Propulsion System Engineer

ispace, inc. is looking for highly motivated Propulsion System Engineer advanced research & development (ARD) group. This position is based in Tokyo, Japan and will require you to relocate. This is not a full remote position. Successful candidate will participate in two types of ARD projects: 1) new technology development/demonstration and 2) next generation lunar transportation, infrastructure, and resource utilization system architecture creation from initial concept to system preliminary design level. This role focuses on high thrust propulsion systems, including earth-storable propulsion and advanced propulsion concepts. You will work within a multidisciplinary, model‑driven design team, developing Python‑based propulsion models, exploring large tradespaces, leading technology demonstration projects, and shaping the propulsion architecture of future ispace vehicles. It is expected that technical solution concepts start at mid/low technical maturity and you develop them to a CML2+ level (see JPL "concept maturity level" scale). #LI-Hybrid Key responsibilities Lead propulsion architecture definition and modeling for conceptual‑level system studies of different elements of lunar transportation missions (e.g., Orbit Transfer Vehicles, landers, orbital infrastructure), following ARD guidance and contributing through the concept maturation. Develop and maintain Python‑based propulsion models for sizing and system‑level tradespace analysis. Assess, compare, and select main‑engine propulsion options - including pressurization, propellant management, feed systems, engine cycles, and key component selections - to optimize system KPIs. Investigate and evaluate cutting‑edge propulsion technologies, generating recommendations for future R&D activities and long‑term capability roadmaps. Support R&D implementation projects, including propulsion‑related technology demonstrations and customer‑driven development efforts from concept to testing campaign. Contribute technically to early‑phase business development, collaborating with Business Development and Government Relations teams to inform proposals and strategic studies. Work closely with multidisciplinary ARD members (structures, comms, thermal, GNC, mission design) to ensure propulsion concepts integrate coherently with system‑level architecture. Basic Qualifications Bsc. or Masters degree / experience in mechanical, aerospace, or related engineering fields. Five or more years of relevant experience in analytical modelling of chemical propulsion, including pressurization system, feeding system, boil-off, propellant transfer, propellant management devices, rocket engine cycle, mass and fluid budget analyses. Solid understanding of mission‑level propulsion considerations (e.g., delta‑V budgeting, propellant selections, pressurization and feedsystem architectures, usable and unusable propellants, sloshing, and mission environments). 3 years of experience with relevant modelling programming languages (Python: NumPy, SciPy, Pandas, Matplotlib, or alternatively strong experience in matlab). Ability to work in fast‑paced, ambiguous conceptual environments and take proactive technical ownership. Preferred qualifications Experience in propulsion system components selection, trading-off technical compatibility, schedule, and cost Experience with advanced propulsion architectures such as cryogenic and hybrid rocket propulsion systems. Experience as systems engineering applying the Model Based Systems Engineering approach Experience with conceptual design methods, low‑fidelity modeling, or early‑phase systems engineering. Eperience using Git for version control in a CI/CD environment, contributing to shared codebases, reviewing merge requests, and maintaining high‑quality, reproducible model development practices.