Grab it with kinesis and fire it into the reactor. By this time when you turn around the core will be available. To save time you should kinesis the dispenser open and turn around and stasis the reactor to slow it down. The best position to take is to the immediate left of a core dispenser as you should have a good view of all three vents as they appear and will not have to move much in order to get a clear shot. There are dispensers along the walls that will give you power cores. The timer for the achievement will begin as soon as you activate it. You can't miss it as it is part of the story. Carver will then direct you to your left along the cat walk where you will find what looks like a small generator and a computer monitor. As you exit you will find yourself in the reactor room. Immediately after finishing your fight with the heretic leader you will enter an elevator. When you shoot the final 3 vents the achievement will unlock! I have a video below showing this all being done just takes a bit of practise and speed. You need to do this three times and shoot the yellow vents below that stick out. Try to stasis the reactor at a good time so your friend can throw the object into the core (it has 3 levels to it so you have plenty of choice on where to throw) 3. Have one person as the thrower and the other as the stasis guy ( I was the stasis guy) 2. As long as you pour a generous amount of ammo into each one before you hit the ON button, they will all die at this point. You can get them out of the way before the timer starts. There are 4 massive Cysts in the room that fire homing bombs. All you need to do is grab the orbs with your kenesis and throw them into the reactor while it is being hit with stasis, then shoot the yellow vents on the floor below you method as follows. I did this in coop so lets consider this a guide for all the coop players out there. This achievement may take a bit of practise its all down to learning the method and remember stick it on casual mode to make it a walk in the park.

Charging slasher dead space 3