## 4 Field Experiment of Fire-Extinguishing Drone
### Firebreak Construction and Fire Suppression Experiment (Second Experiment)
#### 4.2.5 Experimental Results  
As summarized in Table 9, an analysis of the experimental results confirmed that the first and second drones successfully deployed six fire-extinguishing balls consecutively. The GCS operated normally, and the hovering function maintained the drones' balance during the deployment of the fire-extinguishing balls. The accuracy of the RTK-generated paths was 90%, and the error was less than 10 cm. Therefore, the RTK-guided drones  
\begin{table}
\begin{tabular}{c l} \hline \hline  & **Scenario of Demonstration Experiment** \\ \hline
1 & Fire incident near Ansan-Wastadium Development Area; \\ \hline
2 & Transmission of fire location and confirmation of drone flight path; \\ \hline
3 & Although Ansan-Wastadium and the fire location are located along a straight line, the presence of the Central Danwon District Office in between necessitated a route change; \\ \hline
4 & Confirmation of the risk of fire spreading to nearby residential areas, which necessitated the construction of firebreak lines; \\ \hline
5 & Inputting drop locations of fire-extinguishing balls using GCS equipment; \\ \hline
6 & Sequential deployment of two fire-extinguishing drones (drop-type) stationed at Ansan-Wastadium; \\ \hline
7 & Arrival at the fire scene approximately 2 min later at a distance of 500 m; \\ \hline
8 & Accurate route navigation and assessment of on-site conditions using the RTK equipment and camera mounted on the drone; \\ \hline
9 & Upon arrival at the scene, Drone 1 drops six fire-extinguishing balls to establish the first firebreak line; \\ \hline
10 & Upon arrival at the scene, Drone 2 drops six fire-extinguishing balls to establish the second firebreak line; \\ \hline
11 & Fire trucks and firefighters present at the scene directly extinguish the ignition point. \\ \hline \hline \end{tabular}
\end{table}
Table 7: Scenario of demonstration experiment.  
\begin{table}
\begin{tabular}{c l l l l} \hline \hline  & **Performance** & **Performance Result** & **Basis for** & **Measurement Formula** \\  & **Metric** & **and Target** & **Setting Targets** & **Error range within** \\ \hline
1 & Flight accuracy & Accuracy in reaching the mission location & with RTK-GPS & approximately 10 m \\ \hline
2 & Firebreak construction & Construction of first and second firebreaks & Six fire-extinguishing balls per drone & 3 m \(\times\) 6 EA (1.3 kg) \(\coloneqq\) 18 m \\ \hline
3 & Approach to fire suppression & Fire suppression through the first firebreak & Verification of remaining fire & \\ \hline \hline \end{tabular}
\end{table}
Table 8: Performance metrics.  
outperformed the GPS-guided drones; however, there was some variability depending on the weather conditions and solar status.  
During the fire experiment, the six fire-extinguishing balls deployed in the first fire-break activated successfully, resulting in 100% fire suppression. However, a few issues related to firebreak continuity were observed. As illustrated in Figures 7 and 8, the spherical fire-extinguishing balls tended to roll upon deployment, which changed their initial positions. To address this problem, design improvements or system modifications to these fire-extinguishing balls are necessary. For instance, designing the balls such that they split into hemispheres upon impact with the ground could reduce the aforementioned positional shifts and potentially enhance the effectiveness of fire suppression.  
Figure 6: Setting the flight paths of two drones using GCS (Mission Planner) and automatic setting of drop locations at 1.5-m intervals.