Senior Propulsion Engineer, Hall-Effect Thrusters

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 Electric Propulsion Engineer with deep expertise in Hall-effect thrusters to own the design, development, qualification, and production of Hall thruster technology for our electric propulsion systems. Building on Apex's in-house Hall-effect thruster capability, you will drive thruster development from plasma physics and discharge channel design through qualification, flight integration, and design-for-manufacturing at rate.

This is a senior individual contributor role with significant technical ownership and leadership scope. You will drive key Hall thruster 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 Hall thruster 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 Apex's Hall-effect thrusters, including discharge channel geometry, magnetic circuit design, anode and gas distributor design, and thermal-mechanical packaging.

• Develop plasma physics and performance models to drive thruster design, including ionization and acceleration behavior, magnetic field topology, efficiency, thrust-to-power, and specific impulse across the operating envelope.

• Define and execute thruster test and life-qualification campaigns, including performance mapping, plume characterization, thermal testing, oscillation and stability characterization, wear testing, and long-duration life testing in vacuum facilities.

• Develop erosion, degradation, and life models for the discharge channel and pole pieces and demonstrate compliance with mission life and propulsion budgets for power, thermal, throughput, and leak.

• Drive cathode-thruster coupling and overall EP system integration in partnership with cathode, propellant feed-system, and PPU owners.

• Select materials and processes, including ceramics, magnetic materials, and refractory metals, and qualify them for spaceflight and scalable production.

• Optimize thruster designs for performance, mass, 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 PPU/thruster operating points and gimbal integration, 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 Hall thruster 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 Hall-effect thruster design, development, and testing.

• Deep, hands-on knowledge of Hall thruster physics and design, including discharge channel design, magnetic circuit layout, anode and gas distribution, cathode coupling, and thermal management.

• Experience planning and executing Hall thruster or EP test campaigns in vacuum facilities, including plasma/plume diagnostics, performance measurement, and life/wear testing.

• Strong understanding of the failure and degradation mechanisms that drive Hall thruster life, including channel and pole erosion, thermal limits, and discharge instabilities, 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 Hall thruster from development through flight qualification and on-orbit operation.

• Experience with magnetically shielded, wall-less, and/or unshielded Hall thruster architectures.

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

• Familiarity with Hall thruster plasma simulation tools, including particle-in-cell and hybrid codes, and magnetic FEA.

• Familiarity with PPU/thruster 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.

#LI-MO1

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

• 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 to reset and recharge - starting at 15 days vacation, growing to 20+ days annually, plus 10 paid holidays

• Competitive 401(k) plan with 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