Supersonic Electric Aircraft
Commercial aviation is an essential component of the global economy. The cost of aviation fuel is directly determined by the prevailing world price of oil. It accounts for a major proportion of airplane operating costs. Several airline companies now add a fuel surcharge to the ticket cost of a commercial flight to compensate for the recent rapid rise in fuel costs. World oil prices are expected to remain high for several years. The prospect of sustained high aviation fuel prices could propel airline companies to seek alternative aviation fuels. Seeking alternative fuel could become become paramount for the airline industry should the peak-oil phenomena actually occur. The commercial aviation industry would likely compete for fuel and energy in a market of scarcity and escalating fuel prices.
Breakthroughs and Research
It may become possible for supercooled liquid hydrogen to eventually be used as an alternative fuel for some types of commercial airline service. Extensive research will be needed to resolve the numerous logistical problems that are related to its use as an alternative aviation fuel in supersonic and hypersonic aircraft. Other alternative fuels may include high-density energy-storage technologies that result from breakthroughs in research in the areas of nanotechnology and in high-temperature superconductivity.
Sporadic and significant breakthroughs periodically occur in both fields. High-temperature superconductivity holds great promise for use in high-density energy-storage technology. A coil formed into a torus and made from "high-temperature" superconductive material could theoretically store enough energy to enable a full-sized commercial airliner to undertake an extended trans-oceanic or trans-continental flight. Advances in nanotechnology could enable superconductive materials to eventually be manufactured at a cost that could justify their application in airliner propulsion.
Electrical Storage and Propulsion
Energy stored in a superconductive storage technology could power electric motors that drive the identical propulsion fans that are found at the front-end of modern, "high-bypass" turbo-fan aircraft engines. Such fans provide up to 90% of the propulsive thrust of the turbo-fan engine. Each electrically powered propulsion fan may be driven by multiple (induction) lightweight electric motors during take-off. Some electric motors would "cut-out" under reduced power demand at cruising altitude so that the remaining motors will operate at higher efficiency (electric motors have poor part-load effciency).
Coanda fans may propel subsonic commercial aircraft that use high-density electrical storage technology. Such units were originally developed by physicist Henri Coanda and can operate at comparable efficiency and at comparable flight speeds as turbine-driven propulsion fans. Electrically powered aircraft that use either turbine propulsion fans or Coanda fans could be flown in thinner air at higher altitude (up to 65,000-feet) to reduce energy consumption (less drag on aircraft) on extended flights. The cooler air found at such altitudes could assist in keeping the superconductive energy storage systems functioning properly.
Superconductive energy storage systems used in future commercial aircraft would likely be cooled by liquid nitrogen. Both systems would need to be frequently recharged. Commercial aircraft that operate long-haul service usually undergo cleaning and servicing in hangars after long flights. It is during such service periods when the energy storage and cooling systems could be recharged, a process that would likely be both energy-intensive as well as time consuming.
It may be possible to design the energy storage systems along with their cooling systems to be removed and replaceable during shorts layovers. Such technology may be possible and could help reduce the turn-around time of the aircraft. The introduction of superconductive energy storage systems in commercial aircraft in the long-term future would require that future airport terminals be equipt with power generation technology at or near the premises.
Aircraft turbine engines are very flexible in the kind of fuel that they can burn. Short-haul and commuter airline companies that operate routes of under 500-miles would be the most likely candidates to use alternative aviation fuel. Their fleets are mainly powered by turbo-prop or by turbofan engines and may likely have sufficient capacity in the fuel tanks to carry a cheaper fuel with a lower energy content. They may use such fuel if its cost per BTU undersells fossil aviation fuel. Breakthroughs in electrical storage technology could see a future generation of short-haul and commuter aircraft being propelled by electric motors driving propellers or propulsion fans.
Ground-effect aircraft use a specialized wing design that generated a cushion of air between the wing and the surface over which it flies. Large and heavy versions of such aircraft could be flown at moderate speed over water and carry passengers and freight between coastal centres of up to 500-miles apart. Eliminating the need for take-off to at least 10,000-feet would cut fuel costs. The performance of such craft can be enhanced by a recent development from Britain that has been successfully tested in a scale model aircraft.
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