ShotOne
ShotOne:if we're talking about high level contrails, they are caused by the jet exhaust, specifically the water content, being mixed by wingtip vortices.
ShotOne:Yes they were, Roland.
No they weren't. Nor were the contrails on a Nimrod
formed by mixing of the exhaust gases and the wing tip vortices.
Please note that from saudipc9's 747 photo the contrails are most definitely coming from the engines - they appear well before the wing tip vortex could have mixed with jet eflux. What happens further behind the 747 is the mixing of the contrail and vortex - but the contrail is NOT caused by mixing - that just changes the shape and look.
Are you postulating that contrails from aircraft with tail mounted engines behave fundamentally differently from others? I'd challenge you to tell those of, say, an MD80 and a 737 apart a minute after they'd passed
Only that the contrails from any type are formed from the jet exhaust and would be there whether there was a wing tip vortex or not. What happens further behind the aircraft when the two do mix is an entirely different question.
And yes, you can often tell the difference between 4-jet contrails and twin jet contrails.
Now back to the mystery aircraft. Given the graininess of the picture and lack of definition, I'm still sticking with B2. Try copying and pasting the photo into something that you can zoom in on (ie Word - other word processing software is available) and zoom in to 500% - to my eye you can see the "wings" and the trailing edge saw tooth. The trailing edge definition (as shown in Willard's earlier photo) is just lost in the pixelation of this photo.