Page 85 - The Economist Asia January 2018

The Economist January 27th 2018
Science and technology 69
2 gether—for a replacement set of these is re- and improving patient outcomes, metras boundary layer which, Mr Schlaerth says,
quired with each new liverstored. and their competitors can also help ease would act as a “pneumatic cushion” that
In the future, OrganOxhopesto expand the psychological burden on surgeons. softened and impeded downward-propa-
its activities by building a metra for kid- One such, of some 30 years’ experience, gating shock waves. The aircraft’s long
neys, and perhaps also one for pancreases. still admits to having sleepless nights after nose, meanwhile, would be shaped to di-
Meanwhile, the firm has competition in performing a liver transplant. Even if he rect its shock waves upwards and side-
the form ofTransMedics, ofAndover, Mas- has done the surgery perfectly, he cannot ways. Waves from the engine inlets would
sachusetts. This company is developing be sure that the liver he has transplanted be directed upwards too, and put to good
similardevices forlivers, hearts and lungs. will actually work. Metra-storage makes it use. Adding an appropriate downward
Besidesincreasingthe supplyoforgans, quite likely that it will. 7 curve to a wing would trap the wave and
create an area of high pressure that would
give the wingadditional lift.
Supersonic flight To find out whether all this would
Boom boxed work, Mr Schlaerth recruited two experts
in computational fluid dynamics to act as
independent consultants. Tim Colonius of
the California Institute of Technology and
Luigi Martinelli of Princeton University
each carried out a series of tests. Using so-
phisticated computer modelling, one test
found that the shock wave from the wing
Anewidea forquietening sonicbooms
could be reduced by 63% at Mach 1.5, and
HEN a British Airways Concorde Mach 1, at sea level). Those waves are thata similarreduction would be expected
W travelling from New York touched caused because air molecules cannot get at Mach 2 (Concorde’s cruising speed). An-
down at Heathrow airport, in London, on out of the way fast enough during super- other test showed that shock propagation
October 24th 2003, supersonic passenger sonic flight, and thus build up in front of below the engine was virtually non-exis-
travel came to an end. Concorde was a these parts of the plane. The consequent tent. Further analysis, Mr Schlaerth says,
technological marvel, butnevera commer- change in pressure then propagates indicates that the overall shock wave
cial success. Only 14 of them entered ser- through the air and, when it reaches the might be almost inaudible at ground level.
vice. Yet the idea of building a successor ground, is heard as a distinctive boom. The next step is to replicate the comput-
hasneverquite gone away. Aircraft-makers MrSchlaerth’sidea isto reflectand muf- er tests using models in a wind tunnel, a
review the idea from time to time. A num- fle the worst-offending waves. He would taskwhich the group hopes to take on later
ber of groups are working on small execu- do thisnotbyblendingthe enginesinto the this year. Mr Schlaerth and his business
tive jets intended to travel faster than the fuselage, but rather by placing them well partner, Mark Bryan, have founded a firm
speed of sound. The trouble is, something forward of the leading edge of the wing. called New Century Transportation and
else has also refused to go away: the shock That could be done either by mounting Aeronautics Research to exploit the idea. If
wave known as a sonic boom that ema- them on pylons extending from below the all goeswell, itcould lead to an experimen-
nates from a supersonic aircraft. wing, or by attaching them to the fuselage. tal aircraft to demonstrate the technology.
That boom was one of Concorde’s fail- Both configurations would cause the en- Reducing sonic booms to an acceptable
ings. It rattled windows and frightened an- gines’ exhaust plumes to reflect any shock level would allow overland flights, which
imals, which meant the plane’s flights over wave forming in front of a wing up- should make the return of supersonic pas-
land were restricted to subsonic speeds. wards—ie, away from the ground. senger travel more plausible. Much would
Throttling back an aircraft that is designed Further shock waves, caused by the ex- depend on the cost ofbuilding and operat-
to fly fast is inefficient and causes it to guz- haust’s counter-reflection downwards by ing such aircraft. But the prospect of being
zle a lot of fuel. If supersonic air travel is the wing’s wave, could be dealt with by able to fly from New Yorkto Los Angeles in
ever to return, Concorde’s successors will modifying the engine casings to create a less than two hours, instead of a tedious
thus have to quieten theiract. slower-moving stream of air below the six or so, would be welcomed by many a
Several groups are trying to do this by plume. This slower air should form a weary traveller. 7
tweaking designs to take account of ad-
vances in aerodynamics. By 2021 NASA,
America’s aerospace agency, hopes to fly a
small experimental supersonicplane fitted
with some of these modifications, such as
a long, slender nose and engines blended
into the fuselage. The agency expects this
to reduce the sound of the shock wave to
what it describes as a “low boom”. But
John Schlaerth, an aerospace engineer
based in California, thinks he can take
such modifications much further. He and
his colleagues have filed for a patent on a
set of designs which they believe might
eliminate the boom’s sound altogether at
ground level.
A sonic boom is the product of a series
of shock waves arising from various parts
of an aircraft—particularly its nose, wings
and engines—as it flies faster than the
speed of sound (1,240kph, 770mph or Tomorrow, yesterday