Terrain, cover and harbors

Terrain is the rock a fight happens around: asteroids and dense clouds that a ship can hide behind, crash into, or steer round, and a station harbor that fires on anyone who shoots near it.

28 numbers, 3 with an outside source

A0 numbers at grade A
B1 numbers at grade B
C2 numbers at grade C
D0 numbers at grade D
E25 numbers at grade E

Functionality

Values

28 numbers: 1 B, 2 C, 25 E

Each value is read from the game code. Sort by any column heading, or filter by grade or by a word.

Numbers the game runs for terrain, cover and harbors
Quantity	Value	Grade	Source	Why this value
Bulk density of an asteroid, for a body with no published mass	2,000 kg/m^3	BSecondary	Atomic Rockets, usefultables, Rho (density) Table	The density table on the mirror lists an average asteroid at 2,000 kg/m^3.
Which belt each named mid-size body belongs to	Inner Belt Gaspra, Steins, Annefrank, Braille, Donaldjohanson, Lutetia, Middle Belt Mathilde, Outer Belt Ida, Saturn table	CDerived	JPL Small-Body Database: semi-major axes of the named asteroids, semi-major axes of the eight mid-size bodies	JPL gives the semi-major axes: Gaspra 2.210, Annefrank 2.212, Braille 2.339, Steins 2.363, Donaldjohanson 2.384, Lutetia 2.434, Mathilde 2.647, Ida 2.863 AU. Against the game's band edges (2.064, 2.500, 2.824, 3.277 AU) the first six fall in the Inner Belt, Mathilde in the Middle Belt and Ida in the Outer Belt. The table agrees with the game. The band edges are the game's own.
Which belt each of the four giants belongs to	Vesta Inner Belt, Pallas Middle Belt, Ceres Middle Belt, Hygiea Outer Belt table	CDerived	JPL Small-Body Database: semi-major axes of the named asteroids, semi-major axes of Vesta, Pallas, Ceres and Hygiea	JPL gives Vesta 2.361, Pallas 2.770, Ceres 2.766 and Hygiea 3.151 AU. Against the game's band edges (2.064, 2.500, 2.824, 3.277 AU) Vesta is in the Inner Belt, Pallas and Ceres in the Middle Belt and Hygiea in the Outer Belt. This agrees with the game's table.
Radius from a field center within which real members and mined rocks lie	120 km	EAuthored	Atomic Rockets, prelimnotes, Science-Fictional Shibboleths	The game chose a radius that puts several bodies in one fight, far closer than real spacing.
Radius around a field's center in which a fight begins	150 km	EAuthored	No source recorded	A captain comes to work a field, so the game starts a fight at a random point inside this radius.
Height above a giant's surface at which a fight begins	50, 300 km	EAuthored	No source recorded	The game chose a range of altitudes above a giant body.
Smallest body that can hide a hull	2 km	EAuthored	No source recorded	A hull is tens of meters long, so the game chose a body a few kilometers across as the smallest that can hide it.
Dense clouds in a field	1, 3 clouds	EAuthored	No source recorded	The game chose a few clouds, so a field has cover without being full of it.
Radius of a dense cloud	20, 50 km	EAuthored	No source recorded	The game chose a cloud tens of kilometers across.
Boulder size in a cloud, used to set its density	0.5 km	EAuthored	No source recorded	A cloud is modeled as a density and not as ten thousand rocks, so the boulder size only sets how thick it is.
Optical depth at which a look or shot is masked	1 optical depth	EAuthored	No source recorded	At an optical depth of one, light has fallen to about a third. The game chose that as the line at which sight and a shot are masked. The sources are silent on this figure.
Distance the helm keeps off a rock's surface	1.5 km	EAuthored	No source recorded	The game chose a margin that is large next to a hull and small next to a body.
Time the helm looks ahead along its own velocity to avoid rock	240 s	EAuthored	No source recorded	The game chose a look-ahead long enough to turn a hull away at its fastest approach.
Distance past a rock's surface at which a hiding hull sits, away from the foe	3 km	EAuthored	No source recorded	The game chose a margin on the far side of the rock.
Range within which a crew looks for cover	150 km	EAuthored	No source recorded	The game chose a range that makes cover a short move and not a long trip.
Distance ahead along a body at which a hull going round it steers	30 km	EAuthored	No source recorded	The game chose a point ahead so the hull flies the curve and not the chord.
Least rock between a hull in cover and the foe	1 km	EAuthored	No source recorded	The game chose a depth so a foe that drifts sideways does not uncover the hull at once.
Speed above which touching a rock destroys a hull	0.01 km/s	EAuthored	No source recorded	The game chose ten meters a second. No source gives a hull strength against impact. The sources are silent on this figure.
Length of a station as a target for a stray round and its point defense	2,000 m	EAuthored	No source recorded	The game chose a harbor that is much larger than a hull, which is tens of meters long.
Point defense model on a station	35mm PD Autocannon catalog name	EAuthored	No source recorded	The game chose the heaviest catalog mount under the superheavy size.
Point defense mounts on a station	6 mounts	EAuthored	No source recorded	The game chose a number that a stray round cannot overcome.
Distance of a belt harbor from a field's center	150 km	EAuthored	No source recorded	The game chose a distance that puts the harbor inside the fight area.
Height of a giant's harbor above the surface	100 km	EAuthored	No source recorded	The game chose an orbit height above the giant body.
Radius of the no-fire zone around a harbor	25 km	EAuthored	No source recorded	Fights happen just outside the zone, and the zone is a safe harbor to run to. The game chose the radius.
Seconds between a station warning and the garrison firing	5 s	EAuthored	No source recorded	The station hails and waits this long. A longer wait let a stream kill a ship first.
Quiet time after which a shooter counts as having stopped	20 s	EAuthored	No source recorded	The game chose it so the warning ends once a shooter has stopped, while the file entry stays.
Marines in a full level-1 garrison	100 marines	EAuthored	No source recorded	The count is taken from the game's own garrison strength rule. No source gives a station garrison. The sources are silent on this figure.
Marines needed to man one standard coilgun	25 marines	EAuthored	No source recorded	The game chose it so a garrison's guns come from its size.

Real-world basis

4 points

Space is nearly empty, so a body can hide a ship only if it is larger than the ship by a wide margin.
A ship that touches rock at speed is destroyed, so the helm keeps a clearance and looks ahead along its path.
A line of sight through a dense cloud is blocked once the light is mostly absorbed, which is an optical depth near one.
A station garrison fires on a shooter that ignores a warning.

Game and reality differences

2 points

Real bodies over 1 km are about 900,000 km apart. The game puts several in one field and a dense cloud inside 300 km, because a fight needs something to hide behind.
A cloud is a smooth density and not ten thousand boulders. A real field would be a swarm.

Source absences

5 points

Atomic Rockets does not provide values for the following:
1. Safe distance from a rock.
2. Impact speed that destroys a hull.
3. Size of a station harbor. 2,000 m is authored.
4. Size of a harbor garrison. 100 marines in a full level 1 garrison is authored.
No source on the shelf provides values for the following:
1. Bodies in each belt. The orbits are recalled, unverified.

Sources

3 documents

Atomic Rockets, usefultables, Rho (density) Table: An average asteroid is 2,000 kg/m^3; carbonaceous asteroids 1,380 and stony asteroids 2,710 (kg/m^3). (all uses)
Atomic Rockets, prelimnotes, Science-Fictional Shibboleths: Bodies wider than 1 km are on average about 900,000 km apart. "Canon labels the fighting field as the fiction." (all uses)
Atomic Rockets, mining, Asteroid Mining: The four giants Vesta, Pallas, Ceres and Hygiea take their size and mass from here and from Wikipedia. (all uses)