NASA received its all-electric experimental plane recently, the X-57, from Empirical Systems Aerospace (ESAero) of San Luis Obispo, CA. Based on the Tecnam P2006T, an Italian 4-seat twin engine light aircraft, the X-57 utilizes distributed propulsion wings with multiple small, electric motors. Empirical Systems Aerospace delivered the first configuration of the plane, which has two 60 kW electric motors paired with high-performance batteries. In its final configuration, the plane will have 14 electric motors and propellers. Twelve motors will be wing-mounted and two will be located at the wingtips.
The delivery of the first iteration was an important development because it allows NASA engineers to begin testing which starts with ground tests, moves into taxing and then flight testing. With all the developments and preparation related to the plane’s debut and testing, CleanTechnica was fortunate to get some questions answered about it. Answers 1 – 4 came from Matt Redifer, NASA X-57 Chief Engineer.
1. What is the size of the motors, how many will there be, and what is the capacity of the batteries?
There are two cruise motors located on the wing tips, generating 60 kW nominal, 72 kW peak each. There are 12 high lift motors, 6 on each side of the wing generating 10.5 kW each for a total of 14 motors. The high lift motors are operating during take-off and landing to blow air over the wing, generating additional lift. The battery size is 69.1 kWh of which 47 kWh is available for use.
2. When does the extensive ground testing begin, and what will the tests cover?
The ground testing will begin in late 2019, with the Ground Vibration Test (GVT). The GVT is used to collect data used to clear the aircraft flutter envelope. The testing will continue with a post-ship functional where all systems will be checked for basic operation. The testing then continues with Combined Systems Test (CST), Hanger Radiation Test (HRT), and high speed taxi tests. These tests validate system performance in the flight configuration, with various ground assets including the control room operational.
3. How is it possible to achieve a 500% increase in high-speed cruise efficiency?
A combination of factors contribute to the 500% increase in efficiency over the stock Tecnam aircraft. A 3.3x improvement is achieved by going electric. An additional 1.5x improvement is achieved by designing the wing optimally for the aircraft cruise condition and taking advantage of energy recovery through the wing-tip propulsion. The factors contribute together to achieve the overall 500% improvement.
4. What rate would be considered high-speed cruising for the plane?
The aircraft cruise speed is 172 mph at 8,000 ft.
Matthew Kamlet, NASA Media Fusion Aeronautics Public Affairs Specialist, answered questions 5 – 8.
5. What will the X-57 be used for?
As more and more of the aviation industry begins to recognize the potential benefits of electric aircraft, there is an increasingly critical requirement to be able to set standards for these future aircraft. This is precisely what NASA intends to do with the X-57 Maxwell. Through developing the technology and demonstrating it in crewed flight, NASA is helping to establish the airworthiness process for these types of electric aircraft to help set certification standards with regulators.
6. Is the vision that the plane will help pave the way for zero-carbon emissions aviation in the future for other small aircraft?
There are many potential benefits electric aircraft may yield for the future of aviation – the effect on the environment during flight is certainly one of them. While the goal of X-57 is to help set certification standards for emerging electric aircraft markets, NASA has set a ‘design driver’ for the project – a technical challenge goal that will help drive lessons learned and best practices for these technologies. This design driver includes a 500 percent boost to efficiency at high-speed cruise, as well as zero in-flight carbon emissions, and flight that is quiet for communities on the ground.
7. In terms of developing certification standards, how will NASA share the design and airworthiness process with regulators and industry, and which regulators will receive the information?
Once specific areas of the research are developed and successfully tested, NASA shares the design process publicly. In fact, NASA has already published multiple lessons-learned and processes through technical papers and online, including the successful battery system redesign, which successfully isolated overheating issues to prevent thermal runaway, and which has already been adopted commercially. NASA works closely with the Federal Aviation Administration on sharing information.
8. Some NASA pilots have been using a simulator for eventual flight testing of the aircraft, when will that begin?
NASA is targeting 2020 to fly X-57 in its first of three all-electric configurations, called Modification II, or Mod II. Mod II features replacement of the two inboard combustion engines with electric motors. Once Mod II is completed, the Mods III and IV configurations, which NASA has already begun preparing for, will begin its testing. Mod III features the replacement of the standard wing with a high-aspect ratio wing, and repositioning of the electric cruise motors to the wingtips. Mod IV, the final configuration, will feature the addition of 12 smaller high-lift motors along the front of the wing, to provide lift during takeoff and landing.