Laboratory Prototype of a Launcher Device by Electromagnetic Propulsion using Superconducting Materials Ricardo Miguel Ramos Almeida Electrical Engineering Department Instituto Superior Técnico, UTL Lisbon, Portugal Abstract — This paper discusses the design and construction of a This paper addresses the development of a linear electric linear electromagnetic propulsion system that makes use of the launcher device based on the characteristic of a diamagnetic property submitted by the diamagnetic superconducting YBCO superconducting, considering the linear electromagnetic materials. This system consists of two parts: the excitation field propulsion technology [4] [5] [7] as the most suitable for this system (fixed structure), consisting of several independent application. magnetic circuits aligned, and the vehicle (mobile system), where it was used a structure with wheels on rails, where a block YBCO A. Main systems of linear electromagnetic propulsion (Yttrium barium copper oxide) superconducting material is The railgun and coilgun are the two main linear inserted. electromagnetic propulsion systems. The railgun system [8] [9] The operation of the implemented propulsion system is based [10] [12] [15] is based on the principle of the homopolar motor, on creating a traveling magnetic wave in the excitation field and characterized by two conducting current rails and also a system, synchronous with the position of the vehicle which the conducting current material projectile. The flowing current in interaction between the magnetic field produced by each vehicle the system generates in the vehicle a magnetic field with a and the superconducting material in, due to the Meissner effect, vertical direction, which combined with the electric current gives rise to an impulse on the vehicle in synchronism with its displacement. through the vehicle gives rise to a force on the vehicle, pushing It was analyzed the magnetic circuit and magnetic field it along the rails. This system has two major problems: heavy distribution of the excitation field system, was finally given the losses by Joule effect and friction in the contact between the resulting force, vehicle’s velocity, impulse and the contribution of vehicle and rail. The system coilgun [11] [12] [13] as depicted each magnetic circuit. in Fig.1, works by establishing a current in each coil in In conclusion, it was verified that the magnetic circuits have sequence along the propulsion system, producing an attractive different contributions depending on the vehicle velocity. The force on the projectile that will move synchronously with the results were compared and analyzed in relation to those provided sequential establishment of the magnetic field. by the developed model for the propulsion system . Keywords- Linear electromagnetic propulsion system, superconductor, Railgun, Coilgun. I. INTRODUCTION Man has always been compelled to travel, transporting materials and hurl / throw, in order to survive [1]. Currently the Figure 1 - Diagram of the propulsion system "coilgun" four key technologies for propulsion systems are: [2] [3] [6] This system requires a sub-system that controls the current, − The mechanical propulsion brings together, for instance, but can be changed without losing its characteristics. One of gears and mechanisms that leverage renewable energy the changes can be, for instance, putting the coils perpendicular sources. to the path of the vehicle. − The thermodynamic propulsion combines the steam system B. Forces in superconducting materials and internal combustion engines. The superconductor is a perfect diamagnetic material, − The chemical propulsion includes rockets propulsion and because it blocks drilling along the magnetic field due to a rocket launchers. magnetic flux generated by currents induced in the opposite direction to the external magnetic field. This phenomenon is − The electric propulsion covers various electromechanical defined as Meissner effect [14] [15] [16]. When the systems such as electrothermal propulsion, electrostatic superconductor is surrounded by a not uniform magnetic field, propulsion and electromagnetic propulsion. the Meissner effect originates the removal forces on the 1 surfaces of the superconductor, as illustrated in Fig 2. The C. Theoretical analysis of electromechanical propulsion combination of all forces generates a resulting force. system 1) Implementation of the excitation field system by independent magnetic circuits Regarding the synchronism required between the vehicle's position and the position of the magnetic field wave generated by the excitation field system, it is achieved in a discreet form by independent magnetic circuits as shown in Fig.4. The propulsion system consists of independent magnetic circuits in sequence and each magnetic circuit is excited in synchronism along the movement of the vehicle, which is caused by the Meissner effect. Figure 2 - Diagram of forces generated by Meissener effect in the superconductor. z II. MODELLING THE PROPULSION SYSTEM USING x SUPERCONDUCTING MATERIAL B A. Modeling of an ideal solution y The propulsion system consists of two main parts: an excitation field system, responsible for generating a traveling Figure 4 - Representation of the excitation system implemented magnetic field wave (B), synchronous with the motion of the in a discrete form vehicle; and the vehicle itself consists of diamagnetic material (superconducting material) inside and where it operates a force The Fig.5 illustrates the functioning of an independent (F) of magnetic origin, arising from the Meissner effect, magnetic circuit in three dimensions. causing on the vehicle a movement of displacement with a S certain speed. u p e rc o n d B. Concretion of excitation field system . The Fig.3 shows a first substantiation of the excitation field system, which is used two linear stators in parallel, as the superconducting material in the middle of them. B F B Figure 5 - Independent magnetic circuit functioning 2) Defining the Magnetic Field Figure 3 - Schematic of the propulsion system with Using the software Comsol Multiphysic 3.2 is feasible to continuous linear stator in excitation and superconductor simulate the behavior of the magnetic field in the magnetic circuit by the finite element method. Using a continuous linear stator allows a propagation of a continuous magnetic field wave along its length origins a Fig.6 presents the simulation results. It shows that there is continuous force and consequently a continuous displacement a higher density of magnetic field inside the circuit than air in the superconductor. However, the implementation of this gap, where there is no superconductor. Thus it’s determined laboratory excitation field system might be complex for a first the magnetic field B in A and B surfaces, where I is current, N study of this kind of system, due to generation of continuous is the number of turns of the winding, f is the thickness of the magnetic field wave and the need for specific measure circuit, δ is the distance between the superconductor and the materials. magnetic circuit, x is the distance already traveled by the vehicle and Rm the magnetic reluctance in A or B surfaces . 2 Observing Fig.8, it’s conclude that there is greater field density B on the surface A than on the surface B, and there is B f also the highest density of magnetic field in the central area of the surface A, therefore consider useful area (2cm 2) of Fig.9. SupercondutorSuperconductor VistaTop D C Circuito SuperiorView EnrolamentosWinding Magnetic SuperconductorSupercondutor magnéticoCircuit δ d x A Magnétic Magnétic Ferro Ferro circuit circuit Vista Front Áreauseful considerada area FrontalView Figure 9 - Representation of useful area ( 2cm 2) at the surface A Figure 6 - Simulation result of the magnetic field in the independent magnetic circuit Table 1 point out the results of the average magnetic field in useful surface area A measured experimentally obtained by N.I N.I B= B = the theoretical model (analytical and simulation). AR (f.x) B R (f.)δ mA mB Table 1 - Results of field B to 3 x positions Besides the theoretical model of the magnetic field of the x [cm] B [mT] B [mT] B [mT] Error [%] ((B .- B .)/B .*100) magnetic circuit, an experimental prototype was constructed analytical simulated experimental sim exp sim (Fig.7) to validate the model. 1,0 151 121 127 5,0% 2,0 151 125 134 7,2% Supercondutor 3,0 151 124 146 17,7% Analyzing the results presented in Table 1, it’s check that for N=600 and I=4A, the analytical field B is equal to any position x, because the model created is considered uniform throu ghout all the excitation system. On the other hand, the error appears to increase with the position x due to edge effects of the field B, the experimental measurement errors (bad position of the probe and difficult to control the temperature of the superconductor) and the values of magnetic permeability used in the simulation were defined based on some experimental measurements. Windwing Magnetic Circuit 3) Determination of Resulting Force Figure 7 - Photograph of the prototype The resulting force F is a conjunction of vector forces Fs generated by Meissne r effect in superconducting surfaces. For The magnetic field on the surfaces A and B of the the deduction of analytical force Fs, the useful area of the superconductor were measured w ith a probe of Hall effect, surfaces A and B of the superconductor, it’s used the method of considering x=1cm, x=2cm and x=3cm. Resulting on the Maxwell Stress Tensor [17].