Moon & Mars Orbiting Spinning Tether Transport - Tethers Unlimited

Tethers Unlimited, Inc.Tether Rendezvousover half a minute. Figure 14 shows the length of tether deployed in these various cases. The load leveltrace for the 0.1 s braking case shows that halting the deployment instantaneously (which would likely beunrealistic in practice) causes a sharp tension spike to 0.2 of the tetherÕs load capacity. The tension thenbuilds as the tether accelerates the payload along. At T=25 seconds, the tension spike reflected from thefacility end of the tether returns to the tether tip, causing the tension to exceed 0.6 of the tetherÕs capacity.Halting the deployment more gradually eliminates this initial tension spike, allowing the tether tension tobuild more gradually. However, the tether tension still peaks at almost 0.6 of the tetherÕs capacity.Figure 12 and Figure 13 show the tension level at the tip, middle, and facility end of the tether forcases where the deployment is halted immediately and braked over 10 seconds, respectively. In the 10second braking case, rebound of the tether causes the tether to go slack at about T=60 s. This isundesirable because it could permit fouling of the tether on the PCV or Payload.10.8Capture after 5 secImmediate Halt of DeploymentTether TipMiddle of TetherLoad Level0.60.4Facility0.200 20 40Time (s)60 80 100Figure 12. Load level of the tether when payload is captured after a 5-second tether deploymentmaneuver, and tether deployment is halted immediately after payload is captured.10.8Capture after 5 sec.Deployment Braked over 10 sec.Tether TipMiddle of TetherFacilityLoad Level0.60.40.200 20 40Time (s)60 80 100Figure 13. Load level of the tether when payload is captured after a 5-second tether deploymentmaneuver, and tether deployment is slowed to a halt over 10 seconds.9