DEC 2018


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DECEMBER 2018 36 CompositesWorld INSIDE MANUFACTURING FIG. 4 Carbon fiber composite feathers SS2 feather function is tested in TSC facility. The carbon fiber composite feather is folded up 90° to increase drag and reduce speed as SS2 prepares to re-enter Earth's atmosphere. Source | TSC FIG. 5 A Rocket testing Extensive testing has been conducted on rocket technology to ensure perfor- mance of SS2 in its drive to suborbital space. The rocket has now been qualified for human-rated service. The rocket is moved into position for testing (top photo), then fuel is ignited for the hot fire test (bottom photo). Source | TSC wing at its aft spar by four metal clevis-and-lug ttings that allow the aps to hinge up and down (Step , p. •, and Figures). Rocket technology Extending to the rear of the SS2 wing and feather assembly, the aft fuselage houses the rocket and the main oxidizer tank. -e rocket propellant is a hybrid of solid hydroxyl-terminated polybutadiene (HTPB) rubber-based fuel ignited by a carefully controlled ow of liquid nitrous oxide. "Unlike a traditional solid motor fuel, our fuel is stable and does not require special handling procedures to prevent ignition," Palermo explains. A valve in the nozzle assembly connects the HTPB in the rocket motor case with the main oxidizer tank. -e throat nozzle assembly connects the nozzle together with the chamber where the combustion reaction takes place. "It's a very robust architecture having a very limited failure mode, which made rating this rocket motor for transporting people a lot easier," Palermo explains. Following TSC's extensive ground test qualica- tion program, the rocket motor is now qualied and human-rated for service. -e case is lament wound carbon ber composite, but no details about the materials or process are available due to ITAR (International Tra'c in Arms Regulations) restrictions. However, says Palermo, "Like the spaceship, its construction leverages the best properties of composite structures." [Author's note: Unveried reports from within the composites industry suggest that motor cases for solid propellant are generally lament wound — sometimes directly over the solid propellant — probably using a mid-modulus carbon ber and high-temperature resin. Structures for liquid fuel systems, such as liquid oxygen, tend to use automated ber placement (AFP) systems using prepreg tape or fabric.] WK engine cowlings are also composite, as are the inlet duct and exhaust nozzle, made with an unidentied high-temperature composite material. Palermo identies WK's engines as "four highly e'cient high-bypass turbofan jet engines made by Pratt & Whitney, Canada" part of the United Technologies Co. (East Hartford, CT, US) — "a great supplier to our program for many years," Palermo adds. Onward, upward and return On July 28, 2018, WK2 successfully carried and launched SS2 from the Mojave airport up to a height of 8.8 miles, where its rocket shot another 23.5 miles straight up to a record 32.3 miles above Earth — the nearest SS2 has been to its ultimate goal of 50 miles. Several more test ights are planned before the space pair enters commer- cial service. Commercial ights ultimately will take o¥ from Virgin Galactic's Spaceport America facility near Las Cruces. Additionally, Virgin Galactic and TSC have signed a Memorandum of Understanding with Italian aerospace companies for construction of a spaceport in Grottaglie, Italy, to bring commercial spaceights to Italy for science and tourism. "Tourism is certainly our key market," Palermo states, "but we are also pursuing suborbital science. SS is an excellent platform

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