We have not yet had opportunity to examine data, parts or footage.

A tentative speculation on root cause would be simple LOX overload. In other words a problem with measuring the correct amount of LOX in the tank, which we have encountered previously, and worked on solving via several methods. We will look into this.

Too much LOX will result in a too small gas pocket in the tank – which equals too little gas propellant energy and a premature loss of tank pressure in the LOX tank, again resulting in an increasing O/F-ratio mismatch. The engine subsequently extinguished.
The GNC didn’t detect acceleration below minimum, as this detection was removed from the algorithm prior to the mission, based on the fact that the acceleration, through the use of pressure blow-down at relatively low altitude, would be very low before the occurrence of MECO.
The GNC instead used the chamber pressure. This was low at an unusually early time. The GNC treated this as a sensor failure, and instead an estimated pressure, based on a table generated from earlier tests, was used.
Thus the GNC didn’t signal the deployment of the parachute, as it was under the (false) impression that the engine was still operating as expected.

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Published by Rasmus Agdestein on

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