# An Overview of CubeSat Missions and Applications
## 8 The Use of CubeSats in Novel Technology Demonstration Missions
### Propulsion and Maneuvering Demonstration  
The first type of demonstration missions that is going to be presented is missions involving propulsion and maneuvering in space. During space flight, it is essential to have controlled movements for maneuvering, station-keeping, docking into other satellites or space stations, re-entry into Earth's atmosphere, and deep space exploration. One mission involving autonomous rendezvous and docking was the CubeSat Proximity Operations Demonstration (CPOD) [295]. Led by Terran Orbital and launched in May 2022, this mission aimed to demonstrate autonomous rendezvous, safe flying, and, finally, docking of two identical 3U CubeSats, using three-degree-of-freedom thrust control and a guidance, navigation, and control (GNC) framework for optimized fuel efficiency. These CubeSats were initially deployed as a single 6U configuration and then separated into two distinct 3U satellites to begin their mission. At first, they reduced their separation distance, then fine-tuned their relative positioning which established a stable formation that they maintained. Due to several hardware issues, the docking attempts were unsuccessful; however, CPOD validated critical rendezvous and proximity operations (RPO), paving the way for future missions. One other demonstration mission involving propulsion is the Vizard-ion CubeSat mission [296]. Developed by Russia's MSU-STANDART and launched on 4 November 2024, it is a 3U nanosatellite designed to test the VERA plasma propulsion system. This system is an ablative pulsed plasma thruster, a compact and efficient propulsion technology suitable for small satellites. VERA operates by ablating a solid propellant to generate plasma pulses, providing thrust for orbital maneuvers and attitude control. The Vizard-ion mission aims to validate the performance of VERA in space, contributing to advancements in CubeSat propulsion capabilities. Additionally, the satellite carries a GNSS receiver for ionospheric studies and a 2-megapixel optical camera for Earth observation. One significant mission involving green propulsion is the AQT-D (Aqua Thruster-Demonstrator) mission [297]. Developed by the University of Tokyo, it demonstrated the use of a water-based propulsion system for CubeSats. Launched to the ISS in 2019, the 3U CubeSat carried the AQUA Reslstojet propUlsion System (AQUARIUS-1U), which utilizes less than 400 g of water to power one Delta-V Thruster (4 mN) and four Reaction Control Thrusters (1 mN each). The system heats injected water droplets in a vaporization chamber, expelling vapor through nozzles to produce thrust. This design enables precise thrust modulation, avoids nozzle icing, and uses water--a safe, storable, and abundant green propellant. On orbit, AQT-D conducted three test phases, including a 15-hour thrust operation that generated a 54 m/s delta-V, resulting in a 190 km orbital change. The propulsion system maintained three-axis control, demonstrating viability for extended CubeSat operations. With a specific impulse of ~70 s and a thrust-to-power ratio of 0.22 mN/W, AQUARIUS-1U marks a significant step in sustainable propulsion for small satellites. AQT-D's success confirms that compact, green propulsion systems can support meaningful maneuvers and mission extensions, enabling broader applications for future space missions, including deep-space exploration. Another mission that demonstrated re-entry capabilities was Technology Education Satellite-10 (TechEdSat-10) [298]. As part of the nanosatellite flight series TechEdSat by NASA Ames Research Center, this particular mission's goal was to demonstrate the exobrake technology. The exo-brake system had already been used in previous missions of this series; however, this was the largest up until then. The deployment sequence of the exo-brake can be seen in Figure 22. It was designed to deploy an umbrella-like sail to take advantage of the little atmosphere, in order to deorbit, in a controlled manner modulated from ground.