To develop sounding rockets that can be used for various missions, a university, research center, and two enterprises collaborated to conduct a critical-system development project on a small-scale sounding rocket. The Korea Advanced Institute of Science and Technology (KAIST) Rocket Laboratory and Space Solution Co., Ltd. collaborated to develop a hybrid rocket and a propellant-feeding system using hydrogen peroxide as an oxidizer. The KAIST Satellite Technology Research Center has developed a non-pyrotechnic recovery system, and Naraspace Technology Co., Ltd. has developed rocket avionics. Using a 2.39-m technology demonstrator that weighs 16.4 kg, the developed system has been validated at low altitudes, and the applicability of the small-scale sounding rocket has been evaluated. The combustion stability, short ignition delay, and high performance of the H2O2 hybrid rocket were confirmed through static firing and flight tests. The reliability and capacity of the non-pyrotechnic recovery system (which uses a spring) were confirmed by ground and flight tests. Perfect operation of the developed rocket avionics, such as control of the main oxidizer valve and recovery system, emergency functions, data transmission, and data storage was confirmed through ground and flight tests.