BACKGROUND
Modern rocketry is at the forefront of high-performance aerospace engineering as demands on these systems generate the need for optimized solutions to meet performance goals. For example, larger unmanned craft often employ a rocket-assisted take off (RATO) to reduce launch footprints and reduce the launch g-load to allow for a wider variety of payloads to be carried relative to other unmanned craft launching systems. However, current rocket motors present both technical and logistical shortcomings. The major technical shortcoming lies in the composition of solid rocket motors from the largest producers, which lack the burn profiles neutral enough for non-sporting rocket needs, such as RATO unmanned crafts. This problem is often rooted in variance in consistency of fuel grain, and a lack of development into additive manufacturing approaches and novel fuel geometries. Logistically speaking, the manufacturing of most smaller rocket motors is limited to a few companies and dominated by sporting rocketry, these are not located in the United States, and motors are expensive to produce. To address the increasing demands of the aerospace and defense industries, the development of novel composition and fabrication methods are critical.
SUMMARY OF TECHNOLOGY
Researchers at OSU have developed an innovative composition and fabrication approach to ammonium perchlorate composite propellant (APCP). Like many forms of APCP, it uses ammonium perchlorate as an oxidizer (and fuel), a fuel of aluminum, and a binder. However, the improved fuel employs novel methods to ensure specific grain sizes of ammonium perchlorate with differing levels of aluminum powder. Equal size-distributed ammonium perchlorate fuel grains results in precise performance and when combined with aluminum powder to increase the energy potential, a neutral burn curve can be achieved, ideal for RATO systems. The trimodal composition with controlled particle distribution and size can be leveraged to achieve far more specific and reliable performance out of APCP for rocket motors, allowing for a much-needed performance boost in applications, particularly for large unmanned craft systems.
In addition to the aluminum additive and grain size functionality detailed above, researchers have developed a novel system of fuel grain infill levels and shape designs intended for hybrid rocket systems. Using additive manufacturing, fuel with differing grain sizes and a resulting percentage fuel density is possible, as well as generating specific geometric parameters of the printed fuel portion of the motor. Through this novel process, greater control of rocket performance is possible. Test data show adjusting the infill percentage and shape print pattern of fuel achieves different thrusts, burn times, and burn rates due to changes in surface area, density, and oxidizer flow through the motor. Specifically, as the infill percentage increases, burn rate decreases and burn time increases. These advances in additive manufacturing create rocket fuel with specific parameters resulting in small-scale hybrid rocket systems being able to perform on par with solid rocket motors but with increased operational safety, launching large unmanned craft propulsion technology to new heights.
Both of these composition and fabrication techniques for rocket propellent represent an innovative platform which can meet the needs of modern rocketry and open previously unexplored avenues of further advancements to reduce costs and increase precision performance.
POTENTIAL AREAS OF APPLICATION
- Aerospace industry
- Defense industry
MAIN ADVANTAGES
- Substantially lower cost over current systems
- Optimizable to specific requirements (e.g., RATO systems)
- Solve shortage issues with solid-fuel rocket motors
- Reduced operational hazards (in hybrid systems)
- Establish local manufacturing capabilities of solid-fuel and hybrid rocket engines
STAGE OF DEVELOPMENT