Docking Port Drive
The 'Docking Port Kraken Drive', z-Drive or zompi-Drive is a form of physics exploit which, alongside the other Kraken Drive and ladder drives which use phantom force-based exploits to propel or halt ships effectively forever, at no cost, out of stock parts.
Use and "operating modes"
Docking Port Drives are based on the attractive forces of docking ports. By facing two docking ports against one another, and adjusting the force of one port to increase relative to the other, a net force is generated as a vector from the higher force port towards the lower force port. This net force (which has been experimentally determined to be a maximum of around 9kN) can then provide an acceleration on the vessel. The gap between ports is a key factor in determining the force produced by the drive.
Multiple z-Drives can be used in parallel, increasing the overall force.
The power of the force (up to the maximum value) can be precisely controlled through context menu of the docking port. One indirect method for toggling or controlling z-Drives is to use an inflatable docking port, the extent of which activates and (once activated) modifies the force of the drive within a range, then deactivates the drive based on the distance of the port from its corresponding docking port. By binding the extension of the inflatable docking port to an action group it is thus possible to generate varied amounts of force.
reddit user u/dnbattley has demonstrated that, by duplicating a (n x grouping) junior docking port-inflatable docking port set up in an antagonistic pairing (i.e. in opposing directions), then binding their respective extensions to a KAL in an asymmetric manner, it is possible to use the mismatch of forces to generate a continuous and smoothly variable force from 0 to max which can be directly bound to the throttle.
Other indirect methods of control use robotics to adjust the separation or orientation of the ports as a method of disrupting the drive power, however these tend to be difficult to control accurately.
Construction
While it was initially believed that the drive required self-interaction, experimentation has determined this not to be the case. The distance required to maximise the force is approximately equal to the width of 4 structural plates. Both ports must have their port node "active", i.e. no parts must be attached to the open end.
Background
The first known mention of this effect is on a post made by 'u/74oshua' on reddit here z-Drives were first highlighted on the reddit channel by u/zompigespons (after whom the drive has been named) in August 2020. Unlike many of the physics exploits, z-Drives do not require self-interaction or any second vessel.
Notes
https://www.reddit.com/r/KerbalSpaceProgram/comments/h0jf2k/surprisingly_balanced_emkracken_drive_in_stock/ https://www.youtube.com/watch?v=o5E48mG4jZQ https://www.youtube.com/watch?v=jsFcrnfzjh0
