B-21 Raider unveiled

[sumpnz]

Compared to composites, sure. 

Interesting thing about fatigue.  Most steels have a stress level at which the S/N curve goes flat, which means at or below that stress level the fatigue life is actually infinite.  Aluminum has no such effect.  The S/N curve keeps going down until you hit 0 stress.  So no matter how low the amplitude of the stress cycles you will eventually cause a crack in aluminum.

[kgbsquirrel]

Compared to composites, sure. 

Interesting thing about fatigue.  Most steels have a stress level at which the S/N curve goes flat, which means at or below that stress level the fatigue life is actually infinite.  Aluminum has no such effect.  The S/N curve keeps going down until you hit 0 stress.  So no matter how low the amplitude of the stress cycles you will eventually cause a crack in aluminum.

Yeah, but you don't build airplanes out of steel because of the absurd loss in fuel efficiency.  So you use aluminum with the understanding that the parts will fatigue or age out eventially.  This limited life is also true for composites but unlike aluminim you have to replace entire structures whole where as the aluminum can be cut, rivetted, patched, etc.  You can replace small segments as they wear out instead of trashing the entire wing/body/strut every time one spot is critically compromised. This is where the economical replacement factor happens.

So, as I said, sticking to the non-exotic aluminum alloys is very sensible.

[Perd Hapley]

Eh, these days I’m just glad it was the real national anthem, not the “black national anthem”.  Most renditions anymore are not the original version anyway.  Besides, I wasn’t listening to the music so much as watching the fly overs.

The original? Like a poem with no music?

[Lennyjoe]

As a guy who worked for Northrop for 8 years and with Northrop for 5 (in a government program office) I’m sure it’s well over budget and behind schedule…..

That being said, looks like a B2 part duex

[HankB]

I've read that in WWII the Japs used a high strength aluminum alloy in their Zero fighters that fatigued to the point that you could gouge out big chunks of the wing spars with a screwdriver - and that's the main reason that hardly any of the few surviving Zeros are flyable.

[kgbsquirrel]

I've read that in WWII the Japs used a high strength aluminum alloy in their Zero fighters that fatigued to the point that you could gouge out big chunks of the wing spars with a screwdriver - and that's the main reason that hardly any of the few surviving Zeros are flyable.

Thin not fatigue. The skin was made ultra thin to save weight and the pilot accidentally stepping on it climbing in or out would punch through.  There were pop out foot rungs to use.

[kgbsquirrel]

As a guy who worked for Northrop for 8 years and with Northrop for 5 (in a government program office) I’m sure it’s well over budget and behind schedule…..

That being said, looks like a B2 part duex

A lot smaller right off the bat.  Count the wheels.  And the air intakes seem to be recessed down into the upper surface more than on the B2.  Deeper swoop to the belly lines (deeper belly) compared to the B2.  And perhaps better cockpit visibility for the pilots. 

That's all that really sticks out to me from the low rez video of the unveiling.  Also note how they bloviated without ever actually giving any actual performance values or information.  And man did they all suck at speaking.  It was like listening to Ben Stein reading a kindergarden dictionary, but somehow worse.

[WLJ]

Thin not fatigue. The skin was made ultra thin to save weight and the pilot accidentally stepping on it climbing in or out would punch through.  There were pop out foot rungs to use.

Areas marked "No Step" or with similar markings are very common on aircraft of all makes even modern airliners.

[cordex]

Supposedly, (and that's a big supposedly) the B21 will replace the B-52 (~75 active aircraft) the B-1B (~60 active aircraft) and the B2 (20 left in service) which would imply they need about 150 of them or so.  We'll see.

What I've heard is the B-21 is supposed to replace the B-2 and B-1B but not the B-52.  The idea being that the B-21 replaces the stand-in strike capability currently split between the B-2 and B-1B, and the B-52 continues to maintain and expand its standoff strike capabilities.