Space Transport and Engineering Methods/Introduction

To complete a desired space project, historically the transportation to reach a temporary location was the primary engineering problem to solve. In future projects building a more permanent, sustainable infrastructure will become as important as the transportation. This book is intended as a survey and introduction to the available methods, and how to combine them into a complete system.

The first section categorizes the many known and speculative space propulsion methods by the propulsive force and energy source, and additionally by development status. The engineering literature is vast, so we will not attempt to reproduce it here. Instead we will give references to obtainable sources, and where the data is not easily found, include it here. After listing the available concepts, the next section will discuss how to select the best candidates for a given project. This is primarily through the discipline of Systems Engineering, whose goal is to optimize a complex system over it's life cycle.

The third section discusses engineering methods for a more permanent and sustainable infrastructure. Historically all supplies, and some energy have been brought from Earth. For larger future projects that would incur too much transport cost. A more optimal solution is to obtain supplies and energy locally. Since fuel and structural components for vehicles are part of the supply needs, the infrastructure and transportation have to be considered as a combined system, which is discussed in the last section.

Transport Methods

Many more methods have been proposed (about 60) than actually used to date (about 5), and only one, chemical rockets, has been used by far the most. Part of the reason for that is "first mover advantage" for chemical rockets. They were the first type of space propulsion to get extensive development. Therefore they have the most history, optimization of design, and familiarity, and so continue to be used. That does not mean they are objectively the best solution for all time, and there is increasing use of alternate methods. When starting a new project, a complete survey of all the possible methods is warranted before narrowing the list down to the best candidates, so that no good option is overlooked. That is one reason the list in this book attempts to be comprehensive. Additionally, no single method is optimal for all locations and mission requirements.

Engineering Methods

The primary method performing space projects to date has been to launch pre-built and pre-supplied hardware from the Earth, such as communication satellites or interplanetary probes. That is adequate for smaller projects, but as larger ones are contemplated bringing everything from Earth pre-made becomes unreasonably difficult and expensive. The International Space Station is an example where it would be impractical to launch as one complete item with supplies for it's full operating life. Instead it was constructed from smaller parts that fit within rocket launch capacity, and is supplied periodically. This then requires a support infrastructure from the ground. As larger and more distant projects are considered, even delivering in sections/periodically starts to become impractical. This is mainly due to the deep gravity well of the Earth, which requires a lot of energy to climb out of. So at some point it becomes more economical to extract supplies and energy locally in space.

Combined Systems

In addition to interacting at any given point in time, a combined transport and support infrastructure can evolve over time. An analogy can be made to road systems on Earth. They started as footpaths, and were upgraded over time, but not independently of the vehicles that used them, and the existing roads were used to deliver machinery and supplies to construct the upgraded version. So it will be with sensibly designed space projects - using one level of transportation and infrastructure to help build the next improvements.