posted on Jan, 13 2016 @ 09:37 PM
originally posted by: greencmp
a reply to: JimOberg
Wow, that's an impressive plume!
The 'necklace' effect is directly traceable to second stage shutdown and the 'hot start' of stage 3, with the stage-2 plume falling behind at 3,000
meters/sec even as both stages are speeding at about 43% of orbital velocity, or about 3,500 meters/sec. That means the ejected combustion products
have only a 500 meter/sec ground speed, but still forward.
Stage 3 takes a few seconds to emerge from its base atop stage 2, its plume splashes randomly off the stage 2. This interruption in the tailwards
ejection creates that 'gap' in the pictures from the ground AND from the space station.
At an altitude of 170 km, with g = 10 meters/sec/sec, to fall back below the Karman line [100km] into 'sensible' atmosphere would take about 85
seconds, even as it expands and thins.
During that period of falling 70 km, the 2nd stage plume's front end forward velocity carries it 85 x 500 or ~40,000 meters [40 kilometers] down
This 'plume' is more like a comet's tail than ANYTHING we're familiar with down on Earth.
No wonder for thousands of people all over Earth who see such apparitions, the sight blows their minds.