Collins Aerospace, a subsidiary of Raytheon Technologies, is a key supplier of aerospace and defense components. This company specializes in aero structures, avionics, interiors, mechanical systems, mission systems, and power and control systems. As a top innovator across many sectors, Collins Aerospace wants to optimize their current methods of heat storage in space vehicles. Existing PCM heat exchanger configurations contain multiple PCM passages which make fabrication difficult, time-consuming, and expensive. Accordingly, the purpose of this project is to design, manufacture, and test an additively grown Phase Change Material (PCM) heat exchanger. The use of a PCM is desirable because it allows heat to be absorbed without any major changes in temperature as it changes from solid to liquid. It also benefits from the microgravity environment it must operate in. The new design is made up of a unique, monolithic, lattice structure which houses a single PCM volume. This configuration significantly simplifies manufacturing while still maintaining effective heat transfer and operating safely under designated conditions. The heat exchanger’s scalability and resulting data suggests that a full-scale model could be used as a heat sink in a real spacecraft.