might sound like hallucination at this point but till the time aircraft was invented flying was seen as an illusion too. Gaining high speed always remained one of the major objectives of aerospace engineering, particularly in the realms of military and space operations, which take precedence over civil aviation in terms of performance. Later the features applicable to civil aircraft are adopted for them. There are both military and commercial interests in supersonic travel, with plans to travel at hypersonic speed both within the atmosphere and in space – but there's a long way to go.

Dr Paul Bruce, senior lecturer in high speed aerodynamics at Imperial College explained “The step now into making something that passengers might sit on or that might go into space, like for delivering satellites into orbit, is pretty huge,” says Dr Bruce. “We're right on the edge of the materials and technology that we need to do that, the sort of engine technology we need to do that.”

Although two hour flights to Australia are a possibility, Dr Bruce says the main commercial interests would be space tourism or putting satellites into orbit. Satellites are “top of the list” he adds, as, at the moment, putting a satellite into space costs £1,000 per kilo and would be 10 times cheaper with a re-usable plane.

Meanwhile, militaries are interested in hypersonic travel for fast-strike

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capability. “If you have to order an air strike or a missile that takes half an hour to get there, there's a chance that they'll be warned and leave, so the tactical advantage is a big driver for military,” explains Dr Bruce.

Supersonic flight is a common feature of fighter jets and reconnaissance planes but in civil aviation only two aircraft could enter the realm of commercial service and unfortunately both stand retired at the moment. The Concorde and Tupolev Tu-144 were both developed in the 1960s.

Concorde developed in 1960s was a turbojet powered supersonic passenger jet airliner that was in service from 1976 to 2003. Concorde was jointly developed and produced by Aérospatiale of France and the British Aircraft Corporation (BAC) under an Anglo-French treaty. It featured a maximum speed over twice the speed of sound at Mach 2.04, with seating for 92 to 128 passengers. First flown in 1969, Concorde entered service in 1976 and continued commercial flights for 27 years.

Tupolev Tu-144 publicly unveiled in January 1962, was developed and manufactured in the Soviet Union under the direction of the Tupolev design bureau, headed by Alexei Tupolev. The first prototype flew on 31 December 1968 near Moscow, just two months before the first flight of Concorde. The Tu-144 first went supersonic on 5 June 1969, and on 26 May 1970 became the first commercial transport to exceed Mach 2.The passenger fleet was permanently grounded after only 55 scheduled flights due to two crashes however the aircraft remained in use as a cargo plane until 1983, by which point a total of 102 commercial flights had been completed.

Developed with the technological constraints of 1960s Tupolev and Concorde could only achieve Mach 2, double the speed of sound . These planes flew no faster than Mach 2, primarily because the materials weren't available in the Sixties that could withstand greater heat but nowadays with cutting edge technology and computer aided designing, aerospace industry is looking towards horizons of hypersonic flights aiming to fly at the speed 6 times that of sound.

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What hypersonic inventions can we expect?

So far, hypersonic test flights have all been unmanned and experimental, and have lasted for no more than a couple of minutes. But Dr Bruce says hypersonic weapons like the one launched by US military should be fully developed within the decade.

Meanwhile, UK company Reaction Engine is developing a plane called “Skylon”, which will - on completion - be able to take off from a runway and reach the earth's orbit. This ambitious project has just been given £60 million investment from the government – “people have dubbed it the Concorde for the next century,” says Dr Bruce.

The V-2 rocket, first used in World War II by Nazi Germany and later used by the United States in its early rocketry work was the first manufactured object to achieve hypersonic flight. In February 1949, its upper stage reached a maximum velocity of 5,150 miles per hour (8,288 kilometers per hour)—more than five times the speed of sound. The vehicle, however, burned on atmospheric re-entry, and only charred remnants were found.

In April 1961, Russian Major Yuri Gagarin became the first human to travel at hypersonic speed, during the world's first piloted orbital flight. Soon after, in May 1961, Alan Shepard became the first American and second person to achieve hypersonic flight when his capsule reentered the atmosphere at a speed above Mach 5 at the end of his suborbital flight over the Atlantic Ocean. In June, Air Force Major Robert White

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flew the X-15 research airplane at speeds over Mach 5, and broke his own record in November, reaching Mach 6.7.

Lockheed Martin - an American global aerospace, defense, security and advanced technology company that developed SR71 Blackbird long-distance spy plane which holds the air speed record of Mach 3 - three times the speed of sound, revealed in 2014 about developing a successor to the SR-71 the SR-72 spy plane with an engine which could propel it up to 4,567mph, or six times the speed of sound- three times as fast as Concorde. Flying at this speed it will be so fast it will have to be clad in a skin made from titanium crystals wrapped in carbon fiber to resist the extreme friction heat such speeds will create. Able to circumnavigate the globe in six hours at an altitude of about 80,000ft, Son of Blackbird, as it's been dubbed, will be an extraordinary weapon of war: effectively, it will be too fast to shoot down and too fast for moving military targets to avoid it.

The company hopes the same technology could be used in passenger jets. This is a big news for dreamers of hypersonic travel. Getting anywhere in the world within few hours seems to be coming out of realms of sci-fi with innovation and developments at fast pace. Enthusiasts have been talking up hypersonic travel for years and, apart from a few short-lived experiments, nothing much has happened. This is largely because the field is fiendishly expensive to develop and the technical difficulties enormous.

Lockheed Martin claims to have overcome the biggest technical hurdle - the so-called 'thrust gap' in the plane's propulsion. Essentially, while a conventional jet turbine can get a plane up to Mach 2.5, the so-called 'scramjet' - a powerful jet engine that can work at extraordinarily high speeds by sucking in supersonic air - cannot start working until the plane is flying at more than Mach 3.5. The problem is bridging the gap from the lower speed to the higher one. But Lockheed says it has designed an engine that can do just that, powering the aircraft from a standstill to Mach 6.

'It's a significant step forward. ' says Dr Phillip Atcliffe, senior lecturer in aeronautical engineering and specialist in hypersonic flight at

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Salford University. Dr . Atcliffe believes such travel would be a 'great development for mankind, It would shrink the world even more than we already have, but it's not going to happen overnight.' But he believes that if the money were available - and we are talking serious money - a hypersonic passenger jet would not be unfeasible. It could even be developed by 2030.

There's a lot of technology to be developed and we have to have governments and companies who are prepared to research and design it - and then airlines to buy it.' Nobody denies the challenges of building a Mach 6 passenger jet would be far greater than for a spy plane the size of a fighter jet. Pulse detonation engines work by using the force from a series of explosions and these sorts of engines should be able to get planes travelling at five times the speed of sound.

Concorde wasn't allowed to fly supersonic over land because of the 'sonic boom' - the sound associated with the shockwaves created by a craft moving faster than the speed of sound. Any passenger jet to use the engines would be able to reach Tokyo in two hours and have to fly at around 25,000ft to avoid damaging building with its sonic boom - just like the Fireflash jet in the original Thunderbirds. It would have to be a lot bigger and - most important - it would have to protect its passengers from the intense heat created by the plane's extraordinary speed as it passes through the atmosphere.

According to experts, if a passenger jet flew at Mach 6 at current jet altitudes of around 30,000ft, the sonic boom could damage buildings. It may fly 250,000ft - still within the Earth's atmosphere - and Dr Atcliffe reckons this, too, could be about the perfect altitude. It would be sufficiently high to cut down the heat generated because the atmosphere is colder and thinner. As for the flying experience, cocooned inside their pressurised cabin, hypersonic passengers would probably experience little that was different from flying today.

Virgin Galactic has said its SS2 craft designed for space tourism could also be adapted into a passenger jet, allowing travel from London to Sydney in two hours but would rely on gravity in orbit, rather than engines, to reach its destination.

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Aeronautical experts admit this is all uncharted territory - even the Space Shuttle reached such high temperatures only for a few minutes as it re-entered Earth's atmosphere. It's also hard to say how much it might cost to fly hypersonic. Ticket prices will inevitably depend on how many passengers a plane can carry - so the more it can hold, the more commercially viable the flight.

Concorde had room for only 100 passengers, but it was limited by Sixties technology. Experts say there is no reason why a hypersonic jet couldn't take up to 300 passengers. Not that it will look as pretty as a conventional jetliner, and certainly not as sleek as Concorde. It's more likely that the wings would blend into the fuselage more closely and that it would have a stubby shape to cope with the huge air pressures. Aircraft giant Boeing is also researching hypersonic flight and calls it, in a nod to Star Trek, the 'warp speed of today'.

The Victorians believed travelling at more than 30mph would make the human body collapse. What they would have made of technology that could propel people at 150 times that velocity is anyone's guess.

Aurora

The Aurora aircraft has been rumoured to exist for years - but the US continually denies it was ever created.

Rumours about Aurora stemmed from the mid1980s, but there is still no

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substantial evidence that it actually exists - the US government has continually denied such an aircraft was ever built.

In 1990 an aviation magazine spotted that the term 'Aurora' had been included in the 1985 US budget with $455 million set aside for “black aircraft production”. It was supposedly a Mach 5 (five times the speed of sound) aircraft to replace the Blackbird. Lots of people have since reported sightings of unidentified triangular aircraft with odd shaped vapour trails and sonic booms.

Skylon

Skylon is an experimental spaceplane that would fly in Earth's orbit at 25 times the speed of sound It would initially use air-breathing engines to take off and fly at Mach 5.5 before switching to a rocket engine at high altitude to ascend into the Earth’s orbit, where it could travel at a speed of Mach 25 -25 times the speed of sound.

British company Reaction Engines is working on a new type of engine called SABRE (Synergetic Air-Breathing Rocket Engine)that would allow for the development of an unmanned spaceplane (not a spy plane) that could take off and land like a conventional aircraft. Developed by Reaction Engines over the last 20 years, SABRE is a new engine class that can operate in both air-breathing and rocket modes.

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This advanced combined cycle air-breathing SABRE rocket engine enables aircraft to operate easily at speeds of up to five times the speed of sound or fly directly into Earth orbit.

With the Pre-cooler heat exchanger and other SABRE engine advanced technology development programmes nearing completion, the next stage of the SABRE programme is the construction of a full engine demonstrator. A passenger version, called the Lapcat A2, is also under development.The Daily Mail reported on 14th December 2014 that European Space Agency (ESA) now also backs the development of SABRE engines “We are backing this because it's technology that has been tested in the lab, it's been assessed by outside experts as right in principle. Now it needs to be built on a full-scale prototype before it can get commercial. We think it's right to support it through that crucial stage.”

"European Space Agency- ESA are confident that a ground test of a sub-scale engine can be successfully performed to demonstrate the flight regime and cycle and will be a critical milestone in the development of this program and a major breakthrough in propulsion worldwide."

SABRE and Skylon were invented by Alan Bond and his team of engineers at the Abingdon, SABRE burns hydrogen and oxygen. It acts like a jet engine in Earth's thick lower atmosphere, taking in oxygen to combust with onboard liquid hydrogen. When SABRE reaches an

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altitude of 16 miles (26 kilometers) and five times the speed of sound.(Mach 5), however, it switches over to Skylon's onboard liquid oxygen tank to reach orbit. (Hypersonic flight is generally defined as anything that reaches at least Mach 5.)

Two SABREs will power the Skylon — a privately funded, single-stage-to-orbit concept vehicle that is 276 feet (84 meters) long. At takeoff, the plane will weigh about 303 tons (275,000 kilograms).The SABRE heat exchanger is also known as a pre-cooler. It will cool the air entering Skylon's engines from more than 1,832 degrees Fahrenheit (1,000 degrees Celsius) down to minus 238 degrees Fahrenheit (minus 150 degrees C) in one one-hundredth of a second. The oxygen in the chilled air will become liquid in the process.

"The [pre-cooler] performance has always been pretty much what we predicted," Bond explained in an interview with Space.com at the Farnborough International Airshow in England on July 16. "We've now done over 700 actual tests. It's now done as much service as a pre-cooler would in a real engine."

Bond's team has also successfully tested the pre-cooler for a problem aviation jet engines have to deal with: foreign objects being sucked in. Bond estimates that the pre-cooler is now at a technology readiness level (TRL) of about 5. NASA and AFRL use a 1-to-9 TRL Scale to describe a technology's stage of development. According to NASA's TRL descriptions, 5 represents "thorough testing" of a prototype in a "representative environment."

The AFRL work is being carried out under a Cooperative Research and Development Agreement (CRADA) with Reaction Engines that was announced in January. AFRL officials told Space.com that they are using computers to model SABRE.

"The Air Force research laboratories in the States have carried out some modeling to verify that the SABRE does actually work, that it is a real engine, and so I am hoping they are going to confirm that very soon," Bond said.

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"This is obviously opening doors in the United States, and again, I can't say a great deal about that, but we have very good dialogue going across the Atlantic," he added. "In the next couple of years, it's going to be quite exciting."

Bond declined to confirm rumors of organized support within the U.S. aerospace community that involves former senior program managers of the U.S. military's most high-profile defense projects .Bond sees Skylon as an international project that would include the U.S. and Europe.

"We're in dialogue with people across Europe in regard to supplying [rocket engine components]. We don't want to reinvent the wheel; we'd like to be the engine integrator and put it on our test facilities and run it," he explained.

Milestones approaching

Two SABRE engines are expected to be tested in 2019, as Bond is quoted in Space.com saying "Hopefully, the earlier part of 2019, I'd like to feel we can test them on Westcott. That is where the rocket propulsion establishment used to be." The SABRE development program is expected to cost 360 million British pounds ($600 million at current exchange rates). "We've got 80 million [British pounds] of the 360 million lined up. We're well on our way to that," according to Bond.

Of the 80 million pounds, 60 million is from the U.K. government. As with the commercial ventures NASA supports, Reaction Engines has to meet milestones to acquire those government funds.

"We have to meet milestones, but those are programmatic issues," Bond said. "There is nothing contentious about that; it is just a matter of getting the work done to get there. I think of it as an R&D program, and we've done the 'R' bit, and this part forward is the 'D' bit. We've spent years making sure the technology actually works."

In January, this R&D program reached its third phase, which is split into four sections, known as 3A, 3B, 3C and 3D. Sections 3A and 3B are

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being carried out in cooperation with the European Space Agency (ESA).

Section 3A began in January and will last until April 2015. It involves the engine's system design, revising the engine's layout and studying the impact on Skylon's performance. This work will cost 8 million euros ($10.7 million, or 6.4 million British pounds), half of which will come from the U.K. government and ESA and the other half from Reaction Engines' private investment.

"This is it for real now; this isn't studies anymore," Bond said. Section 3A will continue until spring 2015, and section 3B is due to start in January 2015, he added. "That is the preliminary design phase,." Bond said.”

Section 3B will last until the end of 2015. During this section, the characteristics of the engine components will be defined and technical specifications produced.

Section 3C, which starts from mid-2015, will see 10 million euros ($13.37 million, or 8 million British pounds) from the U.K. government spent. The section 3C work with suppliers overlaps section 3B. This is because some of the components will get specifications during 3B before other parts of the engine are fully defined. Those detailed components with specifications can then be given to prospective suppliers during the first few months of section 3C.

"In 3C, we start to do detailed design — what the bearings will look like, who is the supplier going to be, that sort of stuff. This is really exciting stuff. We're starting to pull the real engine together during the course of next year," Bond said.

He explained that for section 3C, his company will spend "some of the U.K. government money alongside some of our own private investment." The government money has "enabled us to raise quite a few millions of private investment to go alongside that, and we're continuing that [fund-raising] activity," Bond revealed to the Space.com

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Will the Wish List Fly ?

There are numerous challenges in the way of wish for hypersonic flight and actually flying with a speed of 5000 mph. Despite developments by Lockheed Martins and Reaction Engines and good news of their adaptability to civil aircraft, still lot needs to be achieved in terms of technological barriers. Though Aerospace engineering is fast covering grounds, breakthroughs are still awaited to translate technology in the realm of civil aviation particularly for hypersonic travel.

There are several constraints in terms of engines for hypersonic flights. Engines work by pushing back air faster than the speed of travel and so it’s incredibly difficult to build an engine that can power an aircraft at hypersonic speeds. “It’s very easy to propel yourself forwards if you’re going slowly – you have propellers and jet engines and even internal combustion engines – which work fine because the principle is that if you’re travelling forward at 10 miles an hour then you need to push air backwards at 20 miles an hour in order to make yourself keep going or go faster,” explains Dr Bruce. “But if you’re travelling at 5km a second, it’s very difficult to push air backwards faster than 5km a second.”Early hypersonic test runs were all rocket-powered, which essentially means strapping a firework to an aircraft that looks like a bullet with wings and seeing how far it can travel before it runs out of power and crashes. Dr Bruce, explains that “when you travel fast, air starts to heat up – as if you put air in a flame and made it several thousand degrees, Travel becomes hypersonic when temperatures get so hot that the air molecules become unstable and start losing electrons.

At low temperatures, the air is made up of oxygen and nitrogen electrons, but at hypersonic speed, the air begins to change chemically and becomes an electrically-charged field”. The interesting challenge is creating an engine that is “air breathing”: it takes in air at the front, burns fuel, and then pushes air out the back, much like low speed engines. This is much more efficient – as 95 per cent of a rocket’s weight is fuel – and easier to control. “If you’ve got a conventional plane, whether it’s low speed or high speed, because you use the oxygen in the air, you’re using the whole atmosphere as your fuel tank. As you fly along you’re getting new fuel in the front so you don’t have to carry it all

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on takeoff, which is what rockets do.”

One of the major challenges is trying to spark combustion. At supersonic speeds, such as Concorde travel, air enters the front of the engine and goes through a series of channels until it slows down. Once air is travelling slowly, it’s easy to inject fuel and ignite it, which releases energy and gives you thrust to move forward.

But at hypersonic speed, when air can enter the engine at Mach 10, it’s very difficult to slow it down to the speed of sound. As a compromise, designers are trying to slow the air down to Mach 2 and then inject and light the fuel while the air is still travelling at supersonic speeds. “It’s a lot like trying to keep a match alight in a hurricane,” says Dr Bruce.

All these challenges are being overcome by development of new engines like SABRE and advancements in use of different materials to be used as fuels. Scientists are unlocking secrets of manipulating nature in their favour at a much faster pace.

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Determining the Future Direction

The demand for air travel is ever growing with increasing global population offsetting all the gains on front of aeronautical technology for reducing carbon emissions by cutting down on use of fossil fuels. The increase in the number of operational aircraft poses a significant threat to global environment not only through CO2 emissions but also the formation of contrails. Until recently the major focus of aeronautical technology was on performance of aircraft, including passenger travel, military and space travel but now a significant shift has taken place in the designs of future aircraft, from high performance to high eco-efficiency taking into consideration the environmental impact, specially so in the case of passenger and freight aircraft as international regulatory bodies have set goals to reduce carbon emissions requiring step changes in aircraft design. There is a clear link between efficiency, performance and environmental impact. Efficiency can be enhanced by reducing drag and weight resulting in reducing fuel consumption per kilometre, hence less CO2 emissions. Efforts are underway to increase the efficiency of aircraft and also to use alternate fuel to cut down CO2 emissions in order to minimize impact on the global environment. Alternate fuels are a potential replacement for carbon emitting fossil fuel but at present they also pose some problems, currently hydrogen storage takes too much space and is also costly to produce as it does not exist freely in air. Solar panels are heavy and not very efficient. Despite gains and achievements in cutting down fuel consumption, switching over completely to environment friendly planes without compromising safety, comfort, performance and economic benefits of airlines is still hampered by constraints such as technological limitations and costs involved in developing environment friendly planes and economically viable alternate sources of energy. The use of lighter/composite materials in the structures has already

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been introduced in aircraft like the Boeing 787 Dreamliner in order to reduce the weight of the aircraft which in turn decreases fuel burn and consequently makes the aircraft more efficient and environment friendly. However, there are limitations such as high manufacturing costs and fire safety concerns. For instance Dr Gratton points out “building aircraft out of composite materials poses fire safety issues.” The Aviation industry is faced with the challenge of striking a balance between costs of operating aircraft and keeping environmental impact low. Though aeronautical technology appears to be a leading sector in addressing environmental concerns by cutting CO2 emissions, a closer look reveals that it is responding more to environment concerns where ever they are aligned with economic gains as not much research is being done to reduce contrails formations and NOx emissions. Fuel efficiency may be helpful in controlling environmental damage, but it also drives research and development because this translates into bigger profits by reducing Energy Liberated to Work Ratio (ETWR). It can be inferred that aeronautical technology is moving to help evolve eco-friendly aircraft through remarkable innovations in aircraft design in terms of better engines, use of light materials, improving shapes and configuration of fuselage and wings however use of alternate fuels still needs greater research before it could be put to commercial use and more attention is needed for addressing the issue of contrails as well. Use of computational fluid dynamics (CFD) will increase in the design process for new aircraft with large eddy simulations (LES) being adopted industrially is likely to help in increasing the pace of design and development of new aircraft. Aeronautical engineering is evolving in response to the requirements of the demands of the aviation industry for greater profits in operating aircraft on the one hand and environmental concerns arising from high level of CO2 from flights on the other, however, less attention on contrails is a factor that indicates that aeronautical technology remains predominantly economic benefit driven and it is fast moving to develop environmentally friendly aircraft in terms of fuel consumption because it does not compromises economics, as Dr Guy Gratton states:

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“There is no real compromise between economics and environment because all the environmentally friendly innovations have tended to save money in the long run. High efficiency engines, more efficient air-frames, a lot of advances in airport infrastructure are ways to support environment friendliness”.

The wish of human kind to fly higher and faster is being fulfilled. Engines like SABRE (Synergetic Air-Breathing Rocket Engine) and Materials like CTi Carbon Titanium composites will prove the key to materialise the wish for hypersonic flights. Research and development in space and military projects leads the aerospace technology and most of it is kept hidden for long times. We don’t know whether the answers to most of the challenges have already been found but have every reason to be sure that Aerospace Engineering, like in the past, will be able to realise more dreams in the future .

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