It's a bit lazy to call StarMade "Minecraft in space", but I'm going to do it anyway because I am more than a bit lazy. Also, it's fairly accurate, and not in an eye-rolling, dismissive way, but in a somewhat excitable way. Hey, it's Minecraft! In space! In this early access space sandbox, you mine, collect, craft, build, fight, and explore, all in procedurally generated and quite attractive voxel-based 3D universe.
You can begin with a tutorial that walks you through shipbuilding, crafting, navigation, and weapons. The tutorial is pretty clunky and only covers the absolute basics, but it's enough to get you out into space in about ten minutes. Shipbuilding, in its most elementary form, is a literal snap. Throw down a core block, snap on a few power source blocks, attach a couple thruster blocks, and you're free to hop in and roam the galaxy without having to worry about things like cockpits or landing gear.
Of course, you'll want some weapons, like laser cannons, and some protective armor to shield you from other ships. You might want a cloaking device to keep NPC pirates off your six, and some salvage beams for mining resources. There's an advanced building mode to allow you to place multiple blocks at once and build both sides of your ship symmetrically, and some neat ways to link blocks together make more effective weapons and better propulsion and defensive systems. Nicely, you can actually work on your ship while you're speeding through the galaxy: pressing the spacebar while in flight takes you into build mode, which lets you hop outside your ship and rearrange your blocks even if you're currently chugging through the cosmos.
Once you're out in space you can fly to any object you can see, and you can usually see quite a few at any given time. You can visit passing asteroids or planets, land on them, leave your ship, walk around on the surface, and mine them for minerals. I found one planet covered in mushrooms, another with lava pockets and minerals, and another that appeared to have already been half-eaten away, either by some very dedicated miners or perhaps a fluke of procedural generation.
You can drop in on friendly space stations to sell what you've collected and buy new blocks from NPC vendors. You can also call up the galaxy map to search for unexplored planets and plot routes to locations in other sectors. It's all done pretty seamlessly, though you might notice a slight hiccup when a new chunk of galaxy loads or as you approach large, detailed objects in space. You can add a jump drive system to your ship to hop across sectors, and you'll encounter warp gates allowing you to slip through a wormhole to more distant locales.
I haven't done much in the way of crafting, but it's fairly intuitive if you've done it in other games. You need to build a factory block and provide it with power. This can't be done on your ship, but if you're visiting a space station you can treat it as your power supply. Place your ingredients in your factory block, wait a bit, collect your new items, and serve while hot.
StarMade's sandbox mode lets you do your exploration, gathering, and building on your own, but you can play on multiplayer servers as well. I've had mixed success with servers. Lag seems common, even when I have a decent ping, and large bases and ships sometimes take a while to draw themselves even when I'm hovering just meters away. I also had a few issues sticking blocks onto my ship while online, as sometimes it would attach the block to an area I wasn't aiming at.
On the plus side, I was always able to connect with a few heavily-trafficked servers, and it doesn't take long to find other players and gawp at their ships, some of which you'll find docked at stations and others zipping through space. One generous server granted me a million credits just for joining, meaning I could buy a bunch of cool blocks right off the bat. Also—and this is by no means a promise—everyone was being really cool and friendly in global chat. Let's hope that lasts.
I recommend checking StarMade out, and that's a very easy recommendation to make because you can get the current build for free from the official website. You don't even need to create an account to try multiplayer. If you're smitten with it, you can also buy it on Steam: it won't be free to play when it leaves early access, and as development proceeds and features are added, the price will climb.