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WBS 17 Design Status

Informal Update

January 6, 2005

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WBS 17 Scope

• 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

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WBS 171 Approaches

• 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

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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

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Fiberglass Construction

Approx wt. 8,000 # (As Shown)

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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

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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

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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

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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

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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.

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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.

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