Six Teams Design Airplanes That May Appear Conventional, But
Incorporate Revolutionary Improvements
Earlier this week, we reported about an MIT project that was
one of several funded by NASA to design an commercial airliner that
was 70 percent more efficient that airplanes flying today. While
the MIT design was interesting, other groups had some innovative
ideas as well.
Some of the ideas resulting from the 18-month NASA research
effort to visualize the passenger airplanes of the future may
appear to be old fashioned. Instead of exotic new designs seemingly
borrowed from science fiction, familiar shapes dominate the pages
of advanced concept studies which four industry teams completed for
NASA's Fundamental Aeronautics Program in April 2010. But Look more
closely at these concepts for airplanes that may enter service 20
to 25 years from now and you'll see things that are quite different
from the aircraft of today.
Just beneath the skin of these concepts lie breakthrough
airframe and propulsion technologies designed to help the
commercial aircraft of tomorrow fly significantly quieter, cleaner,
and more fuel-efficiently, with more passenger comfort, and to more
of America's airports. You may see ultramodern shape memory alloys,
ceramic or fiber composites, carbon nanotube or fiber optic
cabling, self-healing skin, hybrid electric engines, folding wings,
double fuselages and virtual reality windows. "Standing next to the
airplane, you may not be able to tell the difference, but the
improvements will be revolutionary," said Richard Wahls, project
scientist for the Fundamental Aeronautics Program's Subsonic Fixed
Wing Project at NASA's Langley Research Center in Hampton, VA.
"Technological beauty is more than skin deep."
In October 2008, NASA asked industry and academia to imagine
what the future might bring and develop advanced concepts for
aircraft that can satisfy anticipated commercial air transportation
needs while meeting specific energy efficiency, environmental and
operational goals in 2030 and beyond. The studies were intended to
identify key technology development needs to enable the envisioned
advanced airframes and propulsion systems.
NASA's goals for a 2030-era aircraft, compared with an aircraft
entering service today, are:
- A 71-decibel reduction below current Federal Aviation
Administration noise standards, which aim to contain objectionable
noise within airport boundaries.
- A greater than 75 percent reduction on the International Civil
Aviation Organization's Committee on Aviation Environmental
Protection Sixth Meeting, or CAEP/6, standard for nitrogen oxide
emissions, which aims to improve air quality around airports.
- A greater than 70 percent reduction in fuel burn performance,
which could reduce greenhouse gas emissions and the cost of air
travel.
- The ability to exploit metroplex concepts that enable optimal
use of runways at multiple airports within metropolitan areas, as a
means of reducing air traffic congestion and delays.
The teams were led by General Electric, Massachusetts Institute
of Technology, Northrop Grumman and The Boeing Company. The GE
Aviation team conceptualizes a 20-passenger aircraft that could
reduce congestion at major metropolitan hubs by using community
airports for point-to-point travel. The aircraft has an oval-shaped
fuselage that seats four across in full-sized seats. Other features
include an aircraft shape that smoothes the flow of air over all
surfaces, and electricity-generating fuel cells to power advanced
electrical systems. The aircraft's advanced turboprop engines sport
low-noise propellers and further mitigate noise by providing thrust
sufficient for short takeoffs and quick climbs.
GE Aviation Team Concept NASA Image
With its 180-passenger D8 "double bubble" configuration, the
Massachusetts Institute of Technology team strays farthest from the
familiar, fusing two aircraft bodies together lengthwise and
mounting three turbofan jet engines on the tail. Important
components of the MIT concept are the use of composite materials
for lower weight and turbofan engines with an ultra high bypass
ratio (meaning air flow through the core of the engine is even
smaller, while air flow through the duct surrounding the core is
substantially larger, than in a conventional engine) for more
efficient thrust. In a reversal of current design trends the MIT
concept increases the bypass ratio by minimizing expansion of the
overall diameter of the engine and shrinking the diameter of the
jet exhaust instead. The team said it designed the D8 to do the
same work as a Boeing 737-800. The D8's unusual shape gives it a
roomier coach cabin than the 737.
"Double Bubble" MIT/Aurora Flight Sciences/NASA Image
The Northrop Grumman team foresees the greatest need for a
smaller 120-passenger aircraft that is tailored for shorter runways
in order to help expand capacity and reduce delays. The team
describes its Silent Efficient Low Emissions Commercial Transport,
or SELECT, concept as "revolutionary in its performance, if not in
its appearance." Ceramic composites, nanotechnology and shape
memory alloys figure prominently in the airframe and ultra high
bypass ratio propulsion system construction. The aircraft delivers
on environmental and operational goals in large part by using
smaller airports, with runways as short as 5,000 feet, for a wider
geographic distribution of air traffic.
Northrop Gurmman Design NASA Image
The Boeing Company's Subsonic Ultra Green Aircraft Research, or
SUGAR, team examined five concepts. The team's preferred concept,
the SUGAR Volt, is a twin-engine aircraft with hybrid propulsion
technology, a tube-shaped body and a truss-braced wing mounted to
the top. Compared to the typical wing used today, the SUGAR Volt
wing is longer from tip to tip, shorter from leading edge to
trailing edge, and has less sweep. It also may include hinges to
fold the wings while parked close together at airport gates.
Projected advances in battery technology enable a unique, hybrid
turbo-electric propulsion system. The aircraft's engines could use
both fuel to burn in the engine's core, and electricity to turn the
turbofan when the core is powered down.
Boeing Subsonic Ultra Green Design NASA Image
NASA did not specify future commercial air transportation needs
as domestic or global. All four teams focused on aircraft sized for
travel within a single continent because their business cases
showed that small- and medium-sized planes will continue to account
for the largest percentage of the overall fleet in the future. One
team, however, did present a large hybrid wing concept for
intercontinental transport.
All of the teams provided "clear paths" for future technology
research and development, said Ruben Del Rosario, principal
investigator for the Subsonic Fixed Wing Project at NASA's Glenn
Research Center in Cleveland. "Their reports will make a difference
in planning our research portfolio. We will identify the common
themes in these studies and use them to build a more effective
strategy for the future," Del Rosario said.
These are some of the common themes from the four reports:
- Slower cruising -- at about Mach 0.7, or seven-tenths the speed
of sound, which is 5 percent to 10 percent slower than today's
aircraft -- and at higher altitudes, to save fuel.
- Engines that require less power on takeoff, for quieter
flight.
- Shorter runways -- about 5,000 feet long, on average -- to
increase operating capacity and efficiency.
- Smaller aircraft – in the medium-size class of a Boeing
737, with cabin accommodations for no more than 180 passengers
– flying shorter and more direct routes, for
cost-efficiency.
- Reliance on promised advancements in air traffic management
such as the use of automated decision-making tools for merging and
spacing enroute and during departure climbs and arrival
descents.
- The teams recommended a variety of improvements in lightweight
composite structures, heat- and stress-tolerant engine materials,
and aerodynamic modeling that can help bring their ideas to
reality. NASA is weighing the recommendations against its objective
of developing aeronautics technologies that can be applied to a
broad range of aircraft and operating scenarios for the greatest
public benefit.
"This input from our customers has provided us with well
thought-out scenarios for our vision of the future, and it will
help us place our research investment decisions squarely in the
mainstream," said Jaiwon Shin, associate administrator for
aeronautics research at NASA Headquarters in Washington.
"Identifying those necessary technologies will help us establish a
research roadmap to follow in bringing these innovations to life
during the coming years," Shin said.
The next step in NASA's effort to design the aircraft of 2030 is
a second phase of studies to begin developing the new technologies
that will be necessary to meet the national goals related to an
improved air transportation system with increased energy efficiency
and reduced environmental impact. The agency received proposals
from the four teams in late April and expects to award one or two
research contracts for work starting in 2011. NASA managers also
will reassess the goals for 2030 aircraft to determine whether some
of the crucial technologies will need additional time to move from
laboratory and field testing into operational use. The four teams
managed to meet either the fuel burn or the noise goal with their
concepts, not both.
A companion research effort looked at concepts for a new
generation of supersonic transport aircraft capable of meeting
NASA's noise, emissions and fuel efficiency goals for 2030. NASA
envisions a broader market for supersonic travel, with aircraft
carrying more passengers to improve economic viability while
meeting increasingly stringent environmental requirements. Teams
lead by The Boeing Company and Lockheed Martin evaluated market
conditions, design goals and constraints, conventional and
unconventional configurations, and enabling technologies to create
proposed roadmaps for research and development activities. Both
teams produced concepts for aircraft that can carry more than 100
passengers at cruise speeds of more than 1.6 Mach and a range of up
to 5,000 miles.