NASA SSTD-8070-0015-WELD Rev C., Gas Tungsten Arc Weld (GTAW) Procedure for Carbon Steel (ASME P-No. 1, Group 1 or 2), Revision (21-01-11). Active. Scope: This John C. Stennis Space Center (SSC) standard (SSTD) provides for a qualified American Society of Mechanical Engineers (ASME) weld procedure of Gas Tungsten Arc Welding (GTAW) of carbon steel pipe or plate for 0.1875" to 1.50" wall thickness using argon as a backing gas. Public Access. SSC.