The power model

The power model is the set of rules for the ship's electricity: a reactor plant that fills a battery bank, and a table of loads that draw from it.

23 numbers, 5 with an outside source

A0 numbers at grade A
B1 numbers at grade B
C0 numbers at grade C
D4 numbers at grade D
E18 numbers at grade E

Functionality

1 topic

Power and the capacitor

Power is the electrical cost of fighting, as heat is the thermal one.
The CAPACITOR is a bank that starts the fight full.
It holds 2.8 times what the reactor makes in 20 s, and the reactor refills it every second.
Rail and coil guns draw on it, and so do the pumps.
Heavy fire leaves less power for the pumps, and a gun waits on an empty bank.
Autocannons and canisters draw nothing.
A holed reactor makes less power.
SCRAM | with the fins crippled and the tank boiling, the engineer asks to shut the reactor down.
Scrammed, it makes decay heat only, and nothing refills the bank.

Values

23 numbers: 1 B, 4 D, 18 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 the power model
Quantity	Value	Grade	Source	Why this value
Seconds in one round, over which a plant's output is counted	20 seconds	EAuthored	No source recorded	The round keeps the length of the old menu fight round, so one rule serves both fights. No source gives a round length.
Bank size in rounds of the hull's own rated reactor output	2.8 rounds	EAuthored	Atomic Rockets, power, batteries table (Lithium-Ion rechargeables)	Atomic Rockets gives lithium-ion cells at 100 Wh per kg for a bank's mass and no rule for its size. The bank size keeps the ratio of the old size-class ladder. The sources are silent on this figure.
Energy of one power point	9,330,000 J	DAnalogy	Atomic Rockets, spacegunconvent, Navy railgun comment: full scale weapon designed to use 64 megajoules	A Navy handout quoted in Atomic Rockets says the full-scale railgun is designed to use 64 megajoules. The game scales one power point so a standard gun draws that energy at a chosen efficiency.
Share of the plant's thermal power that becomes electricity	0.25 share	BSecondary	Atomic Rockets, power, Space Nuclear Power Program (SAFE-400 and Prometheus)	Atomic Rockets lists the SAFE-400 space reactor at 400 kW thermal and 100 kW electric, which is 25 percent, and the Prometheus reactor at 1 MW thermal and 200 kW electric, which is 20 percent.
Decay heat after a scram, as a share of full thermal power	0.035 share	DAnalogy	No source recorded	The Way-Wigner fit, read on Wikipedia, gives about 4 percent of full power ten seconds after shutdown for a long-run reactor. The game uses a recalled round figure near it. The sources are silent on this figure.
Power a rail firing draws, by gun size (a coil draws a share of it)	Micro 3, Light 5, Compact 8, Standard 11, Heavy 16, Superheavy 22 power points	EAuthored	Atomic Rockets, spacegunconvent, Navy railgun comment: full scale weapon designed to use 64 megajoules	Sizes are chosen so that reactor output covers about two standard guns a round. The 64 megajoule Navy railgun in Atomic Rockets fixes only the scale of one power point.
Coil firing's draw as a share of a rail's	0.2 share	DAnalogy	Atomic Rockets, spacegunconvent, Railgun and coilgun efficiency	Atomic Rockets puts the Navy railgun at no better than 42 percent efficient and a large coilgun at 90 to 95 percent. The share is the energy ratio of two game muzzle speeds times the ratio of those efficiencies.
Guns that draw no power	Autocannon, Canister mechanisms	EAuthored	No source recorded	The propellant in the case throws a cartridge round, so the feed motor draws little beside a rail shot. Atomic Rockets gives no feed motor power. The sources are silent on this figure.
Pump power as a share of the heat moved	0.01 share	DAnalogy	No source recorded	Water-reactor coolant pump motors run several megawatts each, about 1 percent of the heat they move. This is recalled from NRC data, not opened. No source gives a figure for a space plant. The sources are silent on this figure.
Order the rule sheds fight loads in, first shed first	sweep, guns, pumps bill	EAuthored	UK MCA, MSIS003 Part 7: Electrical Equipment and Installations, 7.6, Load shedding	UK surveyor guidance says load shedding must not cut services essential for propulsion and safety, and lets the owner choose the order of the rest. The order here is chosen.
Order the rule sheds voyage loads in, first shed first	services, shop, recycling, cold bill	EAuthored	UK MCA, MSIS003 Part 7: Electrical Equipment and Installations, 7.6, Load shedding	UK surveyor guidance says load shedding must not cut services essential for propulsion and safety, and lets the owner choose the order of the rest. The order here is chosen.
Chance a destroyed reaction chamber scrams the reactor in a round	0.5 chance	EAuthored	Atomic Rockets, emergency, Nuclear Reactor Emergency SCRAM	Atomic Rockets describes a SCRAM button and gives no chance that damage trips a reactor. The value is chosen for play. The sources are silent on this figure.
Full reactor containment, the scale for reactor integrity	100 points	EAuthored	No source recorded	The game counts reactor containment in points on a scale it chose. No source gives such a scale.
Reactor containment at or below which the reactor counts as crippled	40 percent	EAuthored	No source recorded	Chosen by the game as the same 40 every vital system uses; unlike the fins and the air, containment at zero is a kill, so the line warns of the end.
Containment lost per point of damage a round does inside	9.1892 percent per damage point	EAuthored	No source recorded	Anchored to a measurement: the median breaching round carried 3.7 damage (909 rounds, 150 joust fights, 2026-09-28), which keeps the old fixed loss of 34 for that round. The anchor is a game measurement, not a source.
Chance a round that got inside is near the reactor	0.22 share	EAuthored	No source recorded	Chosen by the game and rolled only after a round beats the plate; the notes record 13 percent of kills as reactor kills at the first build and 47 percent once a holed face let rounds in. No source gives a chance.
Capacitor charge by hull class (the old ladder)	LIGHT CRAFT 60, MEDIUM CRAFT 84, HEAVY CRAFT 120 power points	EAuthored	No source recorded	The old ladder of 60, 84 and 120, kept for callers that still read it; the bank now holds the rounds set by BANK_ROUNDS of the hull's own output, and the old steps all worked out to 2.7 to 2.9 rounds.
Output a point of engineering skill adds to the reactor, as a share of the plant	0.0036 share per point	EAuthored	No source recorded	Chosen by the game as the strength it had on the old heavy plant: a veteran engineer at 70 added 10 to 11 of 42 points a round.
Share of the plant's rated output an active sweep draws	0.25 share	EAuthored	No source recorded	The notes take the mirror's one radar at 100 megawatts as a quarter of the largest plant (401 megawatts), so every hull pays that share; the radar figure was not reopened here (UNVERIFIED).
The three fight bills: order the rule sheds loads in	pumps first sweep, guns, pumps, guns first sweep, pumps, guns, sweep before guns guns, sweep, pumps orders	EAuthored	UK MCA, MSIS003 Part 7: Electrical Equipment and Installations, 7.6 essential loads	Three orders chosen by the game; the standard lets the order of shedding suit the owner's convenience (7.6) and keeps propulsion auxiliaries off the list, which supports a bill the captain picks.
Bill a hull follows when its captain has not chosen	pumps first order	EAuthored	UK MCA, MSIS003 Part 7: Electrical Equipment and Installations, 7.6 essential loads	Pumps first, chosen by coldweld; the electrical standard names propulsion auxiliaries essential.
Bill each kind of hostile hull follows	WARSHIP pumps first, RAIDER guns first, MERCHANT sweep before guns orders	EAuthored	No source recorded	Chosen by the game: a warship pumps first, a raider keeps its guns, a merchant would rather see and run; no source covers a raider's power rule.
Hours a reactor that went down in a fight stays down	4 hours	EAuthored	No source recorded	Chosen by the game for every hull; the mirror and the sources shelf are silent for a fast reactor. The sources are silent on this figure.

Real-world basis

7 points

A nuclear plant makes heat, and a generator turns only part of it into electricity.
The rest is waste heat, which is why a plant also needs radiators.
A reactor makes steady power, but a weapon wants a huge burst, so a ship stores energy in a bank and draws on it for the burst.
When a reactor is shut down it still makes heat for a time from the decay of its fission products, so it still needs cooling.
A merchant ship has more than one generator, and if power runs short the ship drops its non-essential loads in a set order.
That drop must not cut the loads a ship needs to move and stay safe, such as pumps, steering and alarms.
The ship's owner may choose the order of the non-essential loads, and on a warship the engineer officer controls the circuits in an emergency.

Game and reality differences

4 points

The sizes in WEAPON_POWER_BY_SIZE are authored so reactor output covers about two Standard guns a round.
The reactor plant is sized from each hull's weapon slots plus pumps for a full drive's heat for one round, not from a real plant design.
The bank starts every fight full, refills each second by the plant's output, and is never carried between fights. The reason is the fight reset.
What is built and what is not changes stage by stage.

Source absences

7 points

Atomic Rockets does not provide values for the following:
1. Restart time for a scrammed reactor. Not built.
2. Decay heat share. 3.5% is recalled from the Way-Wigner formula, unverified.
3. Hotel load per hand, beyond about 30 kW of life support for six crew, unverified.
4. Pump share of the heat it moves. 1% comes from NRC water reactor pumps, unverified for a space reactor plant.
No source on the shelf provides values for the following:
1. Vital load list for a warship. NSTM chapter 320 is the likely source and was not opened.
2. Load shedding. The Navy damage control manual says only that each repair party restores casualty power.
3. Feed motor draw of a cartridge gun. About 115 kW for a GAU-8 is recalled, unverified.

Sources

8 documents

Atomic Rockets, power, Fission power (SAFE-400 heatpipe reactor): The page lists the SAFE-400 as a 400 kW thermal, 100 kW electric heatpipe reactor, which is a 25% conversion. The game uses that ratio. (all uses)
Atomic Rockets, power, batteries table (Lithium-Ion rechargeables): Lithium-ion cells hold about 100 Wh per kg, or 0.36 MJ per kg, with a life of about 400 recharge cycles. The game cites it for the bank's mass. (all uses)
Atomic Rockets, spacewarship, Space Warships: Power Generation, Waste Heat, and Firepower: A warship's power storage can be ultracapacitors, and the page gives 60 Wh per kg and 0.1 TW of discharge for a 5% share of a very large hull. (all uses)
Atomic Rockets, spacewarshipart, multi-mode reactor for burst power: A reactor in closed-cycle mode runs at only 3 to 4% of burst power, and its decay heat goes to radiators. Open-cycle cooling is used for bursts. (all uses)
Atomic Rockets, spacegunconvent, railgun efficiency: The Navy railgun is no better than 42% efficient, so most of a rail shot's energy becomes waste heat. The game derives the coil share of 0.2 from it and a large coil's 90 to 95%. (all uses)
Atomic Rockets, atomicfuel, Power reactors (decay heat): Short-lived fission products keep heating the fuel after shutdown, and this decay heat sets the cooling needed after a reactor stops. (all uses)
UK MCA, MSIS003 Part 7: Electrical Equipment and Installations, 7.6, Load shedding: Shedding must not cut the services essential for propulsion and safety, and the order for non-essential services may suit the owner's convenience. The page is a UK merchant ship surveyor guide, a secondary source here. (all uses)
Standard Organization and Regulations of the U.S. Navy (SORM), 6.4.1 e, engineer officer, item 7: The engineer officer controls electrical circuit usage to prevent further damage. SORM writes no order from the commanding officer for it. (all uses)