Hiya All,
I intend to make some experiments with 85% H2O2, and a kerosene derivate (most probably JP-4). I am however confused as to the best way to burn this mix, as it seems as there are different routes one can take.
Method 1) One source (isn't it the ERPS site?) mentions something along the line of "Catalytically decompose the H2O2 and then inject kerosene in the hot gas stream, which essentially doubles the Isp." This is simple, in the sense that it alleviates the need for an igniter. However, conceptually it doesn't match any methods I've seen described in Sutton or Huzel/Huang (perhaps except for the gas/liquid jet injectors).
We did several dozen tests with this method, and it has a LOT to reccomend it. We put quite a bit of pictures and detail in the armadillo updates on this last year, and overall, it worked much better and easier than we expected. Smooth engine starts, no worry about unburned propellant coming out the nozzle (always stop kerosene first, then finish in monoprop mode), and drastically easier injector design when you have very hot gas to mix with a relatively small amount of liquid. The only caution I would make is to do test firings vertically instead of horizontally. The only explosion we have ever had at Armadillo was when we had a horizontal firing engine test that had a stuck kerosene solenoid, allowing kerosene to drain into the catalyst pack, so the next time we fired peroxide into the pack, it all blew up.
Method 2) Another source works with traditional injection and impinging the propellants into the combustion chamber, which seems to work under the assumption that heat is already present in the chamber to get the reaction going (igniter). I have a strong preference for this, as it allows us to use stabilized H2O2.
We have had to deal with a lot more pools of propellant under the engines with our mixed-monoprop work these last six months, and it isn't a lot of fun. Pools of higher energy propellants are a whole lot worse. Engine explosions from hard starts are very common with storable liquid / liquid injection.
Where are you planning on getting 85% peroxide, stabilized or not?
John Carmack
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