Atmospheric entry and the descent corridor

Atmospheric entry is the descent from orbit to a surface through air, where a ship either burns its engines to land or rides the air with a heat shield to shed its speed.

17 numbers, 0 with an outside source

A0 numbers at grade A
B0 numbers at grade B
C0 numbers at grade C
D0 numbers at grade D
E17 numbers at grade E

Functionality

Values

17 numbers: 17 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 atmospheric entry and the descent corridor
Quantity	Value	Grade	Source	Why this value
Rounds in the Blueshifter dive	3 rounds	EAuthored	No source recorded	The dive is a set-piece and not a real entry. The count is chosen for play.
Base chance that a round of the dive goes clean	70 percent	EAuthored	Atomic Rockets, landing, Aerobraking Landing	Chosen with the shape of the game's boarding chance: a base, a scaled stat, then a clamp. The mirror gives no chance that an entry goes wrong. The sources are silent on this figure.
Chance added per m/s^2 of the ship's acceleration	2 percent per m/s^2	EAuthored	No source recorded	Chosen so that a harder-pushing drive recovers a bad entry, the same stat that evasion uses.
Chance removed per point of danger	1 percent per danger point	EAuthored	No source recorded	Chosen as the unit scale of danger against the chance.
Highest chance a round of the dive can reach	95 percent	EAuthored	No source recorded	The ceiling of the clamp, so that no dive is certain.
Lowest chance a round of the dive can fall to	10 percent	EAuthored	No source recorded	The floor of the clamp, so that no dive is hopeless.
Share of the danger rating a failed round takes from the hull	1 fraction of danger	EAuthored	No source recorded	Chosen so that damage on a failed round scales with the danger. The damage formula follows the game's attack roll.
Least hull damage a failed round does	5 hull points	EAuthored	No source recorded	Chosen so that a failed round always costs something.
Hull share at which a failed round aborts the dive	0.2 fraction of maximum health	EAuthored	No source recorded	Chosen so that the set-piece is a risk and not a kill: health floors at 1.
Chance bonus per point of Navigation competence on the descent corridor	0.15 percent per competence point	EAuthored	No source recorded	The standard department shape: competence times a small rate, capped. A navigation crew flies a better corridor.
Most chance Navigation can add to a descent	12 percent	EAuthored	No source recorded	The cap of the department shape, the same as the Gunnery cap in combat.
Chance bonus of a powered descent	15 percent points	EAuthored	Atomic Rockets, landing, Aerobraking Landing	Chosen because a powered descent flies a wide corridor and the tank pays for it. The mirror says aerobraking lands a ship without a powerful engine and saves reaction mass. The sources are silent on this figure.
Chance penalty of an aerobraked descent	5 percent points	EAuthored	Atomic Rockets, landing, Aerobraking Landing	Chosen because an aerobrake rides a narrow corridor. The mirror says the risk is to run out of heat shield or of altitude, and gives no chance. The sources are silent on this figure.
Share of a missed powered descent that lands long	0.75 fraction of misses	EAuthored	No source recorded	Chosen so that a powered descent cannot fail to arrive: its remainder never reaches SKIPPED OUT.
Share of a missed aerobrake that lands long	0.45 fraction of misses	EAuthored	Atomic Rockets, landing, Aerobraking Landing	Chosen with the hard share, and the remainder is the skip out. The mirror describes re-entry skips (Zond 6 and 7) and gives no odds. The sources are silent on this figure.
Share of a missed aerobrake that lands hard	0.25 fraction of misses	EAuthored	No source recorded	Chosen so that the harder misses are rarer than the softer ones.
Travel days of hull maintenance that a hard arrival bills	6 days of maintenance	EAuthored	Design notes: atmosphericentry, The set-piece and the corridor	Sized against the days of neglect that make a hull overdue for maintenance, so that one bad landing is not a crisis and three are. A hard arrival bills maintenance and never health.

Real-world basis

4 points

Aerobraking lands a ship with a streamlined heat shield, called an aeroshell, and uses air friction to remove the delta-v.
The ship must shed its speed before it runs out of heat shield, which is burning up in re-entry, or before it runs out of altitude.
An aerobraking landing needs no powerful engine and saves a great deal of reaction mass, and a powered landing spends that mass to widen the safe corridor.
A re-entry skip, flown by Zond 6 and Zond 7, turned a hyperbolic orbit into an elliptical one. The perigee was not raised afterward, so the orbit still met the atmosphere.

Game and reality differences

2 points

The routine landing is damage-free by canon, because a 2500-era hull shrugs off re-entry. A hard arrival bills maintenance and never current health.
The Blueshifter dive is an alien-megastructure set-piece and is not a real entry. Its health floors at 1.

Source absences

3 points

The Atomic Rockets landing page does not provide values for the following:
1. Chance that an entry goes wrong. Every chance in the table is authored.
2. Price of a hard landing. The days of maintenance are authored.
3. Fuel cost of a powered landing against an aerobraked one.

Sources

2 documents

Atomic Rockets, landing, Aerobraking Landing: Aerobraking and aerocapture use an aeroshell and air friction to remove delta-v. The ship must finish before it runs out of heat shield or altitude. The page also records the Zond 6 and Zond 7 re-entry skips. "use air friction to eliminate your deltaV" (all uses)
Design notes: atmosphericentry, The set-piece and the corridor: The game's own record: the routine landing is damage-free by canon, and the chance formula follows the shape of the boarding chance. (all uses)