Inter-Dimensional Fatigue — also IDF, dimensional fatigue, or DF — is a catchall term for processes or forces that weaken the boundaries between "dimensions" or space-times, allowing information or objects to pass from one to the other. The form of IDF most familiar to the races of the Alliance is the QuasiSpace Portal Spawner, used to access QuasiSpace from HyperSpace.
The only race known to be familiar with IDF is the Arilou Lalee'lay, who provide the Portal Spawner for The Flagship but otherwise strongly discourage IDF research as incredibly dangerous. The Precursors also had IDF technology, though the only known Precursor IDF devices merely allow for the observation of other realms of existence. Based on strange remarks from the Orz, some have speculated that the Taalo may also have developed IDF technology.
The last known race to have attempted IDF research, the Androsynth, were utterly destroyed as a result. What records exist seem to indicate that acquiring knowledge such as images and other information through experimental IDF technology somehow made the Androsynth visible to entities that exist in other dimensions. The Androsynth's research led to a series of events such as anomalous regions of high gravity ("mosquito mange"), spontaneously generated forces ("poltergeists"), sensory manifestations ("ghosts"), and "reality aberrations".1 In the end, this is probably somehow responsible for the race's disappearance and replacement by the trans-dimensional Orz. The Arilou claim to have protected at least the race of Humans from a similar fate by unknown measures, but warn that any increased knowledge among Humans of IDF phenomena would create similar vulnerabilities.
There is at least one naturally occurring IDF phenomenon, the bi-directional QuasiSpace portal near the Circini and Chandrasekhar star clusters. Interdimensional fatigue is also responsible for the disappearance of the star Alpha Corvi and its planetary system, though whether this was a natural event or not is unknown.2
 Notes and references
- 1The Androsynth computer banks reported several requests for information on phenomena by these names. These are the speculated manifestations and events that might reasonably correspond to these names.
- 2Role Playing Resource Guide, pg. 9
- From a mail by Fred Ford to a Star Control II player:
- This is really just a case of a sleight-of-hand way to cover our incompetence. After we laid out the starmap and assigned names to all of the systems, it was brought to our attention (probably by some accursed tester at Accolade) that two star systems were lacking contiguous sequences (i.e. Alpha, Beta, Gamma, Delta, etc.). Well, we didn't want to rename the stars that we had, because I think we had already sent off a Postscript file for final printing. So the rest is manual history.