LDEF (Postflight), M0001 : Heavy Ions in Space, Tray H03 EL-1994-00316 The postflight photograph was taken prior to the experiment being removed from the LDEF structure. The experiment's damaged multi-layer ther mal insulation blankets were removed from the experiment to accommodate experiment tray cover installation prior to operations that removed the experiment from the LDEF. The postflight photograph of the Heavy Ions in Space Experiment shows the four (4) experiment modules with the multi-layer thermal blankets severely degraded. The paint on the the thermal blankets top layer, previously white, is now a glossy tan or soft brown color. This change in color, from white to tan, was seen on other LDEF experiment surfaces that were coated with the same paint. The tape used to attach the thermal blanket to the module frames, 3M Y966 with a silvered TEFLON_ film backing, failed during flight. The tape failed in tension across the width of the tape leaving portions of the tape on both the frame and the top layer of the thermal blanket. The tape failure is attributed to shrinkage of the thermal blanket which caused a significant buildup in tension across the taped joint. Detachment of the blankets along two (2) sides relieved the tension buildup and the blanket remained in place, although curled, during retrieval and post retrieval operations. The material exposed underneath the curled thermal blanket is the top sheet of the Lexan detector stack. The degraded multi-layer thermal blankets in each of the four modules show details of the blanket construction. The top layer of the thermal blanket is a 5 mil Kapton film with an aluminum coat ing vapor deposited on one side and with an exterior overcoat of Chemglaze II A-276 white paint on the other. The core or center section of the thermal blanket is constructed of approximately twenty two (22) layers of 1/4 mil perforated Mylar film with an aluminum coating vapor depos ited on each side. The bottom layer of the thermal blanket is also a 5 mil Kapton film with an alu minum coating vapor deposited on one side. The aluminum coated side of the Kapton film faces the adjacent Lexan detector stack sheet. A Dacron mesh (bridal veil) separator, clearly visible in the upper right module, is placed between each aluminized Mylar layer of the core material and also between the core material and the alu minized Kapton film used for the top and bottom covers. Insertion of the Dacron mesh between the aluminized layers minimizes heat leaks within the thermal blanket. A close observation of the exposed edges of the Multi-layer blankets shows the vapor deposited aluminum coating has delaminated from from the Mylar film and the Mylar film has eroded. The delaminated aluminum can be seen extending from the blanket material in the lower right module. Small pieces of aluminum have been observed adhered to surfaces of the LDEF, to the surfaces of some LDEF experiments and in the orbiter cargo bay during post-flight inspections. Also note the loss of portions of the Dacron mesh material. The loss of the Dacron material and some of the alu minum delamination is thought to have occurred prior to retrieval, however, a significant portion of the aluminum delamination from the Mylar is thought to have occurred post-landing due to the velocity and direction of air from the cargo bay purge system.
