I wonder about the specifics of "The Emissary". DS9 has torpedo launchers. If SB 153 had those, did they fire K'Ehleyr towards the heroes, and if so, with or without initial warp speed? Or was she fired from a starship that herself for some reason could not be sent to meet with the E-D, but perhaps provide an initial warp boost not just from the launcher, but from the ship being a warp as well? If neither, what SB 153 asset would have featured probes shaped like torpedoes?
We know that torp-shaped probes can be fired by the Amargosa observatory. Did that one feature a bona fide torpedo launcher, that is, a weapon? Or just a chute that could not deliver antimatter-warhead projectiles? Did Soran's torp-shaped probe fly to the star at warp speed just like his rocket-shaped probe to that other star, or did the torp take half an hour or whatever to cross the distance?
Timo Saloniemi
Here's the dialogue from The Emissary:
"RIKER: Data, what ship is carrying the envoy?
DATA: Apparently there were no starships available on Starbase One Five Three. The envoy is aboard a class eight probe.
RIKER: A class eight probe is just over two metres long.
PICARD: Yes, that's true, Number One. But if the transmitters and the sensors were removed and life-support installed, there would be just enough room for one person.
RIKER: And it is designed to travel at warp nine.
DATA: By sending the probe to meet us rather than diverting the Enterprise, they are saving us six point one hours.
PICARD: Obviously Starfleet feels that time is of the essence.
RIKER: But still, to seal someone inside a class eight Probe and launch it off. It's a hell of a way to transport a Federation dignitary."
So, a class 8 probe is designed to travel at Warp 9.
A torpedo doesn't need life-support system, and it likely comes with its own transmitters and sensors (it would need them to receive instructions if course corrections are required), not to mention a Warp drive. Torpedoes would likely need to have the ability to travel great distances in a short amount of time...
If ships are moving at a speed of (at least) 75 000 km/s and close to the speed of light at maximum, they would have to be FTL capable to overcome sublight speeds of starships and to be effective when fighting at Warp.
Also, we know they can have tracking capabilities, but this is not always used (which seems odd)... or it is, and enemy ships simply have countermeasures which effectively confuse torpedo tracking (and why it seems the torpedoes don't always track their targets... but we've seen even in Voyager that Photon torpedoes aren't always fired in a straight line... the USS Prometheus fired (accidentally) on a Defiant class ship which was some distance away on a Z axis... and as such it had to use a curved trajectory to reach its target.
At any rate, it stands to reason the probe was launched from a starbase towards certain coordinates knowing the Enterprise-D would need to intercept it to effectively reach it and greet the ambassador on-board.
After all, the probe likely didn't have infinite range... but just enough to reach those coordinates... although, WHY didn't SF program it to reach a destination, drop out of Warp and then waited for the Enterprise-D to pick it up?
Could have been limited oxygen supply... especially if it was modified to support a single person, not designed outright with life-support in mind.
Shuttles wouldn't work as they didn't travel at high Warp speeds (if they were Warp capable to begin with).