Saturn V engine output colour

[Swoop1]

Watching footage of the initial seconds of the launch of the Apollo missions, particularly the footage from the cameras on the launch pad, I regularly see that the first meter or so of the output of the combustion chambers is dark and streaked before becoming blindingly bright. You can see the demarcation line almost as a living, moving wavy line.

What is it that causes this difference in percieveable colour/ appearance?

[discardedastro]

On the F-1 engines, it's the cold gas from the turbopump, which gets routed through pipes going around the engine bell and then dumped at the "skirt" of the nozzle. This is used to cool the engine bells/nozzles and stop them melting.

But the cold gas undergoes only partial combustion in the exhaust, and also cools the exhaust gases in the outer rim of the nozzle, so the darkening of the flame in those regions.

[tomato]

If the incredible Saturn V is your thing, I recommend the Haynes Manual on this subject, full of facts, figures and great photos on this triumph of 20th century engineering.

[discardedastro]

10 minutes ago, tomato said:

If the incredible Saturn V is your thing, I recommend the Haynes Manual on this subject, full of facts, figures and great photos on this triumph of 20th century engineering.

And if you want to go deeper (much deeper - it's not for the faint-hearted) then Stages to Saturn is an excellent historical look at the engineering and development of the rockets. It is completely mad what they did back then!

[Swoop1]

Thanks @discardedastro, it makes sense now. Contrary to popular belief, it IS rocket science! I shall have to get a copy of Stages to Saturn.

@tomato, I will have to get a copy of the Haynes book as well.