Why are airplanes slower than they used to be? - Alex Gendler
In 1996, a British Airways plane
flew from New York to London
in a record-breaking
two hours and 53 minutes.
Today, however, passengers flying
the same route
can expect to spend no less than six hours
in the air— twice as long.
So why, in a world where everything
seems to be getting faster,
have commercial flights lagged behind?
The British-and-French-made Concorde
began shuttling passengers
across the sky in the 1970s.
Jetting between destinations like
New York, Paris, Bahrain, and Singapore,
it clocked in at over 2,000 kilometers
per hour,
more than twice the speed
of a normal airliner.
However this was also about 800 kilometers
per hour faster than the speed of sound.
And that created a surprising problem
for people on the ground.
When an object moves at supersonic speed,
it generates a continuous moving shockwave
known as a sonic boom.
This produces a loud, startling noise,
as well as rattling windows and dislodging
structural elements of buildings.
Since a plane flying at an altitude
of 15 kilometers
can affect an area with an 80 kilometer
diameter on the ground below,
complaints and concerns from residents
in the Concorde’s flight path
restricted it to mostly ocean routes.
Because of these restrictions and other
fuel and engineering requirements,
supersonic flights turned out
to be very expensive
for both airlines and passengers.
A single transatlantic
round-trip could cost the equivalent
of more than $10,000 today.
With additional strain
on the airline industry
due to decreased demand for flights
after September 11th, 2001,
this became unsustainable,
and the Concorde was retired in 2003.
So even when superfast flights existed,
they weren't standard commercial flights.
And while we might think that advances
in flight technology
would make fast flights less expensive,
this hasn’t necessarily been the case.
One of the biggest concerns
is fuel economy.
Over the decades, jet engines have become
a lot more efficient,
taking in more air
and achieving more thrust—
traveling further for every
liter of fuel.
But this efficiency is only achieved
at speeds
of up to around 900 kilometers per hour—
less than half the speed of the Concorde.
Going any faster would increase air intake
and burn more fuel per kilometer flown.
A standard transatlantic flight still uses
as much as 150,000 liters of fuel,
amounting to over 20%
of an airline’s total expenses.
So any reduction in fuel economy
and increase in speed
would significantly increase both
flight costs and environmental impact.
What about ways to make a plane faster
without burning lots of fuel?
Adjusting the wing sweep, or the angle
at which wings protrude from the fuselage,
to bring the wings closer in can
make an aircraft faster
by reducing aerodynamic drag.
But this means the wings must be longer
to achieve the same wingspan,
and that means more materials
and more weight,
which in turn means burning more fuel.
So while airplanes could be designed
to be more aerodynamic,
this would make them more expensive.
And generally, airlines have found
that customer demand for faster flights
is not sufficient to cover these costs.
So while military aircraft conduct
high speed flights
over water and at high altitudes,
supersonic commercial flights seemed
like a brief and failed experiment.
But recent advances
may make them feasible again.
Research by NASA and DARPA has shown
that modifying an aircraft’s shape
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,
while another proposed design features
two sets of wings
producing waves
that cancel each other out.
And new technologies may solve
the energy efficiency problem
with alternative and synthetic fuels,
or even hybrid-electric planes.
It may yet turn out that the last
few decades of steady flying
were just a brief rest stop.
