About the Role

Apex is seeking a Staff Electric Propulsion Engineer with deep expertise in cathodes to own the design, development, qualification, and production of the cathode technology at the heart of our electric propulsion systems. Building on Apex's in-house Hall-effect thruster capability, you will be the technical authority on hollow and heaterless cathode design, from emitter physics and thermal-mechanical design through cathode-thruster coupling, life characterization, and design-for-manufacturing at rate.

This is a senior individual-contributor role with technical leadership scope. You will set the cathode technical roadmap, drive key design decisions, stand up and run cathode test and life-qualification campaigns, and mentor propulsion engineers as we scale EP production. As one of the anchors of Apex's EP team, you'll have the opportunity to approach cathode development with a clean-sheet, production-first mindset and build the capability, team, and infrastructure around it.

Responsibilities:

• Own the end-to-end design of hollow and/or heaterless cathodes for Apex's electric propulsion systems, including emitter selection, keeper and orifice geometry, heater design, and thermal-mechanical packaging.

• Develop physics-based and empirical models to predict cathode performance, discharge behavior, thermal margins, and life, and validate them against test data.

• Define and execute cathode test and life-qualification campaigns, including ignition and conditioning, coupling voltage characterization, thermal cycling, plume/plasma diagnostics, wear testing, and long-duration life tests in vacuum facilities.

• Drive cathode-thruster integration, optimizing cathode-to-anode coupling, mass flow split, and placement for overall EP system performance and stability.

• Establish cathode erosion, poisoning, and degradation models; perform filtration and contamination-control analysis; and demonstrate compliance with propulsion budgets for life, power, thermal, leak, and contamination.

• Select emitter and structural materials and processes, including LaB6, BaO-impregnated tungsten, and refractory metals, and qualify them for spaceflight and high-rate production.

• Optimize cathode designs for weight, cost, manufacturability, and repeatability, and develop the work instructions, process flows, and AI&T procedures required to build them at rate.

• Partner with systems, power electronics, thermal, structures, and avionics teams to define interfaces, including cathode heater/keeper drive and PPU interaction, and verify requirements.

• Support the build, integration, and test of flight hardware, as well as launch campaigns, on-orbit performance evaluation, and anomaly resolution.

• Lead and contribute to failure analysis, root-cause investigations, and continuous design improvements to support future builds and scalable production.

• Provide technical leadership and mentorship to propulsion engineers and help build Apex's cathode and broader electric propulsion capability, team, and infrastructure.

Qualifications:

• Bachelor's degree in aerospace, mechanical, electrical, plasma/propulsion engineering, applied physics, or a related field.

• 10+ years of relevant electric propulsion experience with a Bachelor's or Master's degree, OR a Ph.D. in electric propulsion, plasma physics, applied physics, or a closely related field with 5+ years of relevant industry experience, with substantial and demonstrable focus on cathode design, development, and testing.

• Deep, hands-on knowledge of hollow and/or heaterless cathode physics, including thermionic emission, emitter materials, plasma discharge behavior, keeper/orifice design, and cathode coupling to Hall or ion thrusters.

• Experience planning and executing cathode or EP test campaigns in vacuum facilities, including plasma diagnostics, performance measurement, and long-duration life/wear testing.

• Strong understanding of the failure and degradation mechanisms that drive cathode life, including emitter depletion, erosion, poisoning, and contamination, and how to design and test against them.

• Working knowledge of spacecraft propulsion system architecture, propellant feed systems, and range safety requirements (e.g., SSCMAN 91-710).

• Ability to decompose requirements and ICDs and communicate clearly across engineering disciplines.

• 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:

• Direct experience taking a cathode or EP thruster from development through flight qualification and on-orbit operation.

• Experience with heaterless cathode ignition and conditioning schemes.

• Experience with alternative propellants, including krypton and other non-xenon EP propellants, and their effects on cathode life and operation.

• Familiarity with PPU/cathode drive electronics and power interface definition.

• Design-for-manufacturing experience bringing propulsion hardware into serial or high-rate production.

• Experience with EP environmental qualification, including vibration, TVAC, and EMI testing of flight propulsion hardware.

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What We Offer For Full-time Employees:

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