Senior Propulsion Engineer, Fluids

Spacecraft represent the most pressing unmet need across the entire aerospace industry. As more launch vehicles come online and the cost to orbit decreases, more companies launching payloads to space continue to emerge.

For the first time in history, this influx of payload companies combined with reduced launch costs has resulted in a massive increase in need for commercial spacecraft platforms, known as satellite buses. These buses hold the payloads of our customers and are flown on launch vehicles.

Apex manufactures these satellite buses at scale using a combination of software, vertical integration, and hardware that is designed for manufacturing. Our spacecraft enable the future of society: ranging from earth observation to communications and more.

We’d love for you to join us on our mission of providing humankind access to the galaxy beyond our planet.

About the Role

Apex is seeking a Senior Propulsion Engineer with deep experience in pressurized fluid systems to own the feed-system design of the propulsion modules that fly on Apex spacecraft. You will be the fluidics authority on the propulsion module team — designing the wet side of the module from the tank through the routing to the thruster and cathode, defining and running the test campaigns that qualify it, and carrying the hardware through range safety and into space.

This is a senior individual contributor role with technical leadership scope. You'll own pressurized fluid architecture, component selection, and routing; the proof, burst, and leak testing that verifies it; and the range-safety and pressure-systems compliance that lets it fly. You'll also work directly with Apex's in-house propulsion component teams (thrusters, cathodes, flow controllers, PPUs) and with manufacturing to design feed systems that are safe, verifiable, and buildable at rate.

Responsibilities

• Own the propellant feed-system design for Apex's propulsion modules — architecture, schematic, component selection (tanks, regulators, valves, filters, transducers, service valves), and end-to-end fluidic routing.

• Design pressurized fluid systems to appropriate factors of safety, defining MEOP, proof, and burst requirements and the design margins that satisfy them.

• Perform the fluids analysis that drives the design — flow and pressure-drop budgets, transient/water-hammer, feed-pressure and blowdown behavior, filtration, and thermal effects on the fluid.

• Design tubing, fitting, weld, and braze joints and routing that survive launch and space environments and conform to vehicle ICDs.

• Define and execute feed-system test campaigns — leak (including helium/mass-spec), proof, burst, functional, and acceptance testing — and author the procedures and GSE requirements to run them.

• Own range safety and pressure-systems compliance for the module (e.g., SSCMAN/AFSPCMAN 91-710), including fracture control for pressurized hardware and COPVs, hazard analyses, and the documentation and approvals needed to fly.

• Support propellant servicing — fill/drain and hazardous operations — from a fluids-design and safety standpoint.

• Partner with Apex's in-house thruster, cathode, flow controller, and PPU teams to define fluidic interfaces and co-optimize the feed system with the components it serves.

• Work with the manufacturing team to ensure a smooth handoff to the floor, and fold their feedback back into the design to improve producibility, cleanliness, and build time at rate.

• Drive design-for-manufacturing and cleanliness/contamination control so feed systems are buildable, cleanable, and testable in serial production.

• Support build, integration, test, launch campaigns, on-orbit performance evaluation, and anomaly resolution, and lead root-cause investigations on fluidic issues.

• Provide technical mentorship to other engineers on feed-system design, testing, and safety.

Qualifications

• Bachelor's degree in mechanical, aerospace, chemical, or a related engineering field.

• 6+ years (Sr) / 8+ years (Staff) of experience in fluid systems engineering, with substantial hands-on work on pressurized fluid or propellant feed systems.

• Deep knowledge of pressurized fluid system design — component selection, routing, joints, and design to MEOP/proof/burst factors of safety.

• Strong fluids analysis skills — flow and pressure-drop, transients/water-hammer, filtration, and thermal-fluid behavior.

• Hands-on experience defining and executing fluid-system test campaigns, including leak, proof, burst, and functional testing.

• Direct experience with range safety and pressure-systems requirements (e.g., SSCMAN/AFSPCMAN 91-710), including fracture control and hazardous operations.

• Demonstrated track record getting fluidic flight hardware through qualification and into space.

• Experience designing to vehicle requirements and conforming to ICDs.

• Must be a U.S. Person (U.S. citizen, lawful permanent resident, or protected individual) as defined by ITAR (22 CFR §120.15).

Nice to Have

• Master's degree in a related engineering field.

• Experience with both electric propulsion feed systems (xenon/krypton, high-pressure storage and regulation) and chemical propulsion feed systems.

• Experience with composite-overwrapped pressure vessels (COPVs) and their fracture control and qualification.

• Experience bringing feed systems or fluidic hardware into serial / high-rate production.

• Experience authoring and executing hazardous operations procedures and obtaining range approvals.

• Familiarity with precision cleaning, contamination control, and propellant compatibility.

• Experience designing and operating fluid GSE for servicing, fill/drain, and test.

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Why Join Apex?

Apex believes in creating a work environment that you look forward to embracing every day. Our employees love working at Apex, and we want you to love it too. We're a fast-growing startup that has raised more than $500M in funding, and we invest heavily in our people from day one.

What We Offer For Full-time Employees:

• Shared upside: Receive equity in Apex, letting you benefit from the work you create

• Cash bonus eligibility: share in Apex’s success with eligibility for a performance-based cash bonus on top of your salary, rewarding the impact you make

• Best-in-class healthcare: 100% company-paid medical, dental, and vision for you and your dependents, plus $100k life insurance at no cost

• Comprehensive PTO package: Starting at 15 days vacation, growing to 20+ days annually, plus 10 paid holidays

• Competitive 401(k) plan: Generous matching - 100% match on first 3%, 50% on next 2%

• 8 weeks paid parental leave: Plus childcare reimbursement up to $350/day for work-related travel

• Daily catered lunch and unlimited snacks: To keep you fueled throughout the day

• Vibrant community: Monthly office socials, pickleball tournaments, run club, and gatherings for you and your family

• Your dream desk setup: All the tools you need to be your most productive self

• World-class Playa Vista office: With the benefit of in-person collaboration with amazing coworkers and flexibility to integrate work and life

• Real impact opportunity: Work alongside experts from aerospace, new space, and other cutting-edge industries to make a lasting difference

Additional Information:

Compensation ranges are set by role, level, location, and alignment with market data. A candidate's specific level and base pay are determined case by case and may vary with job-related skills, education, experience, technical capabilities, and internal equity. Beyond base salary, full-time hires are also eligible for long-term incentives in the form of stock options, along with medical, dental, and vision coverage and a 401(k) retirement plan.

ITAR Requirements

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