In April 2018 Mars X-House was awarded first place winner in 100% Virtual Design within NASA’s Phase 3 3D-Printed Habitat Challenge. Mars X-House employs an evidence-based design process to introduce the design and constructability of a future habitat for a crew of four to live and work on Mars for the duration of one Earth year.
As group leader of team SEArch+ / Apis Cor, we adopted a human-centric approach in the design and engineering of this habitat to prioritize safety, redundancy, and the wellbeing of the crew above the Martian surface. Mars X-House synthesizes radiation protection, natural light, egress, and the required program given the parameters of the competition’s final head-to-head event, such as being scaled to fit within a 4.5m x 4.5m footprint at ⅓ scale. X House presents realizable construction innovations in 3D printing applied within the constraints of a mission to Mars, coupled with research in ISRU manufacturability to introduce an advanced and celebratory vision of human life on the red planet. See below for complete project credits.
Enclosing an atmosphere of pressure in the near vacuum of Mars is a major design driver. Especially in ⅓ gravity, the greatest force is the one pushing outwards from the inside. Usually pressure vessels favor tension structures, like balloons or inflatables, or materials that take tension like aluminum. The structure has been designed and evaluated assuming normal (Earth-based) atmospheric pressure within the habitat, therefore the structure will experience an internal pressure close to 100.7 kPa.
X-House is designed to take advantage of the thickness of the wall structure to create passie radiation “overhangs” at each window, effectively shading each opening against rays that are inclined more than 30°. Additionally, X-House uses thicker shielding in the parts of the habitat where the crew is estimated to spend the most time according to their daily schedule. By accounting for the astronauts’ schedules in the design of the habitat layout, X-House shields the astronauts within the parts of the habitat they spent the most time.
Habitat systems including MEP and ECLSS are built into a pre-integrated mechanical core functioning as a wet core for the habitat. A pre-integrated ECLSS system serves the habitat from the secondary inner vertical walls.
Three independent service zones keep the two lab areas on the ground floor and the living areas safe and cellularized in the event of an emergency. Airlocks separate each lab environmentally from the rest of the habitat.
Emergency egress is provided by an exterior stair on the outside of the building, allowing access from floors 1, 2, and 5. The stair system functions as an area of refuge that is environmentally separate from the main structure, enabling the crew to plan and strategize options prior to performing extra-vehicular activity /or completely vacating the building. Types of emergencies the crew may encounter could include a fire, chemical spill, or a microbe becoming a pathogen in oxygen. Egress paths of travel and the cellularization of high risk zones are again, primary design drivers for the habitat.
Ground / Level 1
The ground floor features an area for communications and operations, in close proximity to the habitat’s main power lines (within the sub-floor) which also provides elevated access to the rover port. Stowage for processing of mission critical items including food is located beneath the habitat’s main staircase, as well as within the sub-floor. In a future Mars mission, astronauts will be actively engaged in analyzing sample rocks and soils on the planetary surface for life detection, metrology, characterization, etc. The analysis of foreign extraplanetary material is highly dangerous and every step must be taken to ensure the crew is protected from potentially lethal pathogens. For this reason it was critical that both laboratories be environmentally separate from the private and public living areas by airlocks and feature separate and independent ventilation systems. Laboratory 2 is intended as an engineering, repair, and medical treatment center for the habitat. The lab features experimental modules for: medical diagnostics, pharmaceuticals, and medical fabrication. The lab also features a large, open working area for 3D-printing parts, tools, repairing hardware, and maintaining other elements of habitat engineering.
Level 2
Level 2 provides access to the pre-integrated mechanical core, featuring all ECLSS hardware in addition to the hygiene program (toilet and shower). Level 2 also provides access to the emergency egress tunnel’s extended landing for use as an area of refuge and planning in the event of an emergency. Additional EVA suits are provided in the event that the rear-entry suitports docked on the exterior of the hab at the ground level are compromised.
Levels 3 and 4
Levels 3 and 4 provide two crew quarters bedrooms each. The bedrooms are sized according to standards from NASA Standard minimum living spaces. A bedroom entrance alcove at each level provides an area for pre and post sleep activities, to enjoy the garden and views to the martian landscape. As the crew spends the majority of their time in the bedroom areas, they are located within a second interior wall and so are more heavily shielded from radiation. These walls also serve as MEP walls hosting air supply and return within 3D printed chase walls.
Level 5
Level 5 features a living and communal area, a kitchen and food prep area, as well as a workstation for mission operations which would benefit from elevated views looking out upon the vast Martian landscape. A small garden area provides herbs for the kitchen and natural plantings which will remediate the air circulated through the plantings below. The air supply plenum passes through the roots of the plantings which offer natural bioremediation opportunities.
A mobile telescoping platform has been developed for supporting two mobile printers and minimizes the risk and costs involved in developing an overly tall gantry system for the printing technology. The mechanical core deploys by telescoping upwards to the second and third levels of the habitat. At the appropriate time, horizontal spokes deploy from the sizes of the core, functioning as support structures for printing horizontal floorplates. The precision-manufactured inflatable membrane for the water bladder deploys from a reverse-umbrella mechanism deploying from the highest plate of the mechanical core.
Diagonal and circumferential hoop (horizontal) basalt reinforcement further act to resist tensile forces, acting as a perimeter truss structure around the hyperboloid. Circumferential hoop reinforcement has been placed in close proximity above and below window penetrations, which are located at regular intervals in elevation. A single layer of expandable polyethylene foam is applied between the HDPE and regolith-concrete shell to anticipate expansion and contraction of the polymer material. An expandable polyurethane foam layer serves as an expansion gap between materials with differing modulus of expansion and contraction.
The following is a simulation of the construction sequence of our habitat design, developed in Navisworks. The regolith foundation is printed first, followed by an HDPE floor at level 1. The mechanical core and rack system for the laboratory experimental modules are then positioned within the habitat. A single layer of concrete regolith is printed prior to the diagonal basalt reinforcement diagrid or the circumferential hoop reinforcement. The emergency egress tunnel is printed after the primary hyperboloid form and reinforcement have been printed completely to ensure stability and prevent overturning of the structure.
X House is envisioned as a pioneering habitat that capitalizes on pre-existing Mars infrastructure elements crucial to mission success but also introduces novel ISRU (in situ resource utilization) materials extraction and processing methods to diversify construction means and methods for scalability of the habitat design. Following NASA’s Design Reference Architecture for Human Missions, and in conversation with EDL and ISRU experts, we employed NASA’s scheme for an autonomous surface site establishment for ISRU water acquisition, propellant production, solar, MMRTG and fuel cell redundant power supply options, in addition to the Hercules Single-Stage Lander. The Hercules Lander precisely delivers payload of machinery, equipment, and supplies, including the necessary mobile 3d-printers, excavation robots, airlocks and pre-integrated hardware modules.
According to the parameters developed in our approach to the competition’s head to head event, the trajectory speed of printing for the regolith-concrete print is 10 meters per 1 minute. Within 1 minute of print-time, the printer lays down material that is 30 mm in width x 20 mm in height. A simulation of the current trajectory speed of printing has been performed to determine the number of passes required by the 3D-printer for each layer of the structure. From this information we derived the overall print time for X House.
Structural analyses of the habitat were performed on two load cases: the pressurization of the regolith-concrete shell as well as the performance of the mechanical core / water bladder. The analysis on the regolith-concrete shell informed a critical design decision to include additional reinforcement running perpendicular to the endpoints of the continuous diagonal reinforcement within the dome structure.
Mars X-House was a collaborative project between SEArch+ and Apis Cor.
Consultants
Sam Austin, PhD, CEAmerica
Daniel Case, University of Colorado
Jeffrey H. Hoffman, MIT Department of Aeronautics and Astronautics
Lance LeBlanc, LeBlanc Design
Matt Melnyk, Nous Engineering
Modulus Consulting
Robert Moses, NASA Langley Research Center
Edward J. Roberts, LERA
Jeffrey Schantz, Sector Leader of Science + Technology at EYP Inc.
Principal
Melodie Yashar, team leader, SEArch+ / Apis Cor
Christina Ciardullo, SEArch+
Nikita Cheniuntai, Apis Cor
Michael Morris, SEArch+
Sergey Nefedov, Apis Cor
Rebeccah Pailes-Friedman SEArch+
Associate
Geoffrey Bell
Layla van Ellen
Nihat Mert Ogut
Tianhui Shen
Reece Tucker