How It Works-Amazing Vehicles

Banishing the boom

Even when active, Concorde was prohibited

from fl ying at supersonic speeds over the

USA due to the impact of sonic booms.

Indeed, the inabilit y of Concorde to fl y over

the majority of habituated land meant it had

to follow elongated and ineffi cient fl ight

routes, greatly damaging its effi ciency.

Eradicating these sonic booms is

therefore key to any future supersonic jet

being greenlit for production, w ith nations

worldw ide concerned w ith the ‘boom

carpet’ (the avenue on a jet’s fl ight path

where sonic booms can be heard). Three key

developments in this area have been the

recent introduction of far thinner wings

than Concorde, the repositioning of the

engines above the w ings – this effectively

turns the w ings into shields, diverting

pressure waves away from the ground – and

the creation of pressure-sculpting air inlets

for the aircraft’s turbines.

While no physical jet has yet to enter

production, experimentation by US space

agency NASA in 2011 into sonic booms

confi rmed that, if the new designs could

adequately hide the engine outlets within a

narrow fuselage, then almost all audible

noise could be cancelled out.

there are still major hurdles that need to be

overcome – something driven by a call from

NASA for companies to investigate ways to cancel

out the damaging effects of sonic booms, increase

fuel effi ciency and improve the abilit y of supersonic

jets to break through the transonic envelope (see

the ‘Shattering Mach 1’ boxout over the page).

These factors represent just a few of the challenges

of not only achieving supersonic fl ight, but also

making it commercially viable where Concorde

ultimately wasn’t.

In this feature, we take a much closer look at

the science of travelling at supersonic speeds as

well as at some of the aircraft and advanced

technolog y currently leading the charge against

Earth’s sound barrier.

The Supersonic

Green Machine

Lockheed Martin’s Supersonic Green Machine

recently piqued interest at NASA thanks to its

inverted-V engine array. The array, which sits

above the w ings, has been designed to

mitigate the generation of sonic booms, the

loud and distinctive cracking sound heard

when an object passes through the sound

barrier. The positioning of the engines is not

just an aesthetic choice either, but a strategic

one that harnesses the wing area to effectively

shield portions of the ground against pressure

waves, thereby reducing the audible noise and

‘boom carpet’ heard on the ground.

Interestingly, the design has also been

developed to get as close as possible to

the ideal aerody namic form for a supersonic

jet, with the fuselage closely resembling the

Sears-Haack model (a cigar shape that

minimises the creation of wave drag).

While no concrete specifi cations have

been released, according to Lockheed

Martin and NASA, which have run model-

sized trials in w ind tunnels, the jet would

offer speeds comparable to Concorde, but

with signifi cant reductions in fuel burn and

noise output.

2x © NA SA; Lock heed Mar tin

Lockheed Martin’s Green Machine passenger plane offers a

glimpse into the future of high-speed, eco-minded air travel

Shield

The engines are positioned

above the wings to partially

shield people on the ground

from the immense pressure

waves that are generated.

The second design for the Green

Machine, a next-gen supersonic jet

created by Lockheed Martin

For the latest supersonic jets to become a reality, special

technology is being designed to keep the noise down

DID YOU KNOW? Lockheed Martin will work closely with NASA to create the Supersonic Green Machine