The next mission in the temporary mission chain was released this morning. The mission is called The Aevax Experiment and it costs 25 energy for 55 experience. 60 shots gets you an NPC battle which rewards a cloak building. You can repeat the mission a total of 15 times. It took me 13 shots to kill the NPC so I'm looking at 1565 energy per building. It will take me more than a week of exclusive energy spend to pick up all 15 of them which is a pretty substantial commitment. So the question is, what does this do and how many do I actually want?
The ergosphere filter is a dedicated defensive structure that provides cloak to a planet. It takes up only 1 space and provides 150 cloak. On top of that it gives your planet a buff for another 20% cloak on top. You can only build one per planet so you can't go super multiplicative on a good planet. Note that even with no other cloak on the planet the 20% buff will give 30 more cloak just from the filter itself so really it's worth 180 by itself.
There is only one building with more cloak per space than 180. It provides 300 for 1 space but you can only get 5 of them total and you can only use 2 per planet. Also note that if you build the filter on a planet with 2 of these buildings the filter is worth 300 for 1 space too. In short even without putting much effort into a planet this is by far the best cloak building in the game. Any planet worth defending with cloak needs one of these bad boys.
But as I said earlier I don't like spend space of defense for most of my planets. Now, 1 space isn't a lot to spend and can end up costing nothing at all just given how space works out. Also there are some good production buildings which will go on every great planet which provide some cloak and the filter will give 20% more from those. From buildings I have access to I can get 40 each from 2 spy uplinks, 150 from a counter intelligence, and 150 from modified grid pylon (also limited to 15 from a mission). Combined with a filter that's 530 base cloak, multiplied up to 636 from 380 without the filter. Double those numbers if you're in a normal full legion (sadly I'm not) and you're looking at 1272 cloak by adding 1 space instead of 760.
What does that much cloak do for you? Planet cloak has only one impact on the game: it makes it harder for other players to scan the planet when they're going scanning. So we need to look at how scanning works to see what this building actually does.
Scanning works on a two roll system. First you make a roll with a chance for success based on your scan value and the number of planets you've already scanned. I don't know the exact formula and it really doesn't matter since cloak doesn't matter here. The game doesn't even know what planet you're looking for at this point. It's just checking to see if you can get anything at all. If that roll succeeds the game picks a planet for you. It isn't clear how that happens but people assume it isn't completely random across every planet. Occupied planets are over-represented it seems but no one knows for sure. If the planet chosen is occupied then a second roll is made. This roll is based on ship scan against planet defense. The chance for success seems to be (1-cloak/scan). So if their scan isn't as good as your cloak you simply can't be found. If they have more scan than you have cloak then how good cloak is depends on how much scan they actually have but it always gives you a chance to stay hidden. (Contrast this with planet defense and attack which can be completely surmounted if you have small amounts.)
To really get a handle on how good cloak is we need to look at some standard scanning values. The actual current maximum scan possible is 15294. However this requires the use of a limited use buff and requires them to have picked the scanning class. (Everyone gets to pick a race and class which each provide benefits. I started with the scan one and did like it a little but have since switched and it seems almost all high level people have also picked something else.) The max without those two percentage buffs is 10620. I have pretty reasonable scanning tech for my level, I think, and my max right now is 3024.
Most of my planets aren't in danger of being attacked by a very high level player, I don't think, even if they find it. Someone around my level, though, would be all over my better selection of planets. Assuming they have 3000 scan, how good is the ergosphere filter? With it they'd have a 58% chance to find it. Without out, they'd have a 75% chance. 17% is a pretty reasonable difference but it doesn't feel game breaking. It feels big enough to justify spending the 1 space for sure, but I'm not as convinced that it's worth all the energy to get them.
In conclusion any planet worth spending a bunch of space on cloak needs to have one of these. And planet with all the production/cloak buildings can make good use of the filter too, but it's not nearly as mandatory. Personally I have one planet that needs to have one. Probably 7 or so that would like one. And I'll probably get more planets that want/need them in the future. If this mission wasn't trapped behind a 500 flux probe mission I'd probably do it a few times and leave the rest for the future. But I'm pretty sure in the long run I'll want all 15 of these at some point and I'm not sure I'll get another chance again. Spending a week's worth of energy isn't something I look forward to doing but it seems like a reasonable price to pay.