Robert Mueller is a Senior Technologist at NASA and the co-founder of NASA’s Swamp Works lab. Swamp Works, based out of Kennedy Space Center in Florida, was created to be a lean development environment for innovation within NASA. Mueller realized that in order to keep NASA innovative, it had to carve out an environment that would empower people to innovate, which can often be difficult in a bureaucracy. In order to develop the right tools and the right culture for innovation, Mueller helped create the Swamp Works as a special innovation environment within NASA. By leveraging partnerships across NASA, industry, and academia, and utilizing iterative testing to quickly drive design improvements and rapidly develop towards application, Swamp Works has driven exploration towards using robotics in construction to work and live on the surfaces of other bodies in our solar system.
NASA's Swamp Works is investigating methods of robotic construction technologies and 3D printing to explore life in space
Additive Construction with Mobile Emplacement (ACME)
The first step in establishing a presence on other planets, whether it’s a base on the Moon, on Mars, or a mining operation on an asteroid, is building shelter to protect humans, robots, and equipment. NASA’s answer is the Additive Construction with Mobile Emplacement (ACME) project, which seeks to utilize 3D printing technology to provide shelter from the extremes of the deep space environment, including both solar and deep space radiation, extreme thermal swings, micro-meteroids, and exhaust plumes from outgoing rockets (which due to the lack of atmosphere, sandblasts everything within up to 5km at 2,000 meters per second).
In addition to withstanding extreme environments, developing shelters in space presents another obvious challenge: launch costs and rocket payload volumes make it cost-prohibitive to send heavy construction materials and supplies from Earth. In order to be feasible, extra-planetary habitats will need to be built with local materials.
Living Off the Land… In Space
One of Swamp Works core technologies is developing in-situ resource utilization (ISRU), which Mueller refers to as “living off the land in space.” ISRU is the idea of harnessing the resources available at destination, whether it is Mars, the Moon, and asteroid or elsewhere. Living and working in deep space means crew members have less access to the to the life-sustaining elements and critical supplies available on Earth, and the farther humans go into deep space, the more important it will be to generate their own products with local materials.
The primary resource available to build structures on other planetary surfaces is regolith. Regolith is the surface layer of loose material and crushed rock that sits on top of bedrock. It includes all the rocks, gravel, and dust, from large boulders to tiny particles, and it exists on Earth, other planets, moons, and asteroids. Regolith is also what a civil engineer might recognize as construction aggregate. The Moon is covered in aggregate, which is a huge opportunity for building. Swamp Works in exploring ways to exploit regolith for as many uses as possible, using one of two approaches: extracting resources out of the regolith, usually with chemical process, or using the regolith as a raw material for building structures. Iron, titanium, aluminum, and other metals can be extracted from regolith, or the aggregate can be used to make concrete.
In order to build the structures, Swamp Works is investigating methods of using robotic construction technologies, primarily 3D printing, in conjunction with Lunar and Martian regolith.
One method involves outfitting the ATHLETE (All-Terrain, Hex-Limbed, Extra-Terrestrial Explorer) Robot, a six-limbed lunar rover created by NASA’s Jet Propulsion Laboratory at the California Institute of Technology, with a 3D print head. Another method being investigated by Swamp Works is additive construction with sintered regolith, which is particularly promising for the construction of landing pads. Sintering involves heating the regolith to just-below-melting temperatures (1200 - 1500 C), which makes the dirt stick together and forms a brick-like material. Robotic 3D printers can then use the material to build landing pads or walls of a habitat.
Swamp Works is also working to develop a Zero Launch Mass 3D Printer, referring to the zero launch mass of construction materials the printer will enable by allowing structures to be 3D printed on demand, with building designs transmitted digitally from Earth and printed in space.
In order to utilize the regolith to actually build also requires reinventing cement. While 3D printed concrete structures on Earth have typically used Portland cement, a shortage of limestone in space makes this prohibitive on the Moon or Mars. To solve this, the team at Swamp Works formed a polymer concrete by mixing 30% thermoplastic polymers with 70% crushed rock (basalt). The resulting material is easy to extrude, so it can put on a robot arm with a print head for printing structures. It’s also much stronger than concrete.
NASA is developing a new kind of concrete structure that can put on a robot arm with print head for printing structures
Using Robotics in Construction to Solve Problems On Earth
Polymer concrete can also have a big impact closer to home. As awareness of the plastic problem spreads, polymer concretes could have a role in helping to reduce the amount of plastic trash in the planet’s landfills and oceans. Plastic bottles can be recycled to form that are polymer concretes stronger than conventional concrete, providing better building materials while also reducing the amount of discarded plastic and lowering the carbon emissions of the cement industry. As one example, the United States Army currently burns the many plastic bottles used in the field. Swamp Works wants to help take those bottles and mix them with local materials such as sand to build structures. The use of polymer composite concrete from local recycling stream polymers and granular materials has the potential to disrupt the construction industry.
NASA has partnered with the US Army to help solve the shared challenge of building long-term outposts in remote locations but here on Earth. Most notably, Swamp Works worked with the US Army Corps of Engineers and the US Army Engineer Research and Development Center on the Automated Construction of Expeditionary Structures (ACES) project. The goal of the project is to develop automated construction systems to replace the plywood-based B-huts barracks currently used by the Army. The resulting 3D printed concrete structures will take less time to build, require less mass brought in-theater, provide better protection, require fewer personnel, produce less waste, and will mimic local construction styles so they can be left for local populations to inhabit when finished. Working out of the Construction Engineering Research Laboratory (CERL) in Champaign, Illinois, the ACES team used a large Robotic Gantry 3D Printer to print a 512 square-foot barracks b-hut. Caterpillar also partnered with the project, and will help explore commercialization opportunities for the technology.
About this series: In June 2018, Autodesk and MassRobotics (a Boston-based nonprofit innovation hub focused on needs of the robotics community) held the Robotics in Construction Summit at the Autodesk BUILD Space in Boston. We've documented the information and discussions from the summit and packaged them into a Robotics in Construction eBook.