All this data is potentially out of date, and should be taken with a truckload of salt
Mineral compression is the practice of building goods that have a smaller volume than their constituent minerals, making it easier to transport a large volume of minerals. Once the goods reach their destination, they are reprocessed in order to retrieve the minerals. The compression ratio of an item, assuming a 100% refine, is given as (volume of output minerals) : (volume of item).
Drone alloys are not player-manufactured, but some, most notably Plush Compound, have quite high compression ratios and are logistically useful, provided that they can be obtained in sufficient quantities and at a suitable price.
As capital ship production first grew, so did the use of mineral compression. One widely employed method was to haul modules inside Giant Secure Containers inside cargo-expanded ships inside carrier ship maintenance arrays. At the time, Strip Miners and Ice Harvesters had compression ratios of 300:1. These modules made it possible to move over 4 billion units of minerals in a carrier in a single trip, enough to construct a Titan.
The Jump Portal Generator I had the highest ever compression ratio, at 420:1, but it was not widely used for this purpose, due to the time required to research the expensive blueprint to a sufficiently high material level. Passive targetters were commonly used, as they provided a source of pure 25:1 compressed tritanium, and the blueprints were cheap and quick to research, making it easy to set up a large number of parallel production lines.
As it was felt that this behaviour was contrary to the intended design of EVE, measures were subsequently taken by CCP to reduce the advantages of mineral compression. Initially, the plan involved a 20% reduction of the reprocessing values of all items with 5:1 or greater compression ratios, with the stated aim of making compression unprofitable. However, this idea was dropped, probably because it would have had significant side-effects on the overall mineral supply; a number of the affected modules also drop frequently in NPC wrecks. Most notably, these include top-tier battleship guns, such as the 425mm Railgun I.
In the end, most items that had compression ratios of 25:1 or higher had their volumes increased by a significant factor- for example, the volume of the Passive Targeter I was increased from 5 m3 to 25 m3. In a related change, carriers lost the ability to move ships that contained any cargo other than charges. Finally, a block was placed on fitting capital modules to sub-capital ships; prior to this, it was possible to fit dozens of destroyers with offline jump portal generators and move them in carrier ship maintenance arrays, circumventing the increased volume of these modules.
The Rorqual was introduced as an alternative, providing a means of ore compression, but it remains unpopular for a number of reasons, none of which apply to standard mineral compression:
- Mineral compression blueprints can only be used in a Rorqual, which costs roughly 2bn isk, and each Rorqual has only a handful of production lines.
- When compressing minerals, the ship becomes immobile for 5 minutes at a time, rendering it vulnerable to attack unless deployed behind a POS shield.
- Rorquals cannot enter high-sec space, and are thus cut off from the largest markets.
- Their cargo capacity limits the amount of ore that can be compressed at any one time.
- Even the best ore compression ratio (40:1, with Dense Veldspar) is equivalent to mineral compression at only a 13:1 ratio, vs as much as 34.4:1 in the case of the 800mm Repeating Artillery I.
Demand for mineral compression has fallen with the advent of jump bridge networks, which make it much quicker and safer for well-established alliances to move large cargoes long distances across 0.0 space. However, it remains a useful option for some smaller producers operating in less developed areas, and there is still at least one active independently-run compression service.
The focus of most current methods is on dreadnought-sized ammunition, and the few remaining modules that have worthwhile compression ratios and short build times. Builders of supercapital ships, however, have been known to purchase carriers in bulk, jump them to the build location, and reprocess them into capital ship components. Although this is a time-consuming and expensive process, it can be outsourced, and it removes the need for a large number of dedicated component build slots in the destination system.