About the Role

Apex is seeking a Senior Electric Propulsion Engineer with deep expertise in cathodes to own the design, development, qualification, and production of cathode technology for our electric propulsion systems. Building on Apex's in-house Hall-effect thruster capability, you will drive hollow and heaterless cathode development, 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 significant technical ownership and leadership scope. You will drive key cathode design decisions, lead test and life-qualification campaigns, and work alongside propulsion engineers as we scale EP production. You'll have the opportunity to approach cathode development with a clean-sheet, production-first mindset and directly shape the hardware, processes, and infrastructure required to take it from development into flight and serial production.

Responsibilities:

• Own the end-to-end design and development 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 testing in vacuum facilities.

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

• Develop cathode erosion, poisoning, and degradation models and perform filtration and contamination-control analysis to 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 scalable production.

• Optimize cathode designs for performance, 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 mentorship to propulsion engineers and contribute to the continued development of Apex's cathode and electric propulsion capability.

Qualifications:

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

• 6+ 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 3+ 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 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 PPU interaction.

• Experience owning hardware through design, development, build, and test.

• 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.

• Experience supporting failure investigations and resolving issues on flight or qualification 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