Moving parts in satellites and in components of exploratory or planetary space missions are critical with regard to their functionality and reliability. These parts range from folding antennae or solar panels, to movable instruments, to propulsion systems, robotic arms and sampling probes on planetary missions. Failure of a moving contact generally leads to failure of the system, and is therefore to be equated with a premature end of the mission. Lubricants are therefore essential construction elements of systems for space. Liquid lubricants in space must fulfil additional requirements, especially related to their thermal outgassing and degradation behaviour under critical conditions. The liquid and solid lubrication solutions currently in use exhibit inherent disadvantages in either performance or applicability. None of the currently used lubricants present an optimal technical solution.
A novel lubrication concept must combine the advantages of liquid and solid lubrication, and balance out the disadvantages. Existing hybrid approaches, which attempt to achieve this, employ modified liquid lubrication or recent developments such as self-assembled monolayers.
The innovative concept of minIONs makes use of the inherent properties of ionic liquids, specifically their basic suitability for thermal vacuum environment, and the lubricity present in many ionic liquids. The latter is based primarily on the easy relative movement of cations and anions, with simultaneous existence of a load bearing microstructure. By polymerisation of specially functionalised cations, a resilient polymeric ionic coating layer is achieved. The envisioned layer should be homogenous and covalently bonded to the surface. The nevertheless mobile anions form a sliding layer, which removes the need to charge the layer with additional lubricious particles such as graphite or PTFE.
This concept of a hybrid coating permits production of thinner but nevertheless strong lubricating layers, and thereby allows greater freedom of engineering design. Subsequent to the synthesis of functionalised ionic monomers on a laboratory scale, activation of the target surface and polymerisation on the activated surface, the tribological properties of polymeric ionic lubricating coatings shall be fundamentally examined. The structure-property relationships determined from minIONs are to be the basis for the development of novel, reliable, and easily deployable lubrication concepts for application in space relevant conditions.
