Moon & Mars Orbiting Spinning Tether Transport - Tethers Unlimited

Tethers Unlimited, Inc.Tether RendezvousRelative Velocity (m/s)500-50-100-150ÆwÆu-200-20 -16 -12 -8 -4 0Time (s)Figure 7. Relative velocity between tether tip and payload during approach. (Æw is velocity along localvertical)Tether Tension BehaviorWhen the tether captures a payload, the tether system must handle a rapid transition from a state oflow tether tension to a state of high tether tension. The sudden loading of the tether causes a longitudinaltension wave to travel up the tether. When this wave reaches the facility end of the tether it is reflectedback, and the wave will propagate up and down the tether until it is damped either by passivedissipation in the tether structure or by active damping by the tether system. Of particular concern is thepossibility that a reflected tension wave could superimpose upon itself and overstress a segment of tether,leading to tether failure. To examine this issue, we conducted a number of simulations of tether-payloadrendezvous, varying the capture time and the methods of tether deployment to affect the tether tensionbehavior.6