Section 3.5 - Processing and Production
The Resource Extraction section discussed how to extract raw materials and energy from the available resources. This section covers how to convert those into finished inventory and components which can be assembled into completed systems and projects.
Existing industry extracts materials and energy, produces bulk supplies and parts from them, and assembles them into finished items entirely on Earth. The methods, however, are independent of location. We just happen to have evolved on Earth, and so that is where industry first was set up. In principle, the same methods used on Earth can also be used in space or on other planets and objects. In practice, we specialize industry on Earth for location where it functions best, and the same will be true for locations beyond Earth. There are some additional methods which only are suited to locations beyond Earth, due to special conditions like available energy, lack of gravity, or vacuum. A 1993 survey of methods and uses specifically for space, Resources of Near Earth Space represented the state of the art at that time. Progress has been made since then.
This section will list the full range of available methods, but thought needs to go into selecting which to use in a given location and circumstance for a space project. Some Earth-based methods assume gravity or air pressure in their operation. Artificial gravity or atmosphere can be provided in space locations where it is not naturally present, but there is overhead and complexity in doing so. Thus in designing a space production facility, you should consider an alternate process that does not require special conditions, rather than automatically adding them to a traditional process that needs it.
The scope of all known production methods is too wide to fit in the confines of a single book. Indeed, the entire fields of Industrial and Chemical Engineering are devoted to this topic. We will give a summary of the available methods, with pointers to more detailed information. A typical industrial process uses multiple steps in series or in a more complex flow of operations with branches or loops, under some method of production control. Here we list individual steps, which are called Unit Operations in process engineering. The range of possible complete processes by combining these steps is quite large. The task of the system designer is then to select the proper set of steps and complete processes for the task at hand.
Processes do not operate themselves. Under the heading of Production Control fall those elements that plan the production, send commands on what to produce to the system elements that actually perform the work, and monitor the status and outputs of the operations. Control can be either manual or automated, and either local or remote depending on circumstances and design. Processes can be repetitive or continuous, producing the same output at some average rate, or singular, where a different part is produced each time.
Process Measurement and Control
Automation and Robotics
Handling and Storage
Materials and parts need to be moved from process to process, or stored between processing operations or when complete.
Materials processing converts raw materials from their state as delivered from mining to finished bulk materials such as water or oxygen, or ready stock such as bars, rods, or sheet.
Mechanical processing changes the physical state but not the chemical composition of the materials
Crushing - This is breaking down a material into smaller pieces by applying pressure. Milling refers to making finer powders. In addition to standard methods of crushing, kinetic impact can be used as a process in space, one that Nature has applied extensively.
Sorting - This is the sorting of material by size or type using gravity, acceleration, vibration, electrostatic forces, or magnetic fields. Besides physical wire mesh or perforated plates to sort by size, methods like electrostatic can sort materials by charge-to-mass ratio.
Heating and Cooling
Refining and Separation
Filtration - Separation of solids from liquids
Synthesis and polymerization
Agriculture and Food Growth
Organics Conversion and Storage
Forming and Molding
Electric Discharge Machining
Electro and photo chemical machining
Plasma arc machining
Beam and Jet Machining
E-beam & ion milling
Abrasive water jet
Powder forming and sintering
One method similar to sintering is to spray coat reinforcing fibers with droplets of molten metal to form a reinforced tape. Then the tape is applied in layers to build up the shape you want. Each layer is heated to just below the melting point then pressed to the previous layer to bond it. For making shapes like cylinders this can be a continuous winding process.
There are three main levels of electronics fabrication. These are making the individual components, connecting those into circuits, usually in board form, and assembling them into finished units.