System Ideas include new, important and radical concepts for important parts of the air transport system but without the need for a complete revision of the total system. Some examples are given im the table below)
Reduced aircraft mass
The pressure upon fuel reduction that will lead to reductions in the climate warming effects of hydro-carbon fuel burn will probably increase. Fuel burnt is a function of the weight, speed and drag of the aircraft. One of the routes to reduce fuel burn lies in reducing the aircraft weight substantially.Weight is made up of structural weight, fuel weight and systems weight.
1. Reduced structural and payload weight
Some of the ideas dealt with in other sections may have relevance here: the use of ground power augmentation (section 2.2) may serve to reduce engine thrust or the use of detachable or ground located undercarriages (section 4.1.3). However, the most effective approach to a better relationship between power, weight and payload seems to rest with new concepts for the aircraft design. The concept that appears to receive most effort to bring it forward is the Blended Wing Body [BWB]. The savings of drag achieved by its tail-less nature are significant and the L/D function in designs being studied is about 15% higher than current design conventions.
Reducing the structural weight of a given concept will bring about benefits dependent upon its operational use. Broadly based figures suggest that the percentage taken off the weight of the aircraft, engines and systems will produce a percentage saving in fuel burn per tonne-kilometre of 1 - 1.5 times greater.
It may be possible to reduce the carried weight of the cabin crew by installing server systems that dispense food, drink and incidental items to passengers in flight. Concepts of zero-baggage or self loading baggage might also serve to reduce the baggage weight carried. It is not known at present how significant the net savings would be.
2. Reduced fuel weight
On long range sectors especially, the carriage of the fuel carried by the aircraft itself implies a considerable cost in fuel used. A number of ways have been suggested to optimise the balance between fuel carried over long stages and the additional fuel used for landing more often. In the UK "Greener by Design" paper5 this optimisation is dealt with more extensively and the conclusion drawn that for many aircraft an optimum stage length is about 4000 Km. This would allow savings on long haul flights of 10-20%.
Already a commonplace for military aircraft the technology is well developed. The benefits would arise from reducing the fuel carried for the latter parts of a journey - this fuel could be loaded much nearer to the destination and allow smaller aircraft with smaller fuel loads to operate. Such a technology could be extended to commercial operations and this has been studied in some depth by Dr Raj Nangia. His preliminary studies indicated significant savings of fuel burn by this method but more study is required to identify practically achievable net benefits when the expenditure of fuel by the tanker fleet are taken into account6. Flight re-fuelling of airliners might become routine, saving some of the fuel used to lift massive fuel loads from the ground and carry it halfway around the world.
Every schoolboy is familiar with pictures of military aircraft flying in tight formation advancing toward the enemy. Every naturalist is familiar with the sight of skeins of ducks flying into the sunset in their typical "V" formation.
The idea put forward is to transport both of these ideas into the air transport system leading to significant benefits in fuel consumption, fuel carriage and in better ATC.
The obstacles of tight formation flying are to avoid on a regular, reliable and secure basis any adverse effects from the weight dependent vortices from the wings of the lead aircraft. Vortices are a function of aircraft weight and commercial airliners are substantially heavier than all other aircraft that have attempted close formation flying.
Conceptually the benefits are very considerable. If the reduced drag that ducks create by wing warping to reduce their individual effort in flying long distances can be harnessed then long range travel could be substantially more economical. Research already conducted shows that cruise fuel savings could be 15-40%.Wings flying within about 0.8m of each other can experience 60% drag reduction7. Practically achievable fuel savings (and fuel carriage) in the order of 10% have been projected. Groups of aircraft (such as on the busy intercontinental routes) could be treated as a single entity by ATC as they sometimes are now. In the further future groups of similarly routed aircraft could form "fixed" formations in which the aircraft became a single flying system under a single control only dissolving as aircraft wished to drop off nearer to destination. The technical resolution of the problem of reliable and secure close flight would be very relevant to other concepts (such as the Cruiser/Feeder above).
3. Reducing systems weight
The section (2.2) dealing with the use of ground power augmentation will be relevant to any attempts to reduce aircraft systems weight. Additionally ideas were put forward that would also bear upon this aim. The benefits of achieving some reduction would naturally play through to overall fuel burn, to economy and to reduced climate impact.
The concept of launched aircraft with some form of airport retained take-off undercarriage was discussed. Were such an idea to be feasible it would bring substantial benefits by eliminating one of the heaviest systems on the aircraft. On initial considerations it is relatively easy to imagine how the take off might be accomplished with the undercarriage being left behind. Landing would be much more demanding. Firstly the loads upon landing are much heavier so the prospect of any lighter weight "landing only" undercarriage is immediately to be rejected.
Landing at normal speeds would have catastrophic consequences. The only idea presently presented that seems to hold out any promise at all of bringing this to fruition is landing within a landing tube (see section 3.2.2) where the "touch-down" speed is effectively zero or extremely low.
Parafoils are used to deliver military supplies. The advantage over a traditional parachute is that these parafoils are steerable. The current loads that can be used with these systems are relatively small.
If the technology could be developed into a system where aircraft could make parafoil assisted landings, noise produced by aeroplanes during decent and landings could be substantially reduced. One could imagine an airport where aircraft are launched by MAGLEV systems whilst runways are only used to recover aircraft using parafoil assisted landings. As the final landing speeds would be extremely low, a simple skid undercarriage would be needed saving at least 5% of the total aircraft weight. Landing strips could be much shorter than the current runways.
The parafoil technology would need to be further developed. First one needs to consider the additional weight that would be carried. Second, the parafoil glider should be able to operate in cross wind conditions. Third, the accuracy of the system should be extremely high with an accuracy of about one meter.
Another issue that needs further research would be the mechanism to open and retrieve the parafoil. This should be done totally automatically. Steering the parafoil should be automatic as well with the possibility of manual override.
Next generation propulsion
The turbo-jet gas turbine engine has been a feature of flight for long enough to be the normal experience of perhaps the majority of travellers. It has settled to a design concept that is reproduced by all the major manufacturers and made in substantial quantities. High by-pass ratio all jet engines power the great majority of the 11,000 or so large commercial aircraft that fly today. In their latest form such engines can each deliver thrust well above 120,000 lbs which would have been received with gasps of astonishment only three or four decades ago.
The question posed by this series of ideas is whether the convergence upon this single formula for design bears any relationship to the form of aircraft engine required in the future.We must ask whether this form, suitable for its age, is entering a new age when another form of propulsion engine will climb to the ascendant position
the turbo-fan has today.
The question is prompted by the pressure growing upon climate impact. The newspapers seem to have become locked onto a "story" that aviation will become the Number 1 polluting mechanism later this century. This is most unlikely to be true and will certainly not be true if it is managed at all appropriately. Aircraft emissions do have an effect, although we are not yet sure exactly what this effect is or how precisely its mechanisms work. It may be the case that aircraft emissions have relatively greater effect than ground level emissions in their effect up on the sunlight coming through the atmosphere.We do not know.
What does seem to be the case, however, is that the continued growth of current aviation practice will be unhelpful to our planet. And that the relatively easy gains of the early jet years in cleaning up the emissions from engines will not now be so easy to repeat.With today’s technology, it is unlikely to be the case that emissions can be reduced sufficiently. Something new is needed.
At the same time great care must be taken in designing the set of pressures and incentives that will encourage and foster these developments. It is interesting that, in a period when fuel taxation is being promoted by some, we also see serious scientific analysis that warns that fuel taxation could bring about more damage to the planet by encouraging airlines to favour more financially economic, but globally more damaging mission profiles.
1. Nuclear engines
Despite the obvious risks and difficulties, nuclear engines have obvious attractions. They make no airborne emissions and their waste can be safely and securely handled on the ground. The technical engine problems are well on the way to being solved. The concerns for safety and security may be overcome but almost more difficult will be the perceptions of society for airborne nuclear engines and the containment of the unit. So any programme of technical research needs to be accompanied by social research into the acceptability of these engines.
Of course, many technical problems do remain but the nuclear engine offers a path from heat to propulsion that utilises many of the same heat exchange technologies that we have already developed. Many of these might make the nuclear engine very similar to a jet engine without the fuel pumping and combustion mechanisms. A number of suitable prototypes for nuclear engines have been built at various powers. Reactor volume and weight as well as containment has always been the intractable issue. Either the weight of the containment becomes excessive for an air vehicle or the containment is selectively reduced and the vehicle becomes a hazard for those outside it. These considerations brought to a halt the last known major attempts to produce a nuclear powered aircraft.
Perhaps with new containment materials and a growth in the size of the intended air vehicle the equations for the containment can be revisited.
Accident considerations offer another major issue of both reality and perception. The public perception will be that nuclear engines are little better than flying bombs able to devastate vast areas around anywhere that they crash. There is no reason to take that view but the public have become fed with similar stories for so long that they will certainly re-surface. The reality is that careful measures would need to be taken to ensure that the nuclear material was prevented from contaminating surrounding areas in any conceivable accident. This not only includes the reactor chamber but the pipes, valves and routing of any of the nuclear pathways in the whole unit.
2. Plasma technology
These electrical effects could be conceived as having two applications; either direct use for propulsive force by having wing and fuselage surfaces made with the correctly embedded electrodes, or by drag reducing measures influencing air flow over the airfoils.
The science of para-electrics is becoming better understood and practical experiments have demonstrated their effects. The task of sustaining these into large-scale structures with adequately robust controls remains to be completed. So too are the power and weight reconciliation’s that would be convincing against the weight and power budgets. It has been asserted, for example, that the plasma effects equate to little more than pushing energy ahead of the aircraft. Making the medium easier to fly through but with the power needed to make this effective interchangeable with the power needed to propel the craft without the plasma effect. It is known that a blunt body can be made faster by forward facing (i.e. reversed) jet engines that work on a similar effect. But these examples do not explain the complexity of plasma science.Work continues in subsonic, supersonic and hypersonic regimes and there is much that remains to be discovered about the benefits and limitations of plasmas.
Other effects besides propulsion may prove to be important including the effect of the plasma on the radar reflection of the craft.
The weight budget required for high power plasma physics on-board is also challenging scientists. The plasma generating equipment will demand its own part of the weight budget and it is not known whether the overall systems outcome would be positive or negative.
3. Fuel cells
The fuel cell has captured the enthusiasm and efforts of many engineers around the world. Its ability to take two common gases, hydrogen and oxygen, and to create energy and water offers a clean, climatically sensitive way to generate energy. Small fuel cells are being produced and marketed already and are well beyond the laboratory stage.
Today’s technology contemplates only auxiliary power unit to augment but not to replace the main power plant of the aircraft. To manufacture large, propulsion level fuel cells will r equire advances in the energy density of the stack. Georgia Institute of Technology has experimented with a UAV propelled by an advanced proton exchange membrane but it generates only 500 watts.
One of the fundamental issues in a large fuel cell of this design is the storage of the compressed hydrogen. The pressure vessels for a liquid gas system are large and heavy and represent a major obstacle to deriving practical designs for significant ranges in full size vehicles.
Another approach is the hybrid fuel cell running on energy dense carbon fuels. The Solid Oxide Fuel Cell (SOFC) hybrid being studied by NASA uses liquid methanol as the fuel. This combined system of directly reforming fuel with a gas turbine end stage offers the best balance of weight and power to date.
4. Solar cells
Solar energy has been proposed as an idea for the future of aircraft propulsion, or as an augmentation to it. The idea is attractive, the sun’s energy is free and in the upper altitudes is easily available. The challenges are also great. The sun does not shine at all times and some kind of interface between the sun and the engine is usually necessary, and most commonly as a battery. The weight of the battery used for this purpose on one long range experimental aircraft8 weighed nearly half of the aircraft weight. Whilst the battery fraction may not always need to be as high as on this aircraft, which was intended for sustained night flights, they still represent a formidable obstacle to the use of solar power.
The power generation of the solar cells is also a problem area. The present efficiency of power conversion to power incident is at a low level, somewhere around 20% with a theoretical maximum believed to be in the mid-30’s per cent. The area needed to produce 1Kw of output power is presently about 5 m2. For a medium 150 seat airliner the wing area is around 122 m2 . The solar power production if the wings were fully covered would be in the order of 25 Kw. This compares to a typical fan-jet engine rated at around 10,000 kW. Whilst the figures may not be precise they clearly illustrate the gulf between solar power and today’s carbon fuel engines. Most solar cell power has been applied to auxiliary power units and to very low-drag experimental aircraft designed on a glider-like principle and able to maintain altitude with very small injections of power.
5. Distributed propulsion
The concept of distributing propulsive force over the aircraft instead of having two or four discrete engines has been interesting engineers in several ways. The idea presented in the workshop was that by having multiple engines, in the limit down to covering the surface with tiny engines, these may be integrated better and more flexibly with the mission. The benefits looked for were to reduce the overall fuel burn whilst making for better control.
Several design schemes have already gone some way towards the idea. One scheme from NASA Langley for a BWB has a modest number of core engines embedded in the wing exhausting across a wider span than usual.
This design shows predicted savings on TOGW of about 5%.
Incorporating blown flaps into the design of distributed thrust also brings benefits and new concepts joining these ideas show considerable promise.
Moving from a modest number of engines to many engines represents further complication and it is not yet clear how this would be accomplished in terms of the mechanical design. The particular benefits of having a mass of very small engines contributing to thrust is not entirely clear.The main purpose of any engine is to provide thrust alone, lift alone or some combination of the two. For a thrust alone set of many engines, each has to be aligned and arranged to contribute to the thrust vector – either directly or via inter-c0nnected ducts. For lift alone the placement of the engines would need to allow the lift component to be achieved, again either directly or via ducts. Engines with a combined role would have some additional complexity ion allowing the force of the engine to be directed to one or the other use in selectable proportions. For very many small engines a ducted system would probably present considerable friction losses to the propulsion system.
Modular, morphing and reconfigurable aircraft
Each of these themes has the connecting idea that the aircraft need not be confined to a single design standard for its entire life. Modular aircraft design seeks to achieve this by connecting different modules together in a flexible and changeable way. Morphing aircraft achieve similar changes to configuration by reversible changes to the structural units in-situ. Re-configurable aircraft are effectively a sub-set of modular aircraft and have changes made by exercising one of a pre-planned series of possible changes to give a limited number of variants of the original design.
The potential mechanisms for achieving these changes are numerous. Modular aircraft (and their re-c0nfigurable sub-set) can be based on relatively changes to equipment loaded into pre-prepared bays in the aircraft. These may have profound importance to the aircraft mission systems but have relatively little effect on the aircraft flight characteristics.
More fundamental changes to the aircraft have been envisaged. These include pods that may be attached to provide different uses for the aircraft, power-plant change routines, individual passenger enclosures or personal seat units, and wing sets for different duties.
Each of these modular changes seeks to achieve a similar end – to provide the aircraft with more flexibility of use, to reduce its use in sub-optimum configurations, to increase its service deployment time or to reduce its load and unload times.
The degree to which they achieve these ends depends upon several factors:
- Is the aircraft type going to be used (mainly) in a single role?
- Is the "modularity overhead" (the excess of weight to achieve the modular changes) going to outweigh the advantages?
- Is the safety of the aircraft compromised?
- Is the cost going to be excessive?
Where the answer to these questions is negative the feature, at least potentially, will be successful.
Modularity concerns different usage for the aircraft. For many conventional airliners in European or US service this seems to have limited appeal since their operations are, for the most part, entirely uniform. Certainly the aircraft have varying load patterns and sometimes have large numbers of unfilled seats. The airlines constantly seek ways to improve their load factors. Those airlines with very focused routes, like budget airlines, generally have better load factors than general service airlines but in both cases the argument for a modular approach seems to be uncertain.
The concept is more relevant to aircraft with varying demands – operating from isolated strips and having to meet a number of different calls. Or aircraft operating throughout the year with demands for snow, land and sea operation – as might apply in parts of Canada, for example. This has been the philosophy that has prompted the design of the Gevers Genesis9 which is designed to operate selectively on all three surfaces. Other change versions might be for an optional cargo/passenger layout or proportion, or an optional passenger/fuel/ water layout, or a long/short range aircraft choice. Each of these has implications for the optimum design of aircraft and modular approaches might well be economical if presenting these choices would obviate the need for another aircraft to be purchased.
Keeping the weight and cost overhead of modularity as low as possible is clearly a challenge. This overhead arises from the provision of additional fixings and strong points that, on an integrated design, would be redundant.
The removal of engine modules (for their replacement by a more role-suitable engine) would be relatively straightforward but the exchange of load carrying sections would be more difficult. An extreme suggestion was to modularise the passenger space down to either single- or a few passengers. The conceptual benefits of this would perhaps lie in loading time and in tailoring the capacity to the number of passengers.
Such passenger pods would need to be attached to the main airframe in a way that maintained aircraft structural integrity that would in practice probably, although theoretically not necessarily, have the main load paths running around the pod constructed zone. This would leave the pods to provide for their own structural security and would also imply that services for passengers – heating, ventilation, pressurisation, in-flight services etc. would need to be connectable to the aircraft either via each pod individually or through a number of pods.
One of the benefits foreseen for passenger pods is that they could be used to transport passengers and their baggage from a remote point – often the home – directly to the aircraft assembly point. This would imply a possible transformation of the airport operating structure and might save very large sums as a result. From an aircraft operating perspective, however, the integrity of these pods would need to be assured in respect of key parameters.
These might concern the fixing points, service connections, outer skin, pressurisation safety margins and so on. This argues against individual or distributed ownership except by agencies able to maintain the pods correctly.
At a lower scale an example of modular design concepts is the personal seat idea. This imagines a seat unit that provides for the standard support of a passenger – connections to in-flight services etc – a luggage container and in-flight ready access supplies. The seat thus becomes the travelling support module for the passenger and can be transported by different means and transferred from one to the other and then to the aircraft where it would clip into a prepared docking station in the passenger compartment. In the aircraft it would require to be plugged into the supply system for entertainment etc but would obviate all other check-in processes because the seat and its contents would be checked-in and security cleared as a unit.
Morphing is an entirely different concept but having somewhat similar purposes. It envisages the use of flexible, moveable or adjustable elements of the structure to change the configuration of the air vehicle in flight. Among the simplest expressions of this idea are the several "swing-wing" aircraft that are in service. But more sophisticated means are also possible. DARPA has a number of projects concerned with aircraft structures and envisages a mixture of mechanical linkages and flexible skin structural elements to achieve much more adaptation than simple wing sweep-back changes. The Gevers Genesis incorporates an extendable wing in its concept that would allow cruise to take place with a more suitable wing form than the extended wing more suitable for landing and take-off. Various forms of adaptable and flexible materials are being researched. To date no morphing designs for large commercial aircraft have been flown.
The passenger experience
Passengers in the late 21st Century may be expected to have very different experiences from that of today if some of the ideas in circulation come to pass. These ideas are driven by considerations of reducing the climatic footprint of the air traveller, by considerations of reduced hassle in reaching and boarding aircraft, and by an altogether less stressful journey experience.
1. The sleeping passenger
This idea proposes that passengers will be able to avail themselves of a drug which will have the effect of inducing gentle and harmless sleep for all or most of the flight. The drug would need to be non-addictive, harmless, with rapid or predictable sleep following its administration and rapid, anxiety-free and alert waking on administration of a signal or injection. The concept of drugs able to be taken by passengers of administered by airline staff would break new barriers and require careful controls not to speak of the safety testing that would be involved.
The benefits would lie in an experience less stressful for many passengers, especially on long flights, and a reduction in in-flight services. With suitable cabin design, passengers might be able to use full horizontal beds in tiers. These would prevent problems with DVT and permit a comfortable and relaxed sleep with very similar cabin volume to a seating arrangement for the same number of passengers.
Combined with the modular passenger pod concept (see 4.3) the passengers could board even before reaching the airport and pass through boarding formalities already in a state of oblivion.
2. The transparent cabin
In contrast to the concept above which would be feasible with no cabin windows at all this concept envisages a totally transparent cabin wall and roof. High strength materials to achieve this do not exist presently but the transformation in passenger experience would be remarkable. The sense of being on a sort of magic carpet flying through the air could be a wonderful new experience for many passengers. For some the experience might be altogether different and alarming, and therefore a quite unwelcome one.
Practical difficulties that would need to be addressed start with the materials to make it feasible without significant weight increase. Research would be needed in the nature of transparency and into possible modifications that might be possible to the efficient materials of the aircraft pressure cabin. Given that such material might be developed it would also be necessary to study how many of the services presently out of sight behind the side walls and roof of the cabin could be routed to avoid these areas. The reaction of the material to sunlight and radiation might also present problems; making passengers too hot, to brightly lit or, at worst, susceptible to increased and dangerous levels of solar radiation.
3. The window-less cabin
Quite the opposite effect is envisaged by the window-less cabin. In this idea the passenger experience is enhanced by virtual reality impressions of flying instead of having widows to look out from.The idea is especially interesting against the studies being done on blended wing aircraft where many passengers would necessarily be seated well away from any windows. Given the continued rapid increase in the capabilities of games consoles, virtual reality simulations and all things electronic the concept of an immersive experience based on artificially provided content is not perhaps very far away. The content supplied could vary, of course, from simply representing the flight in progress to representations of flights at different altitudes, and even over different terrain.
Moving from the field of flight to a wider range of entertainment is an obvious progression and the repertoire of possible programmes is effectively endless.
The benefits would rest very largely with the passenger but the absence of windows might also provide increased flexibility of design and layout to aircraft manufacturers.
4. Multi model service
Demand for air travel is increasing with the development with world GDP. More than 70% of the air travel is for leisure. The question remains if new technologies like virtual reality will reduce the desire to travel and will represent a real alternative.
Unless there are market distortions , for example through government interference in the market based on environmental concerns, through disease or political tension, air travel is likely to be marginally affected by alternative ways to travel or to communicate. At distances above 400Km air is still the most convenient and cheapest way to travel.
In some European countries, high-speed rail connections have been created or are in the process of being established.
But, high speed rail infrastructure costs 30 million _ per Km, and therefore the number of tracks will be limited. IT technologies will certainly have some effect especially on business travel. However, tourists want to see and feel for themselves. Moreover, there is a famous saying that the more (business) communication there is the greater is the need to travel.
In the past, the focus in transport was very much on the type of vehicle; the aeroplane, the car or the train. As travel is now a commodity market, there is, and will be, a strong emphasis on the customer and his comfort zone. Passenger satisfaction will be one of the main drivers in the future transport industry.
The customer will demand a seamless travel from kerb to kerb. In future, the traveller will also demand one single ticket that entitles him or her to make the total journey independent of the travel mode or operator. If the traveller is obliged to use different transport modes, he/she will demand multi-modal solutions that are time efficient and convenient. Aviation has been kept more or less separate from the multi-modal transport discussions up to now. But this has to change, air transport should be seen as one of the building blocks of a global multi-modal transport system.
One of the important issues in multi-modal transport is the requirement for easy transit and avoidance of repackaging.
This is also true for the cargo market. Containers used in aviation are different from the ones used in other transport modes. This is partially because aircraft fuselages are round pressure vessels, which require that separate containers are designed to be stored in the round cargo bay. Furthermore, the containers used in aviation are lightweight. Containers used in other transport modes are designed to be strong and heavy, to be stacked and to be stored in an unprotected harsh environment.
Multi-modality would be enhanced if the same type of containers could be used in all types of transport modes.
New aircraft configurations like the blended wing body aircraft would allow the use of rectangular containers that could be used by other transport means as well without the need to repack. A compromise might be to design air containers that simply stowed as a complete unit inside a standard land container to provide the additional protection and to fit the land standard fixings.
One could imagine the use of a family of standard containers adapted to the different roles foreseen. The universal cargo containers could be made bomb proof as has already been demonstrated by containers made of laminated metal like Glare“. The smallest type of cargo container could be loaded on small lorries that could service inner city distribution points. Bigger containers could be used in shipping, trucking and aviation as well. The passenger container could come in different sizes and be transparent. It could seat different numbers of passengers depending on the size of the container. There could be room to stow luggage and personal belongings in the container. Containers would be adapted for use in aeroplanes, on busses, trains and other transport modes.
Airline passengers could be collected at different locations in different cities and be transported in these containers from the pick up points to the airport.
If need be there could be a transfer point in between the pick up point and the airport or seaport, where passengers would change container according to their final destination. Such a system is already common practice in holiday coach travel: the passengers are picked up at different locations and transferred to a common transfer location where passengers seek the coach to their final destination. A similar set up could be followed using the passenger containers. With these containers a multi-modal pick up and drop system could be created. The containers would be loaded on the aircraft as soon as they arrive at the airport and connected to the aircraft utility systems. Containers would also be connected to corridors inside the aircraft that would give access to general facilities of the aircraft like restrooms, bars and entertainment facilities.
Containerised transport would be the compromise between mass transport and purely individual transport. It would be the link between public and private transport modes as well.
5. Self-load baggage
Being parted from one’s own baggage is just one of the stresses of modern travelling. The efforts that some passengers make to avoid checking in baggage is but one of the symptoms of this sensation and the perception that what goes with it is delay, lost or delayed bags and lost or stolen contents.
One idea to address this is to go with the sentiments of the passenger and assist them to take their own baggage with them onto the aircraft. By redesign of the fuselage interior it could be possible to arrange for vertical luggage bays able to be loaded directly by passengers. Alternatively the redesign of the baggage loading process could place the cargo container as now used at places accessible to the passengers who could load their own bags and similarly unload them at the destination.
There would be disadvantages to the airport in that their baggage-centred process would need to be re-aligned to become a passenger-centred one – no doubt at some cost. But the benefits to passengers might be substantial even if these benefits would exist in their perception given the low percentage of bags that get lost. Detailed process engineering would be needed to ensure that the benefits that passengers want, security, time saving and convenience were actually delivered by any new process. If the aircraft were to be redesigned the issues would be of preserving the pressure envelope without sacrificing too much of it to baggage storage at the expense of passengers.
6. Boarding through multiple doors
Bordering on an evolutionary idea this extends the current provision of multiple doors considerably and envisages many doors with simultaneous boarding and disembarkation in parallel streams. Conceptually passengers would board along an air-bridge dedicated to their entrance and appropriately signed to prevent confusion. They would join the aircraft at a point immediately adjacent to their seat and be able to get settled much more rapidly than at present. On wide bodied a/c these doors might be on both sides of the cabin to permit easy boarding.
For the aircraft manufacturer providing more doors will exact a price in the weight carrying capacity of the a/c and upon cost, both of which would need to be picked up eventually by the passenger.
7. The airborne hot-desk
The number of business travellers grows less quickly than the number travelling for leisure. Nevertheless, the pressure on individual business travellers increases with competition increasingly being fuelled by the electronic devices that enable businessmen to operate from anywhere in the world. This is increasingly the situation but it progresses at a slower rate in the air than on the ground.
A new and important step in this transformation will be to install a genuine "Hot Desk" facility for the ordinary business traveller. This would enable him to operate fully whilst airborne with access not only to the internet and e-mails but also to a useful range of commercial office software. Almost more importantly would be access to his own files and records as fully as he would in any terrestrial situation. For installations of where cost is no object such facilities can now be provided. The challenge will be to supply them at a reasonable and commercially acceptable cost.
Relevant technologies will include secure broadband access from the aircraft, the access to appropriate software, and secure deletion of private files. All these are foreseeable within present or forthcoming technologies.
8. The air traveller
For most passengers travel by air represents a period of time expended on merely getting from A to B. The faster it can be achieved the better. The least that it interferes with "normal" life the more the passenger likes it. But with people looking for new experiences and with limited time to do it a new or rather re-invented kind of passenger may emerge – the Air Traveller. This kind of traveller goes by air for the experience it represents and the places that it allows him to see. In the 1920’s travel by the great German airships was an experience in itself and passengers thought themselves lucky to take part in the Graf Zeppelin’s world tour in 1929.
Today we can contemplate this renewed interest in the world around us, and the chance to see it before it suffers inevitable change. The passengers would be provided with a high level of luxurious accommodation on board with every opportunity to move around and to be comfortable.
Meals may be taken at tables rather than in seats and these may be placed to give excellent views of the passing landscapes. Of course, the aircraft will fly at relatively low altitude perhaps as low as 1,500 m where this is possible.
For this reason the aircraft would be designed for slow (perhaps 120 knots) and quiet flight – perhaps with shielded propellers mounted above the high mounted wings. The passenger cabin would be a single aisle design with every passenger able to enjoy a good external view. This view would be augmented by forward viewing from the front cabin and by an array of real-time video cameras feeding views into the cabin. These could be combined with lecture presentations on the geography, flora and fauna of the area.When possible the concept of transparent cabin section (see The Transparent Cabin above) would be employed to add to the experience.
Few new techno0logies are necessary to bring this idea to deployment. The obstacles would be the assessment of commercially viable demand and the investment in suitably designed or adapted aircraft.
9. No cabin crew
At present there is about one cabin attendant per 50 passengers on board of commercial airliners. Cabin crew has an important function to guide passengers in case of emergency and to serve the passengers during the flight.
But crew costs represent a substantial part of the Direct Operating Cost of the aircraft. Cost efficiency could be increased if no cabin crew would be needed. For passenger service in smaller aircraft the crew could be replaced by automated systems that would use robot type of technology. In larger aircraft the passengers could stroll around and help themselves to what ever service they desire being served via a galley wall by robotics.
In larger modern aircraft the safety drill is already explained via a video presentation. A different approach could be that the passenger receives the information via his or her cellular phone. This phone or a more advanced personal communication device would be used anyway to guide the passenger in the terminal buildings of airports.
In case of an emergency the passenger would be provided with safety instructions via the personal communication device. For those who do not have a personal communication device, the device would be provided by the airline.
ICAO has formulated 11 key performance parameters for the Air Transport System: access, capacity, effectiveness, efficiency, environmentally friendliness, flexibility, interoperability, predictability, safety, security and participation.
The same criteria can be applied to ATM.We need some form of management to ensure safety through separation of the traffic and warnings to traffic of potentially dangerous weather conditions. And we need to ensure that capacity in the air and on the ground can be maximized at the lowest possible cost and in a safe way. How do we avoid traffic jams, especially in the air and near/at airports?
Basic functions are navigation, separation, weather forecast and arrival/departure management.
At the start of commercial aviation the solution was to use maps and to create airways, by flying from beacon to beacon, more or less simulating ground traffic. This made navigation relative simple.
Some oversight was provided by ground based controllers who could "see " relevant traffic thanks to radio bearings and radar and could even recognize the individual aircraft thanks to transponders in the airplanes. As regulated traffic had to fly along these highways and the number of planes increased, some control was provided by the ground controller advising traffic via radio communication, based on the traffic picture provided by radar.
The system became more and more automated with tools provided to the controller. Some planning for airspace use was introduced.
Although INS provided the pilot with an alternative navigation tool, the basis for navigation and separation was still the pilot’s eyes and brain, radio beacons and the controller’s advice.
Weather information is provided to the pilot via weather information services. Some weather predictions are available at the start of the flight. Updates can be obtained by listening to other traffic and via ground information.
Landing and departure sequence is based on first come first served. Slots are given for free to customers of the airport. If there is too much inbound traffic at a given moment, the traffic is routed towards holding areas, where aircraft fly in a holding pattern.
The airspace was divided into controlled airspace and non-controlled airspace. Furthermore large parts of the airspace were allocated to the military where civil traffic cannot fly. This reduces airspace capacity substantially.
Air traffic control sectors were established according to national boundaries instead of the pattern of traffic flows.
Currently there are 36 Air Navigation Providers in Europe and 68 Area Control Centres, handling 8.9 million IFR flights per year.
The Single European Sky initiative by the European Commission tries to get commitment by Member States to restructure the airspace sectors into multinational sectors based on traffic movements and to allow joint use of civil and military airspace. This initiative is aimed at increasing airspace capacity and at reducing the cost of European ATM services, that are twice as high as in the US.
1. A need for pilots?
Based on the traditional concept for the controlled airspace, new procedures and tools are introduced. End to end planning of traffic flows is an important element. So called 4D trajectory planning is aimed at a seamless flow along airways and arrival/departure at airports. It is based on an automated control loop between the aircraft (FMS) and the Air Traffic Control computer for IFR traffic.
If such automation is the way forward, there is no need for pilots on commercial IFR flights anymore. Aircraft can be flown automatically under ground control. (There may be a need for some safety pilot to reassure the passengers and to act in case of emergencies not foreseen by the software. This safety pilot could attend to other duties like cabin service during the flight as well).
The question remains, if such a system based on automation of the traditional ATM concept is flexible enough.
How to handle unscheduled traffic? Can central computers deal with large amounts of traffic data? How to pass on control from one ground station to the other? What about intercontinental traffic planning, as international traffic is more depending on variable jet steam velocities and their 4D trajectory is difficult to predict. If flight control is fully automated, who is liable in case of an accident? Can older aircraft be upgraded to shorten the transition time into fully automated flight? Etc.
2. Free (IFR) flight?
New technologies are now available that would enable totally different concepts. Satellite based navigation, communication and surveillance enables precise navigation and broadband communication, making radar (and mode S) communication no longer needed. The aircraft has now a reliable navigation tool and thanks to advanced communication data-links can see all relevant traffic. In combination with onboard systems like collision avoidance systems (ASAS), automated weather updates, ground proximity warning systems, enhanced vision systems and wind shear/ vortex warning systems (which can be integrated into a single, easy to interpret display), the pilot can obtain total situational awareness. The function of a controller would be at best to act as safety monitor for en-route traffic and to ensure that traffic jams are avoided near airports. However, airlines may manage their own slot priorities at airports via CDM systems. So the extreme alternative is to rely totally on the pilots without a need for controllers or control centres.
3. Non controlled airspace
The air transportation system is going to change. Aeroplanes will become very silent allowing 24 hour operations at airports, even in the vicinity of big cities.
ATS may also shift from scheduled towards more unscheduled operations. There may be a variety of flying vehicles; like personal air vehicles, air taxis, business jets, charters, unmanned aircraft (flying under ground command or flying a pre-programmed track), dedicated cargo planes, and planes from regular airlines using a Hub and Spoke system as well as direct routing to both primary and secondary airports. Inter-city and intra-city traffic will be using VTOL aeroplanes, whilst civil and military aviation will share the same airspace.
Strategic 4-D planning or speed control becomes impossible as trajectories of all this traffic are unknown.
Reserving airspace for particular applications would create artificial shortage and should be avoided. In such a system the prime concern is to ensure that mid air collisions and traffic jams near airports or landing sites are avoided. Thanks to secure satellite CNS and intelligent anti collision systems, aircraft would be unable to collide in the air or with the ground. Flight control and collision avoidance would be automatic by introducing intelligent systems on board. In certain cases, manual override would still be feasible as IFR operations are like VFR operations with total situational awareness based on network-centric communication tools. Onboard navigation systems will select the best route, and ensure that flying through severe weather is avoided. Much can be learned from the route planning and navigation devices currently available for cars.
Airport shortage will be partially offset by introducing different airport layouts, the Metro liner, dedicated cargo airports, floating airports, separating take off and landing and VTOL-aircraft. Scheduled air traffic would be "depeaked" as much as possible. The restructuring of the transport system, by bringing air and ground management in one hand, will help in this respect.
If insufficient airport-slot capacity remains, slots will be sold to the highest bidder. Slots may represent a scarce commodity and thus have a price. Such an economic mechanism will stimulate operators to look for clever alternatives to offload their passengers.
4. Global ATM
By replacing traditional procedures and systems not by automation but by intelligence, a totally different air traffic control will emerge. Control will be back where it all started: inside the vehicle. We need to assure that all aircraft in the world will be equipped or retrofitted with the same standard equipment. If large production series of equipment can be realised, the equipment price will be low. Current developments in onboard equipment for air taxi aircraft are already leading the way. Human factors have to be given more attention than in the past. Certification will stay an important issue.
We need to organise a world-wide consensus on the future of air traffic control. We need to think in different concepts to cope with the future, diversified air traffic.
New aircraft technologies introduction
Many of the ideas collected in this survey concern the design of the aircraft, or have implications for its design.
Rather than present them as a simple list of disparate ideas they have been collected together under eight headings.
These range from new ideas for flight mechanics (under Global Flight Concepts) to the induction of sleep to give passengers a sensation-less flight (under Passenger Experience). Several of the concepts examined in other principal sections have implications for the design of the aircraft – whether in the Cruiser/Feeder concept or the Airport of the Future. In general where individual subjects have been treated at length in other sections they are not repeated here.
We have become accustomed to the "standard" airliner of the early 21st Century. It has a familiar form and most of them have the family characteristics of large twin engines, a cylindrical fuselage, a lower freight bay and upper passenger compartment, swept back wings and a tricycle undercarriage. Some argue that this form is the conclusion of evolution and that it simple demonstrates the limiting form of the idea. Others take the view that any form is only the product of the circumstances that produced it and if these change the evolutionary form will change and can be changed. The ideas presented here follow this path.
Prompted by the pressures for environmental sensitivity some ideas focus on ways to make dramatic, or at least important, savings in the amount of fuel used by the world’s airliners. Previously dismissed contributions to economy of fossil fuel lie behind the thinking of several concepts.
1. The glider-like airliner
Gliders have very high aspect ratio wings. These low drag wings allow them to sustain altitude in the lightest of upward thermals (about 1 fpm) and thereby to carry out long distance flight on no fuel at all. Their glide ratio is extremely shallow – in the order of 1 in 55 compared with a typical airliner of 1 in 15 (B747). Powered gliders are somewhere between a conventional a/c and a glider. Their small engines can be used to gain or to sustain altitude and the consumption of fuel is still only small.
The concept is for airliners with some of the characteristics of a powered glider. It would have high aspect ratio wings and be fitted with substantial engines for climb out but much less powerful than those in current use. Its cruising speed would inevitably be much lower – perhaps in the M0.4 range.Take-off speeds would be lower and runway lengths much reduced. The normal mode of operation would be using the engines but cruising
power demands would be very much lower. A glide ratio of perhaps 1 in 27 would produce a hybrid having many of the advantages of the glider whilst retaining most of the flexibility of the modern airliner.
The benefits are mainly in the consumption of fossil fuel. A 200 seat airliner on a 1000 nm leg will use something like 10 tonnes of fuel. A glider-like a/c of the same capacity would use perhaps an eighth or a quarter of this amount.
The lower speed of the aircraft brings some disadvantages: the aircraft is less able to earn revenue and it offers slower and thereby less attractive journey times. Against this it will be a cheaper product to make and for medium legs the extra journey time will not be hugely significant (the change from say M0.83 to M0.4 would add about 30% to total door-to-door journey times on a 1000 nm leg).
2. Wing in ground effect craft
These WIGE craft have been produced for many years – notably by the former Soviet Union. They give the promise of considerable savings in fuel through operating near to the surface (within about half a span) and gaining from the ground effect of the airflow over the craft.
Large and small craft have been shown to be feasible. A body of design knowledge exists for their design and construction. In the era when most WIGE were subject to experimentation within the FSU the considerations of fuel saving were of a different kind to today. It may now be the time to re-examine such WIGE craft and to adapt them for commercial operation.
The potential benefits lay in their fuel efficiency. For a 200-seat craft over a 1000nm leg the fuel saved might amount to 50-60% or 5 or 6 tonnes.
The disadvantages of these craft are that speeds are generally in the range 150-250 knots and the routes for their operation must be suitable for very low flying craft – i.e. either sea-lanes or barren land. Technically the craft work satisfactorily when properly designed although a natural disposition to pitch instability needs to be carefully considered. (WIGE are also covered in section 3.2.3.)
3. High speed blimps
The technology of lighter-than-air craft has progressed substantially since the heyday of the great German Airships of the 1920’s. At the most obvious level it is no longer necessary to use hydrogen as the lift gas with its attendant dangers. In recent times, several companies have come up with concepts for airships for special purposes including heavy lift operations. The idea put forward here is for an examination of a high-speed airship which might overcome the disadvantages of the relatively slow speed (around 100 knots) of conventional craft.
The essence of a pure airship is that the lift and thrust components of flight are provided for quite separately. Lift is from a large gas enclosure and this lift is almost independent of speed. Thrust is provided by a number of engines which do not provide any component of lift.With modern designs these conventional approaches have been questioned. The very modern Zeppelin NT has rotating engines that can contribute to lift as well as forward speed. Nevertheless the speed is 125 Km/hr in level flight. The Ohio Airships Dynalifter“ is a hybrid style of craft with wings that contribute to lift and control as speed is achieved. A substantial fraction of the weight is lifted by the wings and this is claimed to be a benefit in landing since the craft will sit securely on the landing ground once at rest. Speeds of 100-200 knots are forecast for this type of craft. The Cargolifter heavy lift airship was one of the concepts designed by the company carrying up to 160 tonnes at speeds up to 90 km/hr.
Cargolifter suffered insolvency in 2002 and the present fate of the project is uncertain.
It is certain that new technologies make the construction and use of airships more practical.With hybrid technologies, some of the handicaps of the format may be overcome. Looking for very high speeds will continue to be a compromise between lift, size and construction since an envelope of minimum cross-section would be too long to be practical. Similarly, an envelope of compact length would represent a considerable cross sectional drag.
4. Flying boats
The days of the great flying boats seem to be well past. The unexplored potential of the Spruce Goose, the might of the PanAm Yankee Clippers, the sturdy service of PBY’s and Sunderlands all seem to be from the history books.
However, as we look at the new challenges of the future there are reasons to think that the second age of the flying boat may be coming about.We hear, for example, about congestion at hub airports, and we know the opposition that is raised to any airport extension.We know also that these reactions are set to get worse and not better.
New technologies could be applied to new designs of flying boat and might include better resistance to corrosion, more controlled approach and landing, and more convenient entry and exit arrangements when compared to their forebears. Very large aircraft could be considered given the space and water surface for landing.
5. Flying lower and slower
A high cruising speed has always been a design parameter in airliner design. High speeds mean high productivity and thus low operating cost.Turbofan engines are optimised to operate at high altitude and aircraft are optimised to fly at speeds up to Mach 0.89 for large and about Mach 0.80 for regional aircraft.
Initial studies in the past have indicated that a regional jet seating 100 people and powered by a turbofan engine, flying at Mach 0.77 at 37.000 ft, would need 82.5 minutes to fly a 400nm mission. If the aircraft was powered by a counter-rotating prop-fan engine flying at Mach 0.72 at FL 31.000 ft, the time required would be 83.4 minutes. This represents an increase in time over a 400nm stretch of 1%.Yet fuel consumption would be 35% lower and NOX emissions are estimated to be 50% lower. The effect of flying at lower speeds on long haul flights would of course be more substantial. A trade off between flying slower versus the longer flying time and the consequences for total fuel consumption need to be calculated.
Flying at high altitude creates contrails. It is believed that contrail formations make a significant contribution to global warming. The formation of contrails is depending on the ambient atmospheric conditions. Contrails start to appear when the outside temperature is less than -40 degree Celsius.To avoid contrails, aircraft would need to fly substantially lower especially during wintertime. The temperature conditions can vary significantly between regions and may vary on a daily basis. Consequently, some have suggested adapting preferred flight altitudes in flight plans on a real time basis to minimise contrail formation (note: flying above 40.000 ft also reduces contrails as the humidity level at or above that altitude is low. But flying at such altitudes may have other negative effects due to other emissions).
The current generation of aircraft is not very well suited to fly at lower altitudes like 20.000 ft however. Flying lower would result in longer journey times and hence more fuel burn. On a 6000nm trip this could result for some particular aircraft in a flight time of one to three hours more and up to 30% to 60% more fuel-burn and hence CO2 emissions depending on the flight altitude. Such severe consequences are difficult to accept with current aircraft.
Different fuels will not mitigate the contrail problem, except in the case nuclear energy could be used to power aeroplanes. The alternative would be to design aircraft and engines that would be optimised to fly at lower altitudes.
Trade-offs are needed to demonstrate the optimum, related to the environmental impact of flying high and fast versus low and slow. These studies need to take a full systems view accounting for total carbon emissions, NOx as well as the investment return on the aircraft.
Flying at lower speed or altitude is against the long-established trend in air transport as it results in longer journey times, loss of efficiency and the need to procure more aircraft. On long haul flights, it may even make stopovers necessary again unless mid air refuelling is introduced. But, if the protection of our environment calls for this concept, we should seriously consider changing technological developments in that direction.
6. UAV’s and autonomous flight operations
During the recent years UAV’s (uninhabited aerial vehicles) have become common goods in the military domain. UAV’s in the military are used for dull, dangerous and dumb missions. Two types of UAV vehicles exist: UAV’s controlled by an operator on the ground and UAV’s that fly autonomous missions.
Pilot-less aeroplanes are attractive to civil aviation as well. The cost of the crew is a substantial part of the Direct Operating Cost [DOC] of airliners and the replacement of the crew by automated systems seems to be attractive. However there are serious safety concerns. Even today aircraft can auto-land and fly using the autopilot. However, technology is not fool proof and human intervention is needed from time to time to reset the systems.
One could imagine a future in which planes would be flown in a totally automatic mode. Advanced self-separation and automated station keeping, auto-takeoff and auto-land will be feasible. One could think of a safety pilot who would monitor the onboard systems as an interim phase before accepting fully pilot-less aeroplanes.
Manual override capability would be available to the ground-based operator.
The introduction of this system is related to the reliability of systems, to safety concerns and to security issues. At no time should terrorists be able to intercept the communication with the aircraft and take over their control. Highly secure data links would be needed to ensure these situations cannot occur.
The introduction of pilot-less aircraft in civil aviation could be feasible at first in all cargo UAV’s. There are substantial cargo movements in Europe. In the north/south direction, the cargo has to pass the Alps and the Pyrenees. In the east/west direction surface traffic has to cope with transport infrastructures in the East that are not yet of the same quality as in Western Europe. As rail infrastructure is limited and passenger trains have higher priority than cargo, the average speed of cargo rail is extremely low. Inland shipping is an option but is only slow to re-develop. Therefore, trucking has become the most favoured way to ship goods. However, European highways are already saturated and will be completely blocked in a few years. Unless the personal flying vehicle is introduced quickly, the most desirable option will be to ship goods by air. Aerial freighters could fly standard routes that could easily be handled by UAV’s. The idea of a UAC(argo)V is not new. Its development should take into account the certification related issues.
How to ensure that the vehicle will operate safely? How can we track the aircraft and who would be able to take over manual control. What will be the importance of the interference with other traffic? What about the liability issues?
One possible scenario is to fly these aeroplanes at night and to create special flight corridors for cargo aircraft. These could use direct routes and be monitored and controlled by a single authority. The UACV would fly standard patterns. There would be an automated station keeping and avoidance system installed with autonomous features to fly holding patterns in case of a disruption in traffic.
The next step in flight automation could be the autonomous small flying vehicle. The difference between the cargo liner and the personal vehicle would be that the cargo-liner would fly the same pattern every day whilst the personal aircraft would need to be very flexible.
If the technology proves to be safe and reliable even large passenger aircraft could become pilot-less. Here the key word will be safety perception rather than technology.
7. Vortex control
Vortices have been present behind aircraft since the beginning. As aviation developed the physics of vortex generation has also extended. The importance of vortex management lies in the central factor that determines their strength – the weight of the generating aircraft. So as we move to heavier and heavier aircraft the problem becomes more acute. The forces are considerable. Vortex circular wind speeds of up to 300 ft/sec are generated. The fundamental cause of vortices is well known. They are twin contra-rotating spirals of air that rotate in the underwing to over-wing direction at each wing tip.
Vortices are important to airport efficiency and safety. Where large heavy aircraft are using the airport, the avoidance of vortices can become a limiting factor to airport capacity. This occurs by the application of longer separation distances between heavy leading aircraft and lighter following aircraft. Where inadequate allowance is given to the possibility of vortices affecting following aircraft accidents can happen, with disastrous results given the low altitude of the event. Vortices are at their most serious in just the conditions that apply to landing -heavy, low, and slow.
Vortices also occur in flight but they sink and die away normally within the clearance distances that are usually sustained. They become more important when concepts such as formation flight and linked aircraft are applied. For these reasons, research to understand, to modify and ultimately to control vortex formation has a high priority on both sides of the Atlantic. The introduction of the A380 will raise new issues for resolution as it leads the field in weight. European research programmes like the AWIATOR programme in FP6 has vortex management at its centre.
In the longer term, the control of vortex formation and the ability to modify its behaviour might also bring new opportunities. Arranging the vortices to be favourable to formation aircraft would bring the concept of grouped flying very much into play. Flying onto large structures such as imagined under the Airborne Metro would need this phenomenon to be very well understood.
8. Invisible aircraft
Airports are centres of economic activities. As a consequence airport attract business activities, both directly related to the air station function and businesses that are depending on air freight and easy access to air transport. Consequently, many people want to live near to their working place and thus near to the airport. Cities and airports expand and because of the increasing air traffic, there are complaints from the people living near the airport about aircraft noise, pollution and smell. Experience has shown that when traffic increases even at constant noise levels due to improvements in aircraft technologies, the complaints about nuisance from aircraft noise tend to rise.Noise is therefore not an absolute issue but a question of perception.
One solution to alleviate the problem is to make aircraft invisible and to make them silent. In the military domain work is carried out to create visual stealth. The active camouflage technologies range from using light to illuminate the aircraft, amongst others by using fluorescent panels. Research is also focused on electro optical camouflage using electro-chromic polymer materials. Aircraft could be covered with a coating of LCD’s.
Photosensitive receptors scan the surrounding of the aeroplane and a picture is displayed on the LCD’s. This technology would make the aircraft virtually invisible as it blends with the surrounding.
Anti noise would be used to counter the noise of the aircraft. Already tests are performed to see if anti noise technology can be used to compensate for aircraft noise inside a house. The technology could be expanded to create anti noise in areas located near to the departure and arrival tracks at airports.
Aircraft themselves can be made silent by avoiding airframe noise produced by high lift devices , the undercarriage and aircraft cavities.
Hypersonic and space travel
To satisfy the basic curiosity of mankind, space travel has been high on the want list for many years. Current methods to launch men into space and to recover them to earth are extremely expensive and dangerous. New ventures like that by Rutan could make space travel feasible at acceptable cost. But the idea of using a space plane to visit outer space hotels or densely populated stations on Mars is still a long way off.
Another issue is travelling to destinations on the globe at higher speeds. The sound barrier has proven to be a phenomenon that seriously restricted travel to subsonic speeds. Only Concord flew on a regular basis at Mach 2, but it required substantial amounts of power and fuel to overcome drag in the atmosphere. And thus Concord was expensive to operate and accessible to the happy few only.
Will it be feasible to fly even faster then today to several destinations in the world at reasonable cost? Will hypersonic airliners, flying faster than 5 times the speed of sound, bring us to any destination on the globe in a few hours? The technology is (almost) ready. New supersonic ramjet technology (scramjets), using air breathing propulsion systems based on liquid hydrogen fuel would allow us to reach any place on the globe within 2 hours flying at Mach 10.
New methods of flight like the wave rider method would allow airliners to ride on their own shock waves. The concept of Hyper Soar would lift an aircraft under its own power up to 40Km high. The engines would then be turned off. The plane would still accelerate to 60Km altitude and then fall back to earth. At about 35 Km high it would "skip" on the upper layers of the atmosphere and be bounced back into space. Each skip would represent a 450km travel distance and a trip between Tokyo and the western part of the US (10.000Km) would take 72 min., using 18 skip procedures. The inventors claim that this method would make travel twice as fuel-efficient as today’s airliners. The question remains whether this could become a regular way to travel or just a fun ride as the passenger would be subjected to zero "g" conditions and during the bounce probably to several “g’s”.
We feel that such operations will not replace regular air traffic for a long time to come. The hypersonic aircraft will probably first be used in the military domain. Issues like propulsion, heat and safety need to be explored first before any use in commercial aviation seems feasible. However, if we succeed in attaining speeds up to Mach 24, we could develop an aeroplane that could reach outer space stations, as this speed would represent the same speed as objects in orbit around the globe. Such a vehicle would probably need a combination of scramjet engines and rocket power.
Do we feel that space travel or hypersonic travel is likely to happen on a routine basis in the next 50 years?
Probably not. Unless big steps in new technologies come along that would allow for an efficient, safe and a comfortable (1-g) journey.
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