Method for Estimating the Efficiency of Small Orbital Spacecraft Systems for Optoelectronic Surveillance

The paper presents the results of analysing existing approaches to estimating how efficient small orbital spacecraft systems are for the purpose of optoelectronic surveillance, including determining their shortcomings. We simulated employing an orbital system required to ensure surveying the earth surface at various latitudes, accounting for sunrise and sunset time on the winter and summer solstice days, and discovered that the following parameters show low sensitivity: average daily object sighting number at a preset latitude and maximum time delay between object sightings at a preset latitude. We propose a new efficiency factor reflecting a confidence interval regarding the object sighting time delay. We developed a procedure utilising the factor proposed, expanding the scientific methodology in terms of estimating how efficient small orbital spacecraft systems are for optoelectronic surveillance. We obtained object sighting time delays at a preset latitude as functions of the probability of these delays occurring. We recommend using this procedure to estimate the efficiency of jointly employing several small orbital spacecraft systems and incomplete composition systems, as well as to state and solve the problem of synthesising the ballistic structure of an orbital system intended to improve the efficiency of earth surveillance.

VINCI®, the european reference for ariane 6 upper stage cryogenic propulsive system

The intent of this publication is to provide an overview of the development of the VINCI® engine over the period 2014–2015. The VINCI® engine is an upper stage, cryogenic expander cycle engine. It combines the required features of this cycle, i. e., high performance chamber cooling and high performance hydrogen turbopump, with proven design concepts based on the accumulated experience from previous European cryogenic engines such as the HM7 and the VULCAIN®. In addition, its high performance and reliability, its restart and throttle capability offer potential applications on various future launcher upper stages as well as orbital spacecraft. At the end of 2014, the VINCI® successfully passed the Critical Design Review that was held after the major subsystem (combustion chamber, fuel and oxygen turbopump) had passed their own Critical Design Review all along the second half of 2014. In December, a Ministerial Conference at government level gave priority to the Ariane 6 program as Europe future launcher. In the framework of this decision, VINCI® was confirmed as the engine to equip Ariane 6 cryogenic upper stage engine. This publication shows how the VINCI development is progressing toward qualification, and also how the requirements of the new Ariane 6 configuration taken into account, i. e., offering new opportunities to the launch system and managing the new constraints. Moreover, the authors capitalize on the development already achieved for the evolution of Ariane 5. In parallel to completing the engine development and qualification, the configuration and the equipment of the propulsive system for Ariane 6 such as the components of the pressurization and helium command systems, board to ground coupling equipment, are being defined.