永不落地的无人机

    眼下，当尚处襁褓中的民用无人机行业还在设法优化小型无人机（UAS），以执行设备安保、基础设施监控或精准农业之类的特定任务时，一家位于美国新墨西哥州的航空初创企业却已经有了更宏大、更长期的规划。

    这家公司名叫“泰坦航空”（Titan Aerospace），是一家成立仅有一年、已获风投注资的航空器设计公司。它上周推出了两款无人机：Solara 50 和Solara 60。这是两架硕大无朋、靠太阳能驱动的高空飞机，这家公司计划让它们一次性升空后在空中巡航数周、数月直至数年，中途完全无须降落。

    泰坦并没有把这些概念机叫“遥控无人机”（drone），也不用这个行业所习称的“无人机系统”，而是叫它们“大气层卫星”。因为它们就像轨道卫星一样，能在空中长时间巡航逗留。这家公司希望将这个售价不到200万美元的平台卖给政府、私营企业和研究机构，让它们只需付出卫星成本的九牛一毛，就能在大气层拥有自己的航天器。

    这家公司的理念是，这样一台大气层卫星就能执行轨道卫星的绝大多数任务：大气观测和天气监测，通讯转播，海洋研究和地球成像。而它所能完成的其他任务则是空间卫星无能为力的，比如边境安保、海上交通监控，打击海盗行动，灾害响应以及农业观测。另外，Solara的续航时间长达五年，使用寿命和很多小型卫星不相上下，使它们对上述应用来说成了一个更具吸引力的选择（更别提如果传感器或是仪表坏了，还能让它们降落，然后重新发射升空）。

    泰坦首席电气工程师达斯汀•桑德斯说：“租用卫星服务要耗费巨资。发射卫星也会耗资数十亿美元。而我们要开发的是每台航空器仅百万美元级的平台，而且这个平台的运营成本几乎为零——只需要花不多的钱就能了解实际载荷情况，确保这台无人机不会出问题。”

    而其他长航太阳能概念无人机——包括航空环境公司（Aerovironment）的“全球观察者”（Global Observer）和奎奈蒂克公司（一家英国国防科技公司——译注）为波音公司（Boeing）开发的展示概念机“西风”（Zephyr）——都没能造出泰坦设想的长寿命大气层卫星，但泰坦的工程师认为他们已经基于以前的努力解决了一些棘手问题。比如，Solara 50和Solara 60翼展长达160多英尺的机翼上密集覆盖着先进的太阳能电池板，它们提供的电力不仅足够白天黑夜飞行所用（电池白天存储电力供晚上用），还足以供重达70磅的传感器和仪器使用。

    While much of the nascent civilian unmanned aircraft industry looks at ways to optimize small unmanned aerial systems (UAS) for specific tasks such facility security, infrastructure inspection, or precision agriculture, a New Mexico-based aerospace startup is thinking bigger and longer-term.

    Titan Aerospace, a one-year-old venture-backed aircraft designer, last week unveiled its Solara 50 and Solara 60 unmanned aircraft. These are two massive solar-powered, high-altitude vehicles the company plans to send aloft for weeks, months, and eventually years at a time without ever having to land.

    Titan doesn't refer to these concept aircraft as "drones" or by the industry-preferred "unmanned aerial system," but instead calls them "atmospheric satellites" for their ability to remain aloft for extended periods of time just as orbital satellites do. The company hopes to provide a sub-$2 million platform that governments, private industry, and research institutions can put high into the atmosphere for extended periods of time for a fraction of the cost of a space satellite.

    The idea is that an atmospheric satellite can conduct most of the same operations as an orbital one: atmospheric observation and weather monitoring, communications relay, oceanographic research, and earth imaging. Other operations are impractical for space satellites, such as border security, maritime traffic monitoring and anti-piracy operations, disaster response, or agricultural observation. And with continuous flight time of up to five years, Solara's aircraft would have endurance on par with many small satellites, making them a more attractive option for a range of these applications (not to mention that if a sensor or instrument goes down, you can land and relaunch).

    "If you have to go up to the satellite and rent that service, that's a lot of money," says Dustin Sanders, Titan's chief electrical engineer. "And launching a satellite, that can be in the billions of dollars. We're trying to do a single-million-dollar-per-aircraft platform. And the operation cost is almost nothing -- you're paying some dude to watch the payload and make sure the aircraft doesn't do anything stupid."

    Other long-endurance solar UAS concepts -- including Aerovironment's (AVAV) Global Observer and QinetiQ's Zephyr, a demonstrator for a Boeing (BA) concept -- have had little success in generating the kind of long-term atmospheric satellite Titan envisions, but the company's engineers think they've worked around some of the thornier problems that have grounded previous efforts. For one, 160-foot-plus wingspans of the Solara 50 and Solara 60 will be covered edge-to-edge with advanced solar cell technology that will provide enough energy for both day and night flight (batteries will store power during the day for use at night) with enough left over to power up to 70 pounds of sensors and instruments.