Modular propulsion feed system with integrated refueling and precise flow control, metering and propellant gauging

Flight Works aims to address the DoD’s lack of rapid response and sustained space operations capability by proposing by developing a compact “plug-and-play” pump-fed propulsion feed system module with integrated electric pump, flow control device, valves, accumulator, sensors, refueling port and precise metering capability, and integrated command and control, all having a simple interface with the bus.  This propulsion feed module will enable the ability to precisely meter propellant transfer, and enable a variety of possible propulsion system configurations with its common interface design and integral refueling components. The result is a family of modules which drastically reduces design and implementation cycle timeframes and costs. This module builds upon Flight Works heritage of spaceflight flown or flight-qualified propulsion and avionics components and systems, such as AFRL’s Propulsion Unit with Modular Applications (PUMA). At the core of these and the modular propellant feed system is the electric micropump. With a micropump, the pressurization system is eliminated, and the propellant storage and feed system can be designed for low pressures, thereby removing the need for large high-pressure ullage or a regulated system. Also, it allows the thruster to operate at or near its optimum pressure for maximum performance (Isp). The micropump can enable lighter, conformal tanks that can be 3D-printed instead of using spherical or cylindrical pressurized tanks for greater compactness. For refueling applications, the bidirectional pumps can be used to transfer propellant, either as part of the refueler, or the client.A refuelable propulsion system allows for agile, dynamic vehicle relocation but, the major operational concern of knowing if sufficient propellant is left (how much gas you have left in the tank) will undoubtedly introduce mission risks.  Robust hypergolic propellant fuel level sensors for spacecraft do not yet exist, and the uncertainty of how much propellant resides in a spacecraft tank grows with each propellant transfer and propulsive maneuver. Additionally, the operator must ensure sufficient propellant is left for end-of-life deorbit in LEO (especially given the new FCC regulations associated with deorbiting) or moving to a graveyard orbit when in GEO. This gauging has always been a challenge, leading to conservative approaches being taken. It is usually performed by a combination of bookkeeping propellant used over time, and adjusting based on tank pressure measurements when possible (such as for blowdown systems). Adding refueling in the mix – and potentially repressurization – only makes this a more challenging task.  Flight Works will develop precision metering devices for gauging propellant use/transfer and integrate them into the propulsion module. The targeted high level of accuracy will enhance mission operational efficiency and survivability due to higher confidence of fuel reserves situational awareness.