The concept behind the HEPR is a bang-bang regulator that consists of three solenoid valves in series and a cavity between the last two valves. At each given time, at least one control valve is in a closed position. High accuracy low pressure transducers are used to feedback the propellant tanks pressure to an electronic block. This pressure information is then used to toggle the valves based on the desired pressure set-point. The HEPR is able to regulate with an accuracy of ±0.1 bar a high pressure Helium flow of 0.5 g/s down to an outlet set-point to be chosen between 10 and 24 bar.
The HEPR architecture baseline is presented below. It has four parallel branches, of which two are redundant. Two branches are therefore being activated at the same time to deliver the correct Helium flow rate. The redundant branches (SV4-SV5-SV6 and SV10-SV11-SV12) would be activated in case of failure in one of the nominal one. The cavities are however shared between the nominal and the redundant branches.
The electronics part consists of four identical blocks, each block commanding the three valves on one branch.
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Image credit: Romain Delanoë, OHB Sweden AB
SV = Solenoid Valve
FDV = Fill and Drain Valve
CV = Cavity
HPT/LPT = High / Low Pressure Transducer
TP = Test Port
Several other types of architectures are possible depending on the valve used in the bang-bang regulation and on the expected functionality of the regulator.