From the wiki patch notes for release 6.047.Added new per-control-group toggle to the CTRLS window: Batch Auto-Explore
The idea here is to automatically build and send batches of scouts to get initial scout intel on planets you've never seen before. This is not at all optimal (you'll lose a _lot_ of scouts, and they won't generally concentrate their paths in an optimal fashion) but it can be great for picking up intel on a bunch of planets that are accessible with minimal micro.
Suggested usage:
1) Pick a control group you're not using, and turn this toggle on for it.
2) Build a separate Space Dock, and assign it to that control group.
3) Set the space dock to loop build, and pause it.
4) At that space dock, queue up the number and type of scouts you want in a batch (presumably all you can build, but if you've got some scouts stationed permanently elsewhere they won't be available for this so set the number accordingly).
5) Make sure no other space docks are building those types of scouts.
6) When you're ready to start building the scout batches, unpause the space dock. Having engineers on hand to speed-build the scouts is helpful but not required.
And that's basically it. The dock will build scouts until it has a full batch (according to the numbers you set) and then when the last scout is built it will automatically set the "auto explore" behavior on those scouts. As the scouts die the dock will build more and once it has a full batch again it will set those to auto-explore too. And so on.
This can actually cost a fair bit of metal and crystal, so once your scouts have stopped making progress you'll want to pause that dock again.