HTPB: Building a Hybrid Rocket

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Building a Hybrid Rocket
The hybrid rocket comprises a motor which makes use of liquid rocket propellants and solid rocket propellants. With hybrid rockets, the disadvantages present in solid rockets and liquid rockets can be avoided. Due to the hybrid nature of rockets the fuel and liquid components cannot be mixed together which reduces the chances of engine failure. In addition, the machine can be shut down easily in case of an emergency situation. The hybrid technology also includes control systems, ground support, navigation system and propulsion (Kerr 9). Hydroxyl-terminated polybutadiene (HTPB) fuel is the preferred choice of manufacturers at it allows the vehicle to achieve high performance. The design and development of hybrid rocket require the manufacturers to evaluate all the requirements and specifications included in the project.
-3175024320500Figure 1: Hybrid Rocket
Source: (Surmacz & Rarata 2)
Hydroxyl-terminated Polybutadiene (HTPB) and Hybrid Rocket
The hybrid rocket development issues can be categorized into two subgroups which are technical and non-technical. Among technical tasks includes maintaining combustion instability. It is essential that the solid fuel forms a mixture and vaporizes while oxidizer inflow remains stable (Benhidjeb-Carayon et al. 1 ). Instabilities can temporarily interrupt the process and decreases the temperature to a slight degree.
034798000Figure 2: Hybrid Motor Model
Source: (Surmacz, & Rarata 7)
As the pressure and temperature in the chamber decrease, the combustion process occurs smoothly without any external blockage. It results in increasing the pressure and temperature which expands the oxidizing mechanism. A major problem which occurs is the downfall in the level of fuel regression. The propellant motor and surface reaction become negligible which results in poor quality of heat flow. In addition fuel vapor level decreases to a significant level which reduces fuel mass intensity.
HTPB Design
In developing a hybrid rocket a number of hybrid motors need to be designed, tested and developed before deploying them into real-world applications. The performance parameter needs to be considered in designing chamber. The critical components include impulse, heat and product mass. All the components need to be critically evaluated in developing a flight trajectory and hybrid engines. The atmospheric pressure needs to be above 12.1 psi so that the nozzle and plug section operate smoothly. Separate holes need to be made after drilling so that a balance can be maintained in pressure transducers and oxygen feeds (McFarland & Antunes 2-9). A radial pattern should be followed in injecting holes so that the fuel flows evenly across multiple sections. A well-designed injector plate can ensure that the desired level of flow is maintained across liquid oxidizer and thrust chamber. Cavity area also needs to be designed within the plate in order to provide support to the feed system.
HTPB Performance
The demonstrator engine is a critical component of a hybrid rocket. A basic level design needs to be developed at an initial stage so that the regression flow rate can be maintained at an optimal ratio. The chamber pressure high and low-level pressures need to be set at a fixed limit for all engines and sub-engines. Maintaining a pressure of 20 bar can be ideal for minimizing the variations that occur in different engines. Selecting a good fuel combination will make the system function smoothly (Vorozhtsov et al. 106). The LOX oxidizer needs to be used for enhancing the efficiency of the system. The frozen reactions can be used for applying computation. Furthermore, 800 N impulse, 160 N thrust and 5 second time duration can be maintained for achieving maximum efficiency.
HTPB Combustion Engines
A subscale combustion engine consisting of LOX need to be designed in order to minimize manufacturing expenses. The nozzle is the main component of sub engines due to the presence of thermal loads. Maintain a chamber length of approximately 700 mm is sufficient for the system. In addition, a 73.5 mm chamber diameter can easily manage insulating thickness. The main components of sub engines are showerhead injector, cylindrical grain, injector flange, composite nozzle and combustion chamber. The nozzle is an important part of the system as it is required to tolerate the pressure for a minimum of ten seconds period (Connell et al. 2). The cotton laminate and graphite help in maintaining the insulating properties of the sub engines. Graphite withstands gas and thermal load components. Multiple tests need to be performed for examining the overall performance of the system.
HTPB Chemical Information
The propellant pressurization is the main component of the hybrid rocket system. The pumping mechanism separates the fluids present in the system and maintains a balanced flow rate, volatile chemica...