4 ms·
Serious question: why is it bad to run your rocket engine-rich? If you know you're not going to use the engine and it's nearing its end of life why not get more
by soheil 5y ago
Serious question: why is it bad to run your rocket engine-rich? If you know you're not going to use the engine and it's nearing its end of life why not get more power out of your fuel/oxidizer by hitting the stoichiometric point? Also, if engine is melting maybe allow it to continue to melt, but at a lower rate and rebuild it later.
- pfdietz 5y agoThe optimal (in the sense of maximum specific impulse) operating point of a liquid propellant rocket engine is typically fuel rich. This is because with stoichiometric fuel/oxidizer ratio, the temperature is so high that there's significant dissociation, which robs the gas of some of the heat of combustion. Going a bit fuel rich wins back some of this, enough that the reduction in average molecular weight of the gas from inclusion of more hydrogen atoms is a net win. An exception to this is if your oxidizer is hydrogen peroxide. Peroxide/hydrocarbon engines typically optimize to stoichiometric, because the flame temperature is lower. If you look at photos of that British launch vehicle, the Black Arrow, that used peroxide, the rocket exhaust jet is radiating very little visible light, because most of the carbon has been oxidized. https://ichef.bbci.co.uk/news/976/mcs/media/images/55155000/jpg/_55155523_s2000072-launch_of_a_british_black_arrow_rocket.jpg https://ichef.bbci.co.uk/news/976/mcs/media/images/55155000/...