The Air Force is now building its first “test” aircraft of the new B-21 Raider stealth bomber aircraft engineered to elude the most advanced air defenses for decades to come and destroy high-value targets over enemy territory -- without being seen.

“We’re closely monitoring the build of the additional test aircraft and associated software to support the first flight,” Air Force Chief of Staff Gen. David Goldfein told an audience at an event hosted by the Mitchell Institute for Aerospace Studies.

As for the timing of the first flight and many of the acquisition specifics, they are not available simply because the program is largely secret, in an obvious effort to prevent enemies from getting a jump-start on how they may seek to counter the aircraft. Although few details are known, engineers, observers, program managers and Air Force flag officers are all very clear -- this new bomber will introduce stealth technology the likes of which the world has never seen.

Following a successful critical design review, which closely analyzed many of the aircraft’s technologies, configurations and weapons, the Air Force has brought the program into its Engineering Manufacturing and Design phase - the point in the process where weapons and systems are built.

Much of the construction and prototyping likely involves subsystems, avionics and weapons integration, test aircraft manufacturing, of course, also includes engineering the stealth bomber’s external configuration.

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Building a stealth aircraft requires a deliberate, methodical process of engineering contours from the beginning. As engineers describe it, stealth has to be “built into” the design from inception. Every bolt, seam, curve, wing and weapon needs to be built within specific parameters so as to ensure the lowest possible radar signature. Stealth aircraft have a notable absence of sharp edges, protruding structures and other items potentially more visible to enemy radar. Bombers, in particular, are not only curved but also entirely horizontal, without vertical structures. This creates a scenario wherein a return electromagnetic ping, or radar signal, cannot obtain an actual rendering of the plane. The exterior is both smooth and curved, without visible seams binding portions of the fuselage. Weapons are carried internally, antennas and sensors are often built into parts of the fuselage itself so as to minimize detectable shapes on the aircraft.

The intent is to not only elude higher-frequency engagement radar, which allows air defenses to actually shoot an airplane, but also elude lower-frequency surveillance radar, which can simply detect an aircraft in the vicinity. In effect, the B-21 mission will be to fly into heavily-defended enemy airspace, detect and destroy targets and leave without an enemy ever knowing they were there. Also, stealth aircraft such as the B-2 and B-21 bomber are built with an internal, or buried, engine to decrease the heat signature and various methods of controlling exhaust. One goal of stealth aircraft thermal management is to try to make the aircraft itself somewhat aligned with the temperature of the surrounding air so as not to create a heat differential for enemy sensors to detect.

Finally, the success of stealth relies upon a particular blend of materials used as coating for the exterior. These materials, the components of which are not publicly available, are described as radar-absorbent -- meaning a radar’s electronic signal simply may not bounce off or return with an accurate picture. Some have said that properly-completed stealth construction can make a stealth airplane appear like a bird or an insect to enemy radar.

On the topic of RCS, an interesting essay called “Radar and Laser Cross-Section Engineering,” from the Aerospace Research Central, cites the emergence of new coating technologies, including “radar-absorbing materials and artificial metamaterials.” (Text written by David Jenn, an author from the Naval Postgraduate School).

New stealth technology is being pursued with a sense of vigor, in light of rapid global modernization of new Russian and Chinese-built air defense technologies, some of which may make it harder for platforms such as the existing B-2 bomber to operate. Advances in computer processing, digital networking technology and targeting systems now enable some air defenses to detect even stealth aircraft with much greater effectiveness. However, the B-21, is being engineered with this specific challenge in mind -- to ensure a new generation of stealth will be able to penetrate air defenses for decades into the future.

Russian built S-300 and S-400 air defense weapons are able to use digital technology to network “nodes” to one another to pass tracking and targeting data across wide swaths of terrain. New air defenses also use advanced command and control technology to detect aircraft across a much wider spectrum of frequencies than previous systems could. At the same time, while some of these advances may complicate some elements of the mission scope for the legacy B-2, according to senior Air Force developers -- it by no means indicates these current and future air defense will in any way threaten the B-21. For this reason, many military developers, weapons technology experts and observers are echoing a common refrain -- namely that it is imperative for the Air Force to invest heavily in its emerging fleet of B-21 bombers.

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Barriers related to hitting stealth aircraft also include electronic warfare “jamming” defenses, operating during adverse weather conditions to lower the acoustic signature and conducting attacks in tandem with other less-stealthy aircraft likely to command attention from enemy air defense systems.

EW is likely to figure prominently, in part because emerging hardware configurations are now engineered to quickly embrace software upgrades as new threats emerge, such as yet-to-be-seen frequency combinations or radar-detection ranges.

All of these emerging technical factors continue to inform a growing consensus regarding future war threats -- that the B-21 appears to quite possibly be the only platform that will be able to penetrate certain enemy weapons and advanced air defenses for decades to come. While stand-off weapons are anticipated to bring substantial tactical advantage, destroying enemy air defenses and pinpointing targets in closer proximity, to open up an air corridor for other attacking air assets, appears to many as an absolute necessity. For instance, mobile air defenses can quickly change position, new targets can emerge and certain weapons such as EW application might need to operate within a closer range than stand-off platforms to be effective.

Part of this consensus, according to Senior Air Force weapons developers, is implicitly built upon the fact that the B-21 is being engineered to be perpetually upgradeable. Among other things, this means that new software, sensors, weapons, computers and avionics can quickly emerge as they become available.

While naturally sparing with details, Air Force senior leaders have said the new B-21 will be able to “hold any target at-risk, anywhere in the world, at any time.”

“The computational capabilities that were available to design the F-117 and B-2 are dwarfed by the power now available to design teams,” writes the Mitchell Institute essay,”The Imperative for Stealth.”

“Our confidence remains very high in this program,” Goldfein said.

Kris Osborn can be reached at Krisosborn.ko@gmail.com

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