Astronauts are about 3.33 blocks tall, much taller than the player. This means that they require a 4 block tall space in order to move around. Astronauts of different colors will occasionaly attack each other. If you encounter a random Disk lying around, or craters made by Brown Mobs, enemy Astronauts may be in the vicinity. Astronauts will also attack other Mobs; finding Biogel may also mean that Astronauts are in the area. They also may spawn from out of nowhere. Another way to find Astronauts is if you encouter an Astronaut Lair which is surrounded by Polymer on all four sides and is always deeper than 15 blocks in depth. However, not all Astronaut Lairs have Astronauts.
There are five factions of enemy Astronauts, and a single variety of allied (friendly) Astronauts. An Astronaut's affiliation can be determined by the color of his space suit. Each type of Astronaut varies in speed, deadliness and difficulty to kill.
These Astronauts are the slowest and easiest to kill. They are also the most common.
Mint Green Astronauts
These Astronauts move faster and are harder to kill. They are trouble in numbers.
Powder Blue Astronauts
These Astronauts are very fast and can be very hard to kill, much more than Mint Green Astronauts.
These Astronauts are very fast and deadly, and are extremely difficult to kill.
These Astronauts are the fastest and most difficult to kill. They often pair up and remain hostile towards oposing Astronauts, including the player. Luckily, these are the rarest type of Astronauts.
If the player places throws a Refined Gold bar near an Astronaut, the Astronaut might pick it up; and if it does, it becomes friendly. (In order to throw a gold bar, go into the inventory and move the gold bar to the edge of the screen). After the player throws refined gold at the Astronaut or placed by a beacon,the friendly Astronaut seems to run away from the player backwards.
A bright green Astronaut will fire at other Mobs, including other friendly Astronauts, but not at the player. All Astronauts become this color when made friendly, regardless of their original color.
If you fire at a friendly Astronaut and hit it, it turns back into its original color and begins to fire back at you.
Updates 1.7.0 and above have a bug that causes an unending repeated pistol noise, that is heard even when there is no Astronaut in sight. This seems to happen as a direct result of making an Astronaut friendly, and it also happens in Update 1.8 when you place a Beacon. After a little while, the gameplay slows down so much as to be unplayable.
There are a number of ways to hunt Astronauts. One method is to set a v1 turrent on a high position (as it will shoot farther), and it should come running. Hide by drilling in a hill, and putting a block infront of your foot. You will have a 'window' to shoot out of while the astros try to take out your [turrent], you can shoot at them. for any astro higher than white, rank 2/3 turrents are reccomended.
Another method is to find an unabandoned astro lair, toss around 4 gold bars down, and wait until you hear 2 Astros fighting. Then jump down and join the fun!
Attack patterns (On flat ground)
These results are by no means set in stone on how Astros move while fighting.
White Astros- Move forwards and backwards while shooting. They don't jump and aren't particularly accurate if you stay moving.
Mint Green Astros- Move in zigzag pattern while firing. Do not jump to my knowledge.
Powder Blue Astro's- They run left and right and shooting simultaneously and accurately. They will also very rarely fly and shoot at you. I believe that they can fly for an unlimited amount of time but I have no proof.
Pink Astros- run back and forth very fast and sideways every now and then. aren't very accurate.
Yellow Astros- Mixture of white and powder blue. Jump much more often than any others. I believe that these are the most deadly.
Patterns on uneven terrain.
White- Will go to lowest ground. They seem to stay as far away from you as they can while still being in lowest area.
Mint Green- They do not stop shooting unless everything around them is dead or they're dead. And have no obvious pattern.
Powder Blue-They go to the lowest area they can find and move around as much as possible on that layer. From what I saw they do not change terrain whilst fighting to go to higher elevations.
Yellow- Lowest Ground. Moves side to side. Don't change elevation once on low ground.
This is useful because say the white astronaut always moves left and right, you can aim to it's left and it will run into the bullet. That takes practice. Something immediately useful though. If said astronaut is moving left you move right and it can't hit you as easily.