[Jonsson]

Dear reader,

Being a dumb graphics artist I am here to humbly ask for some information  

I need to work out what the exhaust of the space shuttle liquid hydrogen/oxygen engine looks like when the engine is fired in space. I know the molecular number density in space is much lower than at sea level. There is also going to be a big difference in speed which I assume is going to alter the distribution of exhaust particles. And is that some trail going to appear in space?

This is what the space shuttle looks at lift off:



Aesthetically, how would it look differently in space you think?

Thank you for your time.

Kind regards,
Marius

[rjb]

Jonsson,

I hate to disappoint, but in space it's nowhere near as exciting... at least from an aesthetic perspective! All that pretty smoky rubbish being spewed out is from the SRB's (Solid Rocket Boosters), which are only used during the first 2 minutes of flight after which the shuttle relies on the main engines which give a less than exciting cone shaped blue glow... Like a gas hob on overdrive! Once in orbit, these are no longer used and the OMS (Orbital Maneuvering System) takes over. This uses a nitrogen tetroxide/hydrazine propellent which is even less exciting visually, normally just a white v shaped puff and again normally only for a few seconds...

http://www.youtube.com/watch?v=Bb1bkodii0M - Short OMS burn about 8 seconds in

http://www.youtube.com/watch?v=2ewbD2Pv5ag&feature=related - Can be seen 2 seconds in...

Hope this helps

Kind Regards

R

[Jonsson]

Rjb,

Thanks for your reply. Is it true that liquid hydrogen/oxygen engines burn with a slight blue tint in space?

Just curious to know the theory, why does it go from yellow to blue when going from the atmosphere and out?

Thanks.M

[amorale]

Don't take this as a right answer but my best guess would be that the fuel use in the rockets is different than the one in the actual shuttle engines, and they burn with different colors, also another idea that occurs to me would be that the chemical reaction of the combustion reaction in the atmosphere would produce a different color than in space.

Very interesting topic by the way. Hopefully somebody with more knowledge gives us a better answer.

[Enthalpy]

I confirm the long brilliant white plume here is from the solid boosters, whose exhaust is much hotter and contains tons of alumina.

A hydrogen engine gives a very pale violet plume from hydrogen, in atmosphere as in vacuum, nearly impossible to see. Pictures at Wiki. Nothing blue, nothing brilliant.

One exception is the RS-68 engine with a non-expected hydrocarbon-like yellow plume. I suppose it stems from the ablative heat protection in the lower nozzle, maybe some phenolic resin.

In the upper atmosphere, you may see a condensation trail like behind an airliner. In vacuum, maybe as well... If a part of the water freezes to a cloud. I don't remember seeing any at the Shuttles. It would be very diluted, hence observable only from a good distance.