## 3 Materials and Methods  
### Hardware and Software  
For the trial, the Meta Quest 2 (256 GB) virtual reality headset was employed, four equivalent VR headsets were used, each equipped with the corresponding controllers. Due to the specific requirements of the developed VR simulator and the limited hardware capabilities of standalone VR headsets, the devices themselves were incapable of running the simulation independently. To address this, each VR headset was wirelessly connected to a computer equipped with a dedicated graphics card to render the VR simulator effectively. This configuration allowed the headset to transmit control inputs and receive rendered video wirelessly, eliminating the need for a tethered connection and thereby providing greater freedom of movement for participants. Each computer was equipped with a wireless connectivity card, enabling it to establish a wireless hotspot for its respective VR headset. This setup helped optimise video quality and response time for an enhanced immersive experience compared to using a router or a network access point as the wireless network source. A visual representation of the VR laboratory, the equipment used, and the participant familiarisation process is shown in Figure 1.  
The specifications of all the computers used to run the VR simulator, in conjunction with the Meta Quest 2 headsets, are detailed in Table 1. All the computers operated on a 64-bit Windows 10 Pro Version 22H2 operating system and used an Intel Wi-Fi 6E AX210 160 MHz wireless card. The wireless card was configured to broadcast a hotspot on the 5 GHz frequency band, leveraging its higher bandwidth. However, despite the Wi-Fi 6E AX210 supporting a channel width of 160 MHz, the Meta Quest 2 hardware is limited to only 80 MHz on the 5 GHz Wi-Fi spectrum, thereby restricting the maximum possible bandwidth usable. To ensure the best possible experience given the hardware limitations, the Meta Quest 2 Air Link functionality was utilised at its maximum possible bitrate of 200 Mbps. Figure 1: Familiarisation process with VR laboratory equipment. The HMD-VR Engine Room simulator was developed using the 3D modelling software Blender 4.2 and the Unreal Engine 5.4 game engine. The ship's engine room model was developed based on actual blueprints from a roll-on/roll-off (RO-RO) vessel and designed as a double-deck structure measuring 16.1 m \(\times\) 19.6 m. The lower deck contains the two main four-stroke diesel engines with shaft generators and propeller shafts, along with three diesel generators, cooling systems, pipelines, valves, pumps, and other general equipment. The upper deck contains two starting air compressors, one service air compressor, two heavy fuel oil purifiers, a diesel oil purifier, lubricating oil and fuel pipelines, and tanks and valves. The simulator was designed to be compatible with Windows operating systems and supports multiple VR headsets and systems, utilising both wireless and wired connections. Among its notable features are (i) X-ray vision, enabling users to inspect the equipment's internal components; (ii) simultaneous interactions with various tools and equipment, such as running the engines, taking cylinder pressure measurements, valve manipulations, and fire extinguisher priming and utilisation; and (iii) multiple exercise scenarios such as fire, flood blackout, and evacuation (Figures 2 and 3). \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & & **CPU** & & & **RAM** & & **GPU** \\ \hline
**PC** & **Gen.** & **Model** & **Frequency** & **Capacity** & **Type** & **Speed** & **Model** & **VRAM** \\ \hline
1 & 13 th & Core & & 2.10 GHz & 32 GB & DDR5-4800 & 2400 MHz & GeForce & 12 GB \\
2 & 13 th & Core & & & & & RTX 4070 Ti & 12 GB \\  & & i7-13700F & & & & & & GeForce & 12 GB \\
3 & 13 th & Core & & & & & & GeForce & 10 GB \\  & & i7-13700F & & & & & & RTX 3080 & 10 GB \\
4 & 12 th & Core & & & & & & GeForce & 12 GB \\  & & i7-12700F & & & & & & & \\ \hline \hline \end{tabular}
\end{table}