Less fuel, less pollution, less noise: introducing NASA’s double-bubble D8 aircraft

by PBJ Staff / Jan 10, 2018

D8 Double Bubble

2017 was an exciting year for aviation, brimming with new and adventurous ideas. In Dubai, there was the successful test flight of what could prove to be the first flying taxi. Airbus locked up a patent on their vertical take-off aircraft. And social media giants Facebook launched Aquila, a solar airplane that can deliver broadband to even the most remote places on Earth.

There’s no doubt that these innovations are exciting, and are paving the way for the next generation of flyers. But amidst the glamour of ground-breaking inventions, there are a few issues which have been around since the dawn of aviation. And the importance of tackling them is just as important.

Pollution is a problem, and – rightly or wrongly – the aviation industry is often singled out as a big cause of that. Whether it’s the effect that aircraft have on our air or the level of noise these mighty aircraft emit, pollution has long been a prominent issue for pilots and passengers. The D8 looks to change that.

You may have already heard of NASA’s N+3 program. The long-term research taking place in Nasa N+3 has aspirations that could impact future aircraft from 2030 and beyond, as well as some immediate goals. One goal which has been explored since 2008 is the D8 aircraft. Or, to use its more endearing name, the ‘double-bubble’.

D8 Double Bubble

The D8 Double Bubble in Flight

What is the double-bubble D8?

The double-bubble D8 is a concept for a new aircraft which will look to drastically reduce noise and air pollution, whilst simultaneously consuming less fuel. And though it may sound too good to be true, the craftsmanship behind it is surprisingly simple.

The D8 does not rely on ground-breaking and expensive technology to achieve its goals, but primarily on a rejig of how things are traditionally arranged. In most ordinary aircraft, then engines are placed underneath the wings. For the double bubble, the designers have moved the engine from its standard position and relocated it to the top of the plane at the rear end. Drag is reduced, and ergo less fuel is required.

The main section of the plane, which has room for eight passengers on each row, has had a makeover too. The body is wider than is normal for most passenger jets, leading to the ‘double-bubble’ moniker. “It’s like two bubbles side by side,” says Alejandra Uranga, an assistant professor of aerospace and mechanical engineering at the University of Southern California.

This design helps to create even more lift. To counteract the added weight created here, the tail and even the wings themselves are smaller and lighter. It might sound like the design is stumpy, but the researchers believe this will make the aircraft significantly more efficient.

D8 Double Bubble

The D8 Double Bubble in Flight – Rear View

66% less fuel consumption

Although the aviation sector has made efforts to ‘go green’, criticism is still rife and few would deny that more can be done. If accurate, the numbers being suggested for the D8 would go a long way towards achieving this.

The striking statistic coming from the NASA’s N+3 experts suggests that fuel consumption will be reduced by a whopping 66% under the guidance of the D8 model. Similarly, this means emissions could reduce by the same figure over a period of two decades.

Overall, the D8 needs 37% less fuel than your average passenger jet – another vast improvement. Take-off and landing are well-known for consuming large amounts of power, but this has also been addressed in the D8. Nitrogen oxide emissions are decreased by as much as 87% when the aircraft is departing or landing, taking a major chunk out of the current levels.

Inside Look at the D8 Ultra-Efficient Commercial Aircraft

But what about the noise?

On paper, the double bubble seems to tackle pollution on multiple levels. But what about noise pollution?

The combination of reduced fuel consumption and redesigning of the standardized passenger jet means that the D8 should be precisely half as loud as the existing equivalent. A 50% noise reduction level would go a long way to appeasing communities who complain of loud noises from nearby aircraft.

Of course, the D8 is not able to achieve all of this without making some sacrifices. And one of the most prominent sacrifices may be a pill that is too bitter to swallow for mainstream airlines.

D8 Double Bubble Interior

The D8 Double Bubble Sample Interior

Slower travel

Unfortunately, the speed of the aircraft suffers in the D8’s design. Details on the exact speeds will depend on several factors, but the certainty is that these economic benefits will be offset against slower speeds.

The pressure here is not only on the airlines themselves but also the impact on passengers. It is one sacrifice for an airline to take up more time with their flights in order to have a more positive impact on the environment. But when this also means slower flights for customers, the gamble is increased. How many passengers will be willing to choose a slower, more ethical flight over one which is faster?

With all new technology, there is a bedding-in period where customers and companies must acclimatize to the new way of doing things. With the D8, the benefits are obvious. But so too are the drawbacks.

It will take a bold airline to be the first to step forward and willingly increase journey time in order to reduce fuel emissions. Eventually, it could well be the norm. But taking that first step will require quite the gamble.

The aircraft is not due to be available until 2035, some 17 years from now. By then, perhaps the question of reducing emissions will no longer be optional, but imperative.

Pictures courtesy of NASA and Aurora Flight Sciences.

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