Page 19 - The Future of Aerospace is X - X-Planes 2021

X-57 Maxwell Electric Propulsion Airplane

NASA’s X-57 ‘Maxwell’ is the agency’s first all-electric The X-57 team is using a “design driver” as a technical The design driver for X-57 will also seek to reach the goal
experimental aircraft, or X-Plane, and is NASA’s first crewed challenge, to drive lessons learned, as well as best practices. of zero carbon emissions in flight, which would surpass the
X-Plane in two decades. This design driver includes a 500 percent increase in high- 2035 N+3 efficiency goals. Electric propulsion provides not
The primary goal of the X-57 project is to share the air- speed cruise efficiency, zero in-flight carbon emissions, and only a five-to-10 times reduction in greenhouse gas emissions,
craft’s electric-propulsion-focused design and airworthiness flight that is much quieter for the community on the ground. but it also provides a technology path for aircraft to eliminate
process with regulators, which will advance certification ap- The Maxwell is being built by modifying a baseline Ital- 100 Low Lead AvGas, which is the leading contributor to
proaches for distributed electric propulsion in emerging elec- ian Tecnam P2006T to be powered by an electric propulsion current lead environmental emissions.
tric aircraft markets. system. The advantage of using an existing aircraft design Additionally, since the X-57 will be battery-powered, it can
The X-57 will undergo as many as three configurations is that data from the baseline model, powered by traditional run off renewable based electricity, making clear the environ-
as an electric aircraft, with the final configuration to feature combustion engines, can be compared to data produced by the mental and economic advantages.
14 electric motors and propellers (12 high-lift motors along same model powered by electric propulsion. For more information on the X-57, visit https://www.nasa.
the leading edge of the wing and two large wingtip cruise The X-57 Maxwell project includes four configurations and gov/centers/armstrong/programs_projects/electric_propul-
motors). stages of research, called modifications. sion/index.html.
X-29, from 16
close-coupled canard design used on the X-29 stable aircraft and provided good handling quali- qualities. Flight control law concepts used in the Wind tunnel tests at the Air Force’s Wright
was highly unstable. The X-29 flight control ties for the pilots. program were developed from radio-controlled Laboratory (now AFRL) and at the Grumman
system compensated for this instability by sens- The aircraft’s supercritical airfoil also enhanced flight tests of a 22-percent X-29 drop model at Corporation showed that injection of air into the
ing flight conditions such as attitude and speed maneuvering and cruise capabilities in the tran- NASA Langley. vortices would change the direction of vortex flow
and through computer processing, continually sonic regime. Developed by NASA and originally NASA and Air Force Flight Test Center (now and create corresponding forces on the nose of
adjusted the control surfaces with up to 40 com- tested on an F-8 in the 1970s, supercritical airfoils Air Force Test Center) engineers at Edwards Air the aircraft to change or control the nose heading.
mands each second. Conventionally configured - flatter on the upper wing surface than conven- Force Base performed the detail design work. From May to August 1992, 60 flights success-
aircraft achieved stability by balancing lift loads tional airfoils - delayed and softened the onset of The X-29 achieved its high-alpha controllability fully demonstrated vortex flow control (VFC).
on the wing with opposing downward loads on shock waves on the upper wing surface, reducing without leading edge flaps on the wings for ad- VFC was more effective than expected in generat-
the tail at the cost of drag. The X-29 avoided this drag. The Phase 1 flights also demonstrated that ditional lift and without moveable vanes on the ing yaw (left-to-right) forces, especially at higher
drag penalty through its relaxed static stability. the aircraft could fly safely and reliably, even in engine’s exhaust nozzle to change or “vector” angles of attack where the rudder loses effective-
Each of the three digital flight control comput- tight turns. the direction of thrust. Researchers documented ness. VFC was less successful in providing con-
ers had an analog backup. If one of the digital the X-29’s aerodynamic characteristics at high trol when sideslip (relative wind pushing on the
computers failed, the remaining two took over. Phase 2 flights angles of attack using a combination of pressure side of the aircraft) was present, and it did little to
If two of the digital computers failed, the flight The No. 2 X-29 investigated the aircraft’s high measurements and flow visualization. Flight test decrease rocking oscillation of the aircraft. Over-
control system switched to the analog mode. If angle-of-attack characteristics and the military data satisfied the primary objective of the X-29 all, VFC, like the forward-swept wings, showed
one of the analog computers failed, the two re- utility of its canard and forward-swept wing con- program: to evaluate the ability of X-29 technol- promise for the future of aircraft design.
maining analog computers took over. The risk of figuration. In Phase 2, flying at up to 67 degrees ogies to improve future fighter aircraft mission
total systems failure in the X-29 was equivalent angle of attack (also called high alpha), the air- performance. The X-29 did not demonstrate the overall re-
to the risk of mechanical failure in a conventional craft demonstrated much better control and ma- duction in aerodynamic drag that earlier studies
system. neuvering qualities than computational methods Vortex flow control had suggested. The X-29 program did demonstrate
and simulation models predicted. The No. 1 X-29 In 1992, the Air Force initiated a program to several new technologies, as well as new uses of
Phase 1 flights was limited to 21 degrees angle-of-attack maneu- study the use of vortex flow control as a means of proven technologies, including aeroelastic tailor-
The No. 1 aircraft’s research flights demonstrat- vering. providing increased aircraft control at high angles ing to control structural divergence and use of
ed that, because the air moving over the forward- During Phase 2 flights, NASA, Air Force and of attack when the normal flight control systems a relatively large, close-coupled canard for lon-
swept wing flowed inward rather than outward, Grumman project pilots reported the X-29 aircraft are ineffective. gitudinal control. In addition, the program vali-
the wing tips remained unstalled at the moderate had excellent control response to 45 degrees angle The No. 2 X-29 was modified with the instal- dated control of an aircraft with extreme instabil-
angles of attack. Phase 1 flights also demonstrated of attack and still had limited controllability at lation of two high-pressure nitrogen tanks and ity while still providing good handling qualities;
that the aeroelastic-tailored wing did, in fact, pre- 67 degrees angle of attack. This controllability control valves, with two small nozzle jets located use of three-surface longitudinal control; use of
vent structural divergence of the wing within the at high angles of attack can be attributed to the on the forward upper portion of the nose. The pur- a double-hinged trailing-edge flaperon at super-
flight envelope, and that the control laws and con- aircraft’s unique forward-swept wing and canard pose of the modifications was to inject air into the sonic speeds; control effectiveness at high angles
trol surface effectiveness were adequate to provide design. The NASA/Air Force-designed high-gain vortices that flow off the nose of the aircraft at of attack; vortex control; and military utility of
artificial stability for this otherwise extremely un- flight control laws also contributed to good flying high angles of attack. the overall design.
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