{"id":11814,"date":"2018-07-07T20:43:07","date_gmt":"2018-07-08T03:43:07","guid":{"rendered":"http:\/\/cafe.foundation\/blog\/?p=11814"},"modified":"2018-07-07T20:47:00","modified_gmt":"2018-07-08T03:47:00","slug":"nasa-shares-x57-lessons-freely","status":"publish","type":"post","link":"http:\/\/cafe.foundation\/blog\/nasa-shares-x57-lessons-freely\/","title":{"rendered":"NASA Freely Shares X57 Lessons"},"content":{"rendered":"

NASA and several partner firms have been working on the X-57 Maxwell electric propulsion demonstrator for the past several years.\u00a0 It hasn\u2019t been as easy as it looked at first.\u00a0 Encouragingly, NASA is sharing some of the hard lessons it has learned in the process, much like Elon Musk sharing many of his patents with the world.<\/p>\n

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Technicians at Scaled Composites in Mojave, California, install a wing designed for electric motors onto a Tecnam P2006T to form NASA\u2019s X-57 Maxwell battery-powered plane. Photo: NASA<\/p><\/div>\n

One of the hardest lessons<\/a> involved the multiple battery packs, originally planned to be off-the-shelf units.\u00a0 A December\u00a02016 test resulted in a thermal runaway<\/a>, a situation in which one cell that overheats can self-destruct and cause adjacent cells to follow suit.\u00a0 This, as we\u2019ve seen in Dreamliner incidents, can be dangerous and potentially deadly.\u00a0 Such fires are exceedingly well reported, with any Tesla incident overwhelming the press, which ignores the 174,000 car fires reported by the National Fire Protection Association in 2015<\/a>, which resulted in 415 deaths and $1.2 billion in property damage.\u00a0 Electrified aviation will be even more critically examined if electric fires bring down a craft.<\/p>\n

Intentional overheating of one cell in a test battery module started a \u201ccascade\u201d effect in which heat spread from one cell to the next.\u00a0 Experts at NASA\u2019s Glenn Research Center in Ohio and Johnson Space Center in Houston collaborated with Empirical Systems Aerospace in California<\/a> to redesign and construct safer battery modules.\u00a0 Subsequent tests at an Electric Power Systems laboratory in Logan, Utah demonstrated the redesigned battery pack\u2019s ability to produce flight-ready current levels throughout takeoff and cruise without overheating.<\/p>\n

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Throughout the testing, NASA, EPS and ESAero monitored the battery\u2019s overall capacity, including its ability to remain stable throughout an X-57 flight profile. Thermal runaway and propagation testing was then conducted to confirm that the battery system\u2019s design could keep the pilot and aircraft safe in the case of a thermal runaway event. Testing took place at an EPS co-joint testing facility with Utah State University, following a redesign of the battery system.\u00a0\u00a0Photo: Electric Power Systems<\/p><\/div>\n

New modules will feature a \u201choneycomb block\u201d of aluminum holding individual cells.\u00a0 Space between cells should prevent overheating and thermal transfer between cells.\u00a0 Matt Redifer, chief engineer for the project at NASA\u2019s Armstrong Flight Research Center, says initial data shows repeating December\u2019s test will not cause a thermal runaway.<\/a>\u00a0 To provide more space among cells, the plane will carry 16 smaller modules instead of the original eight, according to an email to Popular Mechanics from Sean Clarke, NASA\u2019s principal X-57 investigator.<\/p>\n

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Battery location shows a major reason for taking all safety precautions in preventing thermal runaway.\u00a0 Final modules will be smaller and twice the number.\u00a0 Only batteries on the left side of the airplane are shown in the cutaway<\/p><\/div>\n

Redifer explains the new modules will add 45 kilograms (99 pounds) to the airplane but are a necessary concession to safety. \u201cThe battery is a means to an end, rather than an area where the X-57 team is trying to innovate. \u00a0Our battery is heavier and probably lower energy density than you might get out of, say, a Tesla [electric car lithium ion] battery.\u201d\u00a0 To help prevent thermal runaway from spreading, the X-57 will now have 16 320 cell modules instead of eight 640-cell units.\u00a0 Containment has been a major concern in the redesigned modules.<\/p>\n

Electric Power Systems\u2019 safer battery packs became part of George Bye\u2019s Sun Flyer 2, and will probably additional data to NASA as they accumulate hours in the production training aircraft.<\/p>\n

The batteries are part of Mod 2, a step in converting an Italian P2006T originally powered by twin Rotax engines to an electric craft with two \u201ccruise\u201d motors on the wingtips and a dozen \u201chigh-lift\u201d motors distributed along the high aspect ratio wing\u2019s leading edge.<\/p>\n