The Electrical Propulsion System of the current generation communication satellite platforms requires unprecedented levels of performance from the GSE loading cart to be used for filling of its Xenon Storage Tanks. Of importance are especially the loading accuracy and the low-ppb level of impurities allowed in the loaded Xenon. The Xenon Loading Cart developed by Bradford consists of a Mass Balance Unit, a Pressurization and Loading Unit. In the past Bradford built a Xenon Loading Cart for the GOCE spacecraft; this Xenon Loading Cart is now fully re-designed for unprecedented levels of performance.

Having experience from the development of the GOCE Proportional Xenon Feed Assembly and XLC in the use of Xenon, Bradford fully understands the unorthodox behaviour of Xenon occurring during the loading into the spacecraft propellant tanks. For this purpose, a high- accuracy Xenon Massflow Controller has been installed into the Loading Unit, which allows a fully controlled and fully automated loading of the spacecraft propellant tank. The flow control is adjustable to a fixed value, allowing the operator in advance to analyze, predict and avoid any thermal issues with regard to compressing Xenon into a storage tank. As such, any loading aborts can be avoided in an already tight spacecraft launch schedule.

XLC Architecture

The Xenon Loading Cart consists of a Mass Balance Unit, a Pressurization and Loading Unit. The Mass Balance Unit allows an accurate determination of the depletion of propellant from the supply vessels, the Pressurization and Loading Unit allows pressurization of the supply gas up to proof-pressure levels, and high-accuracy flow control & loading, low-ppb level purification and verification of H2O and O2 low-ppb impurity levels.

During loading, the XLC H/W provides accurate real-time information on the loaded purity (H2O) and amount on Xenon into the spacecraft Xenon Storage Tank. Therefore, even in the case of a potential loading abort (e.g. caused by S/C system-level issues), the loading procedure can be simply paused and continued at any time of desire.

External equipment, for example an oxygen analyser, can be connected to the XLC. Sample bottles can be extracted for external verification and, for testing purposes, a vacuum loop connection can be made with the space craft.

Performance Characteristics