Pools are excellent places for testing many nautical technologies, as well as training divers or astronauts in simulated weightlessness. The Neutral Buoyancy Laboratory (NBL) is an astronaut training facility and neutral buoyancy pool operated by NASA, and located at the Sonny Carter Training Facility, near the Johnson Space Center in Houston, Texas. In Europe, Blue Abyss Ltd. is currently building the world's largest and deepest indoor pool in Cornwall, also having space applications in mind. However, we believe that an VR solution can overcome the needs of large pools for astronaut training as space equipment can be well-simulated in virtual reality. To this end, we plan in this study to combine diving goggles with a VR head set and to use our small 40 cubic meter pool for simulating a space environment. Besides constructing water-tight VR headsets, tracking systems to determine the position and orientation in space play a crucial role. Two possible solutions are in use: Inside-Out Tracking: The sensors are attached to the VR headset, so the position determination is carried out relative to reference objects permanently installed in the environment. Outside-In Tracking: The sensors are permanently installed in the area, and the mobile object to be measured carries reference markers with it. For optical systems, where cameras are used as sensors, retroreflective spheres or patterns that can be easily and robustly detected optically can be used as reference markers. However, underwater, one has the change in medium, thus refraction, making camera calibration an additional challenge. In the study, we plan to determine the best tracking method and to set up a demonstrator for a sample astronaut training.
