Hi MoJo (and sky-watcher friends!),

Thank you for alerting us to their launch. It has great potential to be a fabulous show in the sky. Pre-dawn and post-sunset launches sometimes make amazing, multi-colored artwork in the sky. As the rocket ascends to altitudes where the sun is still shining, well above the ozone layer, the sun's unfiltered ultraviolet light starts ionizing the rocket's exhaust products and they glow, different colors for different molecules. And the directions and speeds of the winds at high altitudes vary a lot with altitude, so the exhaust trail, initially moderately straight, can get twisted and contorted over a few minutes' time into complex shapes that really make you think of modern artwork.

The Falcon 9 1st stage burns RP-1 (rocket-grade kerosene) and Lox (liquid oxygen) for about 2 minutes and 42 seconds, so we should get about 30 seconds of 1st stage burn while high enough to be sunlit. The RP-1 combustion generates mostly CO2 and water vapor. But there are a host of other molecules you get from not-quite-perfect combustion, much like a car engine's exhaust, and they make a lot more pretty colors than liquid hydrogen / Lox engines. The 1st stage has 9 "Merlin" RP-1 / Lox engines while the 2nd stage has only 1, so the 1st stage should make a lot more psychedelic chemicals in the sky than the 2nd.

But the 2nd stage burn gets into Earth's ionosphere, where not just winds but Earth's magnetic field and electric fields also can move parts of the exhaust trail around. The trail can even split, like a comet's gas and ion tails, when winds push the un-ionized molecules in one direction and the electric and magnetic fields push the ionized ones in another. This isn't seen often, but watch for it around 3-5 minutes after launch, well to the south of the launch site. It might be fairly faint, so binoculars might help.

For those with good cameras, have them ready!

Tom Spilker