This work originated as part of GRASP (Green Advanced Space Propulsion) project, founded by the European Union to research and develope environmentally friendly and sustainable Green Propellants for spacecraft. A preliminary design study of a miniaturised liquid bi-propellant thruster, to be operated with the fuels ethanol or kerosene and hydrogen peroxide as oxidizer was created. The thruster is being cooled by radiative heat transfer into space. An exemplaric model was derived from this study for the coming thermo-mechanical inquiry of the structure by utilizing the Finite elements analysis (FEA). The physics to describe the fluid flow, as well as the heat transfer from the fluid into the wall of the thrust chamber are progammed in the APDL language and implemented during the FEA. A concurrent enquiry to find suitable materials finally resulted in a combination of either a platinum-rhodium alloy or iridium as a material for the thrust chamber and a nickel base alloy used for parts with moderate thermal loads. The physical and mechanical material properties were implemented as temperature dependent quantities. The materials were mechanically idealised for the analysis to be of perfect plasticity post yield type. The thermo-mechanical stress analyses with regard to the stationary operating conditions in addition to transient heating were conducted with a three dimensional thruster model. The results showed that an inquiry of the structural effects, in response to thermal cyclic loading, by using a 2-D axially symmetric thruster model was justified.
It was found that both materials undergo strong ratcheting in the proximity of the bi-material joint in this case.