Michael “Fitzer” Fitzgerald, et al., (2015) reported that the study team took on the challenge of expanding the “body of knowledge” pertaining to the Apex and Geosynchronous elements of the Space Elevator. A special effort was made to describe the elements in the context of an entire Space Elevator. The report complements and expands earlier ISEC Space Elevator reports on the Climber, Operations Concept, Architectures and Roadmaps, and Earth Port. To do so, we have established:
1. A robust set of definitions within the Geosynchronous and Apex Regions
2. The Strategic Approach to Architectural Development of a Space Elevator
The Definitions:
To ensure complete understanding during this study report, the following definitions are provided:
Space Elevator Column: The volume swept out during normal operations starting at the Earth Port [a circular area within which it operates] and extending through the GEO Region up to the Apex Region. This column of space will be monitored, restricted, and coordinated with all who wish to transverse the volume. The current concept is similar to the FAA’s Automatic Dependent Surveillance – Broadcast approach. Satellites, aircraft and ships will announce where they are and coordinate motion through the space elevator column. Each space elevator has a column of allocated volume.
Earth Port Region: The volumetric region around each Earth Port to include a space elevator column for each tether and the space between multiple tethers when they operate together. The Earth Port Region will include the vertical volume through the atmosphere up to where the space elevator tether climbers start operations in the vacuum and down to the ocean floor.
Earth Port: A complex located at the Earth terminus of the tether to support its functions. These mission elements are spread out within the Earth Port Region. When there are two or more termini of tethers, the Earth Port reaches across the region and is considered one Earth Port. [for full definition and explanation of Earth Ports, see both ISEC reports on Architectures and Earth Ports.]
GEO Region: The Space Elevator GEO Region encompasses all volume swept out by the tether around the Geosynchronous altitude, as well as the orbits of the various support and service spacecraft “assigned” to the GEO Region. When two or more space elevators are operating together, the region includes each and the volume between elevators.
GEO Node: The complex of Space Elevator activities positioned in the Space Elevator GEO Region of the Geosynchronous belt; directly above the Earth Port. There will be several sub nodes; one for each tether, one for a central main operating platform, one for each “parking lot”, and others.
[note: at the GEO altitude, the GEO Node complexes can maintain their locations naturally within the GEO Region.]
Apex Region: The region around the Apex Anchor is defined by the amount of motion expected at the full extension of the tether. The region is the volume swept out by the end of the tether during normal operations. When two or more space elevators are operating together, the region spreads to the volume between.
Apex Anchor: A complex of activity is located at the end of the Space Elevator providing counterweight stability for the space elevator as a large end mass. Attached at the end of the tether will be a complex of Apex Anchor elements such as; reel-in/reel-out capability, thrusters to maintain stability, command and control elements, etc..
[Note: nothing stays at that altitude unless attached to a tether]
As will be discussed in Chapter 4 of this report, the GEO Node is not necessary for IOC per se. Prior to IOC, the GEO Node will provide “overhead” services such as loading and offloading supplies, servicing tugs and other things. However, The GEO Region is expected to become the centerpiece of Space Elevator activities after IOC.
Beyond Initial Operational Capability (IOC), Space Elevator operations at geosynchronous altitude will be critical for business. It will provide services to a myriad of customers. This report examines the transformation of the GEO Region and the maturation of its several GEO Nodes. This transformation and maturation link ISEC’s vision of a revolutionary transportation system and the businesses of Space Enterprise of the mid-Twenty First Century.
The above definitions reveal that the Apex Anchor has not been talked about very much relative to the other elements of Space Elevators. In Chapter 3, this report takes a closer look at its main function as counterweight and other functions necessary for operations. The report then looks at the large number of additional services and functions that might evolve at the anchor. A simple way to look at it is to envision a large transportation end-point enabling onoff movement while ensuring stability of the system. As we see the transformations of the GEO Region to the GEO Node, we see the Apex Anchor maturing; becoming a base for supporting construction/refueling/repair; and, a base for exploration initiatives.
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