不久以前，還很少有人會認(rèn)為自己需要一部可以拍照、錄像的手機。但近來卻很少有人會選擇沒有這類功能的手機了。事實上，如此迅速的技術(shù)發(fā)展并不僅僅發(fā)生在個人通信產(chǎn)品領(lǐng)域，也注定會向個人運輸?shù)绕渌I(lǐng)域擴張。
汽車和航空航天行業(yè)都正處于技術(shù)“攪局者”掀起的漩渦之中。在汽車行業(yè)內(nèi)，有人認(rèn)為駕駛車輛可能很快會成為一種“失傳的藝術(shù)”。那時，僅有“極少部分”人需要謹(jǐn)記遇到紅燈是否可以右轉(zhuǎn)，以及路面上虛虛實實的黃線到底代表什么意思，而對于絕大部分人而言，這些事情將全部交給自動駕駛汽車的程序處理。自動駕駛汽車可以接送乘客：比如某天僅靠Skype視訊或電子郵件無法應(yīng)付工作需求時，自動駕駛就可以送乘客前往公司，而在這一過程中，乘客完全可以在車內(nèi)繼續(xù)使用他們的筆記本電腦工作。
未來，除了開車以外，人們或許還將擁有新的日常通勤選擇。看起來，NASA（美國國家航空航天局）至少給出了一個答案！
作為近期公布計劃的一部分，NASA正在開展一系列戰(zhàn)略研究項目，涉及靜音超音速飛行、電動分布式推進及混合翼飛機等，旨在展示多項可以降低油耗、排放和噪聲的先進技術(shù)，并加速從技術(shù)到市場的蛻變。
特別需要指出的是，該計劃的目標(biāo)之一將專注于發(fā)掘新思路，研發(fā)更加安靜、高效、環(huán)保的電力推進通用航空飛機。與當(dāng)下的通勤型飛機相比，這種新型飛機將為人們提供一種更加清潔高速的個人與商務(wù)出行選擇（見“less congest，at least in theory”）。
順著這些思路，NASA將利用一款經(jīng)過專門設(shè)計的X-57試驗機，測試新型推進技術(shù)。據(jù)了解，這款試驗機綽號“Maxwell”，以紀(jì)念19世紀(jì)著名蘇格蘭物理學(xué)家James Clerk Maxwell在電磁感應(yīng)方面的開創(chuàng)性貢獻。這架試驗機的電機驅(qū)動螺旋槳將被整合在經(jīng)過專門設(shè)計的機翼之中。
今年6月中旬，NASA局長Clarles Bolden在一次講話中表示，“隨著X-Plane試點項目的回歸，NASA的研發(fā)能力可以得到極大地提升，這也將成為我們10年計劃‘航空新視野（New Aviation Horizons）’的重要組成部分。這款通用航天尺寸的X-57將帶領(lǐng)我們邁出開啟航空新紀(jì)元的第一步。”X-57是NASA近10年來的首款X-Plane；此外，作為計劃的一部分，NASA還計劃設(shè)計研發(fā)5款尺寸較大的運輸型X-Plane。
具體來說，X-57編號是由美國空軍（U.S. Air Force）指定的。按照要求，NASA會先提出申請，而后負(fù)責(zé)命名流程的美國空軍會為新機型指定一個名稱。在X-Plane系列中，1947年誕生的X1是世界上首款超音速飛機。
NASA航空研究任務(wù)理事會副局長Jaiwon Shin表示，“自此之后，十多款不同形狀、尺寸和用途的X-Plane相繼誕生，不斷鞏固美國作為世界航空航天技術(shù)領(lǐng)導(dǎo)者的地位。”
目前，在美國空軍處登記在列的X-Plane已經(jīng)排到了56號，但這并不意味著世界上有56款X-Plane，這是因為有些機型共用了同一個編號，還有一些試驗性機型歷經(jīng)設(shè)計、制造，甚至飛行等階段，但最終未能獲得X編碼。
事實上，還有一部分編碼從未被真正啟用。比如，美國空軍在為X-Plane編號時直接跳過了X-52，這是為了避免與B-52轟炸機產(chǎn)生任何混淆。還有一些X-Plane完全不是試驗機，而是量產(chǎn)飛機或航天器的原型，NASA主任歷史學(xué)家Bill Barry表示，“這會讓人們很難分辨到底哪些是真正是X-Plane，哪些并不是。”
NASA的可控規(guī)模電力推進技術(shù)與運行研究（Scalable Convergent Electric Propulsion Technology and Operations Research，簡稱Sceptor項目）屬于一項為期4年的飛行演示計劃，主要將借助一款由意大利設(shè)計的新型TecnamP2006T雙發(fā)動機輕型飛機，打造X-57試驗機。
NASA將用一款內(nèi)置14個電機的細(xì)長型機翼替代Tecnam P2006T本身機翼加2部燃?xì)饣钊l(fā)動機的設(shè)計，其中12個電機位于機翼前沿，可在起飛和著陸階段發(fā)揮作用，另外2個較大電機分別位于兩側(cè)機翼的翼尖，主要在飛機處于巡航高度時發(fā)揮作用。
NASA阿姆斯特朗飛行研究中心(Armstrong Flight Research Center)的聯(lián)合首席研究員Sean Clarke表示，利用現(xiàn)有機型打造試驗機有一個好處，那就是可以對比飛機在不同配置下的性能。目前正在建設(shè)中的Tecnam預(yù)計將在阿姆斯特朗停留將近一年時間，完成機身與機翼的整合。阿姆斯特朗中心還曾在去年9月試飛另一架不同配置的Tecnam P2006T，以收集原始配置下的性能數(shù)據(jù)。
NASA的工程師希望驗證一個事實，那就是在時速175mph的巡航狀態(tài)下，采用分布式動力推進系統(tǒng)的私人飛機，其燃料消耗比普通飛機低5倍。
此外，分布式動力推進系統(tǒng)還有其他幾個優(yōu)勢。由于僅借助電池供電，這款綽號“Maxwell”的X-57將不會產(chǎn)生任何碳排放，并且還可以在理想情況下，表明未來通用航空業(yè)對含鉛航空燃料的需求必將萎縮。
借助X-57的技術(shù)，處于巡航高度的小型飛機預(yù)計最高可將飛行時間、燃料消耗及總運行成本降低40％。通常情況下，為了獲得最佳燃料效率，飛機并不會以最高時速飛行。然而，從本質(zhì)來說，電力推進系統(tǒng)并沒有燃油推進機型在全速巡航時的弊端。這款X-57采用的電力推進技術(shù)有望顯著降低飛機噪音，從而贏得更多公眾的好感，并進一步吸引過去曾回避或關(guān)閉小型機場的社區(qū)。
NASA的研究人員預(yù)計將在2019年推出一款500-kW的9座飛機。對比來說，500kW（約700hp）的功率幾乎是常見乘用車發(fā)動機的5倍。
Clarke表示，為了實現(xiàn)這個計劃，NASA在三個領(lǐng)域的研究都取得了一定進展，包括利用一輛卡車測試受試機翼的性能；開發(fā)并使用一款新型模擬器觀察電動飛機的控制與操控特性；以及驗證協(xié)助NASA工程師進行飛機設(shè)計與制造的工具，而這本身也是NASA為了協(xié)助開發(fā)創(chuàng)新低碳推進系統(tǒng)，并將其推入市場的努力之一。
首先，NASA與Joby Aviation和ESAero公司合作，最初先在一輛經(jīng)過特別改裝的卡車上安裝了一款試驗性機翼，并最終打造了一個混合電力綜合系統(tǒng)測試臺（Hybrid Electric Integrated Systems Testbed，簡稱HEIST）。HEIST測試臺曾在多項研究中發(fā)揮作用，主要用于整合復(fù)雜電力推進系統(tǒng)的項目。
HEIST測試臺的功能類似于地面上的風(fēng)道，最高可加速到73 mph（116.8KM/h），協(xié)助研發(fā)人員收集數(shù)據(jù)。研究人員可以利用測試臺測量飛機的升力、阻力、俯仰力矩和滾轉(zhuǎn)力矩，進而對研發(fā)工具進行驗證。
“通過對比真實測量結(jié)果和CFD的預(yù)測，我們可以判斷這些預(yù)測是否準(zhǔn)確。”Clarke表示，“由于這是一個全新的設(shè)計，我們必須保證透徹了解實驗機翼的性能。”
HEIST參與的首個實驗名為“前沿異步螺旋槳技術(shù)”，簡稱LEAPTech。這個實驗今年5月始于NASA的阿姆斯特朗中心，主要是將18個電機整合至一款帶有鋰離子電池的碳纖維復(fù)合材料機翼。
目前的實驗顯示，這款18電機的分布式推進系統(tǒng)在低速時提供的升力是傳統(tǒng)推擠系統(tǒng)的2倍多。
NASA的另一項主要工作是不斷開發(fā)、完善研發(fā)工具。例如，為了評估飛機的操控性能，研究人員計劃將飛機的系統(tǒng)整合至一款供飛行員使用的NASA阿姆斯特朗飛行模擬器。Clarke表示，研究人員還將研究如何平衡電池電機與渦輪之間的功率需求。大家關(guān)心的是這種分布式電機與天然氣渦輪機的混搭能否延長飛機的續(xù)航里程，出產(chǎn)一款9座概念機，甚至永遠(yuǎn)改變未來“minivan飛機”的定義。
作者：Jean L. Broge
來源：SAE《航空航天工程》雜志
翻譯：SAE 中國辦公室
An X-plane for everyone?
Not too, too long ago very few amongst us ever thought we would need a phone that took pictures and video, while more recently, very few amongst us would ever not have a phone with such capabilities. Such technological changes are not limited to personal communication devices, and are destined to include personal transportation devices.
Both the automotive and aerospace industries are in midst of transformative technological disrupters. In the automotive industry, some believe we may soon approach a time when driving becomes somewhat of a lost art. In that scenario, either a “select” group of people are tasked to always remember to take a right turn on red and the significance of yellow dotted lines next to yellow solid lines, or all that knowledge is left to the coding of the autonomous (potentially multi-person) vehicle that picks up people and their laptops at their doorsteps and takes them to work, should Skype and email not be sufficient on any given day.
Or maybe daily tasks such as driving to work merely transform into something else during a commute. As it turns out, NASA may have at least one answer to what that could be.
As part of a recently announced initiative, NASA is in the midst of researching a number of strategic projects that include quiet supersonic flight, electric distributed propulsion, and hybrid wing aircraft, with goals that include demonstrating advanced technologies to reduce fuel use, emissions and noise, and accelerate possible introduction to the marketplace.
In particular, one of the initiative’s goals will be a focus on ideas that could lead to developing an electric propulsion-powered general aviation aircraft that would be more quiet, efficient, and environmentally friendly than current commuter-type aircraft, potentially opening for cleaner, faster (read: less congested, at least in theory) ways for personal and professional travel.
Along those lines NASA will be testing new propulsion technology using an experimental airplane designated the X-57 and currently nicknamed “Maxwell” in honor of James Clerk Maxwell, the 19th century Scottish physicist best known for his seminal work in electromagnetism. The aircraft will have electric motors turning propellers that will be integrated into a specially designed wing.
“With the return of piloted X-planes to NASA’s research capabilities—which is a key part of our 10-year-long New Aviation Horizons initiative—the general aviation-sized X-57 will take the first step in opening a new era of aviation,” said NASA Administrator Charles Bolden in a speech around the middle of June. It’s NASA’s first X-plane designation in a decade; as many as five larger transport-scale X-planes also are planned as part of the initiative.
The X-57 number designation was assigned by the U.S. Air Force, which manages the naming process, following a request from NASA. The first X-plane was the X-1, which in 1947 became the first airplane to fly faster than the speed of sound.
“Dozens of X-planes of all shapes, sizes and purposes have since followed—all of them contributing to our stature as the world’s leader in aviation and space technology,” said Jaiwon Shin, Associate Administrator for NASA’s Aeronautics Research Mission Directorate.
The current list of X-planes that have been assigned numbers by the Air Force stands at 56, but that doesn’t mean there have been 56 X-planes. Some had multiple models using the same number. And other experimental vehicles were designed, built, and flown but were never given X-numbers. And some X-vehicles received numbers but were never built.
In fact, the designator of X-52 was skipped altogether to avoid confusing that aircraft in any way with the B-52 bomber. Some X-planes were not experimental research planes at all, but rather prototypes of production aircraft or spacecraft, “muddying the waters over what is truly considered an X-plane and what isn’t,” according to Bill Barry, NASA’s Chief Historian.
As part of a four-year flight demonstrator plan, NASA’s Scalable Convergent Electric Propulsion Technology and Operations Research (Sceptor) project will build the X-57 by modifying a recently procured, Italian-designed Tecnam P2006T twin-engine light aircraft.
Its original wing and two gas-fueled piston engines will be replaced with a long, skinny wing embedded with 14 electric motors—12 on the leading edge for takeoffs and landings, and one larger motor on each wing tip for use while at cruise altitude.
An advantage of modifying an existing aircraft is that engineers will be able to compare the performance of the proposed experimental airplane with the original configuration, according to Sean Clarke, Sceptor co-principal investigator at NASA's Armstrong Flight Research Center. The Tecnam, currently under construction, is expected to be at Armstrong in under a year for integration of the wing with the fuselage. Armstrong flew a different Tecnam P2006T in September to gather performance data on the original configuration.
NASA engineers hope to validate the idea that distributing electric power across a number of motors integrated with an aircraft in this way will result in a five-time reduction in the energy required for a private plane to cruise at 175 mph.
Several other benefits would result as well. Maxwell will be powered only by batteries, eliminating carbon emissions and, ideally, demonstrating how demand would shrink for lead-based aviation fuel still in use by general aviation.
Energy efficiency at cruise altitude using X-57 technology is expected to reduce flight times, fuel usage, and overall operational costs for small aircraft by as much as 40%. Typically, to get the best fuel efficiency an airplane has to fly slower than it is able. Electric propulsion essentially eliminates the penalty for cruising at higher speeds. The X-57’s electric propulsion technology is expected to significantly decrease aircraft noise, making it less annoying to the public and potentially more appealing to communities that may have in the past shunned or closed smaller airports.
NASA researchers ultimately envision a nine-passenger aircraft with a 500-kW power system in 2019. (To put that in perspective, 500 kW, or ~700 hp, is about five times as powerful as an average passenger car engine.) Clarke says progress in three areas is happening to enable that timeline.
Those areas include testing of an experimental wing on a truck, developing and using a new simulator to look at controls and handling characteristics of an electric airplane, and verifying tools that will enable NASA's engineers to design and build the aircraft, which is also part of NASA's efforts to help pioneer low-carbon propulsion and transition it to industry.
The first area, in cooperation with Joby Aviation and ESAero, is the Hybrid Electric Integrated Systems Testbed, or HEIST, an experimental wing initially mounted on a specially modified truck. It is used for a series of research projects intended to integrate complex electric propulsion systems.
The testbed functions like a wind tunnel on the ground, accelerating to as much as 73 mph to gather data. Researchers have used the testbed to measure lift, drag, pitching moment, and rolling moment that can validate research tools.
"By evaluating what we measured vs. what the CFD predicted, we will know if the predictions make sense," said Clarke. "Since [this] is a new design, we need to validate we have good answers for the experimental wing."
HEIST's first experiment was called the Leading Edge Asynchronous Propeller Technology, or LEAPTech. The experiment began in May at Armstrong and consisted of 18 electric motors integrated into the carbon composite wing with lithium iron phosphate batteries.
Tests so far show the distribution of power among the 18 motors creates more than double the lift at lower speeds than traditional systems.
Developing and refining research tools is another major effort. For example, researchers plan to integrate the aircraft's systems with a NASA Armstrong flight simulator for pilots to evaluate handling qualities. Researchers also will be able to study balancing the power demands of the motors with batteries and then a turbine, according to Clarke. Of interest is whether a hybrid of distributed electric motors and gas-powered turbines could provide power to extend the aircraft's range and enable a possible nine-person concept aircraft, forever changing, perhaps, future connotations of the word "minivan."
Author: Jean L. Broge
Source: SAE Aerospace Engineering Magazine
NASA的航空研究人員將利用Maxwell演示機，展示電動推進系統(tǒng)可以使飛機更安靜、高效、環(huán)保。
去年9月，阿姆斯特朗中心的飛行員曾駕駛一駕意大利制造的Tecnam P2006T飛機，收集飛行數(shù)據(jù)，為NASA正在研發(fā)的改裝機型提供對比材料。一旦此項工作完成，阿姆斯特朗中心的工作人員就可以將一款經(jīng)過專門開發(fā)的機翼整合至安裝了電機的飛機上，進行研發(fā)飛行。（所有圖片均由NASA提供）
工程師正在利用HEIST測試臺，收集新型機翼設(shè)計的空氣動力學(xué)數(shù)據(jù)。
前沿異步螺旋槳技術(shù)（LEANTech）地面測試團隊的成員，從左到右分別為Brian Soukup、Sean Clarke、Douglas Howe、Dena Gruca、Kurt Papathakis、Jason Denman、Vincent Bayne和Freddie Graham。
工程師正在研發(fā)一款配備電機的機翼，這也是綜合HEIST試驗測試臺的一部分。左上為Sean Clarke，右上為Kurt Papathakis，右下為Anthony Cash。
圖為NASA Maxwell X-57概念機，這駕試驗機的特別之處在于經(jīng)過特別設(shè)計的機翼，及機翼上的14部電機。
NASA的航空研究人員將利用Maxwell演示機，說明電動推進系統(tǒng)可以使飛機的飛行更加安靜、高效、環(huán)保。
在X-Plane系列中，1947年誕生的X-1由Bell Aircraft公司打造，可突破“音障”，是世界上首款超音速飛機。
2015年3月，NASA阿姆斯特朗中心中，工程師正在建設(shè)LEAPTech。
JOBY公司的復(fù)合材料技師正在生產(chǎn)LEAPTech的下機翼外皮。
2015年6月，NASA阿姆斯特朗中心內(nèi)的LEAPTech測試臺。
NASA的航空研究人員將利用Maxwell演示機，說明電動推進系統(tǒng)可以使飛機的飛行更加安靜、高效和環(huán)保。
NASA Maxwell通用航空尺寸X-57的早期渲染圖。