Northrop Grumman B-21 Raider (LRS-B)

Interesting that the two engine B-21 contrail appear significantly lighter / narrower than the F-16 chase plane. Since the contrail is formed from freezing water vapor from the burning fuel, does this mean the B-21 is burning less fuel than the F-16 at this flight condition? This assumes they are at the same altitude and contrail conditions, which can change rapidly.

It could also mean that the shape of the nozzle is flattening the exhaust stream, making the contrail thinner top to bottom turns less visible. but you would think this would result in a wider, if fainter, contrail
 
@F119Doctor : I think this is more related to the the lift. The jet expansion is fairly local at subsonic speed but the DelatP in the trailing wake freeze the moisture into contrail. Hence why a higher loaded wing would contrail more white than another one.
 
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F119Doctor said:
Interesting that the two engine B-21 contrail appear significantly lighter / narrower than the F-16 chase plane. Since the contrail is formed from freezing water vapor from the burning fuel, does this mean the B-21 is burning less fuel than the F-16 at this flight condition? This assumes they are at the same altitude and contrail conditions, which can change rapidly.

It could also mean that the shape of the nozzle is flattening the exhaust stream, making the contrail thinner top to bottom turns less visible. but you would think this would result in a wider, if fainter, contrail
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My initial guess would be nozzle shape.
 
NMaude said:
An educated guess however can be made.
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Someone from the B-21 test program was wearing a black jacket with three patches: a B-21 Combined Test Force emblem, a Northrop Grumman-issued B-21 Raider patch, and a patch for the Pratt & Whitney PW1500 geared turbofan (GTF) engine. Make of it what you will.
 
It would be very interesting if the B-21 has production PW1500G high bypass geared turbofan. Getting a 74” diameter inlet buried in the wing would be quite an accomplishment.

The max thrust of the PW1500G is 25k lbs. 2 x 25k = 50K for the B-21 vs 4 x 19k = 76k for the B-2 with the F118. The thrust lapse at cruise conditions would be greater for the PW1500G, although the SFC would be significantly better.
 
F119Doctor said:
Getting a 74” diameter inlet buried in the wing would be quite an accomplishment.
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Feeding high bypass engine with S-duct and it's unsteady separated flows needs some fcuking magic. Flying high with them at B-2 flight envelope ceiling or even higher needs even more magic.
So... No.
GTF core? Quite possible (was discussed here thousand times in context of PW9000).
 
I'm sure modern CFD helped a lot in defining and optimizing the inlet design. During B-2 flight test, the USAF was pleasantly surprise when we had no compressor stalls at max AOA and side-slip during max/min throttle bangs. We also did a lot of ground-based propulsion integration testing as early as possible during the program.
 

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