Hi, I’ve noticed that there’s seemingly no difference between running an engine at 1 bar or 0 bar in a couple of engines, with awkward arbitrary discontinuities at different pressure levels:
This is an extreme example, with ~585bar of chamber pressure, but at 40:1 expansion ratio, and ~1bar flow exit pressure, I’d expect the Isp to drop by at least 20-25s at 1bar. I’ll append the model in question at the end of this post.
In general, engines seem to vastly overperform at sea level. The built-in template of the Vulcain does:
- Vacuum: 963.3kN, 428.5s
- Sea level: 942.7kN, 419.4s
Where I’d expect this type of engine to hit <340s at sea level.
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"title": "Chart 4",
"axes": {
"M": {
"label": "M",
"variableName": "M",
"components": [
{
"name": "Throat",
"category": 2,
"type": "BranchGas"
},
{
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"category": 2,
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}
]
}
},
"isSelected": true
}
},
"samplers": {
"Thrust - BranchGas3": {
"title": "Thrust - BranchGas3",
"branchName": "BranchGas3"
}
}
},
"simulation": {
"simulationState": "ended",
"currentTime": 0,
"maxTime": 1,
"signature": {}
},
"version": "0.3.0"
}