A report on the dangers of SRM.

a reply to: mrthumpy

They were talking about conditions where it wasn't quite right for a persistent trail, but it was close. The high bypass turbofan still left a persistent trail, where the low bypass didn't.

originally posted by: Zaphod58
a reply to: mrthumpy

They were talking about conditions where it wasn't quite right for a persistent trail, but it was close. The high bypass turbofan still left a persistent trail, where the low bypass didn't.

This one?

a reply to: mrthumpy

That might be the one. It's been awhile. They don't always end up persistent, but the instance of persistent contrail from newer engines is definitely higher, because of the engine efficiency.

originally posted by: Zaphod58
a reply to: waynos

One of the studies I read a few years ago talked about the difference between the engines. The newer engines create contrails at a lower altitude than the older engines, and at higher altitudes, where older engines would leave contrails, the newer engines leave persistent contrails. I will have to look up the study again to find it though.

Cheers, that would be good, if correct, I'd like to get my head around the mechanics of that.

Edit. Got it, gonna read it

That's the first chance I've had to read that, only seen excepts from it before. Now that I have, I concur with mrthumpy. I understand the report to be about trails being created by modern bypass engines where an older, less efficient, engine wouldn't, or that where both types create a trail, the one left by the modern engine is more substantial, due to the high water content and cooler exhaust that I mentioned in an earlier post. I don't see anything about persistence though?

does anyone ever think about putting white shingles on our roofs.......there's step one

originally posted by: waynos
I don't see anything about persistence though?

I am pretty sure persistence is universal, depending on conditions. If a contrail can be made, it's there. How long it lasts, depends on temperature, humidity, wind shear. But I could be wrong, that's just how I have understood it.

originally posted by: GBP/JPY
does anyone ever think about putting white shingles on our roofs.......there's step one

Yes they do

originally posted by: network dude

originally posted by: waynos
I don't see anything about persistence though?

I am pretty sure persistence is universal, depending on conditions. If a contrail can be made, it's there. How long it lasts, depends on temperature, humidity, wind shear. But I could be wrong, that's just how I have understood it.

A contrail will form in 0% RHw if the temperature is low enough. Persistence will then depend on the RHi and the size of the ISSR in which it forms

a reply to: network dude

Yes, that is how I understand it too.

a reply to: waynos

The report that I saw, and aren't having much luck finding, was dealing with conditions being almost right for persistence, and the newer engines pushing them over into persistence.

a reply to: Zaphod58
Good luck finding it, I'll keep trying too. I can kind of see what your getting at, but I've never seen it spelled out.