Every year, more airline passengers take to the skies, at home and abroad: In 2013, 826 million passengers flew domestically on U.S. carriers, up 1.3 percent from 2012, and the Federal Aviation Administration (FAA) predicts these numbers will continue to climb over the next few years, to more than 1.3 billion U.S. passengers annually. About 70 percent of these passengers are concentrated at the nation’s 30 busiest airports. By 2016, NASA projects that 3.6 billion passengers will fly annually worldwide.

Such growth will require more planes, more flights, and expanded airport facilities – which in turn could mean more aviation fuel burned, more harmful jet emissions, more air traffic congestion, and more noise near airports.

NASA’s Aeronautics Research Mission Directorate (ARMD), working in close cooperation with government, industry, and university partners, aims to eliminate as much of this potential harm as possible. Many of the earliest studies launched a century ago by its predecessor, the National Advisory Committee on Aeronautics (NACA), were aimed at making powered flight more economically feasible; since the middle of the 20th century, NASA has continued that tradition with a diverse portfolio of projects, many of which target greener aviation. This research touches on all aspects of aviation, including greater efficiencies in air traffic management and alternative lower-carbon fuels for aviation, as well as aircraft-related improvements related to noise, fuel use, and emissions.

Aeronautics Research Mission Directorate’s green aviation work has matured into lines of research aimed at achieving increasingly ambitious goals over different time frames – identifying promising technologies and maturing them to the point where commercial partners can begin integrating them into the designs of future aircraft.

There is much room for improvement: In 2012, U.S. commercial air carriers burned 10.6 billion gallons of jet fuel at a cost of $31.6 billion – numbers that marked considerable progress over the 19.7 billion gallons burned, and $59.1 billion spent, in 2008. This rate of consumption releases more than 250 million tons of the greenhouse gas carbon dioxide (CO2) into the atmosphere annually, along with significant amounts of nitrogen oxides (NOx), sulfur oxides (SOx), and particulate matter. Aircraft noise, particularly near large metropolitan airports, continues to be one of the most significant obstacles to expanding the capacity of the National Airspace System.

ARMD’s green aviation work has matured into lines of research aimed at achieving increasingly ambitious goals over different time frames – identifying promising technologies and maturing them to the point where commercial partners can begin integrating them into the designs of future aircraft. “We’re covering a broad spectrum,” said Jay Dryer, director of NASA’s Advanced Air Vehicles Program, “everything from the very foundational tools up to new configurations that aren’t even flying yet.”

 

The Foundation: Transformational Tools and Technologies

Among the first steps in designing an ultra-efficient aircraft is to develop computational tools that will accurately predict its performance in the real world – its structural loading, its engine performance, and the noise it generates, for example. NASA and its predecessor, the NACA, have been invaluable partners in developing these tools, particularly in the numerical methods and algorithms used to analyze how an airframe and its components interact with air as they move through it – a field of study broadly classified as computational fluid dynamics, or CFD. CFD is used in the conceptual phase; designs are confirmed in wind tunnel tests and later validated in flight tests. A manufacturer’s willingness to invest in these more advanced evaluations is a signal of confidence in the tools used in the design.

Today’s CFD codes have served aeronautics researchers and industry partners well for decades – but the rapid pace of technological change, in both computing and aviation, requires new, more powerful CFD tools for the development of future aircraft. To push U.S. CFD capabilities to the leading edge of this new era, NASA commissioned the CFD Vision 2030 Study, conducted by a team of industry and university researchers who published their report in March 2014.

“CFD Vision 2030 Study: A Path to Revolutionary Computational Aerosciences,” lays out a vision for a NASA-led collaboration in creating new simulation technologies, increasing the availability of high-performance computing for CFD development, and bringing world-class engineers and scientists to the field. NASA and its partners in industry and academia are in the early stages of forming this research collaboration, aimed at laying the foundation for future generations of cutting-edge aeronautics research.

Fundamental tools for improving the efficiency of air transport, developed by ARMD’s Transformational Tools and Technologies Project, are not limited to computational software; NASA researchers also study the performance of advanced materials used in the design and construction of engines and airframes. An area of particular interest to NASA is the development of high-performing ceramic matrix composites (CMCs), which can withstand temperatures hundreds of degrees Celsius hotter than the metal alloys traditionally used in turbofan engines.