## 4 Materials and Methods for Designing Tether-Deployed Constellations
### Conceptual Design
#### 4.1.3 Tether-Payload Release vs. Tether-Deployer Release  
When considering tether release methods for the payloads, the tether can utilize a disconnection between either the tether and the payload, or between the tether and the deployer. Visual depictions of the pre-separation, separation, and post-separation states of such systems, for asymmetric and symmetric configurations, are given in Figures 2-13. It should be noted that these figures are generalizations of each release type, and the true exact locations of centers of mass are dependent on spacecraft design and may shift.  
Figure 1: SwingSat concept as a 3U CubeSat.  
In designs separating the tether from the payload, the tether can be left with the deployer and leave no impact on the lifetime of the payload, aside from requiring a tether release mechanism onboard. Such systems are visualized in Figures 2-7. If this is pursued in a system utilizing symmetric releases, however, it is important that the timing of the prograde and retrograde payloads' release mechanisms are synchronized properly to avoid potentially unstable behavior that would result from delayed release sequencing. For example, if a prograde-released payload were one second before a retrograde payload releasing later off-nominally in the opposite direction, the one second period between releases would have the deployer and retrograde payload spinning in an unbalanced fashion like an asymmetric release system, and also result in the retrograde payload being released into an off-nominal orbital plane because of its angular displacement around the rotating system, thus also sending the deployer into a new off-nominal orbit as well.  
To help combat the risks of non-synchronized symmetric tether-payload releases, it is possible to utilize tether-deployer releases instead. Such systems are visualized in Figures 8-13. With this method, the control of release between the deployer and tether can be controlled by a single system within the deployer, helping to ensure that both the prograde and retrograde payloads are released synchronously. An effect of this, however, is that the tethers would then remain attached to the payloads, which can be detrimental or beneficial to the payloads' operation and lifetime, depending on design and application. Negative effects of leaving the tether attached to a payload include an increase in cross-sectional area that increases atmospheric drag while in LEO (gradually decaying its orbit and reducing its lifetime), electrostatic charging while passing through regions of space with high magnetic field and radiation conditions, and additional mass and moment of inertia to handle while doing propulsive or attitude control maneuvers. While at first consideration each of these factors can be considered negative, some of them can also be reconsidered as opportunities for new functions of the payload. If the payload can actuate the tether's length, extending or retracting it on command, it can be used as a variable drag system for maneuvering and de-orbit operations. If the tether is conductive and able to be connected to other payload electrical systems, it can be repurposed into an electrodynamic tether as a power generation system and/or a low-thrust propulsion system.