SCWalter

動(dòng)汽車(chē)企業(yè)家及火星私人殖民的擁護(hù)者埃隆·馬斯克現(xiàn)在打算重塑鐵路運(yùn)輸。馬斯克提出重現(xiàn)一種叫做真空列車(chē)的老式科幻概念，列車(chē)將以超過(guò)1 200千米的時(shí)速帶著旅客橫穿加州——比噴氣客機(jī)還要快。他的想法至少在理論上是可行的，如果付諸實(shí)踐會(huì)如何呢？

California is home to many clever people. One of them is Elon Musk， the hyperactive boss of Tesla Motors， an electric-car company， and SpaceX， a rocketry business （he also sits on the board of a solar-energy firm）. There is nothing Mr. Musk likes more than revolutionizing high-tech industries. And he thinks he has come up with a better way to get California moving than a standard high-speedtrain—Hyperloop， prompting excited speculation about what he might have had in mind.

Mr. Musks Atmospheric Caper

Essentially， Mr. Musk proposes to revive an old science-fiction idea called the vac-train （short for “vacuum train”）， albeit with a few important tweaks. The Hyperloop would carry passengers across California at more than 1，200 kph—faster than a jet airliner—allowing them to zoom between San Francisco and Los Angeles in little over half an hour， compared with more than two-and-a-half hours for California High Speed Rail project. Mr. Musks notional budget is around $6 billion， less than a tenth of what the high-speed train is supposed to cost.

Vac-trains， as first described in the 1910s by Robert Goddard， would send rolling stock （or hovering stock， perhaps） hurtling through hermetically sealed tubes from which the air has been evacuated. The trains would thus encounter no drag， and be able to reach immense speeds. Goddard reckoned his design—which also proposed magnetic levitation instead of wheels—was good for about 1，600 kph.

This and other designs for transporter tubes inspired much futuristic art， but none was ever built because maintaining a vacuum in a long tunnel is difficult. Even a small leak would scupper a full-fledged vac-train， which relies on no air at all being able to build up in front of it， and thus slow it down. For that reason， the Hyperloop is not actually a true vac-train. Instead， Mr. Musk plans to remove sufficient air from the tubes to give them a pressure roughly a sixth of that on the surface of his beloved Mars， or a thousandth of that on earth at sea level. This would keep the air resistance low enough to deal with in other ways.

The chief of these would be to suck up the air that did accumulate in front of the tubes rolling stock using a fan， and then expel most of it from the pods rear end. Some of this air， though， would be diverted out of the sides through special skis， to create a cushion that would stop the pod touching the tunnel walls.endprint

Each pod would be launched by a linear-induction motor （such motors are also being tested for use as catapults on aircraft carriers）， and booster motors every 110 km would keep its speed up. On reaching its destination， the pod would pass through a motor that works in reverse， converting its kinetic energy back into electricity for storage in batteries or use in motors up the line. And， this being California， the whole thing would naturally be powered by solar panels mounted on the roof of the tube.

Loop the Loop

Its breathtaking audacity aside， the thing does look feasible as an engineering project.

The tube would be held above ground， on pylons， reducing the amount of land it consumed， and would follow existing roads， which should simplify construction and make maintenance easier. And the air cushion surrounding each pod should ensure that the ride is smooth. Moreover， although unexpected engineering problems would be bound to crop up， Mr. Musks experience—and that of his engineers—with space flight and car design would bode well for overcoming them.

With projects like this， though， good engineering is never enough. Politics and economics are more forbidding obstacles. Being new， the Hyperloop is risky.

In the past Mr. Musk has said that， given his other commitments， he lacked the time to try to build the Hyperloop himself. The reason for putting it into the public domain was therefore to give someone else the chance to take it up. “I think it might help if I built a demonstration article，” he mused. “So I think I probably will do that， actually.”

美國(guó)加州有許多聰明人，埃隆·馬斯克就是其中之一。他精力旺盛，身兼一家電動(dòng)汽車(chē)公司——特斯拉汽車(chē)公司和一家做火箭生意的“太空探索技術(shù)公司”（SpaceX）的老板（他還在一家太陽(yáng)能公司的董事會(huì)中任職）。馬斯克最喜歡的就是革命性的高科技產(chǎn)業(yè)。他認(rèn)為他已經(jīng)想出了一個(gè)比標(biāo)準(zhǔn)高速列車(chē)更好的方法來(lái)讓加州動(dòng)起來(lái)——超旋，這激起了人們的踴躍猜測(cè)：他腦子里在想些什么？

馬斯克的空氣把戲

大體上說(shuō)，馬斯克提出重現(xiàn)一種叫做真空列車(chē)的老式科幻概念，但有一些重要的調(diào)整。超旋將以超過(guò)1 200千米的時(shí)速帶著旅客橫穿加州——比噴氣客機(jī)還要快。旅客乘坐超旋在舊金山和洛杉磯之間奔馳只需要半個(gè)小時(shí)多一點(diǎn)，而加州高鐵則需要超過(guò)兩個(gè)半小時(shí)。馬斯克的理論預(yù)算約為60億美元，不到高速列車(chē)假想成本的十分之一。

真空列車(chē)最早由羅伯特·戈達(dá)德于1910～1920年間提出，它通過(guò)密閉排氣的管道高速運(yùn)送輪車(chē)（也可能是懸浮車(chē)）。因此，列車(chē)不會(huì)遇到阻力，能夠達(dá)到極高的速度。戈達(dá)德的設(shè)計(jì)中也提出了用磁懸浮替代車(chē)輪，他計(jì)算后認(rèn)為自己的設(shè)計(jì)可以達(dá)到約1 600千米的時(shí)速。

戈達(dá)德描述的真空列車(chē)和其他有關(guān)運(yùn)輸管的設(shè)計(jì)為許多未來(lái)藝術(shù)帶來(lái)了靈感，但是，從來(lái)沒(méi)有一項(xiàng)設(shè)計(jì)付諸建造，因?yàn)樵谝粭l長(zhǎng)長(zhǎng)的隧道中保持真空狀態(tài)很困難。真空列車(chē)依靠的就是前方?jīng)]有一點(diǎn)兒空氣聚集，因此不會(huì)減速，即使很小的泄漏也會(huì)徹底破壞一列整裝待“飛”的真空列車(chē)。正因如此，超旋實(shí)際上不是一輛真正的真空列車(chē)。馬斯克計(jì)劃從管道中抽出足夠的空氣，使得列車(chē)承受的氣壓大約是他心愛(ài)的火星表面氣壓的六分之一，或者說(shuō)是地球海平面氣壓的千分之一。這將讓空氣阻力降低到可以用其他方式應(yīng)對(duì)。

這一設(shè)計(jì)的重點(diǎn)是用風(fēng)扇吸走管道中車(chē)輛前方聚積起來(lái)的空氣，然后把大部分空氣從運(yùn)輸艙的后面排出。不過(guò)，一部分空氣將通過(guò)特殊的導(dǎo)風(fēng)板從側(cè)面導(dǎo)出，形成緩沖氣墊，防止運(yùn)輸艙碰到隧道壁。

每個(gè)運(yùn)輸艙用一臺(tái)直線(xiàn)感應(yīng)電機(jī)發(fā)射出去（這種電機(jī)也正在進(jìn)行作為航母彈射器的測(cè)試），而且每110千米有助推電機(jī)給運(yùn)輸艙加速。到達(dá)目的地后，運(yùn)輸艙將通過(guò)一臺(tái)反向工作的電機(jī)，將動(dòng)能轉(zhuǎn)化回電能儲(chǔ)存在電池里，或者用在返程線(xiàn)路的電機(jī)上。此外，這是在加州，整個(gè)系統(tǒng)自然會(huì)由安裝在管道頂部的太陽(yáng)能電池板供電。

付諸實(shí)踐

拋開(kāi)它那驚人的大膽不談，這一方案看起來(lái)的確是一個(gè)切實(shí)可行的工程項(xiàng)目。

管道將會(huì)建設(shè)在地上的塔架之上，減少土地占用，而且會(huì)沿著現(xiàn)有的道路修建。這樣一來(lái)應(yīng)該可以簡(jiǎn)化建設(shè)，使維護(hù)工作更容易。同時(shí)，每個(gè)運(yùn)輸艙周?chē)臍鈮|應(yīng)該可以確保行駛平穩(wěn)。此外，雖然意料之外的工程問(wèn)題勢(shì)必會(huì)出現(xiàn)，但馬斯克和他的工程師們?cè)谔诊w行和汽車(chē)設(shè)計(jì)上的經(jīng)驗(yàn)將會(huì)成為克服這些問(wèn)題的好兆頭。

不過(guò)，對(duì)于這樣的項(xiàng)目來(lái)說(shuō)，掌握好工程學(xué)是遠(yuǎn)遠(yuǎn)不夠的。政治和經(jīng)濟(jì)問(wèn)題是更令人生畏的障礙。作為一項(xiàng)新技術(shù)，超旋是有風(fēng)險(xiǎn)的。

馬斯克曾說(shuō)過(guò)，考慮到他承擔(dān)的其他工作，他自己沒(méi)有時(shí)間來(lái)試著建設(shè)超旋。因此，他將這一方案公之于眾的原因就在于把機(jī)會(huì)留給其他人去把握?！拔蚁肴绻以斐鲆粋€(gè)演示品可能會(huì)有所幫助。”他若有所思地說(shuō)，“所以我可能真的會(huì)這么做?！眅ndprint