Speakers
Description
The rapid increase of space debris in Earth orbit has become a critical issue, requiring effective mitigation strategies for both current and future spacecraft.
This challenge is particularly pressing in the Low Earth Orbit (LEO) region,
where, as highlighted in the European Space Agency Zero Debris Charter, space-
crafts are required to deorbit within five years at the End of Life (EOL) phase.
This presentation at ESA Clean Space Days 2026 introduces an innovative
propulsion system designed to support compliant and efficient deorbiting: WaterCube DeOrbiting Module (WTCDM). It is a green hybrid propulsion system for CubeSat and small satellite applications, developed by a consortium led by Capsule Corporation, and funded by ESA through the ”Disruptive Propulsion Technologies For Cubeast De-Orbiting” tender. The system is based on the integration of two distinct proprietary technologies: Capsule Corporation’s water-based resistojet propulsion module (RPM) and Politecnico di Milano’s hydrolitic based chemical propulsion module (CPM), which exploits aluminum–water reactions for thrust generation and control. The water comes stored in a low-pressure tank, enhancing safety and cost savings for satellite integrators due to associated benefits in fuel logistics. Each branch conveniently operates with low electrical power request and within a specific thrust range, particularly the RPM up to 4 mN, while the CPM between up to 0.5 N. This enables enhanced flexibility and scalability across different mission requirements of the users, while requiring a low firing time that brings savings associated to mission operations.
This work investigates how the WTCDM fosters the deorbiting capability of
spacecraft and a debris-free LEO region. It is presented an instance use case study that analyses the modification of a SmallSat slow reentry LEO orbit to decrease its decay time. This is obtained by lowering the perigee altitude with the application of tangential WTCDM thrust on the apogee, coupled with an attitude control strategy to ensure the correct thrust direction before firing. The modified orbit becomes compliant with the five-year deorbiting requirement and the orbital decay times are validated using the ESA DRAMA OSCAR tool.
It is also explored how the intrinsic safety and non-toxicity of water as a propellant contribute to effective spacecraft passivation. Advantages in this sense are also brought by WTCDM hybrid architecture in terms of prevention of fragmentation by explosion, featuring two separated modules, redundancy strategies and a planned water ejection mode to ensure no exothermic reaction in the propulsor is started at the EOL.