Why are airplanes slower than they used to be? - Alex Gendler

譯者: Lilian Chiu 審譯者: Amanda Zhu

In 1996, a British Airways plane flew from New York to London

1996 年，一架英國航空的飛機 從紐約飛往倫敦，

in a record-breaking two hours and 53 minutes.

破記錄地只花了 2 小時 53 分鐘。

Today, however, passengers flying the same route

然而，現今同樣的航線，

can expect to spend no less than six hours in the air— twice as long.

卻至少要花 6 小時——

2 倍的時間。

So why, in a world where everything seems to be getting faster,

世界上的一切似乎都越來越快，

have commercial flights lagged behind?

為什麼唯獨民航客機反而落後了？

The British-and-French-made Concorde began shuttling passengers

英國與法國製造的協和式飛機

於 1970 年代開始在空中運送旅客。

across the sky in the 1970s.

Jetting between destinations like New York, Paris, Bahrain, and Singapore,

在紐約、巴黎、巴林， 及新加坡等地之間，

it clocked in at over 2,000 kilometers per hour,

以每小時 2000 公里 以上的速度飛行，

more than twice the speed of a normal airliner.

速度是一般班機的 2 倍。

However this was also about 800 kilometers per hour faster than the speed of sound.

然而，這個速度也比音速 還要快約每小時 800 公里。

And that created a surprising problem for people on the ground.

很意外的是，這卻給 地面上的人帶來了一個問題。

When an object moves at supersonic speed,

當物體以超音速移動時，

it generates a continuous moving shockwave known as a sonic boom.

會產生持續的移動衝擊波， 即一般所知的音爆。

This produces a loud, startling noise,

這會造成巨大且驚人的噪音，

as well as rattling windows and dislodging structural elements of buildings.

也會讓窗戶嘎嘎作響， 並震落建築上的附著物。

Since a plane flying at an altitude of 15 kilometers

飛機的飛行高度若為 15 公里，

can affect an area with an 80 kilometer diameter on the ground below,

地面上受到影響的面積 就達直徑 80 公里，

complaints and concerns from residents in the Concorde’s flight path

因此，住處位在協和式飛機 航線上的居民會抱怨及關切，

restricted it to mostly ocean routes.

造成它幾乎只能飛海上的航線。

Because of these restrictions and other fuel and engineering requirements,

因為有前述這些限制 及其他燃料和工程上的需求，

supersonic flights turned out to be very expensive

導致對航空公司及乘客而言， 超音速航班都非常昂貴。

for both airlines and passengers.

A single transatlantic round-trip could cost the equivalent

一趟橫渡大西洋的來回旅程，

要價等同現今的 10000 元美金以上。

of more than $10,000 today.

With additional strain on the airline industry

2001 年 9 月 11 日之後， 航班的需求減少，

due to decreased demand for flights after September 11th, 2001,

讓航空業雪上加霜，

this became unsustainable, and the Concorde was retired in 2003.

協和式航班因此無法持續營運

而在 2003 年退役。

So even when superfast flights existed, they weren't standard commercial flights.

雖然的確有超快速的飛機存在，

但它們都不是標準民航客機的航班。

And while we might think that advances in flight technology

我們可能會認為， 隨著飛機技術進步，

would make fast flights less expensive, this hasn’t necessarily been the case.

快速航班的價格會降下來，

但實情不見得是如此。

One of the biggest concerns is fuel economy.

最大的問題之一是燃料經濟性。

Over the decades, jet engines have become a lot more efficient,

數十年來，噴射引擎的效率 已經提升更多，

taking in more air and achieving more thrust—

能吸入更多空氣， 產生更強的推力——

traveling further for every liter of fuel.

增加每一公升燃料的飛行距離。

But this efficiency is only achieved at speeds

但要達到這樣的效率，

速度最高不能超過 約每小時 900 公里——

of up to around 900 kilometers per hour— less than half the speed of the Concorde.

不到協和式飛機速度的一半。

Going any faster would increase air intake and burn more fuel per kilometer flown.

超過這個速度，空氣進氣會增加，

飛行每公里所燃燒的燃料也會越多。

A standard transatlantic flight still uses as much as 150,000 liters of fuel,

一個橫越大西洋的標準航班 就要耗掉多達 15 萬公升的燃料，

amounting to over 20% of an airline’s total expenses.

佔了航空公司總開銷的 20% 以上。

So any reduction in fuel economy and increase in speed

所以，再減少一點燃料經濟性 或增加一點速度，

would significantly increase both flight costs and environmental impact.

就會大大增加飛行成本及環境衝擊。

What about ways to make a plane faster without burning lots of fuel?

有什麼方式可以不要燃燒 大量燃料就讓飛機更快嗎？

Adjusting the wing sweep, or the angle at which wings protrude from the fuselage,

調整機翼後掠角， 也就是機翼和機身之間的角度，

to bring the wings closer in can make an aircraft faster

使機翼更靠近機身，

能減少氣動阻力，讓飛機更快。

by reducing aerodynamic drag.

But this means the wings must be longer to achieve the same wingspan,

但這就表示機翼要更長， 才能達到同樣的翼展，

and that means more materials and more weight,

那麼就需要更多材料， 重量也變得更重，

which in turn means burning more fuel.

也就是說，會燃燒更多燃料。

So while airplanes could be designed to be more aerodynamic,

雖然飛機的設計可以 更符合空氣動力學，

this would make them more expensive.

卻會因此變得更昂貴。

And generally, airlines have found that customer demand for faster flights

而航空公司發現，一般來說， 客戶對於飛行速度更快的需求

is not sufficient to cover these costs.

還不足以讓他們願意負擔這些成本。

So while military aircraft conduct high speed flights

所以，雖然軍用飛機

over water and at high altitudes,

能在水域上的高空高速飛行，

supersonic commercial flights seemed like a brief and failed experiment.

超音速民航機航班 卻像是個短暫且失敗的實驗。

But recent advances may make them feasible again.

但近期的進展可能 讓超音速航班再次可行。

Research by NASA and DARPA has shown that modifying an aircraft’s shape

太空總署和美國國防 高等研究計劃署的研究指出，

改變飛機的形狀 能夠將其音爆的衝擊減少 1/3。

can reduce the impact of its sonic boom by 1/3.

Extending the nose with a long spike can break the shockwave into smaller ones,

加裝一根針將機頭延長，

可以把衝擊波打散變小，

while another proposed design features two sets of wings

提議的另一種設計則是採用兩組機翼，

producing waves that cancel each other out.

產生出來的波能互相抵消。

And new technologies may solve the energy efficiency problem

新技術也可能用來解決能源效率問題，

with alternative and synthetic fuels, or even hybrid-electric planes.

比如替代燃料及合成燃料，

甚至油電混合動力飛機。

It may yet turn out that the last few decades of steady flying

最後我們可能會發現， 過去這幾十年慢慢飛行的情況

were just a brief rest stop.

其實只是在進步的過程中 小歇一下而已。