Fused silica offers excellent optical, thermal and fatigue properties making it an ideal glass for space applications. Using the critical thermoelastic properties data, this paper provides an estimate of thermal and mechanical stresses in Code 7940 fused silica windows during launch and re-entry of the space shuttle. The window design is optimized by keeping the combined stress below 20 MPa thereby ensuring their reliability, crew safety, and mission success over the required lifetime of 100 missions. Such an assurance is gained by 100 % proof testing of all of the windows at a stress of 60 MPa in a dry and inert environment followed by reinspection alter each mission. Both the Power law fatigue model and slow crack growth analysis show that the safety factor of > or = 3 is more than adequate to ensure the safe operation of fused silica windows over the intended 100 missions of space shuttle. To date, none of the windows have experienced any failures after more than 100 cumulative missions.
Fatigue and mechanical reliability of optical glasses for space windows
1998
9 Seiten, 6 Bilder, 5 Tabellen, 22 Quellen
Conference paper
English
Quarzglas , Fenster (Gebäudebauteil) , Raumfähre , Raumfahrzeug , Schätzung , Start , Wiedereintritt , Weltraum , Materialbeanspruchung , thermomechanische Eigenschaft , Arbeitsschutz , Lebensdauer , Ausfall , Sicherheitsfaktor , Tragfähigkeit , Materialbruch , Young-Modul , Biegefestigkeit , Ermüdung , Bruchzähigkeit , Thermoelastizität
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