Description
The objective of the activity is to develop and correlate an evaporation software model for long life (15 years and above) mechanisms (e.g. solar array drive mechanism, reaction wheels, electric propulsion and antenna pointing mechanisms) as needed for geostationary spacecraft. The developed evaporation software model will be validated through testing of mechanism test-vehicles. Targeted Improvements:- increase the accuracy of the current analysis by at least 30%- improved mechanism lifetime by at least 30%- reduced excessive lubricant use and evaporation by at least 20%. Description: Lubrication losses occur in space mechanisms over time due to evaporation under environmental thermal vacuum conditions. Lubrication efficiency of long-life mechanisms for telecommunication satellites is of paramount importance to maintain functional performances at the expected level until end-of-life. Current modelling tools in use by industry (e.g. CABARET) use basic parameters for modelling lubricant loss for ball bearing assemblies. However, these models, used to estimate the total amount of lubricant needed for the duration of the mission, are limited and inaccurate. A new simulation tool based on testing of representative breadboard mechanisms, under representative environmental conditions, has the potential to model the lubricant evaporation phenomena and to estimate the lubrication needs of even complex mechanisms (including labyrinths) with increased accuracy. Test facilities and a testing methodology for vapour pressure assessment will be used to support the correlation of measurements with simulation results.This activity will develop an evaporation model for long life mechanisms capable of estimating the total mass loss of lubricants depending on the duration of the mission and the specific assembly. The model will merge dominant physical processes of desorption/diffusion and evaporation, for representative geometries and operational environmental conditions of the mechanism. An accurate distinction of these physical processes during testing is important to obtain mathematical species and time-constants for desorption (Arrhenius Law first-order kinetics) and a latent heat factor at a reference temperaturefor evaporation (Langmuir Law). This approach will allow lubricant loss prediction to be improved to high accuracy and optimisationof the design of the assembly, even for complex geometries and under different operating conditions. The model will be implemented in software. The software will be validated and correlated against the results of monitored thermal vacuum tests on representative mechanism test-vehicles. The test campaign will include at least one accelerated life test.Footnote: On Delegation Request activities will only be initiated on the explicit request of at least one National Delegation. Procurement Policy: C(1) = Activity restricted to non-prime contractors (incl. SMEs). For additional information please go to: http://www.esa.int/About_Us/Business_with_ESA/Small_and_Medium_Sized_En…