Tales of the Starship Diana (ST:TOS/STO)

[Prince Charon]

I find myself thinking that by the time they do get back to Federation space, the USS Diana will be unrecognisable as a Hermes-class vessel.

 

[Dahak]

The physics of your setting can very easily restrict you to only one type of FTL.

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The Iconians have intergalactic range instantaneous teleportation that doesn't require subspace. And lots of Omega Particles that they appear to need to run a portal big enough to move a Dyson Sphere.

 

[Neruz]

The Iconians have intergalactic range instantaneous teleportation that doesn't require subspace. And lots of Omega Particles....

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Iconian Gateways do require subspace; they are stated to work on the same basic principles as Transporters, only inconceivably advanced, and Transporters use subspace.

I poked around the Memory Alpha Wiki for a good hour or so earlier and I couldn't find a single mention of any kind of FTL transportation that didn't involve subspace in some manner. As far as I can tell, in Star Trek, FTL = Subspace. Full stop.

 

[RevenVrake]

I'd almost not be surprised if the Sphere-Builders were inspired by the Stargate Ancients in what they leave behind that's more than slightly hazardous to the rest of the galaxy inhabitants.