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 of New Space building a modern space business to enable faster, better and cheaper access to space. Our mission is to help democratise space and use it for good in order to improve life on Earth now and for the future generations. We are a fast-growing company aiming to provide sustainable and environmentally friendly launch solutions for small and medium-sized satellites and constellations into Low Earth Orbit. The company is privately funded by world-leading technology investors with strong commitment and support and our team is made of driven and talented people with a real passion for space innovation. We're making rockets in a way that hasn't been done before disrupting a traditional industry. If you are up for the challenge, want to work on cutting-edge projects and be part of a team changing the world for better, come, join us and launch your career! Want to find out more about us? Visit http://www.isaraerospace.com/   Data Protection We process your personal data for the purpose of managing the recruitment process and assessing your application. For detailed information on how your data is processed, including your rights, please refer to our https://isaraerospace.com/privacy-policy.   Disclaimer Isar Aerospace SE is an equal-opportunity employer committed to fairness and inclusivity. We do not prioritize any specific religion, gender, nationality, or background. Due to security clearance requirements, affiliations with countries listed under § 13 para. 1 no. 17 SÜG may affect the application process. All qualified applicants are encouraged to apply. Offices: Ottobrunn, Bavaria, Germany (Ottobrunn, Germany);