NASA’s Involvement in Energy Efficiency and Emissions Reduction

The goal of improving aircraft fuel efficiency is one shared by aerospace engineers everywhere: with increased efficiency come the exciting pos­sibilities of reduced fuel costs and increased performance in terms of speed, range, or payload. American engineers recognized the potential early on and were quick to create a center of gravity for their efforts to improve the fuel efficiency of aircraft engines. The NACA established the Aircraft Engine Research Laboratory—later known as NASA Lewis and then NASA Glenn—in 1941 in Cleveland, OH, as the Nation’s nerve
center for propulsion research.[1376] The lab first worked on fast fixes for pis­ton engines in production for use in World War II, but it later moved on to pursue some of America’s most forward-leaning advances in jet and rocket propulsion.[1377] Improving fuel efficiency was naturally at the cen­ter of the laboratory’s propulsion research, and many of NASA’s most important fuel-saving engine concepts and technology originated there.[1378] While NASA Glenn spearheaded the majority of aircraft fuel efficiency research, NASA Langley also played a critical role in the development of new fuel-saving aircraft structures.[1379]

NASA’s efforts to develop aircraft technology that both increased fuel efficiency and reduced emissions reached their nadir in the 1970s. From the time of Sputnik to the late 1960s, space dominated NASA’s focus, par­ticularly the drive to land on the Moon. But in the late 1960s, and partic­ularly after introduction of the wide-body Boeing 747, the Agency turned increasing attention toward air transport, consistent with air transport itself dramatically increasing as a means of global mobility. Government and airline interest in improving jet fuel efficiency was high. However, NASA Lewis struggled to reenter the air-breathing propulsion game because the laboratory had lost much of its aeronautics expertise during the Sputnik crisis and now faced competition for Government support.[1380] Aircraft engine companies had developed their own research facilities, and the U. S. Air Force (USAF) had completed its propulsion wind tunnel facility at Arnold Engineering Development Center in Tullahoma, TN, in 1961.[1381] [1382] NASA scientists and engineers needed a new aeronautics niche. Luckily for them, they found it with the arrival of the oil embargo of 1973 and the coinciding emergence of a national awareness of environmen­tal concerns. NASA’s "clean and green” research agenda had been born.

The Organization of the Petroleum Exporting Countries (OPEC) oil embargo led Americans to realize that the Nation’s economy and military
were far too dependent on foreign sources of energy. In 1973, 64 percent of U. S. oil imports came from OPEC countries.11 The airline industry was particularly hard hit; jet fuel prices jumped from 12 cents to over $ 1 per gallon, and annual fuel expenditures increased to $1 billion— triple the earnings of airlines.[1383] During the oil crisis, fuel accounted for half the airlines’ operating costs,[1384] and those operating costs were ris­ing faster than the rate of inflation and faster than efficiencies in the air­lines’ own operations could reduce them.[1385] The airline lobby descended on Capitol Hill, warning that its struggles to maintain profitability in the face of rising fuel costs were a bellwether for the Nation’s entire econ­omy. Lawmakers turned to NASA to for help.

In 1975, the U. S. Senate asked NASA to create the Aircraft Energy Efficiency (ACEE) program, with the twin goals of lowering the fuel burn of existing U. S. commercial aircraft and building new fuel – efficient aircraft to match foreign competition.[1386] The 10-year, $670 mil­lion ACEE yielded two of NASA’s greatest contributions to aircraft fuel – efficiency research. The most significant was the Energy Efficient Engine (E Cubed) program, which spawned technology still used in gas tur­bine engines today. The second key element of ACEE was the Advanced Turboprop (ATP), a bold plan to build an energy-efficient open-rotor engine. The open-rotor concept never made it into the mainstream, but aircraft propulsion research today still draws from ATP concepts, as this case study will later explain. Other technology developed under ACEE led to improved aerodynamic structures and laminar flow, as well as the design of supercritical wings, winglets, and composites.

Around the same time as ACEE, NASA began to sharpen its focus on the reduction of aircraft emissions. Space exploration had opened the Nation’s eyes to the fragility of the planet and the potential impact that

ELEMENTS NEEDED FOR DEVELOPMENT OF ADVANCED
TURBOPROP AIRCRAFT

humans could have on the environment.[1387] The U. S. Congress pushed NASA to become increasingly involved in projects to study the impact of stratospheric flight on the ozone layer following the cancellation of the Supersonic Transport (SST) in 1971. The Agency provided high-alti­tude research aircraft, balloons, and sounding rockets for the Climactic I mpact Assessment Program (CIAP), which was launched by the Department of Transportation (DOT) to examine whether the environ­mental concerns that helped kill the SST were valid.[1388]

DOT and NASA’s CIAP research led to the discovery that aircraft emissions could, in fact, damage the ozone layer. CIAP results showed that nitrogen oxides would indeed cause ozone depletion if hundreds of Concorde and Tu-144 aircraft—the Concorde’s Russian cousin—were to fly as planned. Following the release of CIAP, Congress then called on NASA to conduct further research into the impacts of stratospheric flight on the ozone layer, prompting NASA and DOT to move forward with a
series of studies that by the 1980s were pointing to the conclusion that SSTs were less dangerous to the ozone layer than first thought.[1389] The findings gave NASA reason to believe that improvements in combustor technology might be enough to effectively mitigate the ozone problem.

After conducting its breakthrough ozone research, NASA has fairly consistently included clean combustor goals in many of its aeronau­tics projects in an effort to reduce aircraft emissions (examples include the Ultra Efficient Engine Technology program and Advanced Subsonic Technology program). Today, NASA has broadened its aeronautics research to focus not only on NOx (the collective term for water vapor, nitrogen oxide, and nitrogen dioxide), but also carbon dioxide and other pollutants.[1390]

NASA’s research in this area is seen as increasingly important as the view that aircraft emissions harm air quality and contribute to climate change becomes more widely accepted. The United Nations International Panel on Climate Change (IPCC) issued a report in 2007 stating that air­craft emissions account for about 2 percent of all human-generated car­bon dioxide emissions, which are the most significant greenhouse gas.[1391] The report also found that aviation accounts for about 3 percent of the potential warming effect of global emissions that could impact Earth’s cli­mate.[1392] The report forecasts that by 2050, the aviation industry (including aircraft emissions) will produce about 3 percent of global carbon dioxide and 5 percent of the potential warming effect generated by human activity.[1393]

In addition to NASA’s growing interest in climate change, the Agency’s research on improving the fuel efficiency of aircraft has also continued at a relatively steady pace over the years, although it has seemed to fluc­tuate to some extent in relation to oil prices. The oil shocks of the 1970s spurred a flurry of activity, from the E Cubed to the ATP and alterna­tive fuels research. But interest in ambitious aircraft fuel-efficiency pro­grams seemed to wane during the 1990s, when oil prices were low. Now
that oil prices are high again, however, fuel-efficiency programs seem to be back in vogue. (Several alternative fuels research efforts now under­way at NASA will be discussed later in this case study.)

One example of the correlation between oil prices and the level of NASA’s interest in fuel-efficiency programs is the ATP, NASA’s ambitious plan to return to open-rotor engines. The concept never made it into mainstream use, partly because of widespread concerns that open-rotor engines are too noisy for commercial airline passengers,[1394] but also partly because fuel prices began to fall and there was no longer a demand for expensive but highly energy-efficient engines. "We were developing the ATP in the late ’70s and early ’80s during the fuel crisis. And while fuel prices went up, they didn’t continue to escalate like we originally thought they might, so the utility just went down; it just wasn’t cost effective,” said John Baughman, Manager of Military Advanced System design at General Electric (GE).[1395] With oil prices once again on the rise today, however, there are several new initiatives underway that take off where E Cubed and the ATP left off.