Everything a ship carries and spends: the seven resources, what holds each one, what drinks it, and how far it can travel through a stack.
A resource is counted in units, written u on a part's info card and in the flight readout. Every unit but electricity has a weight, so a full tank is heavier than an empty one and your ship gets lighter as it burns. Rates are per second where they are large enough to see, and per day where they are a trickle.
How far a resource travels through a ship is fixed per resource, and it is what decides where a tank has to sit. Electricity and food run along every joint, so any battery or larder aboard feeds any part that needs one. Fuel travels only through the joints that carry it: a tank's, an engine's, a decoupler's or separator's, a fairing's, a docking port's, and those on the parts that stack inline like the bigger batteries. It does not pass through a pod or a cabin, and no joint on a solid booster carries anything at all. Thruster propellant travels through all of those and through a pod's and a cabin's too.Ablator never moves: a heat shield burns its own and cannot borrow another's.
The readout at the top left: one line per resource the stage you are flying can reach, its level, and in brackets which way it is going.
Oxygen
Resource · propellant
Half of what a throttled engine burns. A Fuel Tank holds half as much again of it as of methane, because that is the ratio the engines drink the two in.
An engine reaches only the tanks its own stage can be plumbed to, which is why the flight readout's fuel lines change as you drop stages. Two ships joined at a docking port become one ship, and then their tanks are one supply.
Methane
Resource · propellant
The other half of what a throttled engine burns. It runs out at the same moment the oxygen does, because the tank holds the two in the ratio the engines drink them.
Both halves live in the same Fuel Tank, so there is nothing to balance when you build: lengthen the tank and both go up together.
Solid fuel
Resource · propellant
The cast grain inside a solid booster. It is the heaviest resource in the game per unit, and the only one that is sealed into the part that burns it.
Figure
Value
WEIGHT
12 kg per unit
TRAVELS
Nowhere: it stays in its own case
STORED BY
Solid Booster · 144 u · Solid Booster S · 72 u
DRAWN BY
Solid Booster 2.4 u/s · Solid Booster S 1.2 u/s
MADE BY
Nothing
REFILLED IN FLIGHT
No
No joint on a booster carries fuel, so a booster can neither be topped up from a tank nor feed one. It lights once, burns its grain at a fixed rate and is dead weight after that. It shows on the flight readout as SOLID FUEL while a booster that still has some is in the stage you are flying.
Hypergolic
Resource · propellant
The propellant a thruster block vents and an Escape Motor burns. It ignites on contact with no spark and no pump, which is why the parts that use it are small and instant.
Figure
Value
WEIGHT
8 kg per unit
TRAVELS
Joints that carry fuel, and a pod's, a cabin's and the Sat Controller's as well
STORED BY
HT-2 Hypergolic Tank · 40 u at its base length · HR-4 Hypergolic Pod · 40 u · HR-1 Hypergolic Sphere · 12 u
DRAWN BY
RCS Thruster Block 0.07 u/s per nozzle firing · Escape Motor 5.43 u/s
MADE BY
Nothing
REFILLED IN FLIGHT
Only by docking
It travels through the same joints fuel does, and through a pod's, a cabin's and the Sat Controller's as well, so a tank on the far side of a capsule still feeds the thrusters bolted around it. It never mixes with the tank fuel: an engine that burns oxygen and methane is untouched by the hypergolic aboard, and a thruster block cannot drink from a Fuel Tank.
Heads up
A block with no hypergolic left fires nothing, silently. Its keys on the flight pad go dead rather than pushing weakly.
Electricity
Resource · power
What keeps a pod alive, a wheel turning, an antenna talking and an instrument reading. It is the only resource that weighs nothing and the only one a ship can make more of.
Figure
Value
WEIGHT
None
TRAVELS
Every joint on the ship
STORED BY
B-400 Battery Bank · 400 u · B-90 Battery · 90 u · PB-20 Battery · 20 u · Crew Capsule · 15 u · Command Pod · 10 u · Passenger Cabin · 10 u · Sat Controller · 5 u
DRAWN BY
Pods and cabins idling, reaction wheels while turning, every antenna, and each instrument reading
MADE BY
SP-6 Twin Array 0.24 u/s · SP-3 Solar Array 0.09 u/s · SP-1 Solar Panel 0.03 u/s · any running engine
REFILLED IN FLIGHT
Yes
A panel's figure is what it makes in full sunlight. Its output follows the light: it falls to nothing in a world's shadow, and a stowed panel makes nothing at all. Which way it faces never matters.
Running engines charge the ship as a side effect, from 0.01 u/s on the Lander Engine up to 0.06 u/s on the Heavy Engine. That covers an ascent and nothing beyond it, so anything meant to sit in orbit needs a panel or a big battery.
A flat ship is not lost, only stiff and blind: the reaction wheels make no torque and the instruments refuse to read. The radio keeps talking, and nobody aboard dies of it.
Food
Resource · life support
The crew's rations. Only a seat with somebody in it eats, and an unmanned ship eats nothing at all.
Figure
Value
WEIGHT
1 kg per unit
TRAVELS
Every joint on the ship
STORED BY
Crew Capsule · 40 u · Passenger Cabin · 40 u · Command Pod · 20 u
DRAWN BY
Each filled seat: Crew Capsule 2 u/day · Command Pod 1 u/day · Passenger Cabin 1 u/day
MADE BY
Nothing
REFILLED IN FLIGHT
No
Food runs along every joint like electricity, so a Passenger Cabin eats out of the pod's larder as readily as its own. That is what makes a long mission possible: add another pod or cabin and the whole ship gets its rations.
Careful
A crew with no food left to reach dies. Count the days a mission will take against what the ship carries before you launch it.
Ablation
Resource · heat shield
The layer of char a Heat Shield boils away to carry a re-entry's heat off the ship. It is spent, not cooled, and there is no making more.
Figure
Value
WEIGHT
1 kg per unit
TRAVELS
Nowhere: a shield burns only its own
STORED BY
Heat Shield · 240 u
DRAWN BY
The Heat Shield itself, faster the hotter it runs
MADE BY
Nothing
REFILLED IN FLIGHT
No
Nothing is spent while the disc is cool, and the hotter it gets the faster the layer goes. While any is left the shield shrugs off heat no other part survives. Once the last unit is gone it is a blunt plate that cooks like everything else, so a second re-entry on a spent shield is a lost ship.
