The aerospace industry requires an extensive phase of testing, validation, and certification of components and systems. To support those activities, large testing machines are necessary to test full-scale components. The design and installation of such machines can be challenging because of their large dimensions. The SpaceLab project requires designing and manufacturing a machine to simulate the pyroshock capable of simulating the loads acting on payloads during the detaching of rocket stages using explosive bolts. Moreover, a machine is under development to simulate the outgassing of materials in space. To support the design and installation, an Augmented Reality-based tool has been developed to overlay a CAD model of a testing machine in the external environment. A case study has been implemented to show how the tool can support the design and installation activities. The tool has been applied in the field, and good usability, flexibility, and situational awareness results have been noticed.