In Part 1 we described the fundamentals of physics and engineering that apply to any complex project. This includes Systems Engineering, which is concerned with managing the whole of a complex system across its entire life cycle, the design engineering tools and specialty areas of knowledge, and the organization and economics of projects. Finally we looked at what projects and programs already exist, and the categories of future projects which might be pursued. In Part 2 we began covering the particulars of space systems with the most characteristic element, the transport methods. Since humans are starting from the Earth, then transportation is a prerequisite to doing any other tasks in space, and so we discussed that first. Additionally, the very large number of possible transport methods justifies devoting a large section of the book to it.
In this Part 3 we will cover the particular design factors that apply to space systems, and the remaining subsystem elements besides transport methods. Combinations of subsystem elements then form complete end items or products which execute designed functions and missions. We will review these end functions and the methods available to perform them in a logical sequence by time, starting with exploration and ending with recycling. The final major part of the book with then treat combinations of multiple end items and systems - how they grow, interact, and evolve.
Design factors are those which influence the whole of a design, across different subsystems. These include input requirements, technology level and availability of materials and suppliers, physical design such as margins and wear, and the limits imposed by humans as part of a system and the operating environment.
There are numerous other systems besides propulsion required for most end items. These include structures, mechanical, power, thermal, data, communications, sensors, and environmental protection. When humans interact with an end item, you additionally need displays and controls, internal environment control, and crew support such as furniture, food, and clothing. Items with an extended life require maintenance and repair in the form of tools and spares, and supplies such as fuel.
- Resource Exploration - This includes the methods of finding and characterizing resources located in space, as far as their location, composition, and other physical properties. We only give a summary inventory of the known resources. Full details comprise the entire fields of space science and astronomy, which are both large and ever growing.
- Resource Uses - There are as many possible end uses for the available resources in space as there are things to do on Earth. We list the major applications in terms of what we want to do first. Later sections discuss how we can do them.
- Resource Extraction - Physical extraction is the task of removing materials from their native location, which is called Mining, along with preliminary processing and transport for further processing and production. Since you can only extract a physical material once from it's source, mining is typically mobile, where chemical processing and manufacturing tend to be fixed, since the equipment and connected power supply are often massive. Energy extraction involves converting a primary source of energy into more useful forms such as electricity.
- Processing and Production - These tasks combine a multitude of simpler operations into one or more complete process flows. The process flows convert extracted materials and energy into final bulk materials and finished components.
- Assembly and Construction - Assembly combines components to create a working device or machine. Construction first prepares a location, then assembles larger structures and outfits them with internal and external systems at fixed locations or orbits. The distinction between assembling mobile machines and fixed construction is somewhat arbitrary in space, since even the largest orbital constructions can be moved.
- Operation and Maintenance - Once items are assembled or constructed, they must be operated according to their intended use, and normally will require periodic maintenance to keep functioning. The overall concepts for operations and maintenance should be developed during design, so that necessary design features will be included. If a part will need replacing, for example, a way to access it and remove it should be part of the design.
- Recycling Methods - Most engineered items eventually reach the end of their useful life. Many methods and processes generate waste products, especially living things like humans. On Earth, disposal of scrap and waste has been left as a casual issue, and much of recycling, such as converting CO2 back to Oxygen, happens by natural processes. In space, recycling has to be more deliberate. In many locations there are not surplus resources that can be used, you are floating in a vacuum. You also cannot just dump wastes, as they would end up being a debris hazard. Thus efficient recycling will be both necessary, and less expensive than extracting and delivering new resources in many cases. Thus recycling also needs to be planned for and designed in from the start.
While the topics arise more or less in this order, they need to be designed for in parallel, and will be performed in parallel, and in a connected network with transportation elements. The following pages will discuss these topics in more detail.