An environmentally sensitive dynamic human model for LSS robustness studies with the V-HAB simulation

The development of efficient and safe Life Support Systems is one of the key drivers of the Global Solar System Exploration efforts. For each task performed by Life Support Systems (LSS) a great multitude of sub-system concepts exist and the challenge is to find the optimal combination of sub-systems for a given mission scenario. On a sub-system level the Equivalent Systems Mass (ESM) trade study approach is well suited to effectively compare sub-system options. On a system level in addition to ESM data time dependent sub-system performances within an overall system must be addressed. Criteria such as system stability, controllability and effectiveness must be considered in order to be able to assess the dynamic robustness of systems designed to the averages. In an effort to establish a dynamic simulation environment for this type of LSS optimizations the “Virtual Habitat” tool (V-HAB) is being developed at the Technical University of Munich (TUM). This paper introduces the most important part of the Virtual Habitat simulation, which is the human model.     

CELSS transportation analysis

Regenerative life support systems based on the use of biological material have been considered for inclusion in manned spacecraft since the early days of the United States space program. These biological life support systems are currently being developed by NASA in the Controlled Ecological Life Support System (CELSS) program. Because of the progress being achieved in the CELSS program, it is time to determine which space missions may profit from use of the developing technology. This paper presents the results of a study that was conducted to estimate where potential transportation cost savings could be anticipated by using CELSS technology for selected future manned space missions.

Six representative missions were selected for study from those included in NASA planning studies. The selected missions ranged from a low Earth orbit mission to those associated with asteroids and a Mars sortie. The crew sizes considered varied from four persons to five thousand. Other study parameters included mission duration and life support closure percentages, with the latter ranging from complete resupply of consumable life support materials to 97% closure of the life support system. The paper presents the analytical study approach and describes the missions and systems considered, together with the benefits derived from CELSS when applicable.     

Recent advances in technologies required for a "Salad Machine".

Future long duration, manned space flight missions will require life support systems that minimize resupply requirements and ultimately approach self-sufficiency in space. Bioregenerative life support systems are a promising approach, but they are far from mature. Early in the development of the NASA Controlled Ecological Life Support System Program, the idea of onboard cultivation of salad-type vegetables for crew consumption was proposed as a first step away from the total reliance on resupply for food in space. Since that time, significant advances in space-based plant growth hardware have occurred, and considerable flight experience has been gained. This paper revisits the "Salad Machine" concept and describes recent developments in subsystem technologies for both plant root and shoot environments that are directly relevant to the development of such a facility.     

Development and research program for a soil-based bioregenerative agriculture system to feed a four person crew at a Mars base.

For humans to survive during long-term missions on the Martian surface, bioregenerative life support systems including food production will decrease requirements for launch of Earth supplies, and increase mission safety. It is proposed that the development of "modular biospheres"--closed system units that can be air-locked together and which contain soil-based bioregenerative agriculture, horticulture, with a wetland wastewater treatment system is an approach for Mars habitation scenarios. Based on previous work done in long-term life support at Biosphere 2 and other closed ecological systems, this consortium proposes a research and development program called Mars On Earth(TM) which will simulate a life support system designed for a four person crew. The structure will consist of 6 x 110 square meter modular agricultural units designed to produce a nutritionally adequate diet for 4 people, recycling all air, water and waste, while utilizing a soil created by the organic enrichment and modification of Mars simulant soils. Further research needs are discussed, such as determining optimal light levels for growth of the necessary range of crops, energy trade-offs for agriculture (e.g. light intensity vs. required area), capabilities of Martian soils and their need for enrichment and elimination of oxides, strategies for use of human waste products, and maintaining atmospheric balance between people, plants and soils.     

Life support approaches for Mars missions.

Life support approaches for Mars missions are evaluated using an equivalent system mass (ESM) approach, in which all significant costs are converted into mass units. The best approach, as defined by the lowest mission ESM, depends on several mission parameters, notably duration, environment and consequent infrastructure costs, and crew size, as well as the characteristics of the technologies which are available. Generally, for the missions under consideration, physicochemical regeneration is most cost effective. However, bioregeneration is likely to be of use for producing salad crops for any mission, for producing staple crops for medium duration missions, and for most food, air and water regeneration for long missions (durations of a decade). Potential applications of in situ resource utilization need to be considered further.     

Carbon balance in bioregenerative life support systems: some effects of system closure, waste management, and crop harvest index.

In Advanced Life Support (ALS) systems with bioregenerative components, plant photosynthesis would be used to produce O2 and food, while removing CO2. Much of the plant biomass would be inedible and hence must be considered in waste management. This waste could be oxidized (e.g., incinerated or aerobically digested) to resupply CO2 to the plants, but this would not be needed unless the system were highly closed with regard to food. For example, in a partially closed system where some of the food is grown and some is imported, CO2 from oxidized waste when combined with crew and microbial respiration could exceed the CO2 removal capability of the plants. Moreover, it would consume some O2 produced from photosynthesis that could have been used by the crew. For partially closed systems it would be more appropriate to store or find other uses for the inedible biomass and excess carbon, such as generating soils or growing woody plants (e.g., dwarf fruit trees). Regardless of system closure, high harvest crops (i.e., crops with a high edible to total biomass ratio) would increase food production per unit area and O2 yields for systems where waste biomass is oxidized to recycle CO2. Such interlinking effects between the plants and waste treatment strategies point out the importance of oxidizing only that amount of waste needed to optimize system performance.     

Development of theoretical approaches to the control of a water-treatment system

The Advanced Life Support/NASA Specialized Center of Research and Training (ALS/NSCORT) focuses on research and development of technologies to support human habitation during space missions. This research was done as part of an effort to maintain crewmembers’ water supply in a closed life-support system. The water subsystem was the primary focus of this study because water is one of the most expensive and important resources for human survival.     

An alternative approach to solar system exploration providing safety of human mission to Mars.

For systematic human Mars exploration, meeting crew safety requirements, it seems perspective to assemble into a spacecraft: an electrical rocket, a well-shielded long-term life support system, and a manipulator-robots operating in combined "presence effect" and "master-slave" mode. The electrical spacecraft would carry humans to the orbit of Mars, providing short distance (and low signal time delay) between operator and robot-manipulators, which are landed on the surface of the planet. Long-term hybrid biological and physical/chemical LSS could provide environment supporting human health and well being. Robot-manipulators operating in "presence effect" and "master-slave" mode exclude necessity of human landing on Martian surface decreasing the level of risk for crew. Since crewmen would not have direct contact with the Martian environment then the problem of mutual biological protection is essentially reduced. Lightweight robot-manipulators, without heavy life support systems and without the necessity of returning to the mother vessel, could be sent as scouts to different places on the planet surface, scanning the most interesting for exobiological research site. Some approximate estimations of electric spacecraft, long-term hybrid LSS, radiation protection and mission parameters are conducted and discussed.     

Initial closed operation of the CELSS Test Facility Engineering Development Unit.

As part of the NASA Advanced Life Support Flight Program, a Controlled Ecological Life Support System (CELSS) Test Facility Engineering Development Unit has been constructed and is undergoing initial operational testing at NASA Ames Research Center. The Engineering Development Unit (EDU) is a tightly closed, stringently controlled, ground-based testbed which provides a broad range of environmental conditions under which a variety of CELSS higher plant crops can be grown. Although the EDU was developed primarily to provide near-term engineering data and a realistic determination of the subsystem and system requirements necessary for the fabrication of a comparable flight unit, the EDU has also provided a means to evaluate plant crop productivity and physiology under controlled conditions. This paper describes the initial closed operational testing of the EDU, with emphasis on the hardware performance capabilities. Measured performance data during a 28-day closed operation period are compared with the specified functional requirements, and an example of inferring crop growth parameters from the test data is presented. Plans for future science and technology testing are also discussed.     

Functional, regulatory and indicator features of microorganisms in man-made ecosystems.

Functional, regulatory and indicator features of microorganisms in development and functioning of the systems and sustaining stability of three man-made ecosystem types has been studied. 1) The functional (metabolic) feature was studied in aquatic ecosystems of biological treatment of sewage waters for the reducer component. 2) The regulatory feature of bacteria for plants (producer component) was studied in simple terrestrial systems "wheat plants-rhizospheric microorganisms-artificial soil" where the behavior of the system varied with activity of the microbial component. For example with atmospheric carbon dioxide content elevated microbes promote intensification of photosynthesis processes, without binding the carbon in the plant biomass. 3) The indicator feature for the humans (consumer component) was studied in Life Support Systems (LSS). High sensitivity of human microflora to system conditions allowed its use as an indicator of the state of both system components and the entire ecosystem. Grant numbers: N99-04-96017, N15.     

Biological degradation and composition of inedible sweetpotato biomass.

Many challenges are presented by biological degradation in a bioregenerative Controlled Ecological Life Support System (CELSS) as envisioned by the U.S. National Aeronautics and Space Administration (NASA). In the studies conducted with biodegradative microorganism indigenous to sweetpotato fields, it was determined that a particle size of 75 microns and incubation temperature of 30 degrees C were optimal for degradation. The composition of the inedible biomass and characterization of plant nutrient solution indicated the presence of potential energy sources to drive microbial transformations of plant waste. Selected indigenous soil isolates with ligno-cellulolytic or sulfate-reducing ability were utilized in biological studies and demonstrated diversity in ability to reduce sulfate in solution and to utilize alternative carbon sources: a lignin analog--4-hydroxy, 3-methoxy cinnamic acid, cellulose, arabinose, glucose, sucrose, mannitol, galactose, ascorbic acid.     

Evaluation of optimal configuration of hybrid Life Support System for Space.

Any comprehensive evaluation of Life Support Systems (LSS) for space applications has to be conducted taking into account not only mass of LSS components but also all relevant equipment and storage: spare parts, additional mass of space ship walls, power supply and heat rejection systems. In this paper different combinations of hybrid LSS (HLSS) components were evaluated. Three variants of power supply were under consideration--solar arrays, direct solar light transmission to plants, and nuclear power. The software based on simplex approach was used for optimizing LSS configuration with respect to its mass. It was shown that there are several LSS configuration, which are optimal for different time intervals. Optimal configurations of physical-chemical (P/C), biological and hybrid LSS for three types of power supply are presented.     

Interaction of physical-chemical and biological regeneration processes in ecological Life Support Systems.

Catalytic combustion of inedible biomass of plants in ecological Life Support Systems (LSS) gives rise to gaseous oxides (CO2, NO2, SO2, etc.). Some of them are toxic for plants suppressing their photosynthesis and productivity. Experiments with "Bios-3" experimental LSS demonstrate that a decrease of photosynthetic productivity in a system with straw incineration can jeopardize its steady operation. Analysis of the situation by a mathematical model taking into account absorption parameters of the system in terms of toxic elements makes it possible to formulate requirements for the structure and operation of LSS to provide for its stability. Avenues for further investigation of the problem of toxic stability of LSS are proposed.     

The biological component of the life support system for a Martian expedition.

Ground-based experiments at RF SSC-IBMP RAS (State Science Center of Russian Federation--Institute of Biomedical Problems of Russian Academia of Science) were aimed at overall studies of a human-unicellular algae-mineralization LSS (life support system) model. The system was 15 m3 in volume. It contained 45 L of algal suspension with a dry substance density of 10-12 g per liter; water volume, including the algal suspension, was 59 L. More sophisticated model systems with partial substitution of unicellular algae with higher plates (crop area of 15 m2) were tested in three experiments from 1.5 to 2 months in duration. The experiments demonstrated that LSS employing the unicellular algae play not only a macrofunction (regeneration of atmosphere and water) but also carry some other functions (purification of atmosphere, formation of microbial cenosis etc.) providing an adequate human environment. It is also important that functional reliability of the algal regenerative subsystem is secured by a huge number of cells able, in the event of death of a part of population, to recover in the shortest possible time the size of population and, hence, functionality of the LSS autotrophic component. For a long period of time a Martian crew will be detached from Earth's biosphere and for this reason LSS of their vehicle must be highly reliable, robust and redundant. One of the approaches to LSS redundancy is installation of two systems with different but equally efficient regeneration technologies, i.e. physical-chemical and biological. At best, these two systems should operate in parallel sharing the function of regeneration of the human environment. In case of failure or a sharp deterioration in performance of one system the other will, by way of redundancy, increase its throughput to make up for the loss. This LSS design will enable simultaneous handling of a number of critical problems including adequate satisfaction of human environmental needs.     

Human friendly architectural design for a small Martian base

The manned mission to Mars is expected to last almost three years. A human factor must be taken seriously into account in such a long-term mission. A big comfortable habitat can help to overcome sociopsychological problems, that occur in ICEs (Isolated and Confined Environments). Authors have come forward to this issue and have developed a Martian base design as a human friendly habitat. The project is based on researches of extreme conditions on Mars, architecture in ICEs and contemporary building technologies. The base consists of five modules: a Central Module (CM), an Agriculture Dome (AD), a Residential Dome (RD), a Laboratory Dome (LD) and a Garage (G). Each element has its own functional purpose. The CM is a metal capsule similar to the Reference Mission module (RM, NASA, 1997). Domes are inflatable multilayer structures, which interiors are “open planned”. Interiors can be arranged and divided into rooms by using modular partition walls designed by authors.     

Biosphere 2: a prototype project for a permanent and evolving life system for Mars base.

As part of the ground-based preparation for creating long-term life systems needed for space habitation and settlement, Space Biospheres Ventures (SBV) is undertaking the Biosphere 2 project near Oracle, Arizona. Biosphere 2, currently under construction, is scheduled to commence its operations in 1991 with a two-year closure period with a crew of eight people. Biosphere 2 is a facility which will be essentialy materially-closed to exchange with the outside environment. It is open to information and energy flow. Biosphere 2 is designed to achieve a complex life-support system by the integration of seven areas or "biomes"--rainforest, savannah, desert, marsh, ocean, intensive agriculture and human habitat. Unique bioregenerative technologies, such as soil bed reactors for air purification, aquatic waste processing systems, real-time analytic systems and complex computer monitoring and control systems are being developed for the Biosphere 2 project. Its operation should afford valuable insight into the functioning of complex life systems necessary for long-term habitation in space. It will serve as an experimental ground-based prototype and testbed for the stable, permanent life systems needed for human exploration of Mars.     

Exploration life support technology challenges for the Crew Exploration Vehicle and future human missions

As NASA implements the U.S. Space Exploration Policy, life support systems must be provided for an expanding sequence of exploration missions. NASA has implemented effective life support for Apollo, the Space Shuttle, and the International Space Station (ISS) and continues to develop advanced systems. This paper provides an overview of life support requirements, previously implemented systems, and new technologies being developed by the Exploration Life Support Project for the Orion Crew Exploration Vehicle (CEV) and Lunar Outpost and future Mars missions. The two contrasting practical approaches to providing space life support are (1) open loop direct supply of atmosphere, water, and food, and (2) physicochemical regeneration of air and water with direct supply of food. Open loop direct supply of air and water is cost effective for short missions, but recycling oxygen and water saves costly launch mass on longer missions. Because of the short CEV mission durations, the CEV life support system will be open loop as in Apollo and Space Shuttle. New life support technologies for CEV that address identified shortcomings of existing systems are discussed. Because both ISS and Lunar Outpost have a planned 10-year operational life, the Lunar Outpost life support system should be regenerative like that for ISS and it could utilize technologies similar to ISS. The Lunar Outpost life support system, however, should be extensively redesigned to reduce mass, power, and volume, to improve reliability and incorporate lessons learned, and to take advantage of technology advances over the last 20 years. The Lunar Outpost design could also take advantage of partial gravity and lunar resources.     

Life support for aquatic species--past; present; future.

Life Support is a basic issue since manned space flight began. Not only to support astronauts and cosmonauts with the essential things to live, however, also animals which were carried for research to space etc. together with men need support systems to survive under space conditions. Most of the animals transported to space participate at the life support system of the spacecraft. However, aquatic species live in water as environment and thus need special developments. Research with aquatic animals has a long tradition in manned space flight resulting in numerous life support systems for them starting with simple plastic bags up to complex support hardware. Most of the recent developments have to be identified as part of a technological oriented system and can be described as small technospheres. As the importance arose to study our Earth as the extraordinary Biosphere we live in, the modeling of small ecosystems began as part of ecophysiological research. In parallel the investigations of Bioregenerative Life Support Systems were launched and identified as necessity for long-term space missions or traveling to Moon and Mars and beyond. This paper focus on previous developments of Life Support Systems for aquatic animals and will show future potential developments towards Bioregenerative Life Support which additionally strongly benefits to our Earth's basic understanding.     

Testing a Mars science outpost in the Antarctic dry valleys.

Field research conducted in the Antarctic has been providing insights about the nature of Mars in the science disciplines of exobiology and geology. Located in the McMurdo Dry Valleys of southern Victoria Land (160 degrees and 164 degrees E longitude and 76 degrees 30' and 78 degrees 30' S latitude), research outposts are inhabited by teams of 4-6 scientists. We propose that the design of these outposts be expanded to enable meaningful tests of many of the systems that will be needed for the successful conduct of exploration activities on Mars. Although there are some important differences between the environment in the Antarctic dry valleys and on Mars, the many similarities and particularly the field science activities, make the dry valleys a useful terrestrial analog to conditions on Mars. Three areas have been identified for testing at a small science outpost in the dry valleys; 1) studying human factors and physiology in an isolated environment; 2) testing emerging technologies (e.g., innovative power management systems, advanced life support facilities including partial bioregenerative life support systems for water recycling and food growth, telerobotics, etc.); and 3) conducting basic scientific research that will enhance our understanding of Mars while contributing to the planning for human exploration. We suggest that an important early result of a Mars habitat program will be the experience gained by interfacing humans and their supporting technology in a remote and stressful environment.