Star Trek: The Next Generation had a marvelous little device called a replicator. For the four or five of you reading this who aren't familiar with them, I'll explain. The rest can skip to the next paragraph. A replicator was a device that converted energy, or very simple matter, into much more complex matter, and back. Most of the time on the show, it was used for food. You want a chocolate sundae, you press a button. Zip, it appears complete with glass bowl. When you're finished eating, you put the bowl back in the replicator, and zip, it disappears. But if you wanted, say, a Glock 9mm, you could get that, too. The device was "fueled" by the ship's energy combined with a large store of deuterium in the ship's fuel tanks.
EVE Online has replicators. Really! Only EVE's are better than Star Trek's, because EVE's use no energy and can be 100% efficient.
Say you wanted to move a large amount of minerals somewhere. Enough minerals to build 18 Maelstrom battleships, for instance. It takes about 14.2 million units of the seven basic EVE minerals to build one Maelstrom. Each unit of minerals takes 0.01m3 of cargo space, so you will need 142,000 cubic meters of cargo space per Maelstrom... or roughly three full freighters to move that many minerals. Sounds reasonable, right? Of course, you could build the Maelstroms and just move them. A packaged Maelstrom takes 50,000m3 of space. 18 of them, therefore, take 900,000m3... or about one full freighter.
That's mineral compression. Instead of carrying the minerals for six Maelstroms, one freighter carries the minerals for 18. We've therefore tripled the amount of minerals that one freighter can carry. That's called a 3:1 mineral compression ratio.
If you have well-researched blueprints, you can take a large store of EVE's seven basic minerals and use them to build a full-size battleship, or any other T1 ship or item that you like. But something else you can do: when you are done with the Maelstrom, it is possible -- even without the blueprint! -- to reprocess that Maelstrom back down to nearly the exact amount of minerals that it took to build it. Granted, almost nobody researches the blueprints needed to build a Maelstrom to the fantastically high ME that would required for 100% efficiency. 99.7% or 99.8% is closer to the norm. But you theoretically could.
And in that way, you can move three freighter-loads worth of minerals using only one freighter.
But is that the best you can do? Turns out: that's not even close! Most people use much simpler items, requiring much less complex blueprints. Ammunition, say. Or a 425mm Railgun I. A freighter can hold enough minerals to build 610 425mm Railgun Is. Or, the very same freighter can hold 17,000 425mm Railgun Is... at a mineral compression ratio of 28:1.
Or put another way, that enough minerals to build more than 150 Maelstroms... hauled in one freighter.
The compression ratio for 800mm Repeating Artillery Is is even better: more than 34:1. Once your 425mm Railguns or 800mm Repeating Artillerys arrive where you need the minerals, you reprocess them and get nearly 100% of your mineral investment back. Enough minerals to keep a production line in 0.0 or low-sec going for some time. Perhaps you begin to see why mineral compression is such a big deal. ;-)
Pages 40-42 of the 4Q QEN describes the use of both of these modules in mineral compression. Page 42 even has a cute graphic to show exactly where 425mm Railguns are being built (grey circles) and where they are being reprocessed (red circles).
There's only one hiccup: zydrine. Our freighter hauling 17,000 425mm Railguns is really only carrying enough of them to provide the zydrine for 32 Maelstroms, not 150. We're going to have to supplement our zydrine supply somehow. Of course, if the minerals are going to 0.0, we could just mine the zydrine there, and indeed, that's frequently exactly what happens. It doesn't take very much 0.0 mining to produce the extra zydrine required. In fact, the mineral you run out of most quickly in 0.0 -- every single time! -- is, ironically, tritanium. If only there were a module that we could use to compress large amounts of tritanium, and only tritanium, for delivery to 0.0...
Turns out there is: the Passive Targeter I. Only tritanium is needed for its construction, and it has a compression ratio for tritanium of 25:1. There's that problem solved, and explains why the Passive Targeter I is also prominently mentioned on page 40 of the QEN.
But let's suppose we don't feel like mining. Can we get our zydrine another way? Yes, we can, by hauling Doom Citadel Torpedoes. The compression ratio for them is only 13.7:1, but the bulk of that is zydrine and tritanium... happily, enough zydrine for more than 200 Maelstroms. There are other mods and ammunition that can be used to compress whatever other mineral you like.
Let me be blunt: it's extremely, extremely silly that you can convert minerals to guns back to minerals with no loss at any step in the process. The people who do this go to great lengths to make sure they have perfectly researched 425mm Railgun I or 800mm Artillery Repeating Artillery I BPOs and a 40% station in 0.0 to do the reprocess. Then they go to even greater lengths to make sure they have a toon with the proper reprocessing implant to prevent even the tiniest losses. Even a few percent of loss would probably put the brakes on this practice, given the number of modules that have to be built and then reprocessed, but since we apparently have loss-less Star Trek replicators in EVE, this is how capital ships get built in EVE these days.
If you're flying a carrier, this is probably how that carrier got built. There are people that brag on how much mineral compression they do. There are others that offer it as a service.
Even the danger level can be reduced to ridiculously low levels. Don't want to risk a freighter into a low-sec system to build carriers? Given the high compression ratios, you don't have to. Just use a jump freighter, which can jump directly from high-sec to a low-sec building station with a safe undock. Sure, it reduces your profit margin by a small amount, but for many people, the added cost is worth the greatly-reduced risk. Can't afford a jump freighter? No problem. If you can slip a few T1 haulers into low-sec, you can pack more than 120,000m3 of ammo in their cargo holds, put those haulers into a carrier, and use that.
We're now starting to see second-order effects of this, too. I understand the favored way to build an Aeon super-carrier these days is to use mineral compression to build Archons -- something between 11 and 13 of them, I'm told -- then reprocess those Archons back to the capital ship construction parts they were built from. You can even load the Archon with T1 drones, fill its cargo bay and corporate hangar array with mods, and then fill its ship maintenance array full of haulers full of ammo. Then you put just enough fuel in to make it to your 0.0 station system, unload (and reprocess) everything the Archon is carrying, reprocess the Archon itself, and then load the resulting capital construction components into your CSAA.
Quite efficient, don't you think?
Needless to say, this needs looking at. And it's only one of the threads in the tapestry.