CHAPTER TWO Aircraft Noise 81 Aviation’s Next Advance: Sustainable High-Speed Flight By Aerospace Industries Association (AIA) In the 100 years since the Aerospace Industries Association The idea of supersonic air travel is not a new one, but the (AIA) was founded to represent America’s fledging aviation first generation of supersonic aircraft introduced in the sector, our industry has transformed the way humanity 1970s were not environmentally friendly. Concorde and lives, works, and thinks about the Earth. When far-off the Tupolev Tu-144 faced international challenges due to places are within our reach, we become more connected environmental concerns – in particular the sonic boom to the rest of the world around us. Today, anyone can get they generated limited the number of viable routes. on an airplane and travel thousands of miles in a matter of hours – trips that simply would be too arduous and While these concerns were warranted, aviation technology impractical by any other form of transport. has advanced considerably since then and its environmental impacts have been drastically reduced. These improvements However, what we now take for granted is a result of the from manufacturers are due in no small part to the work that continuous advances our industry has made over the past takes place at the International Civil Aviation Organization century. In the 1930s, a business trip across the Pacific – (ICAO), where governments, aviation stakeholders, and the now a regular occurrence – was far from an easy experience. NGO community all work constructively and collectively. Traveling from San Francisco to Hong Kong on Pan Am’s The standards and policies set through ICAO require China Clipper took 6 days. By the mid-1940s, a journey from manufacturers to continually improve environmental Miami to Buenos Aires still took 71 hours. At these slow performance through technologically feasible and speeds, aviation – and long-distance travel more generally economically reasonable means, bringing broad benefits. – would never become part of most people’s lives. With the dawn of the commercial jet age in the late 1950s, everything Modern airplanes are now 85% more fuel efficient than the changed. Travelers could fly across the Pacific in half a day. first airliners and a flight today emits 50% less 2CO than a comparable flight did as recently as the 1990s. Similarly, While aviation has continued to develop in almost every in the United States, aircraft noise affects a fraction of the other way, the speed at which we fly has remained largely population that it did in the 1970s, despite the number of the same since the 1960s. However, we are close to achieving daily flights more than quadrupling. the next great breakthrough in civil aviation that will shrink our world even further: environmentally responsible Advances in propulsion technologies, materials, and supersonic flight. aerodynamic design capabilities mean the next generation of civil supersonic airplanes will be far more environmentally U.S. manufacturers have announced projects that will responsible than their predecessors. offer the possibility of traveling faster than the speed of sound, at speeds ranging from Mach 1.4 to Mach 2.2. At Sonic booms are widely regarded as the least acceptable Mach 1.4, the voyage from Miami to Buenos Aires takes aspect of supersonic airplanes. Industry is undertaking less than 6 hours. A transpacific flight from San Francisco extensive research and development to reduce or to Hong Kong shrinks from 14 subsonic hours to 5.5 hours eliminate this problem, but until these solutions can at Mach 2.2. And this could become a reality in just the be matured, supersonic aircraft are being designed to next five to ten years. only operate at supersonic speeds over water – to avoid Aviation’s Next Advance: Sustainable High-Speed Flight CHAPTER TWO Aircraft Noise 82 any unacceptable impacts over people. State-of-the- FIGURE 1: Aerion AS2 art aerospace technologies, when paired with advanced operational procedures, will also minimize noise impacts during the landing and takeoff phase of supersonic flight. Airplane noise is only the most noticeable environmental impact; we also need to take our climate responsibilities seriously. AIA was part of the Air Transport Action Group’s 2008 agreement that made aviation the first industrial sector to set goals to reduce its climate impact – including a long-term goal to deliver a 50% reduction supersonic engine program in 55 years, called the Affinity, in net CO2 emissions by 2050 relative to 2005 levels. U.S. which will power the AS2. The AS2 is being designed to be manufacturers remain fully committed to this goal and able to fly on 100% sustainable aviation fuels, and Aerion supersonic airplanes and engines will be designed with is dedicating one flight test airframe with the intention fuel efficiency as a key consideration for both economic of performing its test campaign with 100% sustainable as well as environmental reasons. fuels. The AS2 will cruise at a top speed of Mach 1.4 and operate at “Mach cut-off” speeds over populated areas, New technologies will allow stricter requirements to be set taking advantage of atmospheric conditions to cruise for supersonic aircraft in the longer term, but these aircraft at up to Mach 1.2 without generating a sonic boom that also will be able to leverage other measures to reduce their reaches the ground. environmental impact. Many American manufacturers, including those with an interest in supersonic aircraft, are The AS2 is expected enter service in 2025, shaving hours taking active steps to help spur growth of the nascent from itineraries like New York to Cape Town and London sustainable aviation fuels industry. Supersonic engines to São Paulo. In February 2019, Aerion announced a are being designed to accommodate drop-in sustainable partnership with Boeing, through which Boeing will lend fuels as readily as subsonic engines. In addition, market- engineering, manufacturing, and flight test resources to based measures such as ICAO’s Carbon Offsetting and support the AS2 development program. For decades, Reduction Scheme for International Aviation and optimized Boeing has made significant contributions to supersonic operational procedures also will play their part to ensure technology. In recent years, Boeing has collaborated aviation meets its climate commitments. with the Japanese government and industry on wind tunnel testing and participated in a study on the use of a revolutionary new material called Shape Memory Alloy. AIA MEMBER ACTIVITY Boom Overture Two U.S.-based manufacturers have announced plans Boom Supersonic is focused on making the planet for civil supersonic aircraft projects. Working through dramatically more accessible through supersonic flight. the International Coordinating Council of Aerospace The company’s first commercial product will be a 55-seat, Industries Associations and the International Business Aviation Council, these manufacturers are contributing FIGURE 2: Boom Overture technical expertise, modeling resources, and data to ICAO’s Committee on Aviation Environmental Protection to inform future environmental standards for supersonic aircraft. Aerion AS2 Aerion Supersonic is developing the AS2 supersonic business jet, which is expected to take flight in 2023. In 2018, Aerion and GE Aviation announced the first civil Aviation’s Next Advance: Sustainable High-Speed Flight CHAPTER TWO Aircraft Noise 83 Mach-2.2 airliner called Overture, designed with operating with a prediction of how their sonic boom will propagate, costs similar to today’s subsonic commercial business-class enabling them to mitigate or avoid noise impacts. aircraft. Overture will enter service in the mid-2020s and could dramatically shorten flight times on hundreds of Gulfstream is also a leader in supersonic airplane research, global routes by cruising at supersonic speeds over water. having invested in low- and high-speed aerodynamics, Boom is currently building XB-1, a two-seat demonstrator engine design and integration, field performance, and that will begin flight testing within the next year. XB-1 is both landing and takeoff and sonic boom noise research. the world’s first independently-developed supersonic Since 2014, Gulfstream has contributed to NASA jet and will be the fastest civil aircraft in history when it programs, validating sonic boom prediction models and reaches its Mach-2.2 design cruise speed. developing flight research plans for NASA’s low-boom flight demonstrator. Other U.S. manufacturer activity FIGURE 3: NASA/Lockheed Martin X-59 NATIONAL RESEARCH ORGANIZATIONS U.S. manufacturers also support the work being done by NASA, other research agencies, and national aviation authorities to further state-of-the-art research in supersonic flight. Around the world, these organizations are making valuable contributions to sustainable supersonic travel. NASA NASA has undertaken a number of projects in different areas of supersonic airplane research. Among its collaborations In 2018, the National Aeronautics and Space Administration with other national research agencies are partnerships (NASA) awarded Lockheed Martin the contract to design, with The French Aerospace Lab and the Japan Aerospace build, and complete initial flight testing of the X-59, which Exploration Agency on sonic boom prediction research. is scheduled to fly in early 2021. Producing shaped sonic As mentioned above, NASA is developing the X-59 Quiet boom signatures with a perceived level of noise between Supersonic Technology research X-plane in partnership 70–80 decibels (PLdB), the X-59 is intended to inform the with Lockheed Martin, which is intended to create a sonic design of future commercial supersonic airplanes with “thump” to approximate sounds that may be produced sonic boom characteristics allowing for quiet overland by future large, quiet supersonic aircraft. Community supersonic flight. NASA is developing community response response testing with the X-59 is expected to begin in testing plans using X-59 to investigate public acceptance of 2022. NASA also has undertaken modelling of supersonic quieter, shaped sonic booms.