AppearanceEditDuring FTL transits, the interior of the subspace FTL routes appears as a green spiral vortex with waves of light blue and regular dark space outside the vortex.
The deeper subspace environment beyond the routes used for FTL travel appears as a blue space with the routes and flows appearing as tunnels passing across it and streaks of energy constantly shooting across it .
Subspace is a special, parallel space, apart from normal space, but existing simultaneously and with the same coordinates, in which different physical laws apply and through which ships and transmissions can travel faster than light .
The use of FTL drives causes distortions in subspace - in one case, the distortion caused by multiple drives being used around the same area simultaneously was used to drag a vessel out from subspace . Fluctuations occuring in subspace have to be monitored by navigators  in order for ships to travel safely. There can be collisions within subspace, and when that happens, it slows down the travelling speed of FTL jumps .
Subspace submersibles are capable of diving into subspace and are designed to go deeper into it than other craft. Regular FTL-capable craft are capable of forcibly diving from a transit route, however this will put the ship at risk as it isn't meant to pass through the deeper subspace regions .
The structure of known subspace is generally classified into four distinct regions. The upper layer, also known as the flight layer, is the region which ships normally enter for FTL travel. It is a web-like layer of energy with various streams and flows, some spanning 10,000c. These flows are used as routes for FTL transits, acting as a kind of highway through space .
The middle layer, also known as the turbulent layer, is a high energy region with a disorderly flow, comparable to a blizzard. Normal ships are unable to enter this region safely, though submersibles can safely dive into it. It is also affected by disturbances in the flight layer. The lower layer is a high pressure layer which high energy debris from the flow above may end up. Below that is a dead zone, with no energy flow .
The deepest explored point in subspace is an aggregation zone referred to as the X-Point (Xポイント, X Pointo), discovered by the subspace diver Professor Mugen. At these depths, matter, electromagnetic waves and even nuclear forces are all mixed together, forming a world of pure energy. Under the correct circumstances, the energy stored within this abyss can be released, forming new paths through the upper layers of subspace as it surfaces .
Abyss of HyperspaceEdit
During the spring break before Marika's third year at Hakuoh Academy, a large number of accidents had been occurring in subspace, due to the Yggdrasil Group secretly using submersibles to set off explosives, causing extreme turbulence in the FTL routes .
Following the search for Professor Mugen's legacy, Kanata Mugen reached the X-Point in the Advaseele and penetrated it with the Advaseele's Flint system, releasing the energy within and opening up new FTL routes in subspace .
- The novels use subspace and hyperspace (超空間, Choukukan) inconsistently on different occasions, both meaning the space used for FTL travels.
- The movie's Japanese Kanji title uses subspace but English subtitle uses hyperspace.
- The subspace presented in the anime (including the movie) is vastly different from the novels. The novels gave little mention as to what is inside subspace, and ships seem to get through it with no time spent in it [verification required], there are no specific routes in subspace, and one cannot intercept another in it.