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Tycho station is the largest mobile construction platform in the Sol system, and the Belt headquarters of Tycho Manufacturing and Engineering Concern and, covertly, the Outer Planets Alliance (OPA). It is home to a population of over 15,000 people.[1]

Tycho Station, the Belt headquarters of the company, was a massive ring station built around a sphere half a kilometer across, with more than sixty-five million cubic meters of manufacturing and storage space inside. The two counter-rotating habitation rings that circled the sphere had enough space for fifteen thousand workers and their families. The top of the manufacturing sphere was festooned with half a dozen massive construction waldoes that looked like they could rip a heavy freighter in half. The bottom of the sphere had a bulbous projection fifty meters across, which housed a capital-ship-class fusion reactor and drive system, making Tycho Station the largest mobile construction platform in the solar system. Each compartment within the massive rings was built on a swivel system. This allowed the chambers to reorient and to thrust gravity when the rings stopped spinning. The station then flew to its next work location.

Tycho makes regular campaign contributions to Earth and Mars politicians. If anyone were to attack the station, half of the United Nations General Assembly and all the Martian Congress would be declaring the destruction of whoever attacked the station, easily making Tycho Station the safest place in the Belt.

An artificial ring station 700(+) meters in diameter built around a micro-gravity sphere half a kilometer across with more than sixty-five million cubic meters of space inside, Tycho Station is the only shipyard in the Sol System that has the facilities and capacity to build larger vessels than the Bush Shipyards at Luna. Fifteen thousand workers and their families live on the station—a center of Belter culture run by the OPA’s Fred Johnson—with more OPA sympathizers arriving by the day. The manufacturing dome’s massive construction waldoes can secure and move up to Titanic-sized ships (see Ship Sizes in Chapter 6: Spaceships of The Expanse RPG) and are capable of building structures larger than even the generation ship, the Nauvoo, or Tycho itself. The station’s engineering and auxiliary engineering decks are located in the manufacturing dome. A fusion reactor and drive system equal to that of a third-generation dreadnought essentially makes Tycho Station a massive ship and the largest mobile construction platform ever built, more than able to move at high speeds if necessary. Most of the Belt-native fleet construction and maintenance—as much as it can be called that—happens at Tycho Station. A vast number of Belter ships are prospectors, searching for the mineral or gas vein that will finally make them rich. Along with those thousands of rockhoppers, transports, haulers, and some private cruisers and escort ships make up what could be generously called the OPA fleet. Ships working for the OPA can usually expect at least a discount on repairs and maintenance, especially if the damage was taken in service of the Belt.

Once ships are in Belter hands, they often bear little resemblance to what they once were—either brand-new or in a previous life. While Earthers and Martians may have a home on a planet somewhere, many Belters’ only home is their ship, and they renovate and decorate according to a life lived on the float. Even so, their aesthetic could be best described as ‘shoestring.’ Belters make do for too long with barely enough, though Belter ships’ environmental systems are perhaps more meticulously maintained and monitored than even those on MCRN (Martian Congressional Republic Navy) ships.


Habitat ring

The habitat ring is where the population of the station lives. It utilizes spin-gravity, containing the station‘s docks, offices, as well as many civilian homes and facilities. Habitat ring also has ability to rotate its facilities blocks orientations, adapting them for thrust-gravity that Station is capable of.

Construction dome

The construction dome was the central area of the station in which the majority of ships were constructed. The only known vessel not constructed within the dome was the colossal Nauvoo.

Engineering is within the dome including auxiliary engineering and the stations engines.


Eros Incident

At the time of the Eros incident, the Nauvoo was in construction at Tycho Station.

Tycho station Coup

After returning from Ilus/New Terra the Rocinante docks at Tycho for a major overhaul. Upon nearing the completion of this overhaul a ship in proximity to the Station began firing upon it. Simultaneously two Belters in spacesuits stormed Fred Johnson's office but were killed by Fred and James Holden. At various points across the station, security became engaged with the attackers and successfully repulsed them. Station defences also knocked out the attacking ship, but afterwards, it was discovered that a specialized torpedo was fired into Fred's office that grabbed and removed his safe containing the only remaining Protomolecule samples in existence.

Fred would leave the station with a crew onboard the Rocinante, and left the command to Camina Drummer.

Fred Johnson organized a meeting of the Outer Planets Alliance leaders who had not joined the Free Navy at Tycho, however, Fred's death before reaching the station forced James Holden to lead the meeting. During the meeting, a plan was agreed to where the OPA factions would fight against the Free Navy as part of the Consolidated Fleet Offensive whilst also sending two ships to capture Medina Station.

Under the Transport Union

Tycho station was eventually moved from its position to Pallas where it was semi-permanently docked with Pallas to form Pallas-Tycho Complex. At this new location, Tycho resumed shipbuilding and built three Void cities for the Transport Union. A fourth Void city Assurance of Peace was under construction at the Pallas-Tycho Complex when the Laconian Empire battlecruiser Heart of the Tempest, requested the immediate surrender of the union and of the Earth-Mars Coalition or Pallas Station would be destroyed. Deeming Tycho to be too vital to the Sol powers' shipbuilding the majority of civilians were evacuated onto Tycho and ships. Tycho Station then detached from Pallas Station and withdrew away from the area at top speed leaving the doomed station to total decimation by the Tempest's USM field projector.

The Rocinante travelled to Tycho Station after having been contacted by Fred Johnson. Whilst at the station the ship was disguised as a Gas freighter and sent off on a mission for the Outer Planets Alliance.

When it was decided by Fred Johnson's OPA faction to destroy Eros before the Protomolecule could spread the near-complete Nauvoo was commandeered and moved away from the station.

Having learned of the Hybrid pods being fired at Mars Tycho Station OPA fired their stolen strategic missiles at the pods destroying them.

Having returned from Ilus IV the Rocinante put into Tycho for a refit after sustaining damage. At the same time, the keel was laid down, the first purpose-built OPA Navy ship, the Gatamang Feronte was under construction.

Fred Johnson is assassinated by Sakai as Tycho station is under attack by Zmeya and launches a robot that eventually captures the last remaining protomolecule sample.

After the death of Fred Johnson and the withdrawl of all Martian Congressional Republic Navy and United Nations Navy fleets to defend their homeworlds the station fell under control of the Free Navy.



  • Tycho may be an allusion to Tycho Brahe a Danish astronomer and nobleman, whose observations helped support Johannes Kepler theory of elliptic motion of the planets, namely the "Three laws"
  • The station may also be named after the Tycho Crater, the most visible crater on Luna.


  1. The Expanse Novel Nemesis Games - Chapter 5: Holden