DEC 2018


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DECEMBER 2018 34 CompositesWorld INSIDE MANUFACTURING 1 Tooling is prepared for carbon fiber composite layup of new SpaceShip fuselage sections SS2-003 and SS2-004. Tooling preparations include waxing, and application of an appropriate mold release and primer. Source (all step photos) | TSC 2 Solvay MTM45-1 prepreg fabric is precision cut by automated ply cutter or hand cut by skilled technicians. Gerbercutter from Gerber Technology (Tolland, CT) performs automated ply cutting (top); a TSC technician hand- cuts prepreg to small shapes for custom layup (bottom). continually exploring other automated approaches that might be compatible with our organization," Subero says. Standard assembly procedures are followed, and the various structural sections of both vehicles are bonded together using an epoxy-based paste adhesive plus metal fasteners in some areas. Primary structures Nearly all primary airframe structures for WK2 and SS2 are sandwich structures. TSC builds the sandwich inner and outer skins using MTM45-1 plain weave fabric prepreg made by Solvay Composite Materials in Tulsa, OK, US (headquarters in Alpharetta, GA, US). ‡e prepreg ˆber is Tenax HTS40 standard modulus carbon ˆber, now manufactured by Teijin at its Mishima factory in Shizuoka, Japan (Teijin headquarters is in Tokyo, Japan). One of the key beneˆts of the MTM45-1 system is OOA processing. ‡e sandwich core is aramid Nomex aerospace grade honey- comb, AHNŽ''", made by Advanced Honeycomb Technolo- gies (San Marcos, CA, US); it is said to exhibit high strength and toughness in a small-cell, low-density, non-metallic honeycomb, according to Advanced Honeycomb. It is also known for providing corrosion and ˆre resistance as well as good thermal insulation properties. From a manufacturing standpoint, it is also considered well-suited for adhesive bonding. ‡e Ž'.—m/'Ž"-ft-long wing span on WK is built with two single- piece carbon ˆber composite spars that run nearly the full length of the wing. Built in the manner of a conventional wing, the spars and ribs are installed into the sandwich structure for the lower wing. After various lines and control systems are also installed, the lower wing is closed oš with the sandwich structure for the upper wing. A similar approach is used for building the boom tails for WK and SS, "which are basically a pair of vertical wings," Subero says. Two fuselages for strength and balance WK2 presents the highly unusual design conˆguration of two fuse- lages, right and left of the center wing. ‡is gives the aircraft both strength and balance for its job. ‡e craft has a lifting capacity of 15 tons, which includes the SS2 locked between them, and stability when the weight of SS2 drops away from WK2 by natural gravity upon release. Subero notes that the twin boom tail design allows for the SS2 spaceship to be carried safely between the fuselages during œight and away from the structure when it is released by a pneumat- ically activated mechanism. ‡ese fuselages are identical in struc- ture, each 23.8m/78 ft long, leading with the nose, which houses the landing gear, followed by a cabin, and then a boom section that extends to a 7.9m/26-ft-high horizontal tail. ‡e right fuselage (facing forward) is a pressurized cabin ˆtted for two pilots, with an optional seat for a œight test engineer. ‡e left cabin is unpressur- ized and contains ballast to keep the vehicle's center of gravity along the centerline. SS has the normal single fuselage. It comprises a nose housing the landing gear, which is connected to a pressurized cabin and crew station of the same size, design and construction as WK's pressur- ized cabin, but is ˆtted for up to six passengers, in addition to the two-person crew. "‡e design commonality has multiple beneˆts," Palermo points out, "ˆrst in allowing for common composite tooling, but more importantly allowing the WK to serve as a pilot trainer for SS with a similar cockpit layout." Feathered re-entry ‡e second half of the SS2 includes what TSC calls the feather, which is part of the wing structure. After SS2 has released from WK2, and after its rocket has burned out, SS2 achieves the apex of its œight. At this point the pilot pneumatically actuates the feather to its folded-up position, from 0° to 90° (Figs. 4 and 5, p. 36), to

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