Moon & Mars Orbiting Spinning Tether Transport - Tethers Unlimited

Appendix N. MXER Tether for Deploying MicrosatsTable 1. System Orbital Design for LEO⇒GTO BoostSystem Masses Tether CharacteristicsTether mass 743 kg Tether Length 100 kmCS Active Mass 747 kg Tether mass ratio 3.71CS Ballast Mass 371 kg Tether tip velocity at catch 1,268 m/sGrapple mass 5 0 kg Tether tip velocity at toss 1,148 m/sTotal Facility Mass 1,911 kg Tether angular rate 0.015803 rad/sGravity at Control Station0.70 gTotal Launch Mass 1,540 kg Gravity at payload 1.85 gRendezvous acceleration2.04 gPayload Mass2 0 0 kgPre-CatchJoinedSystem Post-TossPositions & Velocities Payload Tether Post-catch Tether Payloadperigee altitude km 325 405 398 390 470apogee altitude km 325 8446 7199 6103 35786perigee radius km 6703 6783 6776 6768 6848apogee radius km 6703 14824 13577 12481 42164perigee velocity m / s 7711 8979 8859 8739 10007apogee velocity m / s 7711 4109 4421 4739 1625CM dist. From Station m 19765 27365 19765CM dist. To Grapple m 80235 72635 80235∆V to Reboost m / s 240System DesignFigure 2 illustrates the system concept design for the Tether Boost Facility. The Tether Boost Facility is composedof a Control Station, a tapered high-strength tether, and a Grapple Assembly. In addition, a Payload AccommodationAssembly (PAA) will be attached to the payload to provide maneuvering and guidance for rendezvous. ForLEO⇒GTO traffic, this PAA will be an expendable unit incurring recurring costs.To meet the requirement for operational capability with a single launch, the tether facility is sized to be deployedwith a single launch of an Athena-II or comparable vehicle. As Figure 1 shows, the 371 kg Athena Orbit AdjustModule will be retained for use as ballast mass.The control station includes an array of solarpanels which swivel to track the sun as thetether facility rotates. In this design, we havechosen to place the control station at the end ofthe tether, rather than at the center of mass ofthe facility. This choice was made for severalreasons: because it minimizes the dynamicalcomplexity, because it requires only one tetherdeployer, and because the center of mass of thesystem shifts when the payload is captured andreleased.Electrodynamic Tether: The tether in thissystem is composed of Spectra 2000 ® fibersbraided into the Hoytether structure (Forward1995). The nominal length of the tether is 100km. Along the 50 km of the tether closest to theControl Station, a total of 80 kg of insulatedaluminum wire is woven into the structure,Figure 2. The µSat Tether Boost FacilityN-4