Upgrade of a 10-foot diameter by 15-foot long thermal vacuum chamber

An extensive upgrade to a 10-foot diameter by 15-long thermal vacuum chamber located at Goddard Space Flight Center (GSFC) commenced in the fall of 1992 and was completed in the summer of 1995. The facility was completely dismantled removing three 35-inch diffusion pumps, other vacuum system components, the 200 horsepower thermal system blower, thermal shrouds, and all interconnecting piping. The intent of the upgrade was to replace the diffusion pumps with clean pumping and backfill systems, to install a new, efficient thermal system and shrouds, and to place the entire control system on a programmable logic controller. Many enhancements were made in the vacuum and thermal systems with provisions made into the design and the programming to provide the capability for any future automation task. The entire vacuum system was designed and integrated using in-house personnel on a non-interfering basis to other flight related tasks. The thermal system was a competitively bid ''turn-key'' system. Preparation of a thorough specification, pre-bid conferences with vendors, and good communications with the turn-key contractor resulted in an efficient, flexible, and uniform thermal system. The control system, based on a distributed I/O programmable logic controller (PLC) system, was developed, installed, and programmed by in-house personnel for both the vacuum and the thermal systems. Application of several different cleaning techniques, attention to cleanliness, pre-cured optical paint, and ability to operate the thermal system at 150 degrees C resulted in the facility exceeding the GSFC contamination requirements by a factor of 10 within several days of bakeout and virtually eliminated any background contamination from the old diffusion pumps.