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B-21 Raider: The Natural Evolution of the U.S. Air Force’s Stealth Bomber Fleet

B-2 Bomber. The B-21 Raider will look very similar. Image Credit: Creative Commons.

Below is Part II of a multi-part series looking at the origins and importance of the B-21 Raider. You can read part I here,part III here, part IV here, and part V here.  

The unveiling of the Air Force’s new stealth bomber, the B-21 Raider, occurred at Plant 42 in Palmdale, California on December 2, 2022. Timed to coincide with a setting sun, executives of the bomber’s prime contractor, Northrop Grumman, used the drama of the moment to tout their creation as the inaugural sixth-generation aircraft, with the bold claim appearing as the first of “10 key facts” posted on the company’s web page devoted to the bomber.

When aviation historians talk about the categorization of aircraft by generation the discussion generally revolves around fighters, with the first-generation comprised of the planes that jumpstarted the jet age, like World War II’s Messerschmitt Me 262. Each subsequent generation brought one or more standout feature(s) and/or performance characteristic(s) such as swept wings or the ability to fly at supersonic speed that distinguished it from the preceding generation.

The latest fighter generation is the fifth, represented by platforms that most notably incorporate full-aspect stealth in their core designs coupled with advanced avionics and data fusion capabilities, like the F-22 Raptor. What exactly qualifies the new bomber for the distinction of being first to enter the next generation and just how the company defines the sixth generation remain to be explained as the rollout hoopla went only so far in revealing the B-21’s features and capabilities.

Based on the B-21’s outward appearance, it clearly derives from its precursor, the venerable B-2. The two bombers share the same basic stingray planform. But the B-21, which is smaller, has slimmed, slit-like engine inlets, which offer an improved low-observable cross-section. In many ways this is indicative of the engineering brilliance behind the B-21. The revised inlets involved not just reducing their size and blending their shape but the herculean task of finessing the boundary-layer effects to make the airflow over the wing and into the inlets workable.

Also, relative to its down-scaled footprint, the B-21 has a deeper and wider center body. This appears to represent an effort by the design and engineering team to maximize the weapons-bay volume to compensate for the aircraft’s comparatively diminutive stature.

While the ceremony permitted only a head-on view of the B-21 so as to keep powerplant and trailing edge highlights under wrap, Aviation Week & Space Technology dropped a reminder that a previously released Pentagon-approved rendering depicted the new plane’s trailing edge as less saw-toothy than that of the B-2. Fewer serrations would make a cleaner wing, which would indicate a further reduction in radar signature as well as improvements in both service ceiling and stability/control.

Owing to the restricted access, it is not known how many engines are embedded behind the B-21’s inlets. The B-2 has four General Electric turbofan engines while the engines on the B-21 are supplied by Pratt & Whitney. A shorter wingspan along with the shrunken footprint and fewer wheels on the landing gear bogeys point to a weight savings, which would translate into an improved performance envelope with a longer endurance/range.

In fact, the B-21’s extended range capability was essentially confirmed in rollout remarks by Defense Secretary Lloyd Austin. This performance gain will be critical for operational flexibility over the vast distances associated with the Indo-Pacific theater, an area of growing concern because of China’s force modernization and saber-rattling. Intriguingly, Air & Space Forces Magazine reported that Air Marshal Robert Chipman, Chief of the Royal Australian Air Force, was in the audience at the rollout.

This lends credence to the view that the U.S. may be poised to break with precedent and start selling or leasing stealth bombers to allies. Australia shares the U.S. concern over a bellicose China and such a sale or lease arrangement would dovetail with the AUKUS (Australia-United Kingdom-United States) deal announced in mid-September 2022 under which the U.S. and the U.K. will share nuclear submarine technology with the Aussies. Perhaps not coincidentally Air Chief Marshal Mike Wigston of the British Royal Air Force was also in attendance. The possibility of foreign sales is discussed in later parts of this series.

The B-21’s other improvements include a new type of surface coating/installation that provides greater radar-absorbency and substantially more robustness against the elements than what is used to sheath the B-2. The legacy aircraft’s surface coating, though scrupulously smooth, employs delicate materials for contouring curved sections, which require frequent reworking and contribute to the B-2’s notoriety as a maintenance hog. As reported by Time, the B-21 has racked up a dismal maintenance-to-flying ratio of 51 hours in the shop for every hour of flight.

In contrast to the B-2’s coating, the B-21’s outer skin was described by Air & Space Forces Magazine as “smoother still,” resembling “a finely sanded surface.” Incorporating advances in materials science is another example of the engineering brilliance underpinning the B-21. Using new manufacturing techniques to apply the more durable materials is expected to result in significantly less maintenance. In turn, this should enable a higher sortie rate, something Air Force Chief of Staff General Charles Q. Brown, Jr. alluded to in his pre-rollout comments.

Many media outlets mentioned also that the B-21’s surface is a noticeably lighter shade than that of the B-2. This has led to speculation that the new bomber will have greater operational versatility with daylight missions occurring on a more regular basis.     

Tellingly, the government-contractor team did not disclose the bomber’s payload capacity. Given the B-21’s compactness, informed observers have suggested it has a payload capacity well below the B-2’s publicly-acknowledged 60,000 pounds. Because the ill-fated Next Generation Bomber (NGB), which followed the B-2’s development, was planned to have a 30,000-pound payload capacity, some commentators have conjectured that the B-21’s weapons-bay will be rated accordingly.

At first blush, it seems counterintuitive that a new heavy bomber would have significantly less bomb-carrying capacity, by weight, than its precursor. Surely there was a tradeoff that prioritized aircraft performance. But rather than assuming mass was sacrificed for such flight attributes as altitude and maneuverability, it must be noted that under the NGB program there were to be lighter-weight weapons capable of delivering effects equal to heavy munitions. Defenders of the B-21’s payload downsizing would argue that the bomber’s efficacy should be judged not on the mass it carries but on its delivered effects.

Of course, the B-21, like the B-2 before it, is going to have both a conventional and nuclear delivery capability. However, other than the modernized B-61-12 nuclear gravity bomb and the forthcoming AGM-181 Long-Range Standoff (LRSO) cruise missile, little is known about the specific weapons to be carried by the B-21. According to the Air Force’s B-21 fact sheet, the bomber will have the means to “employ a broad mix of stand-off and direct-attack munitions.” But unlike the B-2, the new bomber will almost certainly not have the payload capacity to carry two GBU-57 Massive Ordnance Penetrators (MOPs), the ultimate bunker-busters at 30,000 pounds apiece.

As mentioned, the downsizing of the B-21’s weapons payload capacity can be traced to the NGB program, which envisioned bunker-buster warheads shrouded in less casing but equipped with rocket boosters so that while weighing considerably less they would have the equivalent penetrating power of their big brothers. Not much is known about MOP enhancements, but Air Force Times reported in 2021 that the general principle of rocket-boost was being applied with respect to bunker-busters in the 4,000-to-5,000-pound class with the GBU-28, a gravity bomb, slated for replacement by the GBU-72, a powered weapon.

Importantly, the Air Force describes the B-21 as “a component of a larger family of systems” able to engage in electronic attack. This suggests that the bomber, in conjunction with other components in the family of systems, will suppress and jam enemy air defense radars, clearing the battlespace of anti-air and area-denial systems for itself and possibly a plethora of friendly aircraft types to follow. In this role, the B-21 will be like an F-117 on steroids, knocking down multiple barn doors to let in so-called bomb trucks like the B-52s, with their 70,000-pound payload capacity, to do damage with impunity.

While the initial batches of B-21s are not expected to be equipped with directed-energy weapons like advanced lasers and high-power microwave devices, such weapons could be retrofitted into the bomber’s center-body later on, conceivably turning the bomber into a futuristic, Buck Rogers-like gun platform with the ability to engage multiple targets with deep magazines and at what weapons developers avidly describe as the speed of light.

The Defense Department’s directed-energy roadmap calls for reducing the weapons’ size and weight while boosting power from the currently feasible 150-kilowatt (kW) level to megawatt (MW) levels by fiscal year 2026. While some officials have expressed skepticism, pointing to the cancellation of the Airborne Laser (ABL) program because of disappointing test results over a decade ago, a November 14, 2022 Congressional Research Service study stated that some analysts believe “lasers of 1 MW could potentially neutralize ballistic missiles and hypersonic weapons.”

Probably the best indicator of what the future holds in the emergent field can be ascertained from the enthusiasm of industry leaders like Lockheed Martin, Northrop Grumman, Raytheon and Honeywell, which continue to promote their work on deployable directed-energy systems.

All of these new and developing technologies, if successfully integrated into the B-21, would constitute an immensely impressive engineering feat reflective of American preeminence in aeronautics and associated fields. In the three months since the B-21 was unveiled, various observers have provided eloquent and nuanced commentary on this future “backbone” of the Air Force’s bomber fleet, sometimes not surprisingly evaluating the platform as a binary marvel: one part sculpted ominous object and the other part a store of mysterious yet prospectively spellbinding qualities.

It is fair to ask if the B-21’s known and inferred features and capabilities should be viewed as radical departures from or as natural follow-ons to a first-in-class weapon system fielded decades ago. In the end, as explained in the next part of this series, Northrop Grumman’s new aircraft, as a system of systems, holds the promise of arriving at the next generation, but, as an airframe per se, the B-21, for all its notable refinements in shape, size, weight, structure, materials, etc., appears likely to have a flight profile not wildly dissimilar from its precursor, albeit with margins pressed farther, higher and stealthier, making it more evolutionary than revolutionary.

Admittedly, there is much more to learn about this fascinating but still largely secretive new flying machine. As additional snippets about the B-21 dribble out over time, the bomber created to spearhead the forces that protect the free world is likely to continue grabbing the public’s interest and provoking yet more questions.

Philip Handleman is a pilot and aviation author/photographer. With retired Air Force Lt. Col. Harry T. Stewart, Jr., he cowrote Soaring to Glory: A Tuskegee Airman’s Firsthand Account of World War II. Mr. Handleman’s photograph of the Air Force Thunderbirds was featured on the postage stamp honoring the 50th anniversary of the Department of the Air Force in 1997.

Written By

Philip Handleman is a pilot and aviation author/photographer. With retired Air Force Lt. Col. Harry T. Stewart, Jr., he cowrote Soaring to Glory: A Tuskegee Airman’s Firsthand Account of World War II. Mr. Handleman’s photograph of the Air Force Thunderbirds was featured on the postage stamp honoring the 50th anniversary of the Department of the Air Force in 1997.