Dear Dr. Strangewater

(Badwater Bill) wrote in message . ..

Thanks John for putting that up. You'll notice the effect I was
discussing about the gasses expanding once the rocket is virtually
outside of the atmosphere. What I find interesting is this happens
relatively quickly, like there is some kind of demarcation line of the
upper atmosphere where you are in it, then in a quantum jump you are
outside of it and the gasses begin expanding without bound. I've
watched these launches for years and they all are about the same.
Before I saw one of these 30 years ago I would have figured that the
demarcation of the upper atmosphere would have been more an analog
event than a digital jump as it seems to be.


I suspect it appears to be a more dramatic change than it really is.
If I remember by college rocketry courses, the angle formed by the
exhaust is a function of Mach. At high altitudes, Mach drops off to
effectively zero, so the plume expands dramatically. This probably
appears more sudden than it really is due to the foreshortening effect
- like looking through a telephoto lens. The second stage may also
use a different type of fuel, with different plume characteristics.


In the second and third shots there you'll notice an effect of either
four nozzels or some kind of thrust director in the main nozzel
pushing the gasses symetrically out in 4 quadrants. I wonder what
this is? Anybody know what's going on?

Not knowing the particular vehicle, we can only speculate, but it's
fairly common to use verniers - nozzles mounted at an angle - for
steering and control. Fins don't do much at that altitude.

Corrie