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FTL in Astra Planeta
All known interstellar civilizations in the Astra Planeta canon are capable of faster-than-light travel, in some cases (skae and Calypsians) thanks to the teachings of humanity, but mostly because of their own scientific merits. The only known form of macroscopic FTL travel is the warp drive, which has historically been achieved a few hundred years into each civilization's spacefaring age since the physical and engineering challenges that must be overcome to actually make a working prototype are extremely complex.
A warp drive works by bending spacetime in such a way as to simply amplify the vessel's real velocity; it doesn't actually generate any acceleration. An object's real velocity at warp drive activation determines its FTL velocity, but it takes time to accelerate to that real velocity at a safe acceleration (one standard Earth gravity). What results is a tradeoff between the time spent speeding up and slowing down, and the time spent in warp, which varies depending on distance and real velocity.
Finding the optimal interstellar vector utilizes a simple asymptotic formula (created by @catgirlbionics, thanks again!) involving three variables: the distance to the target in lightyears (d), the warp amplification factor (a), and the maximum real-space velocity of the object as a decimal value of the speed of light (v). This function equates to the total flight duration in days (T).
(707.646*v)+((d/(a*v))*365) = T
By plugging in specific values for (d) and (a), and then deriving the function, its positive local minimum will be equivalent to the shortest possible travel time and ideal velocity for the given interstellar vector. For example: a modern Generation VI warp drive has a maximum amplification factor (a) of about 4000, and the distance between Sol and Alpha Centauri (d) is about 4.34 lightyears. Using these values in the formula results in an optimal velocity (v) of about 0.0237c, and a minimum travel time (T) of 33 and a half days!
Warp drives have limited usefulness due to the enormous amount of power they require and the peculiar effects of bending spacetime. Acceleration must be accomplished in real-space or else the exhaust from the engine will reflect off the drive's event horizon and cook the ship, and the same goes for any heat radiated by the vessel. This is why warp drives typically operate in "stuttered" format: an interstellar flight is composed of multiple FTL segments interspersed with periods of real-space STL flight where the ship dumps the heat accumulated by the drive into space via radiator.
Warp drives are not the only method of circumventing the speed of light. Wormholes are also physically possible; however, the largest stable wormholes ever documented are of atomic scale, and anything with rest mass passing through the singularity will cause it to collapse. Wormholes, therefore, are only used to facilitate FTL communication in the form of ansibles, passing extremely narrow laser beams around a network of linked wormholes to achieve near-instantaneous communication.
Because of their nature as loopholes in relativity, both technologies incur some very bizarre effects when it comes to temporal reference frames. Ansible connections where one end is moving at relativistic speed create a combination of wavelength shift and frame dragging that render it impossible to communicate in lockstep; a warpship with a relativistic real-space velocity will result in some time-disparity between passengers and their destination upon arrival. However, it's generally agreed that these complications are a small inconvenience compared to an interstellar society without FTL, where time-slips of decades or more would be a haunting reality.