Currently an officially supported multiplayer mode is not available. Developers have indicated a willingness to develop multiplayer beginning in 2014, and to complete development after the core single player game is released. However, prior to the "Proof of Concept" multiplayer presented by the KMP alpha, forum threads regarding multiplayer were commonly locked (marked "inaccessible").
The most advanced solution is the community-developed Dark Multi Player, or DMP, a multiplayer plugin developed by forum user godarklight, and is available in alpha. It based on Kerbal Multi Player which isn't developed actively anymore.
This page is a catalog of all ideas for multiplayer which people have come up with on the forums, some of which have been implemented successfully. It appears after much discussion that solutions center around 5 general categories of solutions:
Master Controlled Warp
Master Warp: Only certain players or all players have the power to advance time at the lowest available common warp factor. This idea requires communication between players prior to warping. This is great for small network games where the multiplayer focus is usually on close quarters or EVA/IVA operations. Either designated warp admins have the power alone to advance the time warp, or all players do. The amount of maximum warp is limited to the lowest warp factor available to all players (so if a player is landing, the max factor is lower than if all player ships/evas were in interplanetary space or in an observer mode). Communication between all players would be essential to avoid collision or physics catastrophes. "Battening down the hatches" would be a regular occurrence in such games, but EVAs would certainly be a lot more fun! This seems the most logically doable of all ideas.
- Agreed Warp:
"Solutions to warping problems *IF* multiplayer gets added" (inaccessible)
- The Multiplayer Project:
Time warp only is allowed relative to the player initiating it, or whenever a player's ship or EVA is within a certain distance max time warp availability slows down for both players using it in increments until time is x1 in close quarters, or whenever a player logs off the server advances the shared game state to the most advanced time stamp relative to the most chronologically advanced player. Least realistic of all options since it introduces warping of planets and/or other objects that require sometimes illogical reconciliation, paradox-inducing abnormalities, or unforeseen physics consequences unless players share the same time frame; yet this idea has brought forth the most successful implementation of multiplayer to date.
- DarkMultiPlayer (DMP)(recommended!) - Also supports master controlled warp and no warp:
- Kerbal Multi Player (KMP)(Dead, Not updating) :
- L.O.G Multiplayer System:
"Idea the LOG Multiplayer System" (inaccessible)
- Not Your Average Multiplayer Discussion:
"Not your average multiplayer discussion" (inaccessible)
- another time synch:
Pass the savegame file to the next person in line, or a shared savegame file that is asychronously updated by various players. Successfully doable with current game mechanics.
- Kessler - asynchronous shared save file
- RPG Multiplayer
- Symbolic Link
Not multiplayer but a shared social gaming experience. Think of friends playing individual games of solitare while all at the same table, able to share strategies, view each other's work, or even pass cards (ships) to each other.
- Telemachus Mod - Mission Control style game control where a single player flies the craft, but data is shared with mission control participants who can call out values and course corrections.
- Kerbal LiveFeed - view live game information from other players playing KSP, and share craft files.
- Kermageddon- view other player ship orbits in your game.
No Time Warp
Just as it says. No Time Warp. Games are loaded from a KSP gamesave file to a server, which is then played in by game clients without any time warp option available to them. Games can be exported from the server (or client) to a new KSP compatible savegame file format which individuals can then play in KSP with, and even warp, and then reload that KSP savegame on the server for a new No Time Warp event. This is really a variant of MCW but without specifying a warp process with players in a game.
- EVA Multiplayer
"EVA Multiplayer" (inaccessible)