The most compelling evidence for the impossibility of Time Travel has always been the complete lack of people from the future, when such things will inevitably come to exist.
With the advent of Chronoportology, it became clear that the reason for a lack of travellers from the future was to do with the availability of information, or lack thereof. As the destination of a time jump required accurate, specific information, the earliest jump date possible was generally around the time that Chronoportology itself was invented. In many minds this rendered time travel largely useless, but helped guard its integrity from some forms of abuse by unscrupulous individuals.
In any case, the act of Chronoporting is not something undertaken lightly; involving a gravitas and severity that was previously associated with the deployment of nuclear warheads. Each ship is made to withstand the intense warping and fracturing of no more than one return journey, with one notable exception; the Temporal Navigator Novodantis.