Tethered Ring Notes
The Techno-Economic Viability of Actively Supported Structures for Terrestrial Transit and Space Launch
Philip Swan, 2023, 20 pages
Reading notes. I will only evaluate claims related to space launch, not as a single-route transportation system.
- p01 masses 100 kg per meter
- presumably this linear mass density includes all above-surface components; containment, rotors, cables to the surface. Immobile surface structures such as floating platforms, or stable convex startup ramp structures over land and topography, will add significant cost and mass, but are probably not included in the 100 kg number. Other surface systems to accommodate tides, seismic events, etc. are also not included.
- note that concave regions will have negative lift at full rotor speed. The author does not describe how the system will transition from stopped to full speed to deployed at altitude from concave earth surfaces.
- Page 17, Fig 21 through 25 show rings passing over various Earth regions. Figures 21 and 22 show complete rings, mostly over oceans, though islands and peninsulas north of Australia will introduce startup concavities.
Figures 23, 24, and 25 show portions of rings passing over Siberia, North America, and Mexico respectively, but not the other side of the globe. Figure 24 shows a path over the center of the United States, with tall mountain ranges and 8000+ foot elevations. Figure 25 shows a ring over central Mexico, over the west and east Sierra Madre mountain ranges running north to south. Ridge elevations above 2000 meters, 6600 feet.
For comparison, the first launch loops will be deployed across 2600 km of the eastern equatorial Pacific, and start up inside a containment underwater, below hull-depth of most ships, where wave action is attenuated. That is similar to a somewhat-smaller-ring version of Figure 21 (avoiding land, perhaps 5000 km diameter?), but 3 times shorter and 0.3% as massive, storing 0.2% of the flywheel (rotor) energy.