Question Dniepr - Red smoke at lift-off, after main stage ignition. What is it?

[cyril_13]

Hi everybody,

Just found some photos/videos of a Dniepr launch and I quite amazed !

+ this video :
[ame="http://www.youtube.com/watch?v=fB-vtc-d0Cg"]YouTube- Dnepr rocket launch[/ame]

I was wondering what was that red smoke that can be seen on the picture above as well as in the video around 0:43 ??

It seems they are releasing some gaz or triggering some system.. Have any idea on what this is ??

Cheers!
Cyril

 

[SiberianTiger]

Excess vapours of oxidizer vented away moments after the engine start-up (while still in "hop" out of the silo).

 

[orb]

Nitrogen dioxide.

 

[Hlynkacg]

^ What they said.

 

[MaverickSawyer]

To ensure a safe start, and not a "hard" start, the oxidizer, in this case N2O4, is injected first, followed by the fuel. Most large hypergolic engines use this technique, although there is a nice string of photos from Aerojet Sacramento of a Titan first stage start on the test stand. I'll look for it.