Up in the sky! It’s a bird! It’s a plane! It’s a flying battery!
According to a company called Joby Aviation, in a few years you’ll be able to summon up an air taxi on your Uber phone app for trips of 25 miles or so. And you won’t have to feel guilty about the environmental impact of your trip because the plane will actually be a Joby eVTOL, an electric vertical takeoff and landing, aircraft. Joby envisions a network of “vertiports” fi rst in the U.S. and eventually worldwide, with perhaps 10,000 such six-engined aircraft in service at 20 cities within 10 years.
你可能怀疑，这些计划吸引了很多怀疑。其中：Joby的Evtol称为S4，尚未通过FAA携带乘客认证。尽管FI RM来自丰田的厂房为工厂自动化专业知识，但它从未在S4之前生产过一架飞机，更不用说其中10,000。
怀疑论者还存在S4的技术细节的问题，尽管这些都很难辨别，因为Joby是关于设计的秘密。据说EVTOL的电池由锂 - 镍钴 - 锰氧化物细胞组成，在EV中使用的类型相同，例如BMW I8，Chevy Bolt和Nissan Leaf S Plus。公司官员表示，该细胞具有“几乎”300 W-H / KG的特定能量，为那种电池化学的高度高。
One analysis by Carnegie Mellon University engineering Prof. Venkat Viswanathan used this figure to show what it implies for the plane’s design. Joby says the S4 will have a top cruising speed of 200 mph and a range of 150 miles. The FAA requires passenger planes to have a reserve of 45 minutes of flight time over and above their advertised range. To do this, Viswanathan calculates the S4 would need a battery pack with 200 kW of energy.
Of course, battery packs need insulation and packaging to ensure a thermal runaway in any one cell won’t propagate, as well as a battery management system and some capacity for cooling. Consequently, Viswanathan estimated that the assembled battery pack would have an energy density of 200 Wh/kg. That implies an S4 battery pack would weigh 2,200 lb. (In interviews, Joby officials have claimed an even higher energy density, 235 Wh/ kg.) For comparison, the Tesla Model X currently carries a battery pack sporting 186.21 Wh/kg.
Joby has put the S4’s max gross weight— it’s empty weight plus passengers and baggage- -at 4,800 lb. Subtracting the weight of the battery, as well as 1,000 lb for the pilot and four passengers, leaves only 1,600 lb for the airframe, avionics and everything else onboard. This relatively small fraction of gross weight devoted to the airplane’s structure is also noteworthy. For comparison with a conventional plane, consider the Cirrus SR22 which also carries four passengers and a pilot. It’s empty weight is 2,272 lb and gross weight (which in the case of the Cirrus would include fuel) is 3,600 lb.
回想一下，Joby预计每周七天七小时七小时运行这些飞机。这每年大约为12,000起起飞和着陆，超过客机机架。所以想知道S4中的1,600磅轻的光复合机身是否会达到那种殴打。
Nevertheless, the kind of distributed electric propulsion that Joby envisions has advantages such as motors with a low part count and a design conceived with the help of sophisticated computer software. This approach will probably have a place somewhere in aviation even if the S4 isn’t it.
LELAND TESCHLER
EXECUTIVE EDITOR
Filed Under:ee世界数字问题,数字问题
