The new B-21 bomber was unveiled to keep many of its innovations under wraps, but more than 34 years of technological advances since the B-2’s 1988 rollout were visible.

The majority of what makes the B-21 a “sixth-generation” combat aircraft is “on the inside.” Still, several external features hint at its evolution from the technology of the B-2, which is also a stealthy flying wing.

The Intakes

First off, the intakes. The B-21’s slender, air-eating air inlets are among its most attention-grabbing aspects. The B-21’s wing roots are almost intimately connected to the intakes, unlike the B-2, where the scalloped intakes are higher and more prominent. Radar likes abrupt angles and big cavities, but the B-21’s intakes look too small to draw in air for the plane’s engines adequately.

However, according to other analysts, “as long as you have enough inlet area to accept the required mass flow of air, your engines will work fine.”

The real challenge, however, “is designing an inlet that can handle the distortions and gradients caused by the fact that the air is moving over significant surface area of the inlet before being ingested. That’s more a matter of tailoring the channel shape in the inlet.”

The inlet of the B-21 is shown in the magnified images released by the Air Force to have a vertical vane.

The “Kutta effect” (air’s tendency to remain attached to a surface rather than separating) could be used to advantage if the inlet were located near the wing’s leading edge. That way, the air flowing up and over the wing’s leading edge would flow directly into the inlet rather than over the inlet itself.

“This is a very, very different design as far as airflow,” Rep. Rob Wittman (R-Va.) said. “…and there have been some design challenges there.”

Because of their small size, inlets such as these provide less of a cavity for search radars to detect and thus less of a chance of seeing the B-21’s fan blades, which are a large radar reflector. On the B-2, the engines are shielded by serpentine ducting that prevents them from being seen directly.

The low-observable design was affected by Pratt & Whitney’s desire for more air at the inlet, Wittman reported.

According to Wittman, the engine and ducting must work together to ensure that “all those things are elements that you would usually find in a new aircraft, one that takes a concept from the B-2, refines it, and applies it to this platform.”

Wingspan

Despite reports and some defense officials’ comments to the contrary, the B-21 did not appear significantly smaller than the B-2 at the rollout.

Because of the proximity of a B-2 at Northrop Grumman, the wingspan of the B-21 appeared to be about 150 feet, about 22 feet shorter than the B-2’s. It’s possible, however, that the B-21’s wingspan is shorter than the B-2 due to its greater sweepback angle. Therefore, it also needed to be made clear whether the shrouded B-21 had a greater sweep angle than the B-21 as it was unveiled.

The B-21 also has a substantially deeper and broader keel than the B-2, suggesting larger weapon bays and more internal fuel. In addition, Secretary of Defense Lloyd J. Austin III said in his introductory remarks that the aircraft would operate from U.S. mainland bases. On the other hand, the B-21’s landing gear is higher and has two wheels rather than the B-2’s four-wheel bogeys.

Canopy Quality

Northrop Grumman officials noted that the B-21’s canopy appeared sanded smooth, with no shadows or breaks, even at the edges. Herculean efforts were made to make the B-2 as smooth as feasible to thwart radar readings, but the B-21 gave the appearance of a nearly sanded-smooth finish.

In the B-21 program, the methods used to smooth out those seams, panel lines, and protruding fastener heads on the B-2 are not employed, including tape and caulk. Because the aircraft can make multiple missions per day in full stealth mode, the B-2’s skin is designed to be tough enough that it does not require low-observable touch-ups after each mission. To make the aircraft more stealthy and reduce the use of tape, the B-2 has benefitted from techniques used on the B-21.

Cockpit

The B-21’s windscreen has a unique design with two trapezoidal front windows and two long side windows. The edges of the windows appeared to be thoroughly connected to the airplane’s solid surfaces, with no seams, edges or framing visible. In addition, the B-21’s deeper keel gives the impression of a flying saucer, though it is unlikely to have been intentional.

Gear Doors

The B-21’s landing gear doors are more straightforward than the serrated-edge doors on the B-2.

The serial “00001” appears on the B-21’s main gear doors, the exact location where the serial “0001” appears on the B-2’s gear doors.

Testing will take place at Edwards Air Force Base, California, and “ED” appears on the gear doors just as “WH” appears on the B-2’s gear doors. In addition, a Northrop Grumman flight test wing symbol is stenciled beneath the aircraft’s nose.

Beak

The B-2’s prominent “beak” is located at the very tip of its leading edge. A brief side view of the B-21 at the rollout revealed that feature, though it is set to further forward on the windscreen and is more prolonged and flatter.

Colors and Nighttime Visibility

The B-21, optimized for nighttime operations, is painted in an overall light gray, presumably FS36375 “Light Compass Ghost Gray,” which may help reduce its visual and infrared signatures during the day.

Program officials say they plan to keep the B-21’s tail hidden for as long as possible since it was not visible at the rollout.

Nevertheless, the B-21 is unveiled now because it will soon be undertaking outside-the-factory engine runs and driving tests, making it publicly visible if at a distance. Once this takes place, long-distance images from photographers camped out on public land outside Plant 42 in Palmdale, California, will almost certainly be released, either confirming or refuting initial speculation. The B-21 is anticipated to make its first flight in mid-2023.