1. Development
     LEAPTech project    X-57 Maxwell  

2. Design

3. See also

4. References

5. External links

The NASA X-57 Maxwell is an experimental aircraft being developed by NASA, intended to demonstrate technology to reduce fuel use, emissions, and noise.^[2]

Development

The experiment involves replacing the wings on a twin-engined Italian-built Tecnam P2006T (a conventional four-seater light aircraft) with Distributed electric propulsion (DEP) wings each containing electrically driven propellers. In 2015, test flights were planned to commence in 2017.^[3]

The first test phase uses an 18-engine truck-mounted wing. The second phase will install the cruise props and motors on a standard P2006T for ground- and flight-test experience. Phase 3 tests will involve the high-lift DEP wing and demonstrate increased high-speed cruise efficiency. The leading-edge nacelles will be fitted, but the high-lift props, motors and controllers will not be installed. Phase 4 adds the DEP motors and folding props to demonstrate lift-augmentation.^[4]

LEAPTech project

The Leading Edge Asynchronous Propeller Technology (LEAPTech) project is a NASA project developing an experimental electric aircraft technology involving many small electric motors driving individual small propellers distributed along the edge of each aircraft wing.^[4][5][6] To optimize performance, each motor can be operated independently at different speeds, decreasing reliance on fossil fuels, improving aircraft performance and ride quality, and reducing aircraft noise.^[7]

The LEAPTech project began in 2014 when researchers from NASA Langley Research Center and NASA Armstrong Flight Research Center partnered with two California companies, Empirical Systems Aerospace (ESAero) in Pismo Beach and Joby Aviation in Santa Cruz, California. ESAero is the prime contractor responsible for system integration and instrumentation, while Joby is responsible for design and manufacture of the electric motors, propellers, and carbon fiber wing section.^[7]

In 2015, NASA researchers were ground testing a {{cvt|31|foot}} span, carbon composite wing section with 18 electric motors powered by lithium iron phosphate batteries.

Preliminary testing up to 40 mph took place in January at Oceano County Airport on California's Central Coast.

Mounted on a specially modified truck, it was tested at up to 70 mph across a dry lakebed at Edwards Air Force Base later in 2015.^[7]

The experiment precedes the X-57 Maxwell X-plane demonstrator proposed under NASA's Transformative Aeronautics Concepts program. A piloted X-plane should fly within a couple of years, after replacing a Tecnam P2006T wings and engines with an improved version of the LEAPTech wing and motors. Using an existing airframe will allow engineers to easily compare the performance of the X-plane with the original P2006T.^[7]

X-57 Maxwell

The X-57 project was publicly revealed by NASA Administrator Charles Bolden on 16 June 2016 in a keynote speech to the American Institute of Aeronautics and Astronautics (AIAA) at its Aviation 2016 exposition.^[8]

NASA's first X-plane in over a decade, it is part of NASA's New Aviation Horizons initiative, which will also produce up to five larger-scale aircraft. The X-57 will be built by the agency's {{abbr|SCEPTOR|Scalable Convergent Electric Propulsion Technology Operations Research}} project, over a four-year development period at Armstrong Flight Research Center, California, with a first flight initially planned for 2017.^[13][9][10]

In July 2017, Scaled Composites was modifying a first P2006T to the X-57 Mod II configuration by replacing the piston engines with Joby Aviation electric motors, to fly early in 2018.

Mod III configuration will move the motors to the wingtips to increase propulsive efficiency.

Mod IV configuration will see the installation of the Xperimental, LLC high aspect ratio wing with 12 smaller props along its leading edge to augment its takeoff and landing aerodynamic lift.^[11]

The donor Tecnam P2006T was received in California in July 2016.

Construction of the ESAero high aspect ratio, low drag composite wing was then almost finished, to fly the Mod 3 by mid-2020.^[14]

Design

Modified from a Tecnam P2006T, the X-57 will be an electric aircraft, with 14 electric motors driving propellers mounted on the wing leading edges.^[15]

All 14 electric motors will be used during takeoff and landing, with only the outer two used during cruise.

The additional airflow over the wings created by the additional motors generates greater lift, allowing for a narrower wing.

The aircraft seats two.^[16]

It will have a range of {{cvt|100|mi|km}} and a maximum flight time of approximately one hour.

The X-57's designers hope to reduce by five-fold the energy necessary to fly a light aircraft at {{convert|175|mph|km/h}}.^[8][17]

The propellers are mounted above the wing. They will increase the air flow over the wing at lower speeds, increasing its lift. The increased lift allows it to operate on shorter runways. Such a wing could be only a third of the width of the wing it replaces, saving weight and fuel costs. Typical light aircraft wings are relatively large to prevent the craft from stalling (which happens at low airspeeds, when the wing cannot provide sufficient lift). Large wings are inefficient at cruising speed because they create excess drag.^[3] The wings will be optimised for cruise, with the engines protecting it from low-speed stalls and achieving the small aircraft standard of {{cvt|61|knots|km/h}}.^[18]

The speed of each propeller can be controlled independently, offering the ability to change the over-wing airflow pattern to cope with flying conditions, such as wind gusts. When cruising, the propellers closer to the fuselage could be folded back to further reduce drag, leaving those towards the wing tips to move the plane.

Such aircraft would have no in-flight emissions, operate with less noise and reduce operating costs by an estimated 30%.^[3]

Cruising efficiency was expected to increase 3.5-5-fold.^[18]

The {{cvt|31.6|ft}} span wing with an aspect ratio of 15 compares to {{cvt|37.4|ft}} and 8.8 for the stock P2006T wing, the slender wing's chord is {{cvt|2.48|ft}} at the wing root and {{cvt|1.74|ft}} at the tip.^[18]

The wing features 12 {{cvt|1.89|ft}} diameter cruise propellers that each require {{cvt|14.4|kW}} of motor power at {{cvt|55|knots|km/h}} and turn at 4,548 rpm. The five-blade props fold in cruise to reduce drag. Each wingtip hosts two 3-blade {{cvt|5|ft}} diameter cruise props that each require {{cvt|48.1|kW}} at {{cvt|150|knots|km/h}} and turn at 2,250 rpm. The wingtip location offers favorable interaction with the wingtip vortices, expected to provide a 5% drag saving.^[18]

The {{cvt|47|kWh}} battery packs weight {{cvt|860|lb|kg}} for a {{#expr:47000/{{cvt|860|lb|kg|disp=number}}round0}} Wh/kg density.^[14]

See also

• NASA GL-10 Greased Lightning
• Aeronautics Research Mission Directorate

References

External links

• http://www.nasa.gov/centers/armstrong/Features/leaptech.html
• http://www.jobyaviation.com/LEAPTech/

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