Interstitial Mass Transit System

The Interstitial Mass Transit System — also known synonymously as the STS after the company that maintained it — was a public transport and freight network, derived from transmat technology, that linked humans' settlements throughout the Sol system between the late 21st and mid 22nd centuries AD. It was run by the Sol Transit System company from a central control facility located beneath Olympus Mons on Mars. (DW: Transit)

Characteristics
Like transmats, the system relied on carrier waves transmitted between stations. At each end of a station platform was an induction system — Lorenzo attractors held in a precise pattern by a gravito-magnetic field. It required only a slow but constant rotation of the inductors to generate the multi-frequency carrier waves that connected the station nodes; the presence of a carrier wave could be confirmed by the presence of a visual event horizon. While signals could travel along the carrier wave, physical objects were incapable of moving through; two sets of inductors simultaneously spun at a matching harmonic while the correct amount of power was fed into the carrier wave was required to establish a sub-space tunnel through which a real object could pass. The physical dynamics of the tunnels and the dimensional translation were controlled by field regulators whose output was rated in angstroms. A device called a gateway compensator was responsible for preventing matter annihilation in the event of signals from multiple sources being simultaneously reintegrated in the real world.

Trains were energy shielded as a safety precaution to prevent the torque effects of crossing the event horizon of a tunnel shredding them apart. Freesurfers — individuals using surf boards to traverse the interstitial vortices — replaced the energy shield with a complex sonic wave generated through the use of mantras, but left the surfers exposed to the psychedelic sensory input of subspace-transit. Passage through a tunnel imparted real-world momentum; while trains had technological counter measures to this acceleration, the purpose of a freesurfer's partner was to chant a counter-mantra that acted as a brake.

Originally locomotives had to possess generators powerful enough to generate a shield large enough to cover the entire train in a single field to enable all-at-once dimensional transition, but advances in technology led to the creation of split-section integrators that could handle carriages individually in real-time as they passed the event horizon of a tunnel. (DW: Transit)

History
By the middle of the 21st century, humanity had developed close-ended transmat technology to a degree of technical reliability, energy efficiency and cost effectiveness that it replaced traditional means of freight transfer. However, an attempted Martian invasion exposed a number of critical and systemic flaws in the T-Mat network. This and the manner in which the subsequent war was won through the mass transmat of human troops onto the Martian surface saw T-Mat replaced by an interstitial mass transit system that combined matter transmission with specially adapted trains similar — running on friction fields instead of rails or monotracks — to those of the British Underground.

Significant components of the initial system infrastructure were sourced from the Yamatzi Corporation of Japan, and the Central Line was established before the turn of the 22nd century. Although newer branches were able to benefit from improvement in technologies and methodologies — such as the claimed affinity Africanmanufacturers possessed for using the transient nature of reality as a basic operating principle — older ones were more likely to be serviced than replaced.

By the 2110s, the network had grown into what those familiar with it liked to call a sprawling beast. As a result the STS Special Maintenance crew enjoyed pointing out that very few people understood just exactly how the entire system worked and all of them were on that crew. While the veracity of the claim was never tested, the Chief Controller granted them a great deal of latitude in their behaviour in return for their ongoing expertise.

By the end of the decade, the decision was made to open the first interstellar line. Properly called the Stellar Tunnel — and more referred to more commonly by the portmanteau "Stunnel" — it reached 40 light years between Mars and a planet in the Arcturus system. However,the quantum mechanics involved in maintaining and opening the connection allowed a hostile intelligence to punch through into this dimension from its own and infect the system. The incident resulted in the massacre of high ranking members of the Union of Solar Republics, and led to the abduction and physical mutation of several passengers throughout the network into a beach-head invasion force.

Around the same time, the network's convoluted and complex structure spontaneously generated a self-sustaining high-functioning artificial intelligence. This AI, the Special Maintenance crew, the Eighth Doctor and Kadiatu Lethbridge-Stewart were responsible for defeating the invasion and forcing the hostile intelligence to return to its home dimension, thereby releasing Henrick, who had been functioning as its host. (DW: Transit)