????眼下，當尚處襁褓中的民用無人機行業還在設法優化小型無人機（UAS），以執行設備安保、基礎設施監控或精準農業之類的特定任務時，一家位于美國新墨西哥州的航空初創企業卻已經有了更宏大、更長期的規劃。

????這家公司名叫“泰坦航空”（Titan Aerospace），是一家成立僅有一年、已獲風投注資的航空器設計公司。它上周推出了兩款無人機：Solara 50 和Solara 60。這是兩架碩大無朋、靠太陽能驅動的高空飛機，這家公司計劃讓它們一次性升空后在空中巡航數周、數月直至數年，中途完全無須降落。

????泰坦并沒有把這些概念機叫“遙控無人機”（drone），也不用這個行業所習稱的“無人機系統”，而是叫它們“大氣層衛星”。因為它們就像軌道衛星一樣，能在空中長時間巡航逗留。這家公司希望將這個售價不到200萬美元的平臺賣給政府、私營企業和研究機構，讓它們只需付出衛星成本的九牛一毛，就能在大氣層擁有自己的航天器。

????這家公司的理念是，這樣一臺大氣層衛星就能執行軌道衛星的絕大多數任務：大氣觀測和天氣監測，通訊轉播，海洋研究和地球成像。而它所能完成的其他任務則是空間衛星無能為力的，比如邊境安保、海上交通監控，打擊海盜行動，災害響應以及農業觀測。另外，Solara的續航時間長達五年，使用壽命和很多小型衛星不相上下，使它們對上述應用來說成了一個更具吸引力的選擇（更別提如果傳感器或是儀表壞了，還能讓它們降落，然后重新發射升空）。

????泰坦首席電氣工程師達斯汀?桑德斯說：“租用衛星服務要耗費巨資。發射衛星也會耗資數十億美元。而我們要開發的是每臺航空器僅百萬美元級的平臺，而且這個平臺的運營成本幾乎為零——只需要花不多的錢就能了解實際載荷情況，確保這臺無人機不會出問題。”

????而其他長航太陽能概念無人機——包括航空環境公司（Aerovironment）的“全球觀察者”（Global Observer）和奎奈蒂克公司（一家英國國防科技公司——譯注）為波音公司（Boeing）開發的展示概念機“西風”（Zephyr）——都沒能造出泰坦設想的長壽命大氣層衛星，但泰坦的工程師認為他們已經基于以前的努力解決了一些棘手問題。比如，Solara 50和Solara 60翼展長達160多英尺的機翼上密集覆蓋著先進的太陽能電池板，它們提供的電力不僅足夠白天黑夜飛行所用（電池白天存儲電力供晚上用），還足以供重達70磅的傳感器和儀器使用。

????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.