project09:2024Msc2JIP

MSc 2 JIP Space Architecture & Infrastructure

The Lunar Constructors project is aimed at addressing one of the most pressing challenges in space exploration: creating sustainable, autonomous habitats on the lunar surface. As space agencies and private companies advance their capabilities for lunar missions, the goal of establishing long-term human presence on the Moon is becoming more tangible. However, the Moon's environment presents extreme challenges—including intense radiation, a lack of atmosphere, severe temperature fluctuations, and the impact of micrometeorites—that make traditional human-centric construction methods risky and complex.

The project addresses these challenges by proposing an autonomous, modular system for constructing lunar habitats, utilizing local resources and advanced robotic and manufacturing technologies. The project's approach combines three key technological domains:

1. Building Blocks: For building a very basic structure on the Moon, the Lunar Constructors use a very basic part of a structure, the building blocks. For a structure to be established by a swarm of robots, the building blocks required to be assembled should be simple structures to decrease the complexity of assembling the structure by the robot. Another aspect to be considered is the complexity involved with 3D printing, hence choosing a building block which is simple yet strong is very important.
2. 3D Printing: Additive manufacturing methods, specifically adapted for lunar conditions, are used to transform regolith into interlocking building blocks. Techniques such as binder jetting and selective laser sintering allow the creation of complex structures that are lightweight yet resilient, accommodating the Moon's low gravity and atmospheric conditions.
3. Swarm Robotics: Employing a decentralized system of robots that work collaboratively, each robot is designed to perform specific tasks, such as regolith collection, transportation, and assembly. Inspired by swarm intelligence, this autonomous approach allows a large number of small robots to adapt dynamically, perform tasks collectively, and compensate for any individual failures—critical attributes for construction in the harsh lunar environment.

The Lunar Constructors project tries to address the feasibility of lunar construction through a series of targeted objectives. This includes researching future robust 3D printing processes using lunar regolith simulants, designing efficient robot interactions for swarm-based construction, and simulating the assembly of various structures within the Gazebo simulation environment. The project also evaluates potential building designs, such as pyramidal and dome-shaped structures, which are suited to the lunar environment's unique demands.

By leveraging advanced autonomous systems and local materials, Lunar Constructors aims to contribute significantly to global efforts in space exploration. This project offers a scalable, sustainable approach to lunar habitat construction, helping to pave the way for future missions and long-term human presence on the Moon.

Problem Statement

The project aims to perform a feasibility study of setting up a structure on the surface of the Moon by using in-situ resources to 3D print the structure and assembling it using a swarm of robots.

Concept of Operations

A general concept of operations was developed to have a clear perspective of the mission. Figure 1 illustrates the concept of operations of the Lunar Constructors project. As illustrated in the figure, from the swarm of robots available, one of the robots collects lunar regolith, which is fed to a 3D printer to produce blocks for the structure. The blocks are then transported to a site by the robots, where they use their swarm intelligence to build a structure using a predefined rule set.

Concept of Operations of the project

Building Blocks

For the project, interlocking blocks were chosen as the preferred building component for constructing autonomous, durable structures on the Moon. These blocks are designed to simplify the assembly process, providing a stable and adaptable modular unit that a swarm of autonomous robots can handle and stack effectively. The interlocking blocks offer unique advantages in both structural integrity and ease of manipulation, making them particularly suitable for the challenging conditions of the lunar environment.

The interlocking blocks are engineered with simple yet effective connectors that allow each block to securely interlock with adjacent units. This design enables a robust stacking system that holds up well under the Moon’s low-gravity conditions. An illustration of the interlocking building blocks are shown below.

Illustration of the Building Blocks

3D Printing

The 3D printing component of the Lunar Constructors project is crucial for producing building materials on the Moon, using locally sourced lunar regolith to create modular blocks for habitat construction. By employing in-situ resource utilization (ISRU) and advanced 3D printing methods, the project aims to transform lunar regolith into durable, interlocking blocks that are suitable for autonomous assembly. This approach minimizes the need for Earth-based materials, reducing transportation costs and logistical complexity, while providing a sustainable method for constructing lunar infrastructure.

Lunar regolith, the loose soil covering the Moon's surface, is rich in minerals such as silica, magnesium oxide, and calcium oxide, which can be processed into a form suitable for 3D printing. Its abundance and mineral composition make it ideal for creating building blocks, as it reduces the need for external materials. However, regolith presents unique challenges due to its abrasiveness, reactivity, and the extreme lunar environment, which requires specific adaptations in the 3D printing process.

Selective Laser Sintering

Selective Laser Sintering (SLS) is a key 3D printing technique utilized in the Lunar Constructors project for creating durable building blocks from lunar regolith. SLS operates by using a high-powered laser to selectively heat and fuse particles of regolith layer by layer, forming a solid structure without requiring any additional binding materials. This method is particularly advantageous for lunar applications, as it produces strong, precise blocks entirely from local resources, aligning well with the project’s goal of in-situ resource utilization (ISRU).

SLS stands out as a robust method for producing high-quality, regolith-based building blocks on the Moon. Its precision, durability, and ability to use 100% local material make it ideal for constructing stable, autonomous structures suited to the Moon’s extreme conditions. By incorporating SLS into the Lunar Constructors project, the team can ensure that lunar habitats are both sustainable and resilient, supporting future missions with reliable, locally manufactured infrastructure.

JSC-1 Lunar Simulant

The JSC-1 lunar soil simulant, created by NASA’s Johnson Space Center, is primarily composed of basaltic volcanic ash. Its chemical makeup, mineralogical properties, and particle size distribution closely match those of lunar low-titanium mare soils, such as those gathered during the Apollo 14 mission. Specifically, JSC-1 contains oxides like silicon dioxide (SiO2), aluminum oxide (Al2O3), and calcium oxide (CaO), which are also abundant in lunar soil. In addition, JSC-1 contains minerals like plagioclase, pyroxene, and olivine, which are the main components of lunar basalts and soils. This allows it to simulate lunar soil conditions effectively for 3D printing studies. JSC-1’s physical characteristics, such as the angle of internal friction and cohesion, are similar to those of lunar soils, making it suitable for studying lunar surface construction

Swarm Robotics

Swarm robotics employs a distributed system where multiple robots interact locally and make decisions autonomously, similar to the collective behavior seen in ant colonies or bee hives. This decentralized control allows the robotic swarm to operate with a high degree of flexibility and resilience, crucial for lunar missions where human intervention is limited. Some of the key advantages of swarm robotics are:

• Redundancy: Each robot operates independently, meaning that even if some units fail, the rest can continue functioning, reducing the risk of mission failure.
• Scalability: More robots can be added to the swarm to increase construction speed without requiring changes to the system’s core architecture.
• Adaptability: The robots adapt to changes in the environment, allowing them to navigate unpredictable lunar terrain and collaboratively assemble structures.

The Robot

The project utilizes a modified version of the Lunar Zebro, a compact, six-legged rover originally developed at TU Delft. The Lunar Zebro rover is known for its unique locomotion capabilities, allowing it to navigate challenging lunar terrain with greater stability and agility than wheeled rovers. The robot’s compact size, equivalent to an A4 sheet of paper, makes it ideal for missions requiring multiple units in a swarm.

Lunar Zebro Rover (Image Credit: Lunar Zebro)

Several modifications enhance the Lunar Zebro for the project’s specific needs:

1. Robotic Arm: A robotic arm is added to enable the Zebro to pick up and place 3D-printed blocks accurately. This arm allows for precise handling of building materials, essential for assembling the structure.
2. Regolith Collector: Some units are outfitted with a regolith collection attachment, enabling them to gather lunar soil, which is then transported to the 3D printer for block fabrication.
3. Camera System: The Lunar Zebro’s camera is upgraded to improve situational awareness, enabling accurate navigation and object detection. Options include panoramic or wide-angle cameras to optimize visual processing and assist in obstacle avoidance and block alignment.
4. Processor Upgrade: The robot’s central processor is upgraded to a radiation-hardened model, such as the PowerPC 750, which allows it to handle more complex tasks and operate reliably under the Moon’s high radiation exposure.

Lunar Zebro Rover after modifications

These modifications transform the Lunar Zebro into a versatile, task-specific unit within the swarm, capable of both autonomous navigation and collaborative construction activities. Each robot type in the swarm performs specialized tasks, including:

• Regolith Collection Robots: Gather lunar regolith and deliver it to the 3D printing station.
• Worker and Transport Robots: Handle the transport of printed blocks to the construction site.
• Assembly Robots: Precisely place and interlock blocks to form stable structures.
• Mapping and Beacon Robots: Map the lunar surface and serve as reference points to assist other robots in navigating and aligning the structure.

Structure

The Structure section of the Lunar Constructors project details the design and assembly strategies for building stable, autonomous habitats on the Moon. Given the challenges posed by the lunar environment—such as low gravity, temperature extremes, and micrometeorite impacts—the project prioritizes structural forms that offer resilience and stability. Using interlocking blocks produced from lunar regolith, the robotic swarm constructs the habitats following a predefined set of rules to ensure reliable and efficient assembly. The rule set is explained in detail in the report. The project evaluates two primary shapes for habitat structures:

1. Pyramid Structure: This form, with a square base and an inward tapering design, provides stability as each layer moves progressively inward. Pyramid structures distribute weight efficiently, lowering the center of gravity and allowing robots to stack blocks without needing external support. The estimated design for a 10-meter base and 5-meter height would require approximately 6,337 blocks.
2. Dome Structure: Inspired by natural and architectural domes, this shape creates a resilient, closed structure that provides strong protection against micrometeorite impacts and radiation. However, its curved form requires the robots to use additional supports, such as ramps, to reach higher levels during construction, making it a more complex option.

Illustration of the pyramid and dome type structures

Simulation

Given the challenges of operating in low-gravity and extreme conditions on the Moon, simulating the entire construction process helps evaluate the feasibility of the system and optimize robotic behavior before real-world implementation. The simulation primarily focuses on testing robot interactions, structure formation, and environmental adaptations, allowing the team to refine the swarm’s rule set and assembly techniques. The project employs the Gazebo simulation platform, integrated with the Robot Operating System (ROS2), to create a realistic model of the lunar environment.

ROS2 acts as the communication framework within the simulation, enabling data exchange between the robots and allowing real-time updates on their positions, states, and tasks. This integration supports the swarm’s complex interactions, as each robot communicates its actions and receives input based on sensor feedback, enabling coordinated movement and block placement. Several key elements were successfully implemented in the simulation:

1. World Definition: A virtual lunar environment was created with adjusted gravity (1.62 m/s²) and a single light source to simulate lunar lighting. The ground’s friction was also modified to replicate lunar regolith’s coarse texture, providing realistic conditions for rover movement and block handling.

Gazebo simulation world

1. Building Block Sim 3D models of the building blocks, created in Blender, were integrated into Gazebo, with specific dimensions and densities to match real regolith-based blocks. This setup allowed for visualization and testing of block stacking and interlocking during the construction simulation.

Inserted the building blocks and rover into Gazebo

1. Rover Definition: A simpll of the Lunar Zebro rover was created to represent the robot’s basic functions, including movement, block transportation, and climbing capability. This model allows the team to test the rover’s navigation and block handling in the simulated lunar environment, assessing its capacity to navigate and interact with other robots during assembly.

Model of the rover in Gazebo

1. Visual Processing: Visual sensing ented to support navigation and the pick-and-place operations needed for block assembly. Using camera feeds processed with Python scripts, the simulation allows robots to detect objects and orient themselves relative to the structure, enhancing their precision during construction .

Visual input of the rover

Recommendations

After a detailed analysis, the following recommendations can be made for the future work of the project to be carried out.

1. Optimized 3D Printer: Develop a selective laser sintering (SLS) printer tailored for lunar regolith, capable of autonomous, long-term operation with redundancy to limit maintenance needs.
2. Structural Analysis: Conduct a detailed analysis of block durability to ensure they withstand lunar conditions and offer essential properties like insulation and air-tightness.
3. Entrance Design: Design a feasible, modular entrance that integrates with the autonomous structure and supports future human access.
4. Robot Adaptations: Modify Lunar Zebro robots with improved manipulators and sensors to handle block placement and navigation accurately in lunar conditions.
5. Enhanced Simulation: Refine the simulation environment to include realistic lunar textures and material properties, improving operational testing and swarm behavior optimization.
6. Architectural Flexibility: Explore broader architectural options beyond the current ruleset to support various habitat configurations for future needs.

Conclusion

The Lunar Constructors project demonstrates the potential for autonomous lunar habitat construction using swarm robotics and 3D printing. This method addresses the challenges of the lunar environment by leveraging in-situ resource utilization (ISRU), specifically the transformation of lunar regolith into interlocking blocks. The project concludes that selective laser sintering is the most suitable printing method for creating durable, uniform blocks, which can be effectively assembled by a swarm of modified Lunar Zebro robots.

Key insights include the scalability, autonomy, and sustainability of the proposed construction system, though limitations in structure design and assembly remain. Further research is recommended to validate the final design for structural performance and adaptability. The Lunar Constructors concept has the potential to contribute significantly to sustainable space infrastructure, facilitating long-term human presence on the Moon.

Contributors

Deepanshu Kamlesh Punjabi Rienk Marsman Mikolaj Helinski Yuran Wang Yuanfu Pan