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NCSX. WBS 17 Design Status Informal Update. January 6, 2005. Old: WBS 171 provides the cryostat insulation system to isolate the stellarator from thermal load and atmospheric exposure including moisture
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NCSX WBS 17 Design Status Informal Update January 6, 2005
Old: WBS 171 provides the cryostat insulation system to isolate the stellarator from thermal load and atmospheric exposure including moisture WBS 172 provides the radially-translating base support structure to allow machine assembly and project-long gravity support / CTE compliance New: WBS 17 was selected as the home for the VVSA spacer assembly fixtures WBS 17 Scope
CDR Approach: The CDR plan for the cryostat was an assembled frame of rigid supports which would be subsequently insulated with urethane or other foam in a manner similar to that of large, rigid LN2 vessels Pro: Cost effective Con: Extremely difficult to perform without a mess Huge ES&H issue (methylene di-isocyanurate emerging from firehose) Access to machine would require cutting and subsequent re-spray to restore WBS 171 Approaches
WBS 171 Approaches (cont.) • Current Approach: • A system of bolt-together insulation modules (J. Rushinski) has been designed • Pro: Demountable, no cutting and subsequent spraying to restore • Each fundamental module form can be configured with a blank insert or a custom insert for port extensions, coil services, etc. • Potential for large volume production runs • Joints, midplane supports need additional design work
Fiberglass Construction Approx wt. 8,000 # (As Shown)
WBS 171, Insulation • Penetrations • Use of Robert Childs’ (C-Mod) system of Inspec Solimide foam with inner and outer fiberglass/silicone vapor barriers – No re-invention here • Bulk Insulation • Two part foam has been largely dismissed. NCFI, the Shuttle’s foam supplier, cites CTE concerns that are best avoided if at all possible. • Martin Marietta/New Orleans, Kennedy Space Center, and NCFI seem to be under a gag order on the topic of external tank insulation topics. • The NCFI person threw a bone with his “avoid two-part” comment • Anecdotes available
WBS 171, Insulation (continued) • Bulk Insulation, continued • Dow’s Trymer 2000/4000 polyisocyanurate custom-cut board stock seems a best candidate for filling insulation modules • K=.19 BTU/in*hr/ft**2 or R-6.5/in • Lowest available CTE for rigid pedestrian stock • Similar to C-Mod approach • Small gaps in layered fill can be filled with expanding polyurethane foam with tolerable personnel protection measures
WBS 172 Approach Approach: • The spirit of the CDR design is largely embraced • Gone, however, are the tri-axial thermal breaks in each of 12 towers
WBS 172 Approach (continued) • Each column top is provided with a Lubrite (grease impregnated bronze) skid plate familiar in oil patch industries. The skid plates (shown in brown) reside just below the tower finials that actually penetrate the cryostat. • The above skid plate with appropriate steering/capturing hardware render the triax design unnecessary • Concerns regarding toroidal loops will drive the presence of DC breaks in the 12 horizontal pipe sections
WBS 172 Approach (continued) • T. Brown requests an iteration on the intersection of the tower finials with the radial tie castings Other: • The 12 DC breaks for the horizontal stiffening tubes will be provided without argument. • An electro-magnetics analysis of any need for loop interruption near the floor is probably prudent. • Breaks cost $$$$. The rebar in the floor is certainly without isolation.
WBS 172 New Scope • Recently added to WBS 17 is the mechanical manipulator plan for supporting the VVSA spacers during the final assembly motions. • While this scope does not initially appear difficult, the designer will better know in one or two weeks if any significant issues exist.
