## 4 Conclusions  
An experimental technique was developed to enable the study of a single spherical projectile propelled by the detonation of a spherical explosive charge using an EDST. The steel sphere was chosen to simulate an idealized piece of shrapnel from an improvised explosive device. In a first step, an experimental campaign was carried out to study the flight trajectory of a steel sphere in free air and the dispersion of impacts. The main aim was to examine the influence of charge mass and projectile diameter on projectile velocity and flight trajectories. In a second step, the spherical charge is detonated at the entrance of an explosive driven shock tube. Optical techniques using high speed cameras were applied to the blast test arrangement to visualize both the shock wave front and the projectile trajectory. Investigations on the blast loading characteristics, the projectile characteristics, and the time interval \(\Delta t\) have been performed. The different phases of the projectile flight were analyzed using an in-house developed fragment tracking software. As a proof of concept, a case study application where Aluminum plates were subjected to the combined effect of blast wave and projectile impact loading is presented. Finally, the experiments were numerically simulated based on an Eulerian approach using the LS-DYNA FE software. The experiments revealed:  
1. The capability of the steel spheres to maintain an oriented path in free air until impact on the target. The dispersion of impacts is circumscribed within an area which corresponds to the cross-sectional area of the used EDST. 2. The optical measurement technique is able to determine the spatiotemporal evolution of the shock wave and the projectile in all different flight phases. 3. The established laboratory scale technique is able to generate a repeatable combined blast and single projectile impact loading on the target. 4. The capability of the steel spheres to maintain an oriented path inside the explosive driven shock tube when aiming a structure placed at its exit and to limit the dispersion of impacts on the target. 5. The setup guarantees the reproducibility of a planar blast wave (magnitude and arrival time) applied on a target plate placed at the tube's exit. For the same charge mass, the time interval \(\Delta t\) increases with increasing projectile diameter. The numerical work revealed:  
1. The FE model is able to reproduce the peak pressures, the blast wave and projectile arrival times, the projectile velocity, and the time interval. Figure 20: Comparison between experimental and numerical simulation results of the time interval \(\Delta t\) (shown by mean and standard deviation for experiments) at the tube’s exit (1200 mm) for the different explosive charges and projectile diameters. 2. The FE model allows to uncover details about the projectile flight characteristics (three flight phases) and driving mechanism inside the tube. In conclusion, the experimental and numerical investigations performed in this work will prove useful in the domain of the effect of explosively driven inserts in improvised explosive devices. The laboratory experimental technique can be used for future experimental work. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app12146854/s1](https://www.mdpi.com/article/10.3390/app12146854/s1)]([https://www.mdpi.com/article/10.3390/app12146854/s1](https://www.mdpi.com/article/10.3390/app12146854/s1)), Video S1: Typical flight trajectory of a 7 mm diameter projectile attached to the front surface of a detonator after being propelled by the explosion. ([[https://doi.org/10.5281/zenodo.6799391](https://doi.org/10.5281/zenodo.6799391)]([https://doi.org/10.5281/zenodo.6799391](https://doi.org/10.5281/zenodo.6799391))); Video S2: A typical result from the high-speed camera HSC for the flight trajectory of a 7 mm diameter projectile propelled from the explosion of 10 g C4 at the entrance of the explosive driven shock tube.