Fluids Engineer (m/f/d)

Mission Brief As a Fluids Engineer in the Reusability Program, you analyse propellant behaviour across changing thermal conditions, transient operating states, and mission phases including ascent, shutdown, coast, reentry , and relight. Your work directly drives propellant management, pressurization, and feed system design for next ‑ generation reusable launch vehicles. Your Role in Our Space Mission Define and analyse the overall propellant management architecture, including propellant location, acquisition strategy, residuals, depletion behaviour, and their interaction across mission phases Analyse microgravity and low-acceleration propellant dynamics, including propellant surface behaviour modelled with VOF methods and coupled heat and mass transfer, to drive architectural choices Derive tank pressurization concepts from mission requirements and reusability constraints, including transient behaviour across mission phases Perform NPSP and inlet margin trades, including the influence of propellant thermal state and transient operating conditions on engine behaviour Analyse propellant routing, including feedlines and valves, with focus on transients, operability, and reuse robustness Define pressurization and consumables architecture in the context of reusability, including sizing logic, margins, and operational envelopes Develop reduced order models from high‑fidelity analyses to support vehicle‑level and program‑level trade studies Qualification Checklist Education & Technical Background Degree in mechanical, aerospace, or chemical engineering, or a closely related field Strong fundamentals in fluid mechanics, thermodynamics, and cryogenic systems Solid understanding of multiphase flow, including liquid–vapor interfaces and heat and mass transfer Experience 3–5 years of experience in propulsion, fluids, or propellant management related roles Hands‑on experience analysing propellant behaviour at system or architecture level, not only single components Practical experience with VOF or comparable multiphase modelling, including thermal effects and free‑surface behaviour Exposure to microgravity or low‑acceleration propellant dynamics and their impact on system operability Experience deriving or contributing to tank pressurization architectures, including transient behaviour Experience abstracting high‑fidelity analysis into reduced order models for vehicle or program‑level trade studies Skills & Competencies Ability to derive propellant management and pressurization architectures from mission requirements, operating envelopes, and reusability constraints Capability to quantitatively assess trade‑offs between propellant management concepts using first‑principles analysis, scaling laws, and targeted high‑fidelity simulations Critical judgement of model assumptions, numerical limitations, and validity ranges Comfortable balancing analysis fidelity, computational cost, and engineering timelines Clear communication of complex fluid behaviour to non‑fluids specialists Structured, physics‑driven problem‑solving mindset Fluent in English (German is a plus) Benefits Employee Participation Program: Share in our success through our virtual company share program 30 days of vacation: Enjoy the days off to relax and recharge Company pension plan: Secure your future with our company pension plan, featuring a 20% employer contribution after the probation period Subsidised lunch: Stay energised with delicious, subsidised lunches every day Public transport ticket: Commute with ease using a fully financed Deutschlandticket Sport Clubs membership: Stay fit with our sponsored sports club memberships (EGYM Wellpass) Individual learning allowance: Grow your skills with an individual learning budget granted after the probation period Childcare allowance: Receive a childcare allowance for your non-school-age children And Much More! Discover additional perks and benefits when you join our team Who we are We are Isar Aerospace and we are at the forefront