T'au Protection Fleet - Canon Conflict: When the T'au were first introduced into the Warhammer 40,000 universe, their vessels made use of a superluminal drive that still made use of the Warp in a limited fashion. According to the original version of T'au canon, at the time of the First Sphere Expansion, T'au vessels already used a form of gravitic propulsion called an Ether Drive.This technology projected a sheath of gravitic energy ahead of and around the vessel which was continually re-projected further ahead, drawing the ship behind it rather like an archaic sail. For two hundred tau'cyr the Earth Caste unsuccessfully grappled with the problem only for the breakthrough to be handed to them.On the innermost of T'au VII's moons a routine geological survey discovered the remains of an alien vessel. The significance of the find did not disrupt T'au society as much as might have been expected.T'au theorists had long reasoned that other intelligent life forms existed and the verification helped confirm the belief that there was a greater destiny awaiting them. No T'au commented on the unlikely good fortune of finding the technology that they so desperately needed on their doorstep just when they needed it.The T'au were able to reverse-engineer and duplicate the Warp-Drive of the alien starship but the initial test flights were disastrous. Achieving transition to the Warp required more than technology, it required psychically attuned minds and the T'au race had developed no psykers.Without them to guide the transition, no amount of power could breach the dimensional barriers. The best the T'au could do was make a partial transition, forcing themselves into the void that separated Warpspace and realspace before they were hurled out again like a ball held under water, then released.Data gathered at great cost during the test flights was studied closely. The Earth Caste scientists made the observation that the boundary between realspace and Warpspace was not a neat line.It was closer to a turbulent ocean fomented by the tempestuous Warp tides below. By carefully angling their descent toward the Warp and extending the field generated by the gravitic drive into a wing, shaped to hold the vessel down, a T'au vessel could extend the duration of the dive considerably.The speeds achieved in the ascent back to realspace were staggering and this coupled with the effect of the Warp on space-time ensured that the real distance covered by this "Warp dive" was immense. Early tests lost several drone ships because they inadvertently passed far beyond the sensor range of their recovery vessels. The details were soon resolved.There was still a major constraint, only the most powerful (and bulky) drives could sustain the gravitic wing throughout the dive and the power drain meant that considerable recharge time was needed between dives. Also by comparison to actually navigating the Warp the pace was still very slow. Compared to typical Imperial Warp speeds the T'au drive was slower by a factor of five. The speed was consistent though, did not continuously expose the T'au to the perils of the Warp and enabled the T'au to expand beyond their home star system for the first time.