This is a bit of a pain to set up, there are five science weapons in the game.
You can follow a quest to do this but I'll tell you the locations so you don't have to spend bits and still get the quest rewards and XP.
When you first travel away from Terra-2 you have access to Hawethornes terminal in his Quarters. Read everything on the computer and it'll start the quest.
Phineas' Lab
In front of his booth when you go there as part of the main quest line.
Groundbreaker
When you first enter the ship and go passed the security guard that impounds your ship the first time you enter. Go passed the security sections office and on the same side of the hall you can find the Bunkhouse of the officers. By the door there is a box, use that to climb on top of the beds. Crouch at the end and force your way through. The Hammer is in there.
Monarch
UDI Labs. More specifically the secret labs of Rizzo.
Go back up to the lab where you went for the Sublight quest for the Good doctor ("The Chimerist's Last Experiment"). At the back of the office right at the end, the back right, you'll see a hole in the wall with a ladded leading up. Run and jump, climb the ladder, jump across again and climb the second ladder to find the weapon.
Cascadia. The wepaon is near the temrinal used during "The Space-Crime Continuum" Sublight side quest.
Scylla
Abandoned Mines. Kill the robots gaurding it and then head to the back. There is a building that is barred from the inside, look to the building on the left and open the door, search the containers to get the second melee science weapon (which is the only useless one).
Now for the annoying part of this trophy.
I gave the Shrink ray to one ally and the Gloop gun to the other, the AI seems to struggle with the Mind-control and when to use it. I had the Mind Control ray and the Hammer. Find an enemy, preferably the last one in the group. Use mind control and wait til you see the effects of the other two guns. quickly switch and hit the enemy with the hammer.
If done correctly the hammer should be the killing blow and the trophy will pop.