[See-Bee9]

Summary

This closes the README TODO "Adjust technology tree make it reasonable, such as can only be researched after you landed on the frozen planet." With Space Age, refrigeration now depends on a supply chain that starts on Aquilo. It is also researched at the same tier as the other Aquilo technologies.

Without Space Age, the recipes and technology costs are unchanged. The new storage logistic refrigerator is the only addition there.

Why

A refrigerator slows spoilage 20×. That changes how you play Gleba and how you ship spoilables between planets. Until now it unlocked with red and green science, so a player could get past most of the spoilage logistics Space Age is designed around before even reaching Gleba.

Aquilo is the cold planet, so gating refrigeration there fits the theme. It also makes refrigeration a late-game reward rather than an early shortcut.

What changed (Space Age only)

New supply chain

Step	Recipe	Made in	Notes
HFC refrigerant (new fluid)	20 fluorine + 30 petroleum gas → 50 HFC (2 s)	Cryogenic plant	Only on Aquilo (surface_conditions pressure = 300). Listed under Aquilo processes.
Sealed cooling coil (new item)	50 HFC + 5 copper plate + 2 plastic bar → 1 coil (5 s)	Cryogenic plant, or assembling machine 2 or 3 (cryogenics-or-assembling)	Needs a fluid input, so it can't be handcrafted. Only HFC is tied to Aquilo: it can be barrelled, and coils can be shipped.
Refrigerator	1 coil + 1 electric engine unit + 10 iron plate	By hand or in any assembler	Replaces the old recipe of steel chest, processing unit, fuel cell and plastic.
Logistic refrigerators (×4)	The refrigerator's ingredients + the matching logistic chest	By hand or in any assembler	Uses the refrigerator's ingredients rather than a finished refrigerator, which saves a crafting step.

Only the coil step is locked to particular machines. HFC already ties every coil back to Aquilo, so the refrigerator and the logistic refrigerators can be handcrafted. Locking them to the cryogenic plant as well would make placing a few refrigerators tedious and would not strengthen the gate.

Technologies

• Refrigerator:
  • New prerequisites: cryogenic-plant, cryogenic-science-pack and agricultural-science-pack. The existing ones (electric engine, processing unit, plastics) are kept.
  • Cost: all ten science packs, the same set as the vanilla Aquilo-tier technologies (quantum processor, fusion reactor, railgun). Metallurgic and electromagnetic packs are included because reaching Aquilo already requires them. Leaving them out would make a technology gated on Aquilo cheaper than the trip to Aquilo.
  • Unlocks HFC, the sealed cooling coil, the refrigerator and cryogenic oil processing.
• Logistic refrigerator, preservation wagon and preservation inserters: raised to the same ten-pack set. Each is built on the refrigerator, so none should cost less than the technology it depends on. Each technology gets its own copy of the science list, so another mod can change one of them without changing the rest.
• Science counts and research times are unchanged. See my comment below.

Cryogenic oil processing (new recipe)

100 crude oil + 50 ammonia → 90 petroleum gas, in 5 s. It runs in the cryogenic plant, allows productivity, and is unlocked by the Refrigerator technology.

HFC needs petroleum gas on Aquilo, where crude oil only arrives by ship. This recipe gets more gas out of that imported crude without a full refinery and cracking setup:

Method	Petroleum gas per 100 crude
Basic oil processing	45
Cryogenic oil processing	90
Advanced oil processing, fully cracked	97.5

It gives twice what basic oil processing does but less than full cracking, so cracking stays the most efficient option. The tests check both limits, so a later change can't quietly make the recipe too strong.

The recipe has its own entry in the fluid recipes group, next to the other oil processing recipes. As in vanilla, its icon shows the product (petroleum gas) in front of the ingredients (crude oil and ammonia). Like vanilla's basic oil processing, it sets main_product = "" so it doesn't merge into the petroleum gas entry.

What changed (all games)

• Storage logistic refrigerator. With this, there is a refrigerator for each logistic chest type: passive provider, requester, buffer and storage.
  • The Logistic Refrigerator technology unlocks it.
  • It has one filter slot, the most the engine allows a storage chest.
  • It is added to the list of containers that control.lua tracks, so it actually slows spoilage.
• Locale: English and German names and descriptions for the storage refrigerator, HFC, the sealed cooling coil and cryogenic oil processing.

Existing saves

Every existing prototype keeps its name (refrigerater, logistic-refrigerater, logistic-refrigerater-*) and is changed in place, so no migration is needed:

• A save that has already researched Refrigerator keeps it.
• On load, Factorio re-applies the unlocks of technologies that are already researched. In those saves the new recipes (HFC, the coil, cryogenic oil processing, the storage refrigerator) should appear automatically. This is on the checklist below.
• Refrigerators that are already placed keep preserving.

Tests

This adds a busted test suite in spec/, run on Lua 5.2, the Lua version Factorio uses.

• spec/support/data_stage.lua runs the real data.lua against minimal stubs of the base and Space Age prototypes. The specs check the result both with Space Age and with the base game alone:
  • the supply chain
  • the Aquilo-only surface condition
  • the science costs
  • the yield limits for cryogenic oil processing
  • that nothing is added without Space Age
• spec/preservation_tracking_spec.lua checks that control.lua tracks every refrigerator, including the new storage one.
• Running the tests:
  • Locally: bash spec/run.sh. It runs in Docker, so you don't need Lua installed.
  • In CI: the new .github/workflows/tests.yml uses the same Docker image. It runs on pull requests and on pushes to main, with read-only permissions.
• spec/ and .busted are left out of the release zip (release.yml).

Result: 32 passing, 0 failing.

The stubs only include the fields data.lua reads, so the suite can't catch errors the real engine would raise when loading the prototypes. It still needs to be loaded in-game.

Manual verification checklist

• The game loads with no prototype errors, both with Space Age and with the base game alone
• With Space Age, Refrigerator appears after the cryogenic plant in the tech tree
• HFC can only be made in a cryogenic plant on Aquilo
• The coil can be made in an assembling machine 2 and in a cryogenic plant
• The refrigerator and the logistic refrigerators can be handcrafted
• The storage logistic refrigerator accepts robot deliveries and slows spoilage
• The cryogenic oil processing icon looks right in the crafting menu and in alt-mode
• An existing save with Refrigerator researched still works and gains the new recipes

🤖 Generated with Claude Code

[See-Bee9]

A note on research cost: this PR changes which science packs the refrigeration technologies need, but not how many units they take or how long each unit takes. Those numbers are unchanged from when the technologies unlocked with red and green science:

Technology	Units	Packs per unit (Space Age)
Refrigerator	50	all 10
Logistic Refrigerator	200	all 10
Preservation Wagon	100	all 10
Preservation Inserters	50	all 10

The counts were left alone on purpose, so this PR only changes where the technologies sit in the tree and not the balance. I recommend increasing them significantly in a follow-up, though. These are now late-game technologies, and 50 units is very cheap compared with vanilla's Aquilo-tier research. They take 500 (quantum processor), 2,000 (fusion reactor) and 2,000 (railgun) units. Somewhere in the 500–2,000 range for Refrigerator, with the dependent technologies scaled to match, would put it on par with the rest of that tier.