Blended Wing Commercial Aircraft: If We Can Imagine It, Why Can't We Build It?
The picture above is a fake, but the concept may very well be viable...
A false rumor, complete with pictures, has Boeing developing a revolutionary new passenger jetliner that can carry 1,000 passengers at mach .88 or 654 mph (+-1046km/h) 8800 nautical miles. According to the e-rumor, the aircraft would be designated the "797" with what's called a "blended wing" design.
Boeing tests the X-48B Blended Wing Body Concept
It may be fiction, but I admit to being reeled into it a bit, and after looking into it myself, I found that it's not such a radical concept after all. In fact, Boeing, while perhaps not currently developing a blended wing superliner, has actively been testing the blended wing design. Still, after all the sweeping denials over this rumor, I found myself asking, why not explore the concept of a commercial blended wing jetliner? And if we find it viable, why not build it? If the Europeans can build an airbus that can seat 830 passengers, why can't we lead the way in developing a commercial airplane that shatters conventional wisdom--and capabilities for that matter?
It turns out that this isn't just a random good idea. Blended wing technology exists and it's in full use (the B2 Stealth Bomber is the obvious example). NASA Senior Aerodynamicist, Al Bowers calls it "a high-risk, high-payoff conceptual platform," and believes NASA’s involvement is appropriate for this project. There are some formidable obstacles to overcome for this to become a reality (pressurizing a non-cylindrical aircraft body, for instance), but if we could assemble our great minds, I'll bet it's doable.
Thanks to NASA, MIT and University of Cambridge, we already have some blueprints to see what may be on the horizon, perhaps during our lifetimes....
Body: The flying wing would be constructed out of advanced composite materials and be divided by 10 intermediate ribs that run from the front to the back of the aircraft. These ribs divide the aircraft into 10 separate passenger bays. The body is fused together with the engine and wings, creating one lifting surface. This lightweight design allows the flying wing to use 25 percent less fuel than a 747.
Passenger Bays: The aircraft would carry 800-1000 passengers in a double-deck cabin that is divided into five bays per deck. Most passengers won't have a window, so the aircraft will have video screens that display window views. Each bay will have doors at the front and back to make emergency exits easier.
Engines: Three jet engines, called high-bypass-ratio engines, would be constructed into the rear of the aircraft's body. Air that is on and near the surface of the wing would flow through the flying wing's curved inlets and into its engines.
Potential Advantages:
-Improved fuel economy
-Reduced noise impact (if the engines are placed above the wings)
-Enormous payload advantages in strategic airlift/air freight and aerial refueling roles
Problems that need to be overcome:
-Difficulty in control, owing to the lack of a tail
-Greater strength needed to maintain internal pressure, compared to tube-shaped body
-Due to the majority of passengers' location far from the roll axis of the aircraft, passengers will be far more affected as a result of a steep turn than they would be in a conventional tube-with-wings airliner, where all the passengers are located immediately next to the roll axis
-Most of the aircraft's occupants will not be able to see a window for looking outside the aircraft at their immediate disposal; a system of 'false-windows', such as LCD displays at each seat or each group of seats that would simulate the presence of a window through use of an externally mounted camera. -Emergency evacuation of a passenger aircraft may also pose a challenge.
'Silent aircraft': How it works
Engineers from the University of Cambridge and the Massachusetts Institute of Technology have unveiled a radical design for a "silent aircraft".
The team says any noise from the concept aircraft, known as the SAX-40, would be "imperceptible" beyond the boundaries of an airport. It would also burn far less fuel than conventional planes.
The design is the result of three years' work and includes both new and existing technologies.
Here, the BBC News website details some of the design's key features.
1. Airframe
2. Engines
3. Exhausts
5. Trailing edge
4. Undercarriage
6. Leading edge
AIRFRAME
Turbulent air around conventional aircraft creates a lot of noise
The shape of the plane is what is known as a "blended wing" design. This hybrid design uses the wings of a conventional plane smoothly blended into a wide tailless body.
As turbulent airflow, generated by irregular surfaces, causes noise, the designers tried to make the airframe as smooth as possible.
The aerofoil shape of the body means that it also contributes to the aircraft's lift, meaning it can make a slower approach on landing, again reducing noise.
The improved lift also means that the plane can do away with flaps on the wings, which are a major source of airframe noise on conventional aircraft.
Because the design does not need a tail, used to provide additional lift and stability on conventional craft, it also cuts down on turbulent airflow and noise from the back of the plane.
The design, made of lightweight composites, also improves the fuel efficiency of the craft whilst cruising.
ENGINES
The engines are embedded into the body of the aircraft
The engines of the SAX-40 are embedded within the blended wing design with the air intakes on top. This means that the upper surface of the aircraft shields people on the ground from engine noise.
The engines are also mounted deep within the intake ducts, lined with mufflers, to maximise the noise absorption.
By embedding the three engines in the aircraft frame, it also reduces drag and therefore noise.
The "ultra-high bypass ratio turbofans", as they are known, are also arranged in a novel way to minimise noise output.
Instead of having one large fan, they have three arranged side-by-side. The smaller fans means the noise from each one is easier to absorb with surrounding "acoustic liners", or muffling materials.
EXHAUSTS
The exhaust system optimises the engines performance
The output of the engines is channelled through what is known as a "variable area exhaust nozzle".
This means that the cross sectional area of the exhaust can be changed to generate different amounts of thrust and to maximise the engine's performance.
At take-off the exhausts would be open-wide to generate the maximum amount of thrust. Whilst cruising they would reduce in size to burn fuel more efficiently.
They can also be rotated, or "vectored", to generate thrust in the optimal direction for take-off and landing.
The exhaust are also lined with "mufflers" to reduce the noise of the engines.
UNDERCARRIAGE
The landing gear of the SAX-40 is designed to minimise noise
Turbulent air swirling around the undercarriage at take-off and landing are major sources of noise.
To reduce this, the SAX-40 would have fairings to cover the wheels and braking systems, creating as smooth a flow of air as possible. This could reduce the noise from the landing gear by up to 7dB.
However, by doing this it makes the landing gear more difficult to stow and service, and also makes cooling the brakes more difficult.
TRAILING WING EDGE
The trailing edge of the wings minimises turbulent mixing of air
When turbulent air moving over the top surface of the wing shoots off the trailing edge it abruptly meets non-turbulent air. The result generates a huge amount of noise.
To minimise this, the SAX-40 would have "trailing edge brushes", a series of long, thin protrusions off the back of the wing.
These allow a smoother transition between turbulent and non-turbulent air and could reduce trailing-edge wing noise by up to 4dB.
LEADING WING EDGE
The Airbus A380 uses the drooped design on the front of its wings
The leading-edge of the wings are slightly drooped. These further help improve the lift of the aircraft, particularly at lower speeds.
To cut-down on the amount of noise generated by air whistling through a slat between the main wing body and the leading edge, the gap is covered in a flexible material.
The edges would be stowed whilst cruising for optimum performance
This drooped design is already being used on the Airbus A380
Northrop Aircraft Co. pioneered the flying-wing design and developed the YB-49, which first flew in 1947.
The B-2 bomber is a descendent of the YB-49 bomber.
LINKS:
Blended Wing Body: Design Challenges for the 21st Century, by Al Bowers
Blended wing’ craft passes wind-tunnel tests , NewScientist.com news service, 14 November 2005
What are the potential military applications? Add Burnelli's safer Extremely Short take-Off and Landing (ESTOL) tracked landing gear to the design in order to provide more lift, slower take-offs and landing speeds; or, for rough terrain or even water landings, incorporate air cushion landing gear-- and you have the ability to land up to 1000 troops into a crisis spot within eight hours. But be careful...such expeditionary capabilities are the stuff empires are built upon....
