## 1 Introduction
Suck-back force limits the launcher efficiency, and it is a costly challenge. This work deals with the first four challenges. It introduces a new design based on adding an iron yoke around the launcher coil to reduce the launcher's magnetic reluctance to increase the number of flux lines at a lower current. This modification will lower the required rating of used electronic devices and save money. This iron yoke is manufactured from thin laminated silicon steel to reduce the eddy current and gain high saturation flux density. The magnetic field, the main product of any coil, can only operate in the presence of magnetic dipoles, as in the case of ferromagnetic materials. The ferromagnetic material has a massive array of magnetic dipoles or any material of higher magnetic susceptibility. The authors of [13; 18] demonstrated that magnetic forces could theoretically work according to classical electromagnetism on specific types of materials consisting of intrinsic and permanent primary dipole moments. Here, this theoretical claim has been proven experimentally in the proposed work. This theory and the experiments confirm that the projectile must be made of ferromagnetic materials that contain many magnetic dipoles to provide higher velocity and even motion, in contrast to diamagnetic and paramagnetic materials. Many researchers, as in [8; 19; 20], assumed that the effect of mutual inductance between the solenoid and the projectile, which is considered a one-turn coil according to their theoretical claim, is the reason for the projectile propulsion. The latter claim may come true under some circumstances but not in the case of a solid cylindrical projectile. The proposed research considers the single-coil gun as a building block for a substantial electromagnetic launcher. So, this work focuses on enhancing a single-coil gun to reach an optimal design. A launcher with an exit velocity of 54.3 m/s and efficiency of 0.32% was developed in [7]. In [21], a 2000-joule two-coil launcher was modified to accelerate a 5-g projectile to 54.84 m/s with an efficiency of about 0.375%. In [16], seven cascaded coils are used to reach 130 m/sec exit speed with an efficiency of 1.32% without focusing on the enhancement of a single-coil launcher before cascading many coils. And in [22], a three-winding launcher was developed to accelerate a 7 cm long projectile to 15.66 m/s with efficiency of 2.04%. As the magnetic force is highly related to the magnetic circuit reluctance, as shown in [23], we theoretically and experimentally study the effect of decreasing the magnetic circuit reluctance on the projectile velocity by introducing a new design with a soft iron laminated yoke around the coil. The design depends on decreasing the air gap between the two ends of the projectile. This produces higher magnetic flux density and boosts the number of flux lines. This may cause saturation of the iron yoke earlier than usual, therefore high saturation flux density material is used to avoid that. The presence of an iron yoke around the coil makes a huge change in its inductance according to the armature position which results in an enormous force according to Equation (1). This equation shows that the force is directly proportional to the ratio between the change in the inductance to the change in position. And because the change in position is approximately constant, the force increases as the change in inductance increases. Moreover, referring to previous work [24], the coil is wound in a double circuit to reduce copper losses and increase the efficiency compared to the case of using a single wire. In addition, this configuration extends the launcher voltage range. \[F(x)=\frac{d}{dx}(\frac{1}{2}L(x){i_{L}}^{2}(x,t)) \tag{1}\]  
Researchers in [25] concluded that the armature (projectile) material should be have high saturation flux density as an essential requirement. They also demonstrated the eddy current problem, which negatively affects the device's efficiency because it consumes a significant amount of energy.