Canadian Space Agency (CSA): OASYS Lunar Greenhouse Levelling System
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The OASYS Lunar Levelling Mechanism is a deployable support structure developed in collaboration with the Canadian Space Agency (CSA) to enable bio-regenerative greenhouse testing on uneven lunar terrain.
My primary responsibility was the structural design and validation of the load-bearing systems, including the stabilizer beam, hinge and pin mechanisms, and lead screw, supported by extensive hand calculations and FEA results.
System Requirements:
Terrain Compensation
Terrain Compensation
Level platform on slopes up to ±15° from horizontal with ±1°accuracy.
Load Capacity
Load Capacity
Support 130 kg distributed load under lunar gravity (1.62m/s²).
Power Independence
Power Independence
Function without dedicated electrical supply; using external tools only.
Compact Storage
Compact Storage
Fit within 1020 mm × 660 mm envelope when fully stowed.
Ground Clearance
Ground Clearance
Maintain minimum 1 meter clearance from ground to highest point when levelled.
Thermal Operating Range
Thermal Operating Range
Withstand thermal cycling from -200°C to +100°C throughout a 6-week operational lifespan.
Lunar Dust Resilience
Lunar Dust Resilience
Prevent abrasive dust contamination of moving parts and maintain functionality in regolith environment
System Architecture and Load Path Definition
The system uses a four-leg independent outrigger architecture, allowing each leg to deploy and adjust height independently for precise leveling. Each leg consists of:
Rotating stabilizer beam that swings outward from the chassis
Pin-locking hinge that provides discrete, repeatable deployment angles
Vertical lead screw actuator that raises or lowers the chassis
Ball-and-socket foot interface to accommodate terrain slope
The core design objective was to ensure clean, deterministic load paths. Vertical loads are carried from the chassis through the stabilizer beam into the hinge shaft, then into the lead screw and footpad. Locking pins are intentionally excluded from axial load transfer and serve only to prevent rotation, which improves reliability and wear resistance.
Stabilizer Beam Design and Analysis
For the stabilizer beam design, a comparison of different cross-sections was made (I-beam, box beam, circular tube, and truss). The dominant loading case is uniaxial bending, so an I-beam was selected for its high bending stiffness per unit mass.
Worst-Case Load Case
To ensure integrity, the beam was analyzed assuming the entire system load supported by a single leg and the centre of gravity offset by 20% from geometric centre.
Under this case, hand calculations yielded a peak bending stress of 3.64 MPa, corresponding to a safety factor of ~108 relative to Aluminum 2219-T87 yield strength. This confirmed that the stabilizer beam would not be the governing failure component and allowed focus to shift to the hinge mechanism.
Hinge and Pin-Locking Mechanism
The hinge assembly was identified early as one of the governing structural component due to the large combined bending and torsional loads during deployment and operation.
Geometry and Function
Single-axis rotational hinge
20 mm diameter solid shaft secured by an M18×1.5 nut
Locking holes spaced at 37° increments, providing 142° total swing
Achieves optimal 32° deployment angle for maximum stability
Hand Calculation
I performed detailed bolted-joint analyses and stress analyses on the hinge shaft and locking pin:
Hinge Shaft (20 mm diameter)
Hinge Shaft (20 mm diameter)
Worst-case torsional load: 190 N·m
Resulting shear stress: 48 MPa
Shear safety factor: 4.1
Locking Pin (8 mm diameter)
Locking Pin (8 mm diameter)
Worst-case shear load: 3.8 kN
Shear stress: 75 MPa
Shear safety factor: 3.3
Bearing stress: 13 MPa, safety factor ≈ 30
The locking pin normally carries zero axial load, and even under worst-case assumptions retains large margin, validating the design philosophy of isolating load paths.
Finite Element Analysis
A comprehensive FEA was conducted in SOLIDWORKS Simulation to verify that the hinge assembly satisfies structural requirements under maximum predicted bending and torsional loads. All components were modelled using Aluminum 2219-T87. Boundary conditions were applied to represent the hinge’s fixed interface with the chassis, and external loads were derived from analytical calculations of the maximum torque imposed by the deployed I-beam.
FOS Plot:
The simulation reported a minimum factor of safety of 2.73, located at the fillet transition between the hinge plate and shaft interface. The remainder of the hinge assembly exhibited safety factors within the 4-5+ range, demonstrating substantial structural margin beyond the required minimum of 1.4.
Von Mises Stress Plot:
The maximum von Mises stress observed in the hinge was 6.26 MPa, representing only 1.6% of the yield strength of Aluminum 2219-T87. This is far below the allowable limit of 279 MPa. Stress concentrations were small, localized, and entirely within the elastic regime.
Lead Screw Selection and Analysis
The lead screw controls the vertical adjustment of the system.
Selected Component
TR32×10 trapezoidal lead screw
32 mm diameter, 10 mm pitch
Governing Load Cases
The screw was analyzed for:
Axial compression
Bending due to CG offset
Buckling at maximum extension (700 mm)
Thread shear and bearing
Combined von Mises stress
Results
Axial load (with safety factor): 163.5 N
Von Mises stress: 2.4 MPa (SF ≈ 165)
Critical buckling load: 22 kN (SF ≈ 134)
Bending stress: 281 MPa (SF ≈ 1.4)
Torque and Deployment
Required torque: 1.5 N·m (raise), 0.8 N·m (lower)
Compatible with NASA Pistol Grip Tool
Deployment speed: 18.2 mm/s
Full deployment (4 legs): ~66 s
Other System Architecture Considerations
Beyond primary structures, the mechanism was designed holistically to operate in a lunar environment:
Ball-and-socket footpads allow ±15.2° articulation, isolating the lead screw from bending moments (compressive SF > 1300)
FEP dust covers protect threads from abrasive regolith
Custom insert bearings decouple screw rotation from dust cover motion
Keronite coatings prevent cold welding and provide self-locking behaviour
MoS2 dry lubrication enables vacuum operation without outgassing
These elements were integrated into the architecture to reduce failure modes and ensure long-term reliability without active systems.
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