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

翻译人员: Jiasi Hao 校对人员: Yanyan Hong

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

在 1996 年，一架英国航空的航班

破记录用时 2 小时 53 分钟 从纽约抵达伦敦。

in a record-breaking two hours and 53 minutes.

Today, however, passengers flying the same route

不过如今，乘坐同一航线的乘客

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

至少要在空中花费 6 小时—— 记录时长的 2 倍。

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

那么，为何当整个世界加快步伐时，

have commercial flights lagged behind?

商业航班是否已经落后？

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

在 1970 年代， 英法共同制造的协和式飞机

across the sky in the 1970s.

开始运送乘客，

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

穿梭往返于纽约、巴黎、 巴林和新加坡等目的地。

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

该机型能以 2000 公里的时速飞行，

more than twice the speed of a normal airliner.

这是普通客机时速的 2 倍。

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

然而，由于这个时速 比音速还要快上 800 公里，

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

给地面上的居民 带来了意料之外的困扰。

When an object moves at supersonic speed,

当物体以超音速移动，

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

它会产生连续移动的冲击波， 也就是所谓的 “声震”。

This produces a loud, startling noise,

声震会发出巨大、吓人的噪音，

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

同时造成窗户震动， 使建筑物部件发生脱落。

Since a plane flying at an altitude of 15 kilometers

一架飞在 15 千米高空的航班

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

可以影响到下方 直径为 80 公里内的地区，

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

因此，遭到协和式飞机航线 周边居民的控诉与忧虑，

restricted it to mostly ocean routes.

而将飞行限制在跨海洋航线。

Because of these restrictions and other fuel and engineering requirements,

因为这些限制以及 其它的燃料和技术需求，

supersonic flights turned out to be very expensive

超音速飞行对航司和乘客而言

for both airlines and passengers.

就变得十分昂贵。

A single transatlantic round-trip could cost the equivalent

一次跨大西洋往返的费用

of more than $10,000 today.

相当于今天的 1 万美元。

With additional strain on the airline industry

自 2001 年 911 恐袭事件后， 人们对航班需求的减少

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

给航空业带来了额外的压力，

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

高成本使其不可持续， 协和式飞机也于 2003 年退役。

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

因此，即使有超高速航班存在， 它们也不适用标准商用飞行。

And while we might think that advances in flight technology

同时，我们可能会想 随着航空技术的进步

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

提高飞行速度的成本会降低， 事实却非如此。

One of the biggest concerns is fuel economy.

其中一个最大的担忧就是 燃油经济性。

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

过去几十年， 喷气发动机变得更加高效，

taking in more air and achieving more thrust—

它们能吸收更多空气 并获得更大的推动力——

traveling further for every liter of fuel.

每升燃油支持的航程会增加。

But this efficiency is only achieved at speeds

然而达到这一燃油效率的前提是

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

保持时速 900 公里左右的飞行—— 协和式飞机时速的一半。

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

再快就会增加进气量 并在每公里的飞行中消耗更多的燃料。

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

一次标准的跨大西洋航班 仍要使用多达 15 万升燃料，

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

占航空公司总支出的 20% 以上。

So any reduction in fuel economy and increase in speed

因此，任何燃油经济性的降低 和速度的提高

would significantly increase both flight costs and environmental impact.

都会大大增加 飞行成本和环境影响。

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

那有办法不消耗大量燃油 使飞机飞得更快吗？

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

调整机翼的后掠角 或机翼从机身延长出的角度，

to bring the wings closer in can make an aircraft faster

使机翼更接近， 可以通过减少空气动力阻力

by reducing aerodynamic drag.

使飞机更快。

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

但这意味着机翼必须加长 以达到相同翼展，

and that means more materials and more weight,

意味着机翼需要更多材料， 飞机会因此变重，

which in turn means burning more fuel.

结果还是要增加燃料。

So while airplanes could be designed to be more aerodynamic,

所以，尽管飞机可以设计得 更符合空气动力学，

this would make them more expensive.

但这会增加成本。

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

总体来说，航司发现 乘客对于飞机提速的需求

is not sufficient to cover these costs.

不足以弥补这些成本。

So while military aircraft conduct high speed flights

所以，当军用飞机能在水上和高空

over water and at high altitudes,

进行高速飞行任务时，

supersonic commercial flights seemed like a brief and failed experiment.

超音速商用飞机 似乎就像一个短暂且失败的实验。

But recent advances may make them feasible again.

不过，近期的科学发展 或许能让它们再次变为可能。

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

美国航天局和国防高级研究计划局的研究 表明改进飞机外形

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

可以减少三分之一的声震影响。

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

一种方案是用长钉子延长机头 将冲击波分解成更小的冲击波，

while another proposed design features two sets of wings

另一种拟议的设计 则以两组机翼为特征

producing waves that cancel each other out.

产生冲击波，互相抵消。

And new technologies may solve the energy efficiency problem

而新技术可以用替代和合成燃料，

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

甚至是混合动力飞机， 解决能源效率问题。

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

事实可能证明， 过去几十年的稳健飞行

were just a brief rest stop.

只是短暂的休息。