Space Transport and Engineering Methods/Introduction

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About This Set
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&emsp;This is the second volume of a two-volume set about building a better life for ourselves, our community, and the world. Building is meant in both the literal sense of construction and production, and in the social sense of how people work together to reach our goals. The core ideas behind our approach can be summarized as follows:


 * Resources and energy are abundant on Earth and in space.
 * With enough knowledge and tools they can be used to build a better life.
 * With planning this can be sustainable and avoid unwanted side effects.
 * Cooperation makes it affordable and self-improvement makes it scalable.
 * Smart tools can do most of the work and make it easier.

&emsp; Volume I on Seed Factories and Self-Improving Systems covers the basics of these ideas, including their history, elements of designing such systems, and a design process. We then present several examples of projects and systems that use this approach on Earth. Each example is designed to grow internally by self-improvement, and externally by enabling copies of their starter sets. The examples are linked as earlier ones can grow into later ones, can make parts for them, or can make complete starter sets for later ones.

&emsp;This volume covers the very different conditions and locations of space beyond Earth. We first look at the science and engineering fundamentals that relate to space. Since you must get there before doing anything else, second are technologies for reaching space and moving once there. Third are specific engineering technologies that apply to space projects. Part 4 continues the series of projects and systems from Volume I to orbital and planetary locations, ending with those beyond the Solar System. Part 5 provides some design studies as examples and for practice while learning the subjects discussed. We finish with references and sources that don't fit elsewhere in the book.

&emsp;We cover past and current space projects and programs, but also many future methods, technologies, and projects which require research and development. Not all of these will prove useful, but we include all that we know of. When starting a project it helps to know what other people have done and thought of. This avoids repeating work and helps identify options. The online format is also intended to address some of the limitations of traditional printed textbooks:


 * Their high cost in recent years. Wikibooks are free and open-source.
 * Difficulty including or linking to other media types, such as audio, video, simulations, and software.
 * The relative difficulty of updating printed books in a fast moving field.
 * The very large amount of information in this field. These volumes are not limited by printing technology and we are building a supplementary reference library.
 * Learning involves more than just reading. So we include some projects which interested readers or teams can use as design practice, or even build.

About Space and Space Projects
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&emsp;Our planet is located in space, as thus photo of the Earth from a distance shows. Space is not a different place to go to - we are already there. We think of it as somewhere else because most of us spend most of our lives in the most usable areas near the surface of a single planet among the billions in the Galaxy. This is where we evolved, and where conditions are reasonably habitable for us, so we think of it as normal.

&emsp;In reality, our comfortable planet is the exception. The vast majority of environments are hostile to life as we know it. We can use and live in such places with technology, just like clothes and fire allowed us to live in cold parts of the Earth, and boats allowed us to cross oceans. For space, we first learned how to build equipment that can work there. After that we started building artificial environments like capsules, spacesuits, and space stations. These let people live in space for varying amounts of time. So far the most people in space at one time is about 17 out of 8 billion total population. So living in space has only barely started.

&emsp;In the future we may start changing space environments to make them more livable. In principle we can also change ourselves to better live in space, but it would be hard to do that for all the other kinds of life that exist on Earth. Reproducing earth-like environments is simpler to start with.

&emsp;As of 2021 the Global Space Economy had reached US $386 billion/year, about 0.4% of global economic activity. This is expected to greatly increase in the future as we learn more about using space and expand into it. The energy and material resources of space are vastly larger than those on Earth, and using them can minimize side-effects to the Earth's environment. Both economics and protecting the planet make space systems engineering is a worthy field of study.

&emsp;The main challenges for space projects in the past were rockets that could reach space at all, and designing relatively small satellites (as a percentage of their weight) with finite lives that they could carry. These topics are adequately covered by existing textbooks such as Sutton's Rocket Propulsion Elements and Griffen and French's Space Vehicle Design.

&emsp;Starting with more recent projects, like the International Space Station (ISS), new design features have become more important. These include long-term habitation, evolution and growth, sustainability, and industrial capacity. Future projects will require new types of propulsion, life support, production, and assembly. Single projects can no longer be considered in isolation, either. For example, the ISS depends on multiple launch vehicles to deliver crew, supplies, and hardware, and on relay satellites to communicate with Earth. One reason for this volume is to address these recent and future changes that are not covered by past textbooks.

Links to Additional Material
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&emsp;We cannot fit the entirety of knowledge about space systems and projects into a book-length introduction such as this one. So we will include extensive links and references to more detailed sources. The Seed Factory Project, of which this volume is a part, has built a reference library of some of the more useful publicly available articles and books to supplement this set. We cannot distribute copyrighted works from that collection without permission, but we can provide lists and where to find them for interested readers.

&emsp;Note that popular culture incorrectly calls Space Systems Engineering "Rocket Science". It is part of engineering rather than science and not exclusively about rockets. We hope that serious students understand the difference.

&emsp;Engineers use other tools besides books to do their work, such as simulation software and spreadsheets. Wikibooks does not support including software files, so links to where these items can be found are intended to be added over time.

&emsp;A 2023 Report we produced is a shorter introduction to our ideas and proposed projects. We are incorporating ideas from it into this set.

Detailed Book Organization
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&emsp;This book is organized as a progression from science and engineering fundamentals (Part 1), to technology elements (Parts 2 and 3), to complete projects linked into a combined program (Part 4). Part 5 is intended to present example design studies that show details of the process. The volume ends with general references and sources not already included in the body of the book, and data appendixes.

&emsp;Each part is divided into numbered chapters, and chapters have sections and subsections for internal referencing. We will try to emphasize underlying principles and key design parameters, as those have more lasting value than, for example, the particulars of a current rocket.

&emsp;We include many methods and concepts which are not in current use. The reasons are first, when starting a new project, it is a good idea to at least briefly consider all the possible alternatives, before narrowing down to the most relevant ones. Second, this is a future-oriented book. While a concept may not be useful today, knowing what the state of the art is and what technology areas to watch helps to tell when it will become useful. Third, having all the ideas in front of you might spur a new combination or application that had not been thought of before. This has happened to me (Eder) more than once, so I can attest to its usefulness.

 Part 1: Science and Engineering Fundamentals
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&emsp;All of engineering depends on underlying knowledge from mathematics and the sciences. So we start with some basic information the reader should be familiar with, and the more important principles, formulas, and methods which apply to space systems (Chapter 1.1). The largest part of this is Physics, but also some key ideas of the other sciences, including Astronomy, Planetary Science, and Chemistry.

&emsp;Bodies in space are always in motion relative to others, and far from each other compared to distances on Earth. So next are orbital mechanics (1.2), and what forces (1.3) and energy sources (1.4) are available to artificially move to chosen destinations.

&emsp;Following that we introduce general engineering methods, including the discipline of Systems Engineering (Chapter 1.5). The goal of systems engineering is to optimize complex systems over their life cycle. Larger space projects are complex enough that this method is very useful. Complexity also demands ways to track the details and keep a project as a whole a coherent. Note that smaller and simpler projects, like some of those in Volume I, don't need this level of design and analysis.

&emsp;We then introduce the tools that engineers use in their work (1.6), followed by the variety of specialty engineering disciplines such as structural and electrical design which are used in parallel with the overall system optimization (1.7). Most larger projects use specialists in different areas, because there is too much knowledge for any one person, and simply a lot of work needed.

&emsp;Early concept work can be accomplished by one or a few people. As larger projects develop, more people are brought in with the right skills to work on the details. This in turn demands efficient organization and coordination within a project team (Chapter 1.8). Economics addresses other resources needed in a project besides people and knowledge, including funding and financial analysis.

&emsp;The last two chapters of Part 1 summarize existing programs (1.9) and topical areas for future projects (1.10). Proposed future projects should be compared to existing ones to see if they give enough improvement to justify their creation. The range of future activities also helps identify goals, requirements, and growth paths.

 Part 2: Transport Technologies
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&emsp;We noted that before you can do anything else in space, you first have to get there. So Part 2 discusses ways to reach and then move around in space. Past rockets could only carry 5% or less of their total weight as cargo to orbit, and less to farther destinations. Increasing the cargo fraction and reducing cargo weight became the primary focus of space projects. But those efforts made the cost very high. Although still important, we take a more balanced approach in this book. Improved transportation and using materials already in space will shift the mass balance towards the destination. So this book gives equal attention to transport and using local resources.

&emsp;Many more technologies have been proposed (about 75) than have actually been used so far (about 5), and one of them, Chemical Rockets, has been used by far the most. Chapters 2.1 through 2.10 list the many known and speculative technologies by category. After listing the available concepts, the last chapter (2.11) makes some comparisons, and discuss how to select the best candidates for a given project.

&emsp;Part of the reason chemical rockets have been used so much is "first mover advantage". They were the first type of space propulsion to get serious development. They have the longest history, most optimization of design, and most familiarity, so they continue to be used. That does not mean they are objectively the best solution for all time, and all circumstances. Use of other methods, such as electric propulsion, is becoming more common in recent years.

&emsp;As we noted above, when starting a new project, a survey of all possible technical choices is worth doing, before narrowing the list down to the best candidates. That way no good option is overlooked. That is one reason Parts 2 and 3 attempt to be comprehensive. Also, no single method is optimal for all locations and project needs. For example, it is now common to use a chemical rocket to reach an initial Earth orbit, and electric propulsion for orbit changes afterwards.

 Part 3: Engineering Technologies
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&emsp;Part 3 considers the production and operation technologies used to reach space, and how to use its resources once you get there. Reaching space is a subset of manufacturing on Earth. Use of self-improving systems on that scale is covered under in Chapter 7.0 Industrial Production in Volume I. Production in space, and later use of the products, can use many of the same methods and technologies used on Earth, but adapted to local conditions. There are also some new methds unique to the space environments and resources. The mix of which to use will generally be different for space than for Earth, and differ by location in space.

&emsp;Chapter 3.1 lists overall design factors which affect multiple parts of a space project. Having accounted for transport in Part 2, we then explore the other subsystems that make up a complete system or project (3.2). A large program or project will often have multiple system elements with different purposes and functions.

&emsp;The remainder of Part 3 covers technologies adapted for or unique to space. This includes finding resources (3.3), extracting them (3.4), turning them into useful materials and parts (3.5), assembly and construction (3.6), verification and test (3.7), operation and maintenance (3.8), and finally recycling and disposal (3.9). As we use those terms, a "technology" includes the knowledge and tools needed, a particular "method" describes in general how a given task is done, and an engineering "design" then implements that method in a specific instance.

&emsp;The approach for most space projects so far was to do all the design and construction on Earth, and then launch pre-built and pre-supplied complete items like communication satellites or interplanetary probes. This was adequate for smaller projects. As larger ones are developed it becomes unreasonably difficult and expensive.

&emsp;The International Space Station is an example where it was too large to launch as one complete item, with supplies for its full operating life. Instead it was assembled from smaller parts that each fit within a single rocket launch. Supplies and new equipment are delivered periodically. This reduced the payload per launch to a manageable size, but all the parts and supplies are still being brought from Earth.

&emsp;As larger and more distant projects are considered, the transport requirements continue to go up, and becomes very expensive. This is mainly due to the deep gravity well of the Earth, which requires a lot of energy to climb out of. At some point it becomes more economical for a space project to extract supplies and energy, and eventually do production, locally. Our book gives a lot of attention to these tasks. Doing them in space is new, but there is a long history of engineering on Earth which can serve as a starting point.

 Part 4: Complex Programs
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&emsp;Part 3 looks at individual systems or projects. Part 4 then considers complex programs that evolve over time or involve multiple systems. A key point to understand is no single system works best in isolation. For example, a vehicle without a fuel supply can only travel once, with it's original fuel load. A fuel extraction plant can do nothing without raw materials to work with. Combining these, vehicles can transport raw materials to the plant, and get fuel from the plant for later trips. Then the combined system can operate indefinitely as long as a surplus of fuel is produced from each trip. To design a complete program, you then need to look at all the component systems and how they interact.

&emsp;The parts of a program not only interact, but they can also evolve over time. We can use a highway program on Earth as an analogy. Individual roads started as footpaths, and were upgraded in steps. The upgrades depend on the types of vehicles that will use them, and the existing roads were used to deliver machinery and supplies to construct the upgrades. Individual road projects also connect to form a highway network whose parts must work together. So it will be with sensibly designed large space projects: one set of vehicles and facilities are used to help build the next level of improvements, with all the parts working together.

&emsp;Part 4 has an extensive example of a complex program that both interacts with itself and grows over time. This example serves several purposes. One is to demonstrate how such a program is analyzed and defined. Where different options are presented, we explain how to choose among them. Another purpose is to serve as a proposal for a real-life program that begins with improving life on Earth, then moves into space. In that context you have to go past pure design questions and consider economics and other external factors that apply to such programs.

&emsp;The final purpose is for learning by the "class project" or "lab experiment" method. Skills like working in a team are best learned by doing, and using new knowledge in a project helps fix it in memory. Taking an unfinished part of our example to the next stage of design can be used as a learning tool. Experience working on a realistic design can also be useful if someone intends to work in this field in the future.

&emsp;Our proposed program is likely not the best one imaginable, but it is intended as a starting point to develop further. As individuals and teams use these volumes for their own learning and self-improvement, we hope they will make suggestions and provide feedback so it will improve over time, both as a proposed program and teaching tool.

 Part 5: Design Studies
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&emsp;In this part we include or link to the details of design studies for elements of the program described in Part 4, and other studies we have done. This allows the narrative in the earlier parts of the book to flow without interruption by a mass of detail, and also serves as examples of the types of studies and reports which engineers are frequently asked to work on. The full details showing the step by step assumptions and calculations are usually kept as part of a project's work history, and the results are distributed as reports and other document types for others to use.

&emsp;The first study is a concept-level design for human expansion beyond Earth. It starts by identifying goals and benefits, then criteria for deciding among multiple options. Program-level requirements are then developed to meet the desired goals, and a design approach to meet those requirements. The next part of the study is identifying functions and phases within the overall program. Since various space programs and private projects already exist, the last step is identifying what changes or additions are needed to them. The results of this study have been incorporated into the program described in Part 4.

&emsp;The first study was a broad one covering a complex future program. The second one is more specialized to identify difficult and extreme environments on Earth and in space. Knowing the environment conditions guides the design of equipment and projects that must operate in those environments. The third study is about the need for, justification, and design of an "Open-Source Space Program", by analogy with open-source software. Past government and commercial space projects have been "closed-source" for national security or business reasons. Open-source software development has been fairly successful, so it is worth at least considering using such methods in other areas.

 References and Sources
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&emsp;This volume includes links to references and additional data in two main ways. References or sources that are specific to one method or idea are linked in the main body of the book. In-line links are boldface and capitalized. Additional references that cover multiple topics are included in this last section, along with appendices for data that does not fit in the main text. T

&emsp;The first appendix, for example, lists fictional transport methods which do not have any scientific or engineering basis. They are there for completeness, but as there are no practical prospects to use them, we put them in a separate section rather than the main body of the book. Additional appendices will include reference data that are particularly useful. Most reference data will be linked to as outside references.