Journal of Aeronautics & Aerospace Engineering
Open Access

Design Considerations for Efficient Low-Impulse Monopropellant Rocket Propulsion Systems

Galyna Kotliuk^{* *}Correspondence: Galyna Kotliuk, Department of Aircraft and Rocket Engineering, National Technical University of Ukraine, Kyiv, Ukraine, Email:

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About the Study

Monopropellant rocket propulsion systems have gained significant interest in the aerospace industry due to their simplicity, reliability and performance characteristics. Unlike bipropellant systems that require the handling of two separate components, fuel and oxidizer monopropellant systems utilize a single propellant that decomposes or reacts in the presence of a catalyst.

Propellant selection

The choice of propellant is important in designing a monopropellant rocket system. The primary factors influencing this selection include energy density, stability, toxicity and handling characteristics. Common monopropellants such as hydrazine, hydrogen peroxide and nitrous oxide each have distinct advantages and drawbacks.

Energy density: Higher energy density propellants provide greater thrust per unit mass, which is advantageous for achieving specific mission profiles. Hydrazine, for example, has a high energy density and is widely used in spacecraft propulsion systems, despite its toxicity and handling challenges.

Stability and shelf life: The stability of a monopropellant is important for long-term storage and operational reliability. Propellants that decompose or degrade over time can lead to performance issues or system failure. Hydrogen peroxide is known for its relatively long shelf life but requires careful handling to prevent decomposition.

Toxicity and safety: Monopropellants often pose health risks to personnel and the environment. Designing systems that reduce exposure, such as using nontoxic alternatives or incorporating robust containment strategies, is important. Furthermore, the propulsion system must incorporate safety measures to handle spills, leaks or accidental ignition.

System architecture

The architecture of a monopropellant propulsion system directly impacts its efficiency and reliability. Key considerations include the propulsion cycle, system integration and thermal management.

Propulsion cycle: Monopropellant systems typically operate on one of two cycles: Cold gas or catalytic decomposition. The choice of cycle affects thrust-to-weight ratio, specific impulse, and response time. Catalytic decomposition systems, which utilize catalysts to promote the rapid breakdown of the propellant, generally offer higher performance than cold gas systems, making them suitable for applications requiring higher thrust levels.

System integration: Efficient integration of propulsion components, such as tanks, pumps, valves and thrusters, is necessary for minimizing mass and maximizing performance. This requires careful consideration of component placement to optimize flow paths, reduce pressure losses and improve system responsiveness. Additionally, modular designs can enhance maintenance and scalability.

Thermal management: Heat generated during propellant decomposition can affect system performance and integrity. Implementing thermal management strategies, such as insulation, heat sinks and active cooling systems, can prevent overheating and make certain consistent performance. Effective thermal management also aids in maintaining the efficiency of the catalyst used in decomposition reactions.

Performance optimization

Optimizing the performance of low-impulse monopropellant systems involves fine tuning various parameters, including nozzle design, thrust modulation and control mechanisms.

Nozzle design: The nozzle plays an important role in converting thermal energy into kinetic energy, thereby influencing the overall efficiency of the propulsion system. The design must account for the specific Impulse (Isp) requirements, thrust levels, and operating conditions. Conical nozzles may be suitable for low-impulse applications, while aerospike nozzles can offer improved performance at varying altitudes. Computational Fluid Dynamics (CFD) simulations can aid in predicting performance and optimizing nozzle shape.

Thrust modulation: Efficient thrust modulation is necessary for missions that requires adjusting to different operational needs. Implementing variable thrust capabilities, such as through adjustable nozzle geometries or propellant flow modulation, allows for improved control and efficiency during different mission phases. Low-impulse missions, in particular, benefit from finely-tuned thrust profiles to achieve optimal trajectory adjustments.

Control mechanisms: The integration of advanced control mechanisms, such as feedback loops and sensors, improves the responsiveness of monopropellant systems. These controls enable real-time adjustments to thrust levels and direction, improving overall system performance. Employing algorithms that account for external factors, such as atmospheric conditions and vehicle dynamics, can further improve efficiency.

Reliability and testing

Providing reliability in monopropellant propulsion systems requires rigorous testing and validation.

Testing protocols: Comprehensive testing protocols should contain component-level and system-level tests. This includes static firing tests, thermal cycling and vibration tests to assess the system’s response to various operational stresses. Data gathered from these tests can inform design modifications and identify potential failure points.

Reliability metrics: Establishing reliability metrics based on historical performance data and predictive maintenance models can help identify trends and potential issues. Implementing redundancy in important components can further improve reliability, allowing mission success even in the event of a subsystem failure.

The design of efficient low-impulse monopropellant rocket propulsion systems necessitates a multidisciplinary approach that involve propellant selection, system architecture, performance optimization and reliability testing. By carefully considering these design aspects, engineers can create propulsion systems that deliver the necessary thrust while maintaining safety, reliability and efficiency. As the demand for small satellite launches and space exploration mission’s increases, the development of effective monopropellant systems will play an important role in advancing aerospace capabilities.