The Silver Spur series, which includes Silver Spur 1, 2b, and 3, marked USCRPL's first attempts at understanding and using minimum thickness carbon fiber motorcases. These vehicles were designed to test high stress vehicles at a small scale, to anticipate contingencies in the manufacturing processes and design for larger and more powerful future vehicles. The project spanned over three of USCRPL's formative years, from Silver Spur's launch attempt in September 2007 to Silver Spur 3's flight in September 2010.
Silver Spur 1
Silver Spur 1 featured a USCRPL designed carbon fiber encased 5,000lb-sec O3730 solid propellant motor, and debuted in the Black Rock Desert in September 2007. This motor case was the first of its kind for RPL; previous vehicles employed aluminum motor cases. Carbon Fiber is favorable because of its extremely high strength to weight ratio -- a relatively small amount of carbon fiber is needed to hold in the high pressure of a solid rocket engine, an amount much less than that would be required of aluminum. This means that lower class motors can send the vehicle higher, exactly what one would want to get to space. Its motor design was originally intended to be used as a booster for the later Traveler series of vehicles when Traveler was in its early design stages, an idea later turned on. However, the carbon fiber motor case technology implemented in the vehicle paved the way for all future USCRPL vehicles
However, as is often the case for early stage experimental technologies, everything did not go as planned. Silver Spur 1's attempt at launch resulted in a CATO, or Catastrophe At Take Off. The tube inside of the carbon motor case suffered a shear failure, which led to an over-pressurization of the motor case, and an explosion.
Silver Spur 2b