Henry Spencer wrote: HS> Jenkins3 says that the outer layer (except in a few very-high-heat areas HS> like cable trays) was originally CPR-488 (the CPR-421 derivative), since HS> replaced by another polyurethane and then another. In high-heat areas -- HS> the aft dome, the nose, and some areas which see very high interference HS> heating -- there is an underlayer of SLA-561, which the 1983 paper notes HS> is cork-based.
HS> So both versions are actually right: there *is* an inner layer of cork- HS> based insulation, but only in selected areas. The main insulation over HS> the whole tank is just the urethane foam. Found the following specs to SLA-561 on the LokMart page: http://www.lockheedmartin.com/michoud/products/tpp/tpp_sls.htm SLA-561 is a low density, low conductivity ablator/insulator. It is a highly filled elastomeric silicone composition containing cork as one filler ingredient. During ablation, SLA-561 forms a sturdy, well adhering and substantially crack free char. Density is about 16.0 lb/ft3 / 269kg/m3 The material is available in molded panels with or without honeycombed support. The panels can be bonded with silicone adhesive using vacuum bag processes. SLA-561 can be machined to contour by sawing, sanding or grinding techniques. It is also available as a three component sprayable coating. The components have a six month shelf life. Spray applications of SLA-561 require a 24 hour ambient temperature cure, followed by 48 hours elevated temperature (135-150o F) cure. SLA-561 Applications: Viking Lander Aero Shell Heat Shield Space Shuttle External Tank Interference Heating Locations LH2 Aft Dome and LO2 Ogive (ascent heating protection) Hans Ulrich Ammann mailto:[EMAIL PROTECTED] http://www.spl.ch _______________________________________________ ERPS-list mailing list [EMAIL PROTECTED] http://lists.erps.org/mailman/listinfo/erps-list
