Moon & Mars Orbiting Spinning Tether Transport - Tethers Unlimited

Appendix F: Tether Boost Facility Design Final Reporttake the tether from a strong thrust region to a zero-thrust region (e.g. 2000 km) inevery orbit.Collision avoidance. Collision avoidance is a demanding application of flightcontrol. All the flight control capabilities listed above may be used. In addition,collision avoidance requires a timely flow of information from a satellite trackingsystem to a decision making system and then to the flight control system. Raisingtether collision avoidance to TRL 6 could be accomplished without performingcollision avoidance against real threats. Rather, the satellite tracking system wouldreport realistic simulated threats to the decision making system. The decisionsystem prioritizes each threat, chooses an avoidance strategy, and sendsappropriate commands to the flight control system of a real tether in flight. Thetether's motion is then monitored to assess whether it would have avoided eachthreat, had the threat been real.Erosion protection. A ground-based program is needed to identify andcharacterize coatings that adhere well to Spectra or to insulation while beingstretched, bent, heated, cooled, and exposed to atomic oxygen and ultraviolet. Thisground-based effort can reach TRL 4. When promising materials are identified, theywould be tested on a pallet attached to Space Station or Shuttle. The pallet wouldprovide bending and stretching forces and temperature control. This experimentwould bring erosion protection to TRL 5. A subscale tether with samples returned toEarth for analysis would be needed to reach TRL 6. Such an experiment could beattached to Space Station, Shuttle, or some unmanned re-entry system.High-voltage, high power conversion. Components of this technology may beseparately developed and demonstrated before an integrated, operational highvoltage,high power system is demonstrated. One is thermal control. Heat rejectionof several hundreds of kW may be developed by Air Force programs or may bepurchased from Russia. A tether-oriented program might do a separate shortdurationdemo of high-voltage, high power conversion itself. This would run for onlya few seconds at a time, demonstrating that the requisite voltage and power can behandled safely. The short run time would prevent heat from building upcatastrophically. It would use stored energy, so PV arrays need not providehundreds of kW. (The energy storage system would have to provide hundreds ofkW for a few seconds.) Such a demo done in space could bring the conversiontechnology by itself to TRL 6. However, an integrated, continuously running systemfor power conversion would only reach TRL 5 (component validation in a relevantenvironment) from that demo and the Air Force thermal demo. To reach TRL 6would require flight demonstration of an integrated, continuously running system.High-power plasma contact with FEAC. A technology demonstration program forFEACs must address two issues: high-power performance and lifetime. We candefine a demo that addresses both issues economically. For high-powerperformance, the issue is how well the large FEAC array contacts the ionosphere.That can be measured with a run time of a few seconds. A brief test like this couldF-20