Scope of the Work Any complex device@ such as a rocket@ is better understood when broken down into smaller sets@ through a process that may be repeated as many times as necessary until satisfactory results are reached. The more complicated the project is@ the more iterations it requires. A good engineering practice consists of breaking down the product into systems (propulsion@ hydraulics@ electronic)@ followed by another division into elements (valves@ actuators@ controllers)@ until one reaches the level of the thousands of parts (nuts@ screws@ rivets) that make up the most basic level of the product. The application of this concept as illustrated in Figure 1.1 defines the systems needed to build a rocket such as structure@ guidance@ payload@ and propulsion. The thrust chamber shown in Figure 1.1 is a subdivision of the propulsion system. Generically speaking@ the rocket engine is a device used to control the combustion resulting from a mixture of highly volatile elements@ and the thrust chamber is the location where this activity takes place [6]. The thrust chamber can be divided into three main components [7]??the injector@ the combustion chamber@ and the nozzle??as described below: 1. The propellant injector is responsible for dosing@ injecting@ and atomizing propellants through its injection elements. This work deals with two models: the swirl and the pintle injectors. 2. It is within the confines of the combustion chamber that propellants turn into high-temperature and high-pressure gases. This work addresses the cylindrical combustion chamber. 3. The convergent-divergent nozzle is a device through which the gases resulting from combustion expand and accelerate until they reach supersonic velocities. This work will present the procedures for dimensioning the conical nozzle and the parabolic nozzle. Changing the analysis from a technical perspective as described above to a managerial approach necessitates the breakdown of the activities required to complete a project into a hierarchical architecture@ from the most to the least complex elements [8]. An organizational chart@ such as the diagram in Figure 1.3@ contains the specified product at the top [9] and the system@ subsystem@ and components at successively lower levels. Each lower level in the hierarchy represents a more detailed work package than the activities at the respective higher levels. Defined by the lower-level blocks in the hierarchical sequence are work packages covering technical details@ costs@ and the delivery schedule. The organizational chart in Figure 1.3 shows@ at its highest level@ a block that represents the entire rocket assembly in all its complexity. It is followed by four second-level blocks representing the main systems@ namely structure@ payload@ guidance@ and propulsion. A block called ??Others?? accounts for future expansions. The focus now shifts to the rocket engine and the thrust chamber@ which still incorporates a huge amount of complexity@ requiring further division before a comfortable limit of work to assign to a manager or an engineer is reached. When the WBS is too large to fit into a single diagram@ it may be necessary to construct a second chart to define the remaining work@ picking up from where the first chart left off. With the ??Thrust Chamber?? at the top of the new diagram in Figure 1.4@ it is now possible to define the deliverable items. The first division@ called ??Hot Section@?? deals with the elements that form the combustion chamber and its nozzle. The next block@ called ??Cold Section@?? addresses the propellant injectors. At the lowest level on the diagram are the five work packages that are the focus of this publication. Three of them??the conical nozzle@ the parabolic nozzle@ and cylindrical combustion chamber??are related to the ??Hot Section@?? while the remaining two@ the swirl injector and the pintle injector@ are linked to the ??Cold Section?? block.