No abstract

No abstract

No abstract

The objective of this continuing study is to specify the anodic coatings and optical properties to be used for passive thermal control of the Space Station Freedom. The first task initiated was to define the beginning-of-life or as-fabricated optical properties of anodic coatings for the structural alloys most commonly used in the aerospace industries. and the expected variations in these properties caused by normal material and process variations. The second task initiated was to predict the degradation of optical properties during 30 years on the Space Station Freedom. The end-of-life properties will be influenced in low earth orbit primarily by contaminant deposition and ultraviolet radiation exposure and. to a lesser extent. by atomic oxygen. This study resulted in ( I ) defining the beginning-of-life optical propertiea for aluminum alloys suitable for structural or radiator applications. (2) defining the statistical variation in the beginning-of-life properties, and (3) estimates of the endof-life properties of the alloys based on ultraviolet radiation testing and flight test results. From these studies in conjunction with an assessment of other NASA requirements. it was concluded that anodic coatings can be used for thermal control of long life. low earth orbit spacecraft. Some use restrictions were defined for specific cases. Anodic coatings were selected as the baseline thermal control coating for large portions of the Space Station Freedom.

Additional experimental data were desired to support the selection of candidate thermal control coat-Results to date support the design practice of shielding solid film lubricants from the low Earth orbit environment. Post-flight optical property analysis of the anodized specimens indicated that there were limited contamination effects and some atomic oxygen and ultraviolet radiation effects. These effects appeared to be within the values predicted by simulated ground testing and analysis of these materials, and they were different for each coating and substrate.