High-Pressure Flow Control Unit (HP-FCU) - Product Datasheet

Product Overview

AST’s High-Pressure Flow Controller (HP-FCU) can be used to provide a constant massflow to one or two devices in the low-pressure section. The HP-FCU combines the functions of a two-stage pressure regulator and flow controller in one unit: high pressure at the unit inlet is measured and reduced by controlled expansion in two steps to intermediate pressures, with massflow control achieved through precision massflow limiters. The unit can control one or two output massflows, with the two flow lines served by a fixed massflow splitting; typically a fixed operation point (e.g. one fixed massflow setting) is selected, but variation of massflows around the design point is possible through different operation-parameter settings (e.g. in-orbit).

The stainless-steel HP-FCU is an all-welded design providing robustness against rupture and propellant loss; all high-pressure joints are made by electron-beam welding, and each unit is proof-pressure and leakage tested before shipment, with inlet and outlet filters protecting the unit during handling and integration. Customers can select from a large range of configuration options to best fit specific operational and interface needs, and AST proposes a generic set of acceptance tests, with specific verification addable to customer needs.

Through its integrated functions, the HP-FCU can simplify the fluidic architecture of an EP subsystem, with a typical use-case for single- or dual-thruster configurations with one operation mode, benefiting from the very compact HP-FCU design, which can also be equipped with a Fill-and-Drain Valve for direct propellant tank filling. The HP-FCU design is fully qualified for use with Xenon and has extensive flight heritage; the configuration operating at higher pressures (e.g. for Krypton) is currently under qualification.

HP-FCU Characteristics

Operating media: Xe (heritage), Kr (under qualification). Inlet pressure MEOP 300 bar (Xe operation up to 150 bar qualified); inlet pressure EOL 2 bar, flow dependent. Proof pressure 1.5× MEOP (design value > 450 bar). Low-pressure line MEOP 1 or 4 bar (depending on LP sensor selection), with low-pressure line proof pressure of 7 bar (limited by LP sensor). Burst pressure > 2.5× MEOP (design value > 750 bar). Nominal anode flow 0.6 mg to 10 mg/s, selectable by design and gas-dependent; nominal cathode flow e.g. 10% of anode flow, selectable by design. Throttle range -25% to +50%, settable during operation. Propellant throughput capability > 50 kg, depending on flow level. Regulation precision better than 1%, depending on electronics and control loop. Output flow ripple < ±2.5%, depending on electronics bandwidth and line volume. Flow response time up to 5 s (down) and up to 20 s (down for full range), to achieve 95% of a full-scale step at line outlet (e.g. during start-up).

Internal leakage < 1×10⁻⁵ sccs GHe and external leakage < 1×10⁻⁸ sccs GHe, both verified during acceptance tests. Thermal range -20°C to +80°C non-operational (including qualification margin) and +25°C to +65°C operational (full performance), with -10°C to +65°C for cold start (limited performance, heater recommended). Fluid filtration rate 11µm (5µm mesh at inlet and outlet). Mass under 900 g without harness, varying with configuration. Average power consumption under 10 W, depending on valve actuation frequency. Valve operating voltage 24V to 32V (minimum pull-in voltage required for motorization margin, 50% hold-voltage), with pressure sensor excitation voltage of 10V in sensor voltage excitation mode. Vibration qualification levels 26.9 gRMS on all three axes, and shock qualification loads of 2000 g at frequencies higher than 1000 Hz. Radiation tolerance is 30 Mrad TID.

Customization Options

A configuration map allows customers to select from a range of options for each individual HP-FCU configuration, covering variants such as outlet port count, fill-and-drain valve integration, and interface types. The HP-FCU characteristics and configuration map are subject to change; customers should contact AST for details and requests regarding further options.