Icarus Fall Dictionary (IF)

Hard Science-Fiction Setting

Acceleration

The rate of change in a ship’s velocity. In practice, this determines how quickly you can get anywhere and how much punishment the crew takes. Measured in meters per second squared or in Gs. Long burns at low acceleration are standard for most Belt hauls. Compare Delta-V.

Accelerator

A fixed mass driver used to hurl cargo into new orbits. Belt accelerators range from small ore launchers to massive facilities capable of sending kilotons toward the inner system. Those mounted on asteroids require regular station-keeping to counter recoil.

Albedo

The fraction of sunlight a surface reflects. Dark asteroids have low albedo and absorb more heat, while high-albedo bodies can be spotted more easily at long range. Useful for identifying asteroid type from a distance.

Artificial Gravity

Any method of simulating gravity in space. This means rotation (spin habs) or constant acceleration, which is only possible for a limited time due to constraints of Delta-V and Reaction Mass. All currently inhabited places except Earth and Venus have problematically low gravities, and long-term health depends on Artificial Gravity.

Carbonaceous Asteroid (C-type Asteroid)

Asteroids rich in carbon, organic compounds, and often water ice. Typically classified as C-type. Appear dark due to low Albedo. Valuable for life-support materials and feedstocks in organic chemistry. Often have a loose rubble-pile structure with deep Regolith, making them fragile and prone to dust hazards during mining. Rare on Luna. All of these factors keep the price of carbonaceous substances high.

Degrav

The cumulative physiological harm from long-term residence in insufficient gravity. Symptoms include bone density loss, muscle atrophy, cardiovascular weakening, and balance impairment. Often unavoidable in poorly designed or low-spin habitats. Various health regiments can reduce degrav, but full recovery requires living in conditions of 0.8 to 1.2 Standard Gravity for extended periods, this is called Regrav.

Degrav and Regrav are terms invented for the icarus Fall setting.

Delta-V

The measure of how much you can change your velocity with the fuel or Reaction Mass you have. A ship with plenty of delta-v can pick its fights and its ports; one running low is at the mercy of local traffic and tides. Compare Acceleration, Reaction Mass.

Deuterium

Hydrogen isotope with one proton and one neutron. Valuable for fusion reactors, naturally found in trace amounts in water and ice. Very little is consumed in fusion power, making available supplies abundant and cheap.

Earth Standard Gravity

1 g, the acceleration due to gravity at Earth’s surface: 9.80665 m/s². Used as a benchmark for habitat spin rate, acceleration in space, and human health limits. Gravities in the range from 0.8 g to 1.2 g are considered healthy for long-time residence.

This term is real but the health range is for the Icarus Fall setting.

Fusion Rocket

A spacecraft propulsion system using controlled fusion reactions to heat and expel Reaction Mass. Offers high thrust and high Delta-V for long-range operations. See main entry.

Golden Age

The period from 2102 to 2310. Rapid technological and colonial expansion, ending in Icarus Fall. Characterized by large-scale infrastructure projects, high living standards, and Earth prestige dominating the Solar System.

Gravity

In technical terms, gravity is the force of attraction between masses, with its strength determined by the gravitational constant G (a fixed value) and the masses involved. In day-to-day usage, “gravity” means the apparent gravity a person feels as weight, measured in Earth-standard units of g (~9.81 m/s²).

Apparent gravity can come from three sources: natural surface gravity on a planetary body; acceleration from thrust; or centrifugal force in a rotating habitat. In specifications and scientific notation, g is lowercase. In speech and informal writing, Belters often use a capital “G” (e.g., “the deck’s at one-point-two Gs”).

Habitat

Also called cylinder habitat or rotating habitat. A large, spinning station that generates artificial gravity through rotation. Common long-term living space. See main entry.

Hydrogen Fuel

Common propellant and fusion feedstock. In Belt terms, usually refers to ordinary hydrogen (protium) stored as cryogenic liquid or bound in water ice. Can also refer to Deuterium or Tritium in casual language.

Icarus Fall

Also called the Fall or simply Fall as in the expressions post-Fall and pre-Fall. The catastrophic collapse of the Solar Alchemy Project, which destabilized the Sun and destroyed much of the inner system’s infrastructure. Marks the end of the Golden Age and the beginning of the fragmented, hard-scrabble present.

Ion Drive

A highly efficient electric propulsion system that accelerates ions using electromagnetic fields. Provides low thrust but extremely high specific impulse, ideal for constant low acceleration in long-duration travel. Characterized by low Acceleration and high Delta-V. See main entry.

Kessler Syndrome

A chain reaction of orbital debris collisions, creating clouds of high-velocity fragments that make certain orbits hazardous or impassable. In the inner system, this still blocks some Earth orbits.

Microgravity

An environment where gravity is extremely weak — near weightlessness — such as on a spacecraft in freefall. Prolonged exposure leads to Degrav effects on human health unless mitigated by Artificial Gravity.

This term is scientific, but the Degrav is a concept developed for use in the Icarus Fall setting.

Radiation Shield

Any mass placed between crew and harmful radiation. In space, this usually means tanks of water, layers of Regolith, or waste slag wrapped around the living areas. Small spacecraft shields are lighter and less effective, making storm shelters necessary during solar events. Full spaceships must have good shielding.

Reaction Mass

Propellant expelled from a spacecraft’s engines to produce thrust, as in Newton’s third law. Can be anything from hydrogen plasma to water or even mined rock, depending on the drive type.

Regolith

The loose surface material on an asteroid, moon, or planet — dust, gravel, and broken rock. Can range from soft powder to boulder fields. For Belters, regolith is both a resource and a hazard; it gets everywhere, wears down tools, and can drift into dangerous clouds in microgravity.

Regrav

The period of readaptation to higher gravity after suffering Degrav from extended time in low gravity. Recovery time depends on the severity of the Degrav, overall health, and the gravity difference between environments. Most habitats have Regrav elevator rooms where gravity can be adjusted by going up or down from the central axis for optimum treatment.

Degrav and Regrav are terms invented for the icarus Fall setting.

Remote

In Icarus Fall, a “remote location” is generally only reachable in certain time windows, due to factors such as an eccentric orbit, a high inclination relative to the planetary plane, or a nearby cluster of objects that form a navigation hazard. In this last sense, Earth could be called “remote” due to the remaining Kessler Syndrome, but as the center of human life, it is never considered truly remote.

This term is invented for the Icarus Fall setting.

Small Craft

Often just Craft, or by subtype. Spacecraft not capable of interplanetary journeys or other extended travel. Usually powered by Fusion Rockets. Common types include shuttles for transportation and rated for load versus fighters, further subdivided into interceptors (high Acceleration, low Delta-V), attackers (more balanced), and boarders (extreme Acceleration, very low Delta-V). Endurance measured in hours.

This term is invented for the Icarus Fall setting.

Solar Alchemy

The vast Golden Age project that attempted to manipulate solar fusion output for energy production and stellar engineering. Its failure triggered the Icarus Fall.

This term is invented for the Icarus Fall setting.

Solar System

The Sun and all objects gravitationally bound to it — planets, moons, asteroids, comets, and artificial satellites. In Belt slang, “the System” often refers specifically to the human-inhabited inner system and Belt.

Solar Wind

A constant stream of charged particles from the Sun. In the Belt, it can cause electrostatic charging, erode exposed surfaces, and sometimes create detectable X-ray emissions from certain minerals. A hazard during storms, and a subtle tool for prospectors who know how to read it.

Space Ship

A spacecraft capable of interplanetary travel, usually powered by Ion Drive. Similar to habitats, these feature Artificial Gravity and a Radiation Shield. Endurance measured in weeks.

This term is invented for the Icarus Fall setting.

Spin Gravity

Artificial gravity generated by rotation. In habitats, measured at the inner surface; in ships, often combined with partial thrust. Too fast a spin causes vertigo and gravity gradients. Further from the central axis gravity increases, making lower levels in a habitat suffer progressively higher gravity.

This term is scientific, but the definition had been developed for use in the Icarus Fall setting.

Surface Gravity

The strength of gravity at the surface of a body. Only on Earth and Venus is Surface Gravity suitable for long-term health.

Tritium

Radioactive hydrogen isotope with one proton and two neutrons. Extremely rare naturally; produced in reactors. Used in advanced fusion fuel cycles, mostly for military applications.