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The pressure histories tell the story of what happened

The pressure histories tell the story of what happened
The pressure histories tell the story of what happened The regulated upstream pressure P2 (not shown) remains constant at 1.4 MPa throughout, as it should. The oxidant pressure P4 also behaves as it should, roughly constant at 1.4 MPa, although with a slight drop while oxidant is flowing into the engine until 152 seconds. However, the fuel pressure drops precipitously during the burn due to inadequate helium flow. When the burn is stopped at 152 seconds, the pressure slowly increases, implying that some helium is getting through, just not enough to keep pace with the expanding ullage volume above the fuel when the engine is firing.