A reusable launch vehicle refers to a rocket designed to be reused either partially or entirely. Compared to traditional launch vehicles that are discarded after a single use, reusable launch vehicles can significantly reduce both the time and cost required for production. This advancement makes space missions more economically viable and sustainable. As a result, various organizations and companies around the world are actively engaged in researching and developing reusable launch technology to perform innovative space missions. In Korea, Innospace successfully launched the Hanbit test launch vehicle (Hanbit-TLV) and is now focusing on researching the foundational technology for reusable launch vehicles using hybrid rockets. Innospace's research and development efforts are centered on creating a demonstration model for reusable launch vehicles. This model, reusable launch vehicle demonstrator(RLV demonstrator), is being rigorously tested and validated through various trials conducted at Innospace's test facilities. The RLV demonstrator developed by several units: the computing unit, the sequence unit, and the control unit. To verify the performance of the reusable launch vehicle, each unit is modeled and verified through Program In the Loop Simulation (PILS) or directly tested using the actual hardware units in Hardware In the Loop Simulation (HILS). PILS is used to design the control of each system and validate the stability of the algorithms, and HILS helps in observing the response characteristics of each hardware unit's performance, thereby validating the overall performance of the actual system. After the comprehensive validation through PILS and HILS, Innospace conducted a series of step-by-step flight tests with the RLV demonstrator. One such test is the 1D altitude control test, which aims to verify the dynamic characteristics and thrust control performance of the RLV demonstrator. During this test, the demonstrator is fixed to a rail to minimize uncertainties and ensure accurate measurements. Another test is the tethered flight test, designed to verify the guidance control performance and stability of attitude control. This test allows the model to fly freely while executing given guidance commands, effectively simulating real flight conditions and external disturbances. This paper details the progress made by Innospace in developing reusable launch vehicle technology. It presents the flight results of both the 1D altitude control test and the tethered flight test, providing insights into the performance and capabilities of the RLV demonstrator. Furthermore, it outlines future development plans and discusses how the verified technology will be applied to Innospace's next-generation launch vehicles. Through these efforts, Innospace aims to contribute significantly to the advancement of reusable launch vehicle technology and make space exploration more accessible and sustainable.