New in-flight photos of the B-21 Raider released

B-21 Raider continues flight test, production > Air Force > Article Display (af.mil)

You know, when it's up in the air, it looks very flying saucer-esque.

Well that's neat.

I see an upside-down narwhal

The shape is rather similar to the B2, so from below, it looks more like origami. 

I also hear it is capable of both piloted and autonomous missions.  Not sure why you would want autonomous missions.  Maybe for extreme endurance?   You would need autonomous in flight refueling of course.

B2:

B21:

I saw a B2 flying over Lancaster, CA a few years back. It looked like a glitch in the sky.

B21 autonomous missions? Uh-oh....Skynet is here!

B-1, B-2...B-21. What where B-4 through B-20?

Appleseed said:

B-1, B-2...B-21. What where B-4 through B-20?

Only those with the right clearance Clarence.

That leading edge sure looks sharp for a slow moving plane which I thought broke all of the rules. I would love to hear Sleepyhead the Buffalo's response and analysis to the airflow over that thing. Here is a B2 for comparison. One is a model.

Appleseed said:

B-1, B-2...B-21. What where B-4 through B-20?

That would be a Bingo 

In reply to VolvoHeretic :

Flying wings are generally swept for stability reasons, not trans and supersonic reasons (though the B2 and B21 might get into transonic speeds, so I suspect it helps a bit).  The sharp angles are for radar reflectivity reasons (a round shape reflect from every angle).  The B2 and B21 will be VERY hard to see on a radar from the front and much easier (certainly still hard) to see from the angle of the wings (33 degrees). Radar absorption certainly plays into this also, so... who knows... secrets...

As an example, the N9m (test bed for the XB-35), which is clearly very low speed:

In reply to aircooled :

I ment that the B2's leading edge looks razor sharp. Absolutely no rounded leading edge that I can see, at least not at the canopy area.

The sharp leading edges are compromise between aero effects over a wide range of airspeed and the radar cross section (RCS). As noted above generous radiused edges generate a larger RCS. The aero effects of the leading edge trade offs can be managed and the aircraft is primarily designed for a very specific part of the flight envelope (altitude and speed) so the design is set work best there. Another possible effect is to work as a lifting body at low speeds (takeoff and landing) by using vortex shedding over the top surface to maintain lift but pay the price for the extra drag induced by it at the low speeds.

I was duscussing this with some coworkers the other day and reminded them that the f117 stealth fighter was activated as a program way back when under Carter's administration. It went to active use in the early 80s and was publicly acknowledged in the mid to late 80s.

These programs are not usually acknowledged until the have been in use for a while, even after primary flight testing. 

Keith Tanner said:

I saw a B2 flying over Lancaster, CA a few years back. It looked like a glitch in the sky.

Back when the B2 was first announced to the public I was doing some consulting work at NASA Langley /Langley AFB, and one day I was walking down the street when one of them flew overhead.  You'd think the people there would be used to seeing strange things in the sky, but Everyone stopped and gaped at it.

aircooled said:

I also hear it is capable of both piloted and autonomous missions.  Not sure why you would want autonomous missions.  Maybe for extreme endurance?   You would need autonomous in flight refueling of course.

I'm pretty sure that's (refueling of autonomous aircraft) has already been tested/proven.

The aero effects of the sharp leading edge and irregular trailing edge are "bad" in the traditional human piloted aircraft realm. But this aircraft is flown by a quick thinking computer with lots of sensors inputs. The human 'pilots' the aircraft by manipulating conventional looking controls that are input devices for the flight computer. The flight computer then flies the aircraft to approximate what the pilot is requesting. The computer will not let the sharp leading edge get into stall regime, nor allow large aileron input to give adverse yaw, etc.

So, that old saying, "With enough power, you can make a barn door fly." is the working theory here?

VolvoHeretic said:

That leading edge sure looks sharp for a slow moving plane which I thought broke all of the rules. I would love to hear Sleepyhead the Buffalo's response and analysis to the airflow over that thing. Here is a B2 for comparison. One is a model.

This falls under the lesson I learned from Dr. William H. Mason, which I bring up from time to time, when asked if the design approach we were taking was "correct":

"I don't know, is it?"

it's one of a kind similar to stafford or I's reactions to a question of "what's the best...?".  Answer being: "it depends".

as for "breaking all the rules"... keep in mind, this thing flew and didn't have multiple computers keeping it from departing controlled flight:

(Wainfan FMX-4 Facetmobile)

so, yes, rounded noses can be important... but, depending on the flight environment, other considerations might be more important.  Further, as aircooled alluded to we're definitely dealing with transonic flows... iirc, depending on who you ask, can start as low as Mach 0.6.  With transonic, and considering the Airforce isn't limited in runway length like commercial airlines (i.e. this probably doesn't need the Clmax for takeoff other designs have to account for), then having a sharp leading edge isn't much of an issue (most early supersonic foils had particularly sharp leading edges to aid in delaying shock formation)... especially with a significant amount of the "lift" for transonic foils coming out of the bottom trailing edge of a foil (see "aft loading")... and the shadow contours of that one shot indicate to me significant aft-loading potential.