**8. Conclusions and Future Work**

In this paper, we designed and laboratory tested a dual-head electromagnetic propulsion device for the new generation high-endurance quadcopter drone for lucrative earth and other planetary explorations. The beauty and novelty of this model comes from the fact that the proposed quadcopter can fly in an unknown environment without any lift loss for a longer duration than any existing design in the world. The fact is that a feedback control system is invoked for regulating the spinning speed of each rotor separately to retain the predetermined flight path and its hovering uninterruptedly in accordance with the density of the local atmosphere of the planet. In the case of any unexpected vacuum bubbles experienced during the surveillance, the feedback control system regulates the rotors to steer the drone in a favorable region through the polarity changer timing circuit and laser-based timing circuit. We conclude that the proposed new generation quadcopter drone integrated with lightweight electromagnetic propulsion devices is a viable option for achieving high-endurance with improved payload capability for earth and other planetary exploration with the aid of a mixed-reality simulation to meet the flight path demands of the mission. Using the base model of a drone, in this study, we developed a visualized ground control station using a Matlab/Simulink-based control system with mixed reality simulation. Additionally, we addressed mixed reality simulation based on a quadcopter and the X-Plane flight simulator. Through our comprehensive studies, mixed reality simulation is verified and validated. Herein, we connected the real quadcopter to the Mission Planner ground control station, through a radio telemetry device. Thereby, the real quadcopter could send real-time flight data to the Mission Planner. Note that we used X-Plane as the simulation platform. For mixed reality simulation, we developed a connection interface between Mission Planner and X-Plane in MATLAB. By using the developed connection interface, the virtual quadcopter in X-Plane could follow the real quadcopter in real time. The flight data from both quadcopters were gathered and compared. The comparison results show that the flight data from the real and the virtual quadcopters were almost the same at every point. In addition, we could see a similar flight trajectory from both quadcopters. Therefore, we concluded that the virtual quadcopter in X-Plane interacted and followed the real quadcopter in real time, which means that mixed reality simulation of the quadcopter UAV was executed and validated herein.

By using mixed reality simulation, we developed and tested a visualized ground control station that could control a quadcopter from a remote location, without a remote controller. Finally, in this phase, we introduced our mixed reality simulation technique with a dual-head electromagnetic propulsion device to control the quadcopter in any planet atmosphere. The real-time space flight experiment of a quadcopter drone with four electromagnetic propulsion devices and its mixed reality simulation is beyond the scope of this paper. However, it will be executed with the support of the space agencies worldwide, in the next phase of our work.

Note that, in this mixed reality simulation, we mainly focused on the interactions and performances of both quadcopters. In future work, we plan to consider more accurate scenery, weather conditions, and real-time movement of other objects, and also develop a ground control station for mixed reality simulation instead of the Mission Planner. We envision the advent of a new era of drones, a popular nickname for UAVs, that can autonomously fly in natural and man-made environments [41,42] with dual-head electromagnetic propulsion devices for a longer duration in any planet with high payload capability. Briefly, this paper provides insight for a credible mixed reality simulation for Mars explorations using quadcopter drones regulated by dual-head electromagnetic propulsion devices through multiple channel ultra-high speed wireless communication systems.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/2076-3417/10/11/3736/s1, please see the video "MRS" provided herein for corroborating our claims on the mixed reality simulation of quadcopter UAV. Data converter program is available at https://github.com/ashishkumar2025/Data-converterprogram-in-MATLAB.git.

**Author Contributions:** Conceptualization, A.K.; Methodology, A.K.; Experimental design, A.K.; Manuscript preparation, A.K.; Supervision, S.Y.; Review and editing, V.R.S.K. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was supported by the Agency for Defense Development, regarding the project of Design Study of Electronic Warfare Based on Modeling and Simulation

**Acknowledgments:** We thank our colleagues, Dong Cho Shin from the Agency for Defense Development and Ki Byung Jin from the LIG Nex1 Co., Ltd., who provided insight and expertise that greatly assisted the research, without prejudice to the final outcome of this manuscript.

**Conflicts of Interest:** The authors declare no conflict of interest.
