Propulsion Mechanical Engineer

Hop Aero is a venture-backed startup building rockets that deliver cargo anywhere on Earth in minutes.

Our mission is to enable resilient global logistics to protect and improve our way of life.

Our founding team has prior experience founding a satellite startup and taking it to orbit, launching 20+ Falcon 9 missions at SpaceX, and leading engineering teams at some of the world’s most advanced aerospace organizations. The company is well-capitalized through venture funding and government contracts.

About the role

We’re hiring a Propulsion Mechanical Engineer to own the development of electric propellant pumps (e-pumps) and high-speed rotating machinery for Hop Aero’s rocket propulsion systems.

This is a foundational technical role. You will establish our internal electric-pump capability from first principles, taking hardware from early architecture and analysis through detailed design, manufacturing, test, and ultimately flight. You will also work on designing key mechanical interfaces in the propulsion system.

We’re looking for someone who is comfortable owning difficult hardware problems end-to-end. You should be equally happy running a cavitation or rotordynamics analysis, reviewing an impeller design, talking through tolerances with a machine shop, instrumenting a test article, and standing next to the test stand when it runs.

This is not a narrow analysis role. You will work directly with propulsion, fluids, avionics, manufacturing, software, and test teams to develop tightly integrated propulsion hardware in a fast-moving environment.

Job Description

• Serve as the responsible engineer for electric propellant pumps and associated high-speed rotating machinery
• Own electric-pump development from architecture through design, manufacturing, integration, and test
• Design pump components including impellers, inducers, volutes, housings, shafts, bearings, and seals
• Design propulsion component interfaces, sealing surfaces, flanges, mounting features, and related mechanical hardware
• Integrate high-power-density motors, inverters, controllers, sensors, and associated electrical systems
• Perform hydraulic, cavitation, rotordynamic, structural, and thermal analysis
• Define mechanical, fluid, electrical, and software interfaces with the engine and vehicle teams
• Develop practical manufacturing strategies and work directly with machine shops and suppliers
• Plan, instrument, and execute electric-pump development testing
• Analyze pressure, flow, vibration, temperature, current, and speed data to diagnose hardware performance
• Own technical risks through design reviews, test-readiness reviews, and development campaigns
• Work in person with the team at our shop in Orange, CA.

Requirements

• 3-6 years of relevant engineering experience in centrifugal pumps, high-speed rotating equipment, turbomachinery, or similar fluid machinery
• Demonstrated ability to design, build, and test rotating mechanical hardware
• Strong understanding of pump hydraulics, cavitation, rotordynamics, bearings, seals, balancing, and high-speed shaft systems
• Experience taking mechanical hardware from analysis and CAD through manufacturing and test
• Experience working directly with machine shops, vendors, and manufacturing suppliers
• Ability to interpret pressure, flow, vibration, temperature, current, and rotational-speed data
• Ability to work effectively across propulsion, fluids, avionics, software, manufacturing, and test disciplines
• Willingness to be highly hands-on in a small, fast-moving hardware organization
• Must be a US Person under ITAR - Hop Aero will not sponsor visas for this role.

Nice to have

• Experience with rocket-engine turbopumps or electric propellant pumps
• Experience integrating high-power-density electric motors and inverters
• Experience with very high-speed shafts, bearings, seals, and rotating assemblies
• Experience with additively manufactured impellers, volutes, housings, or other propulsion components
• Experience developing cryogenic or other demanding fluid systems
• Experience transitioning development hardware into repeatable flight hardware
• Prior experience at a fast-moving aerospace or hardware startup

What we offer

• Competitive salary and meaningful stock options
• Healthcare, office meals & snacks
• Direct mentorship and collaboration with founders & engineers with rich flight heritage
• Significant technical ownership from day one
• Fast upward mobility as the company grows

Even if you don’t meet every single requirement, we’d still love to hear from you. Greatness looks different in every one of us - and we need the best tackling this problem.

Interview Process

Step 1: Screening call (20 mins). Brief company and role intro.

Step 2: Resume call (60 mins). Deeper dive into your background, prior and current work.

Step 3: Take-home technical brief (Varies). You’ll be given a task to complete.

Step 4: Technical Interview (2 hours). You present your work on the technical brief to a group from Hop Aero. This is our collective chance to all get to know each other and see if we’d work well together.

Step 5: Offer. We will call you by phone if we’d like to put forward an offer.