The international space community is contemplating long-duration crewed missions to Mars in the near future. In this regard, human space mission simulators play an important role in developing and testing hardware and software technologies required for such missions. Simulators also provide an ideal platform for conducting research in psychology, physiology, medicine, mission operations, human factors and habitability. These research areas are critical in ensuring crew well-being and performance for long term space missions.
The main goals of the MARS CITY PROJECT are:
- Provide effective test beds for field operation studies in preparation for human missions to Mars. These test beds will help develop and facilitate tests of key habitat design features, field exploration strategies, tools, technologies, and crew selection protocols that will enable and help optimize future crewed missions to Mars.
- Generate public support for sending humans to Mars. They will inform and inspire audiences around the world. As the Mars Society’s flagship program, the MARS CITY program will serve as the foundation of a series of bold steps that will pave the way to the eventual human exploration of Mars.
As operational test beds, the stations serve as a central element in support of parallel studies of the technologies, strategies, architectural design, and human factors involved in crewed missions to Mars. The facilities also feature field laboratories in which data analysis can begin before scientists leave the field site and return to their home institutions..
Unlike researchers in typical laboratory facilities or in scientific expeditions, crew members who live and work at Mars Analog Sites are forced into a unique mindset, as if they themselves were exploring the surface of Mars and living in an early Mars habitat. This mindset and environment provide scientists a unique opportunity to analyze technical, psychological and programmatic challenges to which they may otherwise be unaware, developing new solutions and testing those solutions first-hand. Only through such first-hand experience would it be possible to develop the knowledge that will prove critical for human safety and productivity on the surface of Mars Thus, the analog stations help develop the capabilities needed on Mars to allow productive field research during the long months of a human stay.
The MARS CITY project goals will constitute the framework for the major technical objectives of the MARS CITY Project. Within this framework we intend to maximize the scientific returns by focusing on the remaining most compelling open issues, which are known in literature as the “Five Showstoppers for Mars”.
These showstoppers are threats to human health and safety which can prevent a human Mars mission from succeeding or even starting. This list includes:
- Need for Regenerative & Bioregenerative Life Support
- Martian Dust
- Planetary Protection (Forward-contamination and Back-contamination)
Except for hypogravity (0.38% Earth’s gravity), which cannot effectively be tested using available technology on Earth, MARS CITY will be specifically designed as a test bed to validate technologies able to mitigate the Showstoppers.
Thus, MARS CITY project objectives are as follows:
1. Provide full in-field assessment of hybrid/inflatable habitat technologies
- Demonstrate technical feasibility and long term operational performances
- Assess long term effectiveness of adopted dust control and mitigation technologies (particularly associated with airlock design)
- Assess feasibility and operational procedures (ie. partially automated, robotic support, etc) for regolith-based shielding
2. Provide an effective test bed for key enabling technologies
- Within a complete simulation of the command, control & communication system, provide the possibility of identifying new breakthrough management concepts and technology to support interfaces, information flow and sharing, managements, controls, operations , procedures, and man-machine interfaces.
- Achieve adequate power generation and storage in Mars replicated conditions. Demonstrate sustained and robust performances at least over the lifespan of the reference surface mission (18 months).
- Assess long term performances of In-Situ Resource Utilization (ISRU) technologies, including Sabatier reactors
- Allow for short range Extravehicular Activities (EVA) dedicated to hardware components (such as Martian surface exploration suits, rovers, tools) testing in simulated Martian conditions
- Include simulation of most relevant physical-chemical regenerative and bioregenerative life support systems.
- Equip the astrobiology laboratory in order to effectively validate procedures which incorporate Planetary Protection in sample collection and handling
3. Effectively implement Human Factors advanced research into the Habitat Design
- Definition of crew safety, crew health, and crew productivity Figures of Merit (FoM)
- Definition of human factors standards requirements and specifications
- Review of habitat design, construction and testing to assess compliance with those performance-based standards, requirements and specifications
4. Provide an environment able to maximize scientific productivity of researchers
- Conduct regular discussions between the engineering support crew and mission crews pre- and post- occupancy
- Set up a series of long-term analog studies that produce scientifically and statistically valid, evidenced-based, reproducible results, and ensure dissemination
- Provide support to mission crews in order to plan and conduct scientifically valid research
- Facilitate missions participation from various countries, facilitating international cooperation and collaboration
5. Ensure effective transfer of results to the scientific community
- Develop system models and maintain an archival database of mission reports, lessons learned, operational results and key design information
- Conduct and publish regular, periodic comprehensive, systematic and scientifically valid Post Occupancy Evaluations (POE)
- Disseminate timely scientific and technological information through journals, the Internet, electronic and video media, workshops, and special programs
6. Ensure effective outreach
- Setup a dedicated education center and organize access of visitors to the facility
- Work in partnerships with the entertainment industry, media, museums, etc. to bring Mars exploration to the general public
- Participate in preparation of instructional materials reflecting the discoveries and adventures inherent in Mars exploration through partnerships with educators
- Publish and distribute engineering and scientific findings in the open literature
7. Inspire the next generation of scientists, engineers, and entrepreneurs to pioneer the space frontier
- Make very close ties with universities
- Build the bulk of the engineering support crew from local engineering faculties
8. Become a reference center for Small and Medium Enterprises (SME) wishing to test and integrate their advanced technologies with potential space applications
- Pursue active participations from SMEs both from within and outside the space community
- Implement a well defined plan for managing and protecting the Intellectual Property (IP) of participating SMEs
State of the Art
NASA’s active analog missions
Mars Society active analog missions
- Martin-Marietta Mars Direct MSR Mission Design Habitat 
- First Mars Outpost Habitation Strategy, by Marc M. Cohen [1992 /1993]
- Mars Design Reference Mission (MDRM) 1.0/2.0 
They are examples of pre-integrated habitats (in the specific version known as ‘tuna can’) – hard shell modules which can be delivered complete to the surface. These types of habitats can usually be used as the crew habitat during the voyage to the planet, and are then landed on the planet where they continue to serve as habitats for the remainder of the mission.
Technical limitations of existing stations
The major technical limitations of the existing stations with respect to the mentioned Mars mission Showstoppers are the following:
- HABITAT SHIELDING
The existing terrestrial analog stations do not simulate shielding as part of their missions.. In particular, the tall profile of the ‘tuna can’ habitats makes shielding difficult.
- HABITAT SEALING
The great majority of the existing stations are not sealed structures. This implies that a closed life cycle environment cannot be simulated, particularly in terms of air recycling and thermal management. This also makes dust control practically impossible.
- HABITAT LOCATION
All the listed analog projects are located in remote areas. Such locations imply:
– Elevated costs of logistics: transportation and supplies.
– Only short seasonal use. A facility not used full-time is very expensive per man-hour of use
– Simulations implying advanced technologies are avoided because too difficult to be supported and maintained remotely.
Generally, existing facilities lack an integrated approach in the sense that they tend to be “partial simulators” or “single event simulators”. For testing long duration planetary missions, a planetary simulator that enables full interface with all habitat and surface exploration systems is imperative. Indeed also NASA has well identified this compelling need and the Advanced Integration Matrix (AIM) project at the Johnson Space Center (JSC) was chartered to study and solve systems-level integration issues for planetary exploration missions.
AIM will be able to benefited from the acquisition of hardware and modules from some completed NASA projects. In its final stage, AIM will become a multi-enterprise, multi-center concern focused on developing and testing integrated mission concepts and publicly pursuing participations from academia and other NASA Centers.
The MARS CITY will be unique in design, in that it will include the newest technologies and latest developments in the field, providing the ability to study and solve systems-level integration issues for Mars exploration missions.
The main innovative contents will focus on the areas of habitat typology, shielding, sealing, and location, as well as long-term testing of electric power technologies. These elements are described below.
- HABITAT TYPOLOGY
Latest developments, such as those summarized in the Mars Design Reference Architecture (MDRA) 5.0 have introduced the concept of pre-fabricated, inflatable deployed or assembled structures.
According to the MDRA 5.0:
“Limited volumes and the complexity of packaging the Mars lander and surface systems within the aerodynamic shell of the entry system would most likely require advanced inflatable structures. Key technology thrusts include habitat concepts and emplacement methods (including remote and autonomous operations) as well as advanced lightweight structures (inflatable vs. traditional “hard shell”), and developing integrated radiation protection for crew health and safety.”
The main advantages of advanced inflatable structures are:
- Larger usable/habitable volume
- Lower mass
These advantages are of particular importance, since they are key enablers for crewed missions to Mars, enabling the goal of maximising habitable volume while reducing launch mass, and therefore simplifying mission architectures and reducing the number of launches needed – drastically reducing overall mission costs. Secondary benefits to using these structures include:
- Higher crew productivity
- Higher crew morale and quality of life (Lower stress)
- High reliability & easy to repair
Concerning the issue of puncturing, it should be considered that modern multi-layer flexible materials are extremely tough. They are designed so that one (or even multiple) hull breaches will not result in the structure’s destruction. They can also absorb or deflect much of the energy from any impact. Inflatable modules have a distinct advantage over traditional hard shell ones in that they are more easily repairable. Metal can be snapped, bent, shattered or otherwise broken, whereas a more flexible structure can ensure that any damage is more localised and, in some cases could even be self-repairing by using passive self-healing systems. Some of the layers can also be designed to identify penetrations (occurrence and location) and communicate them to a warning system.
According to existing and ongoing studies, one of the most recent and interesting designs is the “planetary” version of the hybrid inflatable habitat module originally developed by NASA for the Mars crew transit (TransHab) mission. This design, known as a “Surface Endoskeletal Inflatable Module” (SEIM) essentially adapts the hybrid structure to the surface mission requirements. The MARS CITY habitat will be based on such design with the needed modifications for radiation shielding (see next point) and for any unavoidable terrestrial analog conditions and constraints. In Figure 1 is shown a draft possible configuration of the MARS CITY Habitat modules which is currently being evaluated.
- HABITAT SHIELDING
MARS CITY proposes the provision of radiation shielding, thermal mass, and micrometeorite protection using recently proposed composite materials obtained by adding high-performance polymer binders to Martian regolith.
Regarding the challenge of layering these materials on top of the inflatable habitat, it should be considered that the loading is inconsequential compared to the internal pressurization load. In effect, heaping a 1m layer of Martian regolith on top of the habitat’s exterior surface actually reduces the stress on the plastic fabric.
The construction and operation of an inflatable structure, covered with a layer of shielding material will be one of the major technical challenges that MARS CITY intends to address.
- HABITAT SEALING
MARS CITY will be designed to be as air-tight as possible, relying on air-exchangers, filters, plants and proper design of entrances (airlocks). This will allow for the development and validation of mission critical technologies, such as dust filtration, isolation, and mitigation.
- HABITAT LOCATION
A location is suggested for MARS CITY where:
– Logistical costs are minimized (the location is easily accessible)
– The facility could be fully supported by a local Engineering Crew
– Full time use the entire year would be possible
– Proximity to touristic areas could be exploited for public outreach, education, and stakeholder engagement
The facility’s time and resources would be shared between scientific and outreach/educational periods. A MARS CITY visitor center is proposed, where guests could see how and where crews live and work, both by walking through a near-identical layout and through live web-cams to all of the activity areas. Visitor donations could contribute to supporting the running costs, and the outreach effectiveness would be largely increased over existing terrestrial Mars Analogs.
A further distinction with respect to the existing M.A.R.S. Stations would be the location of the habitat inside a hangar of suitable dimensions. Within this enclosed area, some features of the Martian environment could be reproduced, particularly lighting conditions (diurnal cycle, absorption, diffusion etc of light by the Martian atmosphere) and the Martian dust environment. These are elements that have yet to be simulated terrestrially, and are critical to technology development, testing and validation as precursors to crewed missions to Mars.
- ELECTRIC POWER TECHNOLOGIES LONG TERM TESTING
The electric power system is a crucial element of any mission for the human exploration of the Martian surface. It is proposed to equip MARS CITY with a photovoltaic power-generation system with regenerative fuel cell (RFC) energy storage in order to assess the feasibility and long term performances of such a system. Testing of other electric power technologies will also be possible as soon they become available.