Unveiling the technologies that have shaped the most iconic stealth bomber, the B-2 Spirit

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Conceived and developed to perform the USAF’s vital penetration missions deep into enemy territory, the B-2 is capable of evading the most advanced radars and defense systems up to date and deploy its ordnance — which could include nuclear weapons — to highly sensitive and strategic targets.

The B-2 Spirit is a very special aircraft from every point of view. It was conceived to be the stealthiest asset of its time using curved surfaces instead of facets, like those used in the Lockheed F-117 Nighthawk.

It belongs to the third generation of low-observable aircraft which were designed using computer technologies of the ’80s, with an estimated Radar Cross Section (RCS) of less than 0.1m². …

The golden commandments of Clarence L. “Kelly” Johnson that once ruled the Skunk Works.

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Clarence L. “Kelly” Johnson is the Albert Einstein of aerospace design. Johnson’s aircraft programs were so groundbreaking and historically influential, that he and Lockheed’s Skunk Works are forever enshrined in humanity’s technology hall of fame.

Kelly Johnson, the father of today’s Skunk Works, is sometimes cited as the originator of the “keep it simple stupid” (KISS) principle, and his famed "down-to-brass-tacks" management style was summed up by his motto:

"Be quick, be quiet, and be on time."

The Lockheed Electra, P-38 Lightning, Constellation, P-80 Shooting Star, F-104 Starfighter, C-130 Hercules, U-2 Dragon Lady, Jetstar, and of course the almost supernatural A-12 Oxcart and its successor, the SR-71 Blackbird are just a few of the nearly 50 designs Johnson worked on during his 50-year career with Lockheed. …

How frequency hybridization of inertial and air-data measurements can provide enhanced control robustness against turbulence, without impairing the controller stability margins

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Atmospheric perturbations are evil for every pilot. It takes guts and magic touch to land an airliner with a wind shear profile and severe turbulence. And believe it or not, it takes even more expertise to land a Cessna under the same adverse conditions.

The lower the flight speed, the higher the effect of turbulence on the aircraft’s movements. If you have ever flown a drone or an RC plane in windy weather, you know what I’m talking about.

When I started working in the aerospace industry, one of the first problems I had to deal with was closely related to atmospheric turbulence at low flight speeds. The task at hand was to design the feedback filtering strategy for the Flight Control Laws (FCL) of a Medium-Altitude Long-Endurance (MALE) unmanned aircraft. …

Lighter wings, higher wing aspect ratios, and less fuel consumption — all of this can be achieved when you fly flutter-free, but well beyond the flutter speed, all thanks to robust adaptive control technologies.

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The race to achieve improvements in airliners’ energy efficiency seems to never end.

Currently, the improvements in aerodynamic efficiency and specific consumptions in the new generation of aircraft and engines do not exceed the 10% threshold compared to the previous generation.

These improvements have been achieved mainly thanks to the latest innovations in the following fields:

None of these technologies by itself provide a massive increase in aircraft energy efficiency, but when they are combined in the right way, voilà! …

Introducing one of the most simple frequency estimation algorithms for digital signal processing applications

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GPS, radar systems, or even satellite communications; all these applications and devices have one thing in common: they work using frequency-encoded data. In order to decode the valuable information, all these systems use special algorithms to accurately estimate the main frequency of the digital signals they work with.

Many of these algorithms have been proposed throughout the second half of the 20th century and are used to estimate the main frequency of a certain digital signal in real-time, however, only a bunch of them are simple enough (in terms of numerical complexity) to be fit for the embedded software of limited computational-capability devices (such as the Raspberry Pi). …

How optimization-based methodologies are improving the flight control systems’ safety

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Since the introduction of the first non-experimental digital fly-by-wire system in the F-8 Crusader, the exponential growth of the embedded control systems computing power has enabled the military aerospace industry to develop more efficient and agile aircraft.

Generally, modern fighters are designed to be naturally unstable for the sake of maneuverability and agility, requiring the use of Flight Control Laws (FCL) to artificially stabilize the aircraft dynamics and to provide diverse safety-critical flight envelope protection functions, along with automatic or semiautonomous flight modes.

To ensure the safe operation of the aircraft and the correct functioning of the FCL, a clearance assessment must be performed. …

Unveiling the sequence of errors that lead to the one and only accident of the famous B-2 Spirit stealth bomber, and the lessons that were learned after the investigation.

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It was a humid morning on February 25th of 2008 in the Andersen Air Force Base in Guam.

That day more than $1,400,000,000 were lost, two lives were saved, and an engineering work of art was scrapped, the B-2 stealth bomber “Spirit of Kansas” crashed and burst into flames seconds after the lift-off.

The first accident of a B-2 stealth bomber since it passed its testing period, 20 years ago, was caused by humidity that affected the aircraft’s air data system, providing erroneous lectures of airspeed and angle of attack to the Flight Control System.

The erroneous voting and consensus between the different Air Data System’s sensors feeding the “fly-by-wire” control system led to a catastrophic combination of large airspeed over-reading and angle of attack under-reading errors. …

Beating the Fast Fourier Transform algorithm for a small number of selected frequencies is possible. Here you will learn how.

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The frequency-domain analysis allows extracting information that is not obvious by simply observing a signal in time.

Nowadays frequency-domain algorithms are the backbone of many lossy compression data methods like the JPEG for image files or the MP3 for music files.

Most of these algorithms are a derivation of the Continuous Fourier Transform (CFT), originally proposed in 1822 by Jean-Baptiste Joseph Fourier, the father of modern engineering.

The problem with CFT is that it can only be applied to analogical signals, and we all live in a digital/discrete world.

Squeezing the most out of past and present information to improve the controller’s neural networks convergence speed

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Today, countless industrial and technological applications have benefited from the latest advances in the field of Artificial Intelligence (AI).

From mobile applications, that put you in the shoes of Robert Downey Jr. in an Iron Man movie scene, to planes that take off and land autonomously using image recognition algorithms to detect the position of the runway.

However, in most practical applications, the neural networks have been previously trained off-line, and in the deployment and industrialization stage, their parameters, weights, and architecture are frozen.

In other words, these neural networks are static, and their ability to learn during their in-service life has been restricted. …

How autonomous systems technologies will provide unprecedented capabilities to the air forces in the next decade

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Fill ‘er up, Sir!

I want you to visualize this scene. Imagine you had to fill up your car while you are traveling at 300mph, and the pump is also moving, and also the hose is moving around the pump?

You can’t just roll down the window and grab the nozzle with your hand, you have to drive your car — a car which is more like a truck — and align the filler with the nozzle just so.

And now let’s add wind and turbulence to randomly perturb the motion of your car, the pump, and the hose of course.

Oh! And now let there be complete darkness, on a dark night with a new moon and rainy weather. …


Rodney Rodríguez

Aerospace Engineer at Airbus Defence and Space with a great passion for Technology and Science.

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