Due to strict constraint regarding the volume of a PocketQube (50x50x50 mm) it is crucial to reduce the space that is consumed by the satellite bus subsystems. This paper focuses on a new architecture for the electrical subsystem in order to reduce its volume and increase the usage of empty surfaces inside the satellite. This increment in volume efficiency is going to be achieved by splitting the electrical power system on different surfaces and reducing the number of required voltage regulators. This modular approach is going to be realized by two main steps. First, removing the regulated bus from the satellite and delivering an unregulated bus to the subsystems. This will also give flexibility to other subsystems to use a voltage level which are more suitable for their requirements. Secondly, the internal side of the solar panels’ are going to be used for MPPT (maximum power point tracking) circuits, actually achieving a distributed power generation system, similar to ground-based solar power generation systems. The battery board is going to be a separate board with its dedicated communication lines and will also act as an interface between the solar panels and power distribution board via simple spring loaded connectors. This latter solution helps reducing dramatically the number of cables in the satellite,thus simplifying integration. The main objective of this work is turning the EPS (electrical power system) into a more flexible, scalable and volume-efficient system by a physical relocation of its components and a lean approach. The new EPS will be functionally and environmentally tested in a flight representative satellite model with the aim to verify its simplification in integration, assess its true performance as well as its reliability during launch vibration which especially includes spring-loaded connectors. ... Read more

Microelectromechanical systems (MEMS) techniques uncovered new opportunities in satisfying the mission requirements of the growing next generation nano- and pico-satellite missions. In particular, micro-propulsion is universally recognized as one of the key enabling technologies to help this class of satellites making the next step and become credible candidates to a wide range of scientific and commercial applications. In this context, TU Delft is developing a miniaturized electro-thermal propulsion system operating with green liquid propellants, for application on a wide range of nano-satellite formats from CubeSats (10x10x10 cm units) to PocketQubes (5x5x5 cm units). A breadboard of the complete micro-propulsion system is under development at TU Delft, including the thruster, propellant tank, the valve and the driving electronics. The design of the system shall be easily adapted to both CubeSat and PocketQube standards, with particular attention to the second one since the system is scheduled for an initial flight demonstration on the first Delfi-PQ satellite. To address this need and to fill an existing gap in the state-of-the-art of micro-propulsion, two kinds of micro-thrusters are considered in this development; a Vaporizing Liquid Micro-resistojet (VLM) and a Low Pressure Micro-resistojet (LPM). A number of test results will be shown in the paper on the electrical, mechanical and functional characterization of the MEMS thrusters, fabricated in the Else Kooi Laboratory at TU Delft, and the other components of the system. Keywords: Micro-resistojet, Microthruster, MEMS, Cubesats, Pocketqubes ... Read more

In the last two decades, CubeSats have changed the perception of satellite missions aided by standardization and usage of commercial-off-the-shelf components. CubeSats have also proven the feasibility of low cost and short development time space missions. The PocketQube with a form factor of 5x5x5 cm has been proposed as the next class of spacecraft to benefit from miniaturization. This paper presents a comparison between the two standards and analyzes the impact of miniaturization on spacecraft design and performance. At satellite level, the reduction of volume has a tremendous impact on the available power and makes energy management and efficiency critical. Thermal issues become important due to the reduced thermal capacitance, leading to higher thermal swings and larger temperature variations than CubeSats. The other important impact on the satellite bus is the reduced communication capacity due to several reasons: the reduced volume limits the available antenna size and also the available power available. At mission level, other factors have a substantial impact: de-orbit time becomes a major criterion in the launch selection process to comply with orbital debris policy. The volume reduction also affects the radar cross-section making the satellite more difficult to detected for space surveillance radars. Despite these challenges, PocketQubes are an attractive standard currently for academic and research groups as a way to reduce the cost and development time considerably. Payload capabilities also can force a paradigm shift from single to multiple satellites more than it was already happening with CubeSats: PocketQubes could better fit certain niches where high spatial or temporal resolutions are required instead of full resolution. Distributed space weather monitoring could be an interesting application where specific phenomena could benefit from multi-point sensing. All these strong points can also be coupled with a bigger satellite to complement and enhance its capabilities. Delfi-PQ is a PocketQube currently being developed at TU Delft using an agile approach, contrary to the typical V-model design. Shorter life cycle development benefits students, allowing them to get more involved in every iteration. The reduction in cost and development cycle increases the launch frequency. Incremental engineering becomes fundamental, also providing benefits on the reliability side because flight experience becomes more frequent than when following traditional development strategies. End-to-end development motivates students and provides them with a better insight into real-world engineering opportunities and training experiences. With this strategy, technical and educational objectives are more aligned, and the integration of such a project in the curriculum is facilitated. ... Read more