Mechanical Engineer

Castelion Corporation•Allen, TX

2h•Onsite

About The Position

Castelion is rapidly developing and delivering advanced defense systems, emphasizing focus and technical excellence. This early-stage opportunity allows individuals to directly shape critical systems and influence major technical decisions with immediate, real-world impact. As a Mechanical Engineer (Test & Tooling), you will be responsible for the design, development, and deployment of mechanical systems crucial for rapid, high-fidelity testing and scalable production of avionics and integrated weapon subsystems. This includes leading the creation of environmental test fixtures (vibration, thermal, HALT/HASS), hardware-in-the-loop (HITL) and vehicle-in-the-loop (VITL) support hardware, production test equipment, and production tooling. The role requires strong mechanical design fundamentals, a deep understanding of test environments and failure modes, and the ability to translate ambiguous test objectives into robust, repeatable physical systems, executing with high ownership and continuous improvement.

Requirements

2–5+ years of experience in mechanical design, preferably in test, tooling, or hardware development environments.
Strong proficiency with CAD tools (NX, SolidWorks, or equivalent).
Proven experience designing fixtures or tooling for mechanical, thermal, or environmental testing.
Solid understanding of structural mechanics, thermal behavior, and material properties under dynamic loading.
Experience designing for vibration and shock environments, including bolted joints and interface design.
Familiarity with tolerance analysis and GD&T.
Experience working with machine shops and external fabrication vendors.
Strong problem-solving skills and ability to iterate quickly in fast-paced environments.
High ownership mindset with the ability to drive designs from concept through deployment.
Ability to work effectively across cross-functional engineering teams.

Nice To Haves

Experience in aerospace, missile systems, spaceflight, defense, or other high-reliability hardware environments.
Hands-on experience with: Vibration and shock testing (random vibe, sine burst, pyroshock)
Hands-on experience with: Thermal and thermal vacuum testing
Hands-on experience with: HALT/HASS methodologies and reliability engineering
Experience designing fixtures for HITL or VITL systems.
Familiarity with instrumentation (accelerometers, strain gauges, thermocouples) and data acquisition systems.
Experience with FEA tools for structural and thermal analysis (e.g., ANSYS, Nastran, Abaqus).
Experience using and tailoring relevant environmental standards (MIL-STD-810, MIL-STD-1540).
Experience optimizing production tooling and assembly workflows.
Ability to rapidly prototype (CNC, additive manufacturing, sheet metal).
Experience supporting hardware through environmental testing and qualification campaigns.
Demonstrated ability to mentor engineers and elevate team design quality.

Responsibilities

Own end-to-end design of mechanical fixtures for environmental testing, including vibration, shock, and thermal cycling.
Design and develop HALT/HASS profiles and the associated fixtures to expose product weaknesses and validate reliability margins.
Create test fixtures for avionics systems, ensuring accurate mechanical, electrical, and environmental interfaces.
Create test racks & interface chassis containing electronics & test equipment
Design and optimize test and production fixtures and build tooling to improve assembly efficiency, repeatability, and throughput.
Translate test requirements into robust fixture designs that ensure proper load paths, boundary conditions, and instrumentation access.
Perform structural, thermal, and tolerance analyses to validate fixture performance under test conditions.
Select materials, fasteners, and manufacturing processes appropriate for dynamic, thermal, and high-reliability environments.
Partner with test engineers to instrument fixtures (strain, acceleration, temperature) and validate correlation to expected conditions.
Drive design for manufacturability (DFM) and design for assembly (DFA) for all fixtures and tooling.
Interface directly with machine shops, vendors, and internal manufacturing teams to fabricate and iterate on designs quickly.
Support test execution, troubleshoot failures, and rapidly iterate fixture designs based on test outcomes.
Develop and maintain drawings, CAD models, and documentation for all fixtures and tooling.
Contribute to internal standards and best practices for test infrastructure and mechanical design.

Benefits

meaningful long-term equity, sharing in the company's significant growth trajectory.
four (4) weeks of paid time off
ten (10) company-paid holidays
comprehensive health benefits - including 100% employee-covered medical and strong dependent coverage, along with dental and vision plans.
paid parental leave to support growing families
a $100 monthly fitness stipend to promote health and performance
onsite EV charging for convenience
catered meals
company-covered food during high-demand periods
a fully stocked kitchen to stay fueled throughout the day.