The CU Boulder Sounding Rocket Laboratory’s Composite Motor Development team brings together our expertise in solid rocket propulsion and composite manufacturing to create custom solid rocket motors at an unprecedented scale for a student team. We’ve accumulated a wealth of knowledge over the past three years of the program, and have static fired upwards of two dozen composite motors, ranging in diameter from 1 inch to 8 inches.
Current Projects
3G 98mm Composite Motor
6G 98mm Composite Motor
3G 152mm Composite Motor
6G 152mm Composite Motor
R Class Motor Dev
Since the beginning, Composite Motor Development has had one end goal: an inexpensive and lightweight motor capable of getting us to space. The R motor is an 8-inch diameter, all carbon fiber casing beast with 200 pounds of propellant capable of producing 5000lbf thrust, accelerating the SpaceShot vehicle to 23 Gs at liftoff. SRL completed and static fired our first R class motor in February 2020, in hopes of securing an FAA waiver to fly SpaceShot soon after. However, propellant deficiencies and inadequate adhesion of the thermal protection system led to an overpressure event and loss of the motor. After this test, SRL decided to step back and take a more stepped approach to everything that goes into making an R motor, including its materials, the design design, propellant manufacuring, and all fabrication methods. Currently, SRL is building and testing smaller O-class motors to perfect our technology before scaling up again to the bigger and more expensive R class.
What We Do
The composite motor team is responsible for designing, manufacturing, and testing the propulsion systems that power all of SRL’s solid-fueled motors. Our long-term goal is to create low-cost and lightweight carbon fiber motors to enable frequent research flights from the CU community. We work with new materials such as carbon fiber, kevlar, ceramics, and more to develop casing and nozzle designs as we improve motor technology. Composite motor rapidly designs, builds, tests motors to scale up to the R class booster powering Spaceshot.
38mm Test and Dev Motors
The first solid motors SRL ever produced and tested were with 38mm diameter propellant grains in an aluminum casing, producing 25 lbf thrust for just over 2 seconds. Although the team quickly grew out of these into much larger motors, they were recently resurrected to serve as testing and validation processes for various projects.
Currently, SRL is in the process of manufacturing solid cast ceramic nozzles in the interest of reducing erosion and increasing lifetime. A key step in this process is making and firing several small-scale ceramic 38mm nozzles as the production process is studied and refined. By observing the nozzles’ behavior during and after a 38mm static fire, the team identifies areas that need more improvement or attention before scaling to O and R motor nozzles.
Consistent and reliable propellant performance has been a struggle of SRL from our first motors, and 38mm tests are one of the several ways we are working to fix these issues. Along with testing the mechanical properties of each propellant mix, the Composite Motor team fires three samples 38mm grains produced in every batch. Only after verifying that each grain performed nominally are the full-size O or R class grains from the batch used in any larger motors.
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