# Research Progress in the Flight Characteristics of Flyers Driven by Different Technologies
## 3 Research Progress in Flyer Velocity
### Factors Affecting Flyer Velocity
#### 3.2.1 Explosive-Driven Flyer  
Generally, the driving ability of the explosive is positively correlated with its density, while in other conditions it remains unchanged. Furthermore, [PERSON] et al. found out that the flyer velocity can reach a high value when the length-to-diameter ratio of charges is 1.5, which considers the safety and space of the charge at the same time [56].  
According to the Gleny model, the flyer velocity is related to the flyer mass, and a flyer made of lighter material is beneficial to improve its speed. The flyer is mainly driven by the back-and-forth reflection of the shock wave in the flyer. When the charge structure remains  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Measurement Technology** & & **Advantage** & **Disadvantage** \\ \hline Displacement & PDV & Compact, robust, strong speed & \\ interferometer & DISAR & meeting ability & \\  & & DISAR & Direction judgment, no fringe loss & \\  & & & & \\ \hline  & Discrete VISAR & Broad measurement range, high & \\  & & time resolution & \\  & & & Compact structure, short coherence & \\  & & AFVISAR & Length, easy-to-adjust light path, any & \\  & & & time constant & \\  & & & & \\ \hline Continuous & Velocity & ORVIS & High time resolution, simplified & \\ method & interferometer & & data processing & \\  & & Line-VISAR & \(\mu\)m-level spatial resolution, ps-level & \\  & & & temporal resolution & \\  & & 2D-VISAR & Two-dimensional spatial velocity field & \\  & & Fast response, easy operation, compact & \\  & & & structure, low cost, nanosecond level & \\  & & temporal resolution & \\ \hline  & & & Radio transparent materials & Low time resolution, slightly \\  & & measurement, insensitive to surface & \\  & & roughness, low bandwidth requirement & \\ \hline  & Optical beam blocking & Simple structure, anti-vibration, & \\  & & high reliability & \\  & & & high reliability & \\  & MAVIS & Non-contact measurement, has high & \\  & & measurement accuracy & \\ Discrete method & Sensor method & Simple, strong operability, low cost & \\  & & High-speed photography & Simple operation, wide application, & \\  & & reliable results and moderate accuracy & \\  & & & \\  & & Simple and convenient for & \\  & & on-site installation & \\ \hline \hline \end{tabular}
\end{table}
Table 2: Comparison of different velocity measurement technologies.  
unchanged, the flyer velocity decreases with increasing thickness. [PERSON] et al. detected that the maximum flyer velocity is a power function of the flyer thickness [57]. There is an optimal value for the flyer thickness of each material that maximizes the kinetic energy.  
In addition, the barrel diameter should not be greater than the charge diameter under a certain charge structure. Considering the energy utilization rate, the barrel diameter is preferably equivalent to the charge diameter [56].  
Furthermore, [PERSON] et al. studied the influence of submillimeter-sized gaps or cushions on the behavior of flyers propelled by the explosive detonation. According to the results, the jump-up velocity of the flyer under the effect of a submillimeter-sized cushion is lower than the case of the flyer attached to an explosive. However, the submillimeter-sized gap has a greater impact than the submillimeter-sized cushion [58]. [PERSON] et al. obtained comparable results [59].  
Most of the existing work uses test or simulation methods to study the influence of a single factor on the flyer, and it is unable to grasp the correlation between the detonation structure parameters and the flyer effectiveness as a whole.