Simulating Lunar Regolith Interaction with Spacecraft Landing Gear in Aerosimulations

Understanding how lunar regolith interacts with spacecraft landing gear is crucial for the success of lunar missions. The surface of the Moon is covered with a layer of loose, fragmented material known as regolith, which presents unique challenges for landing and surface operations. Modern exploration initiatives, from NASA's Artemis program to international robotic missions, demand landing systems that can safely touch down on this unpredictable terrain. Aerosimulations has emerged as a leading platform for modeling these complex interactions, enabling engineers to predict landing dynamics, reduce risk, and optimize gear designs before hardware is built.

What Is Lunar Regolith?

Lunar regolith is a fine, powdery soil formed by billions of years of meteorite impacts, solar wind bombardment, and thermal cycling. Unlike Earth soil, it contains no organic matter and is composed primarily of silicate minerals, oxides, and glassy particles. The average grain size ranges from 40 to 800 micrometers, with many particles sharp and angular due to lack of weathering. Regolith depth varies widely: on the mare (basaltic plains) it can be 4–5 meters deep, while in highland regions it may exceed 15 meters. Its physical properties include low cohesion (typically 0.1–1 kPa), variable compaction, and high abrasiveness. These characteristics make it extremely challenging for landing gear to achieve stable contact without sinking or kicking up damaging dust clouds.

One of the most hazardous aspects is its electrostatically charged nature. Ultraviolet radiation from the Sun causes the regolith to become highly charged, causing it to adhere to surfaces and penetrate seals, bearings, and thermal control systems. During the Apollo missions, astronauts reported that regolith caused significant wear on spacesuits and equipment. Understanding these microscopic and macroscopic properties is essential for any simulation tool that aims to predict real-world landing behavior.

For further reading on lunar regolith composition and engineering properties, refer to Lunar and Planetary Institute resources and NASA technical reports on regolith mechanics.

Why Simulate Regolith Interaction?

Building physical prototypes and conducting full-scale drop tests in vacuum chambers with simulated regolith is extremely expensive and time-consuming. Even the most advanced terrestrial simulants (such as JSC-1A or NU-LHT) cannot perfectly replicate the low gravity, vacuum, and electrostatic conditions of the lunar surface. Computational simulation offers a cost-effective, scalable alternative that can explore thousands of landing scenarios in days rather than months. Aerosimulations addresses this need by incorporating high-fidelity physics models that capture the unique dynamics of regolith under lunar gravity (1/6g).

Simulating regolith interaction is critical for several reasons:

  • Landing Gear Design Optimization — Shapes, materials, and damping systems can be iterated rapidly.
  • Plume Ejecta and Dust Mitigation — Simulations reveal how engine exhaust interacts with regolith, causing cratering and debris clouds that can damage sensitive spacecraft components.
  • Touchdown Stability and Sinkage — Predicting how fast a lander will sink or tilt upon contact prevents tip-over scenarios.
  • Risk Reduction for Crewed Missions — Ensuring that crewed vehicles can maintain a safe upright position after landing is non‑negotiable.

Effective simulation also supports operational planning: mission controllers can run landing simulations in real time for different terrain profiles, adjusting approach angles or touchdown velocities before committing to a landing site.

Aerosimulations: An Overview

Aerosimulations is a sophisticated software platform designed specifically to model the interactions between spacecraft landing gear and lunar regolith. It integrates discrete element method (DEM) calculations for granular material behavior with finite element analysis (FEA) for structural response, all within a custom physics engine tuned for reduced gravity and vacuum conditions. The platform is used by leading aerospace organizations to validate landing gear concepts for both crewed landers and robotic payloads.

Key technical highlights include:

  • High‑fidelity DEM regolith models that capture particle shape, size distribution, adhesion, and charging effects.
  • Multi‑body dynamics for landing gear mechanisms, including shock absorbers, footpads, and articulated joints.
  • Plume‑surface interaction modules that simulate gas flow from thrusters and its effect on regolith erosion and redeposition.
  • Real‑time visualization and post‑processing tools that track forces, displacements, and energy absorption during touchdown.
  • Validation against Apollo mission data and laboratory experiments with lunar simulants.

Aerosimulations also supports a modular architecture, allowing engineers to swap regolith models, gravity settings, or gear designs without rebuilding the entire simulation. This flexibility is essential for rapid prototyping and trade‑off studies.

Physical Modeling of Regolith Behavior

The core of Aerosimulations lies in its physics engine. Regolith particles are represented as discrete elements with contact laws that include normal and tangential stiffness, damping, rolling resistance, and adhesion. The particle size distribution can be customized to match Apollo core samples or remote sensing data. For large simulation domains (hundreds of thousands of particles), the platform uses spatial hashing and parallel computing to maintain acceptable runtimes. Cohesion is modeled using a Johnson‑Kendall‑Roberts (JKR) approach, while electrostatic forces are added as user‑defined constants derived from in‑situ measurements.

One unique feature is the ability to simulate regolith compaction under repeated loading. As a landing gear footpad presses into the soil, the local void ratio decreases and bearing capacity increases—a behavior critical for predicting final sinkage depth. The software tracks this state change and updates soil properties in real time, providing a level of accuracy that simpler continuum models cannot achieve.

Simulation of Different Landing Gear Designs

Engineers can import CAD models of various landing gear configurations—tripod legs, bending beams, crushable legs, or even tracked mobility systems. The platform then simulates the deployment sequence, contact with the regolith, and the subsequent structural loads. Parameters such as footpad diameter, curvature, and surface treatment (e.g., spikes or grousers) can be tested to see their effect on sinkage and lateral sliding. Aerosimulations also allows the inclusion of shock absorber hysteresis curves, making it straightforward to compare passive vs. semi‑active damping strategies.

For example, a recent study used Aerosimulations to compare a four‑legged configuration with wide footpads against a three‑legged design with articulated ankles. The simulation predicted that for landing slopes above 10°, the four‑legged design reduced induced tilting by 35%—a finding later confirmed by scaled drop tests in a reduced‑gravity aircraft.

Applications of Aerosimulations in Lunar Missions

From early concept studies to pre‑flight qualification, Aerosimulations plays a role across the entire lunar mission lifecycle. Below are key application areas:

  • Concept & Trade Studies — During the proposal phase, engineers use the tool to assess different landing gear architectures against mission requirements. Multiple gear designs can be scored on mass, stability, and dust generation.
  • Landing Site Assessment — Given a digital elevation model of a candidate landing zone, Aerosimulations can simulate hundreds of landings with randomized terrain inputs. This probabilistic approach identifies the likelihood of reaching a safe touchdown orientation.
  • Dust Plume Hazard Analysis — The platform models how regolith particles are ejected during landing engine throttling. Engineers can determine the distances at which particles will impact solar panels, radiators, or adjacent payloads, informing protective baffle design.
  • Guidance, Navigation & Control (GNC) Validation — By coupling with GNC simulation suites, Aerosimulations can close the loop: the lander’s control algorithms adjust thrust and attitude based on real‑time simulated ground interaction, testing the full descent and landing sequence.
  • Post‑Landing Performance Analysis — After a mission lands, telemetry data (e.g., accelerometer readings) can be fed back into the simulation to validate models and improve predictions for future missions.

A prominent example is the use of Aerosimulations in the design of the VIPER rover’s landing system. By simulating off‑nominal scenarios such as landing on a rock or a steep slope, engineers were able to choose a landing gear geometry that provided a 97% probability of stable touchdown on the lunar south pole terrain.

Integration with Real Mission Data

Aerosimulations is designed to work with actual mission telemetry. For instance, the platform can ingest landing radar altimeter data, onboard camera imagery, and inertial measurement unit (IMU) records to reconstruct a simulated landing after the event. This closed‑loop validation is invaluable: mismatches between simulated and observed outcomes reveal model deficiencies that can be corrected before the next mission. The system also supports importing soil mechanics test results from Apollo core samples and lunar simulant experiments, ensuring that the regolith properties used in the simulation reflect real, site‑specific conditions.

NASA’s Artemis III program is currently leveraging Aerosimulations to certify landing gear for the Human Landing System (HLS), with a focus on touchdown stability on rugged polar terrain. By running Monte Carlo simulations with thousands of random terrain profiles, engineers can statistically demonstrate that the design meets risk requirements.

Advantages Over Physical Testing

While physical drop tests remain an important part of qualification, simulation offers clear advantages:

  • Cost and Schedule — Physical test campaigns can take months and cost millions. Aerosimulations reduces the number of physical tests needed, often by 70% or more, by downselecting designs virtually.
  • Parameter Flexibility — Gravity, regolith type, and environmental conditions can be changed instantly. Physical testing would require a KC‑135 flight or a drop tower for each gravity setting.
  • Insight Into Microscopic Behavior — Simulations reveal force chains, particle velocities, and energy dissipation paths that are invisible in physical tests without extensive instrumentation.
  • Safety — High‑energy crash scenarios (e.g., failed engine, high descent rate) can be explored without risking personnel or hardware.

That said, simulation is not a replacement for all physical testing. Final qualification typically requires a limited number of integrated drop tests in a 1/6g environment, but those tests are far more likely to succeed when guided by robust simulation data.

Future Directions

Advancements in computational power, machine learning, and material science will continue to enhance Aerosimulations’ capabilities. Several areas of development are already underway:

  • Higher‑Resolution DEM Models — Particle counts of tens of millions will become feasible, allowing simulation of whole landing zones at microscopic scale.
  • Real‑Time Coupled Simulation — Future architectures will enable the landing gear simulation to run in real time, connected to actual GNC flight software for hardware‑in‑the‑loop testing.
  • Integration with Autonomous Landing Systems — Aerosimulations could be embedded in onboard computers to perform dynamic hazard avoidance: if the terrain beneath the lander is predicted to cause instability, the system could command a last‑second retargeting.
  • Expanded Terrain Models — Future versions will incorporate remotely sensed data from the Lunar Reconnaissance Orbiter and retroreflector arrays to simulate specific landing sites with centimeter accuracy.
  • Multi‑Body Interaction — Simulating multiple landers or rovers interacting with the same regolith field will become possible, supporting scenarios like cargo offloading or establishing a lunar outpost.

These advancements will be critical for establishing a sustainable human presence on the Moon, where reliable landing systems are the foundation of every surface mission. International collaboration, such as the European Space Agency’s lunar exploration program, will also benefit from open‑source data and shared simulation standards.

Conclusion

Simulating lunar regolith interaction with spacecraft landing gear is not merely a technical convenience—it is a fundamental necessity for safe and successful lunar exploration. The unique properties of regolith—abrasiveness, low cohesion, electrostatic charge, and variability—demand a simulation approach that captures the granular physics of particle‑structure interaction. Aerosimulations provides that capability, offering engineers a powerful, validated platform to design and certify landing gear under a wide range of conditions. From early concept studies through post‑mission analysis, its high‑fidelity models and data integration reduce risk, save cost, and accelerate the development of reliable lunar landers.

As humanity returns to the Moon with missions like Artemis and international partnerships, the role of advanced simulation tools will only grow. By combining physics‑based modeling with real‑world data, platforms such as Aerosimulations bridge the gap between theory and practice, ensuring that when a spacecraft touches down on the dusty lunar surface, it does so safely, stably, and predictably.

For more information on discrete element modeling of granular materials, see ScienceDirect’s overview of DEM. For details on current lunar lander designs, the Lunar Exploration Analysis Group provides ongoing white papers and reports.