Marc van Eesbeek

Influence of X-Ray Solar Flare Radiation on Degradation of Teflon in Space

Tee on ® samplesretrieved after exposurein orbit on the Long Duration Exposure Facility and on thesolar array of the Hubble Space Telescope were subjected to mechanical, infrared, and x-ray photoelectron spectroscopic testing. Testing wasalso performed on virgin samplesexposed to atomicoxygen, vacuum ultraviolet radiation, and soft x-ray radiation. Comparison of the measured mechanical and spectroscopic properties of the samples and analysis of theexposure environmentof the two missions showthat thelow-energy part ofthe x-ray radiation from the solar e ares plays a major role in the degradation of Tee on in space. Vacuum ultraviolet, atomic oxygen, and equivalent sun-hour exposure are not correlated to the observed degradation in bulk material properties.

Environmental Testing of Thermal Control Materials at Elevated Temperature and Intense Ultraviolet Radiation

This paper presents two test campaigns in the frame of the ongoing program for the European Space Agency’s mission toMercury. Improvements on the experimental setup are presented that enable ground-based simulation of such a harsh space environment. The thermal endurance of white ceramic paints is investigated at 350 C. The solar absorptance of all paints increased significantly. Two types of ceramic woven fabrics were irradiated by 17 solar constants of ultraviolet light at an elevated temperature. The available data from the solar absorptance as a function of an ultraviolet dose up to 52,000 equivalent sun hours was extrapolated to the mission’s end-of-life dose of 100,000 equivalent sun hours. The custom-baked Astroquartz 2 was the best performing material with an estimated end-of-life solar absorptance of 0.35.

Progress on the Physical Approach to Molecular Contamination Modeling

A review of the contamination physics and of the most widespread engineering approaches to contamination assessmentwas carried out. The twomain approaches are the physical and the empirical one. Themain questions still open to validate the physical approach to outgassing and deposit physics were then studied. Among others, special attention was paid to the important point of a realistic separation of chemical species, probably a prerequisite for a physicalmodeling. Several original results were obtained. Some lead to a quite clear conclusion, like the preeminence of the limitation by desorption over the limitation by diffusion for outgassing. This observed trend needs yet to be validated on other materials. Other major results are progress on the validation of the physical approach and on the ambitious species separation program.

Soft X-Ray Radiation as a Factor in the Degradation of Spacecraft Materials

The post-flight investigations performed on FEP Teflon® material after sixty-nine months exposure on the LDEF mission and forty-three months on HST/STSA have shown large variations in the mechanical and chemical properties between these two missions and between different positions on LDEF.

A mini-spectrometre for the on-orbit control of optical window ageing on the ISS

Optical windows transmission, and their evolution as a consequence of the exposure to the space environment are of primary interest for spacecraft designers and must be accurately predicted.

Design and Testing of a Mini-spectrometer System for On-Orbit Degradation Studies of Optical Materials

The degradation of optical materials exposed to the near earth orbit space environment is of primary interest for spacecraft designers and must be accurately predicted. Optical materials generally have highly polished and accurately formed surfaces so that even low levels of degradation may have a significant effect on the long-term performance of the component. This paper describes the design and testing of a miniature spectrometer system which will be used to actively monitor the on-orbit degradation of optical materials placed on the exterior of the International Space Station.

Materials Testing Activities within ESA in Support of Future Inner Solar System Missions

In this paper the ESA internal approach regarding the assessment of materials for inner solar system missions is presented. A main part of the work is devoted to the assessment of thermal control materials and space environmental testing at elevated temperature. As these materials are the most exposed it is important to understand how they will interact with the relevant space environment at elevated temperature. Driving parameters for materials degradation are discussed and on-going testing efforts are described. An important input parameter for thermal models is the knowledge of the end of life values for the thermo-optical properties as these determine the equilibrium temperatures. In certain cases end of life testing needs to be done when the uncertainty of extrapolation is too high.

Ranking of Wire Insulation for Spacecraft Use

Insulated wires are important for the reliable supply of electrical energy in aircraft and spacecraft applications. Damage to the wire insulation in the electrical network can lead to a high-current arc burning between the metal conductors of the wire, which may cause a breakdown of the whole electrical system. In the past, numerous fault arc tests on insulated wires for space application have been performed at Darmstadt University of Technology, High Voltage Laboratory (TUD/HVL) in cooperation with the European Space Agency (ESA/ESTEC). Based on these studies a test proposal was prepared and is discussed in relevant standardization organizations up to the present time. This proposal is referred to as the ‘advanced fault arc resistance test’ Proposal International Standard 1998 Space systems–arc tracking test, cables and wires: advanced fault arc resistance test ISO/TC20/SC14/WG 1, 14N118. The insulated wires are tested under different stress and environmental conditions. The experimental results as well as their physical background are discussed.