DIETZ@USC-ECL@sri-unix (05/14/82)
From: Paul Dietz <DIETZ at USC-ECL> You have to be careful talking about the SSME chamber pressure because the engine has (I think) two chambers. The first is where the H2 and O2 get mixed together. They finish buringing in the second, which is connected to the nozzle. The SSME pressure is quite high; I seem to remember it being at least twice that of the Apollo engines. Also, what does the Ariane first stage burn? Kerosene? This may give a lower pressure. -------
karn (05/15/82)
The Ariane engines on both the first and second stages burn hypergolic fuels: UDMH (Unsymmetrical Dimethyl Hydrazine) and nitrogen tetroxide. The third stage is LH2/LOX. The amazing thing to me is how they can handle tons of that stuff without accidents. After the launch failure of L02 (the one carrying the Amsat Phase 3 satellite), ESA made some Viking-5 (first stage engine) chamber modifications that lowered slightly the combustion chamber pressure. I'm not sure of the exact figure, but 50 bar is approximately correct. This would seem to be lower than the SSME figure. I have some info on the Ariane from an Amsat poster which might be of interest: Total launch mass: 207 metric tons Overall height: 47.388 meters First stage - four Viking V engines mass: 145 tons fueled Thrust: 2745 kilonewtons Burn time: 145 sec Diameter: 3.8 meters Height: 18.387 meters Second stage - one Viking IV engine mass: 34 tons fueled Thrust: 743 KN Burn time: 132 sec Diameter: 2.6/3.8 m Height: 11.468 m Third stage - one HM7 engine mass: 8 tons fueled Thrust: 60 KN Burn time: 570 sec Diameter: 2.6 m Height: 8.88 m Payload Shroud mass: .81 ton diameter: 3.2 m Height: 8.653 m Sylda (dual payload carrier) mass: .3 ton Phil