The Federal Aviation Administration (FAA) reported that last year, U.S. and foreign air carriers transported an estimated 161.8 million passengers between the United States and the rest of the world. The FAA estimates there will be one billion passengers in 2024. So how does the aviation industry handle the prospect of a billion passengers with rising fuel prices, crowded airspace, out-dated systems, and increasing environmental concerns? The answer is new technology that is both in use today, and on the horizon for air travel tomorrow.
Green aviation is about taking responsibility for the impact of aviation on the environment, which includes carbon footprint, other emissions, and noise. Last year, ASTM International, the global standards body that oversees jet fuel specification in North America, published new rules allowing the use of biofuels (made from living things or the waste they produce) on all commercial flights. The revision to standard D7566, Specification for Aviation Turbine Fuel Containing Synthesized Hydrocarbons, includes requirements for synthetic fuel components manufactured from hydroprocessed esters and fatty acids (HEFA) produced from renewable sources. The standard allows new components to be manufactured from jatropha, camelina, and fats, and combined with conventional aviation jet fuel.
Biofuel (or drop-in fuel) must have energy density equal to or greater than conventional jet fuel, and must be able to function in desert heat or in cold temperatures at 40,000 feet. Boeing has been leading the push for approval of synthetic paraffinic kerosene (Bio-SPK) jet fuel, and is also testing algae- and camelina-based fuels.
France-based Airbus also has been in the forefront of developing and testing new jet biofuels. They are helping to develop the second generation of biofuels, known as biomass, which avoid competing with food resources. Some options being investigated are algae, woodchip waste, camelina, yeast, and halophytes such as salicornia (plants grown in salt water).
Boeing recently flew the world’s first commercial airplane from Everett, WA to Paris using biologically derived fuel. The 747-8 Freighter’s four General Electric GEnx-2B engines were powered by a blend of 15% camelina-based biofuel mixed with 85% traditional kerosene fuel (Jet-A). Boeing did not need to make any changes to the airplane, its engines, or operating procedures to accommodate the biofuel.
Carbon dioxide (CO2) is produced as a result of fuel consumption, so with reduced fuel use comes an equivalent reduction in carbon dioxide emissions. Another key emission standard for commercial jetliners is nitrogen oxides (NOx). Specific regulations have already been set for future airplanes, using a complex formula that is based on the thrust ratings of an airplane’s engines. The Boeing 787 is being designed to be more than 30 percent better than today’s 767s — and it will be better than the future, more stringent regulations being incorporated by the Committee on Aviation Environmental Protection (CAEP).
Other energy sources such as solar power and energy harvesting also are being investigated for aircraft. While even the most efficient solar panels would still not be enough to propel a large aircraft, solar energy could provide electricity onboard the plane once it has reached altitude, or it could help reduce fuel burn and emissions during ground operations at airports.
Likewise, energy harvesting also has applications within the aircraft as an alternative power source. The body heat a passenger gives off when seated for a number of hours could be collected by the seat, and combined with energy collected from other sources like solar panels to fuel cabin appliances or power cabin lights.
On the Wings of Innovation
Airbus has pioneered the use of wingtip devices in aviation for decades, beginning with its A300 and A310 jetliners. Both were outfitted with wingtip fences, which help reduce the spiral-
shaped vortices that form at the wingtips of any aircraft during flight, creating aerodynamic drag.
These wingtip devices — arrow-shaped surfaces attached to the tip of each wing — enhance the overall efficiency of aircraft, saving fuel by reducing drag, while also lowering noise emissions by improving take-off performance.
The next innovation is the large Sharklets™ wingtip devices for the Airbus A320 family. Introduced in 2009, Sharklets provide aerodynamic improvements that result in multiple benefits including lower fuel burn, reduced emissions, increased range and payload, better take-off performance and rate-of-climb, higher optimum altitude, reduced engine maintenance costs, and higher residual aircraft value.
These fuel-saving devices completed their first flight in November 2011 on an A320 development aircraft. Sharklets are expected to reduce fuel burn over long sectors by at least 3.5%.
A New Generation of Engines
As people who live near airports know, reducing the noise created by planes during takeoffs and landings is an important measure of environmental performance. Boeing has worked to reduce the sound footprint — the distance across which disturbing noise is heard. The 787 Dreamliner uses a number of new technologies — most importantly, acoustically treated engine inlets and chevrons, the distinctive serrated edges at the back of the engine, and other special treatments for the engines and engine casings — to ensure that all sound of 85 decibels (about the level of loud traffic heard from the side of the road) never leaves the airport boundaries.
Conventional airplanes use pneumatic systems powered by hot, high-pressure air diverted from the engines. This requires a complex system of manifolds, valves, and ducts to power secondary systems located throughout the plane. The 787 design eliminates the engine bleed air system and the associated pneumatic system, improving efficiency. Also, the plane’s engines are interchangeable at the wing, making it easier to reconfigure, update, or transition the plane from one fleet to another.
The Dreamliner belongs to a new class of planes made from advanced materials like composites and plastics that are stronger, tougher, and lighter than traditional metal alloys. GE developed a new engine for the aircraft, the GEnx. The GEnx engine uses advanced materials and design processes to reduce weight, improve performance, and lower maintenance. It delivers 15% better specific fuel consumption (which translates to 15 percent less CO2) than the engines it replaces. Its twin-annular pre-swirl (TAPS) combustor will reduce NOx gases as much as 56% below today’s regulatory limits.
The GEnx feature large, more efficient fan blades that operate at a slower tip speed, resulting in about 30% lower noise levels. It is the world’s first commercial jet engine with both a front fan case and fan blades made of carbon fiber composites.
A Material Advantage
Because the 787 Dreamliner is made primarily of carbon-fiber composite material, which is trimmed like cloth, manufacturing processes will produce less scrap material and waste. Today’s airplanes are made primarily of aluminum, which must be milled and machined from large sheets or blocks to create airplane structure. In general, as much as 90 percent of the raw aluminum used to create airplane parts is turned into scrap during the manufacturing process.
A majority of the primary structure of the Boeing 787 is made of composite materials — most notably the fuselage. Composites do not fatigue or corrode, they resist impact better, and are designed for easy visual inspection. Minor damage can be repaired at the gate in less than an hour. Carbon Sandwich is a special class of composites fabricated by attaching two thin, but stiff, skins to a lightweight, but thick core like a honeycomb. The core material is low-strength, but its higher thickness provides the sandwich composite with high bending stiffness and overall low density. Carbon Laminate structures on the plane are composed of strands of carbon formed into a tape infused with resin. The layers are laminated to create the desired thickness and shape of the structure, and then cured through a cycle of high heat and pressure over several hours.
Materials within the plane also will have a major impact on passenger comfort. The Airbus Concept Plane, which embodies what air transport could look like in 2050, features a biopolymer membrane coating for the cabin that would control the amount of natural light, humidity, and temperature. Self-reliant materials (such as the leaves of a plant that water rolls off of in beads, taking contaminants with it) could be found on the fabric of seats and the carpet to keep them clean.
Changing How We Fly
The Aviation Safety Program (AvSP), part of NASA’s Aeronautics Research Mission Directorate, helps develop new ways to achieve exceptional levels of safety for air travel despite increasingly crowded skies and congested airports. Working with partners from academia and in the public and private sectors, AvSP conducts foundational research and develops new technologies to overcome the emerging challenges created by the nation’s transition to the Next Generation Air Transportation System (NextGen).
NextGen is a transformative change in the management and operation of how we fly. NextGen enhances safety, reduces delays, saves fuel, and reduces aviation’s adverse environmental impact. It integrates new and existing technologies, including satellite navigation and advanced digital communications. Airports and aircraft in the National Airspace System (NAS) will be connected to NextGen’s advanced infrastructure, and will continually share realtime information to provide a better travel experience.
NextGen technologies and procedures are helping to restore flexibility to an air transportation system that is nearing the point where growth may be inhibited. Performance Based Navigation (PBN) capabilities and procedures, enabled by satellite positioning and other aircraft- and ground-based technologies, are freeing aircraft from the old highways in the sky that are dependent on ground-based beacons. PBN enables more direct, fuel-efficient routes and provides alternatives for routing around NAS disruptions, such as bad weather or unexpected congestion. Likewise, automation system improvements are providing air traffic controllers with greater decision-making tools, while digital information sharing is helping aircraft operators, controllers, and traffic managers work together to maximize efficiency in the air and on the airport surface.
NASA is one of several U.S. government agencies that plays a crucial role in helping to plan, develop, and implement NextGen through new ideas and technologies. These ideas include software that reduces airport runway and urface congestion, new landing techniques that save fuel and time, computer models that predict more accurately the influence of weather on flight paths, and air traffic control solutions that allow more takeoffs and landings in the same amount of time.