This is my idea for how I think Fast Travel could be implemented. Please feel free to comment and let me know you're thoughts.
So basically the idea would require to main things. A new element, for now I'll call it a FTL Drive. An the second thing would be Data for the location of the celestial body the player wants to travel too. I say celestial body because it doesn't have to be a planet necessarily.
Here are the basic rules I came up with on how it would work.
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FTL Drive Element:
The FTL Drive is a craftable item that basically works by distorting space and allowing dynamic constructs to travel to and from celestial bodies only within a single solar system.
The FTL drive must be linked to at least one or more space engines on a dynamic construct to access this function.
The FTL Drive requires its own special fuel in order to work.
The FTL Drive also requires spatial data of a celestial body, in order to travel to that location.
The type of Celestial bodies that can be traveled too depends on the spatial data gathered by the nanoformer.
The FTL Drive is not instant, it takes a few minutes travel time (similar to super cruise in Elite Dangerous) and depends on the space engines size/quality/ or quantity.
The FTL Drive will only drop the player off in orbit, or near the celestial body, but not to close.
OTHER IDEAS
By default, the basic function only allows fast travel to the closes celestial body that the player has data for.
Linking the FTL drive to more then one engine can increase the range, and/or speed.
The FTL drive doesn't work if its linked to damaged engines.
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Spatial Data
Players can use their nanoformer to gather general spacial data of celestial bodies that they visit. this data can then be used with a FTL Drive to fast travel to that location.
In order to collect this spacial data, a player must be at that location in orbit or the surface, but it will take time (1 hour for example), and the player must stay in range of that celestial body until the process is done. But, how long it takes to collect this spatial data depends on a players Talent tree.
The nanoformer "basic" function can only keep data for a limited amount of celestial body's, and must be upgraded via the skill tree to hold data for more locations.
This function must also be upgraded, using the "talent tree", to save spacial data for different types of celestial bodies for example: Terrestrial planets, Jovian planets, Asteroids, orbit of the Star, Comets, etc.....
This data can be saved to a Chip, and sold or traded to other players.
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That's the basic idea. I tried to think of limits and link certain aspects of its use to the Talent tree, to add some gameplay reasons for it being in the game.
The reason I suggest using the nanoformer for collecting spatial data, is so that a player is never left out of being able to use fast travel. Even if you're a new player you can collect spacial data with you're nanoformer, and have the basic means to fast travel. Maybe this could be even linked to the Pilot Talent Tree to make navigation a even more viable skill.
I'm against using gates for inter-planetary fast travel, because this would just become a PVP bottleneck that only Pirate groups, and large orgs would benefit from, An that would defeat the intended purpose. Traveling to planets will be a common thing for players, so fast travel should be accessible to all players.
I agree with JC that fast travel is a necessary gameplay mechanic for the longevity of DU. long travel times is great to scifi enthusiast, but in a videogame, taking hours to go from planet to planet will get old very fast, and most gamers aren't that patient.
Please share you're thoughts in the comments.