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NASA is planning to return to the moon and then explore Mars. A permanent base at the south pole of the moon will be the test bed for Mars. At the moon base, two crewmembers are expected to conduct Extravehicular Activity (EVA) six days every week. Current spacesuits are cooled by the sublimation of water ice into vacuum. A single 7 hour EVA near the lunar equator in daylight can expend up to 5 kilograms of water. Because of the high cost of transporting spacesuit cooling water to the moon, the water for one EVA could cost hundreds of thousands of dollars. The lunar south pole and Mars have low surface temperatures that make cooling much easier than at the lunar equator. Alternate cooling methods and staying in cool environments can reduce or eliminate the use of water for spacesuit cooling. If cooling water is not needed, a recycling life support system can provide all the required crew water and oxygen without transporting additional water from Earth.

The design and mass cost of a starship and its life support system are investigated. The mission plan for a multigenerationai interstellar voyage to colonize a new planet is used to describe the starship design, including the crew habitat, accommodations, and life support. Cost is reduced if a small crew travels slowly and lands with minimal equipment. The first human interstellar colonization voyage will probably travel about 10 light years and last hundreds of years. The required travel velocity is achievable by nuclear propulsion using near future technology. To minimize mission mass, the entire starship would not decelerate at the destination. Only small descent vehicles would land on the destination planet. The most mass efficient colonization program would use colonizing crews of only a few dozen. Highly reliable life support can be achieved by providing selected spares and full replacement systems.

Dynamic simulation of the Lunar Outpost habitat life support was undertaken to investigate the impact of Extravehicular Activity (EVA). The preparatory static analysis and some supporting data are reported in another paper. (Jones, 2008-01-2184) Dynamic simulation is useful in understanding systems interactions, buffer needs, control approaches, and responses to failures and changes. A simulation of the Lunar outpost habitat life support was developed in MATLAB/Simulink™. The simulation is modular and reconfigurable, and the components are reusable to model other physicochemical (P/C) based recycling systems. EVA impacts the Lunar Outpost life support system design by requiring a significant increase in the direct supply mass of oxygen and water and by reducing the net mass savings of using dehydrated food. The mass cost of EVA depends on the amount and difficulty of the EVA scheduled.

This paper considers the design of a Mars Transfer Vehicle (MTV) water processor. The Constellation Program has begun to consider the first human mission to Mars, and the MTV water processor is of special interest. Mars transit system design is not affected by Extra-Vehicular Activity (EVA) or In-Situ Resource utilization (ISRU). The total duration of Mars transit and return is relatively fixed at about four hundred days, while Mars and lunar surface stays can vary from a few days to many years. The Mars transit water processor will operate in zero gravity, like the International Space Station (ISS) Water Recovery System (WRS), so the ISS WRS design can serve as a reference baseline for the Mars transit system. The paper develops the MTV water requirements and considers the suitability of the ISS WRS for Mars transit. The ISS WRS meets MTV requirements and requires less mass than direct resupply for Mars transfer, but it has excess capacity for the requirements.

This report considers crewmembers’ life support needs for air, water, and food in a long duration lunar surface base. It also considers requirements for washing and clean-up water, waste recycling, and the crew's use of air, water, and food during Extravehicular Activity (EVA). The life support mass flow is described, including the needs of the statistical average crewmember, the expected variation between crewmembers, and the potential range of the total crew's average requirements. To develop the lowest cost, most reliable life support system that meets the crew needs, we must understand how the requirements impose design constraints and cost drivers and provide options and opportunities. We also must be aware of the degree of flexibility and potential change in requirements as their costs and implementation become defined.

Ultra reliable space life support systems can be built with small additional mass for direct material supply or about twice the minimum mass for recycling equipment. The required direct supply of a material such as oxygen, water, or food for space life support can be provided in some number “r” of identical packages. If only one of the r packages fails, the life support system fails. But by providing n > r packages, so that there are n - r spare packages to make up for failures, the reliability of direct material supply can be greatly increased. Ultra reliability can be achieved if the required direct supply is provided in 10 to 100 or more packages with 1 or 2 spare packages, so the additional mass required for ultra reliable direct life support is only a few percent.

This paper considers the cost and benefit of planetary surface ExtraVehicular Activity (EVA) on the Moon and Mars. The Exploration Systems Architecture Study (ESAS) scenarios are used as a basis. The benefits of surface EVA depend on the number of sites visited, the total duration of EVA, and the maximum distance of exploration. The costs of EVA are measured by the total emplaced mass required to support a sortie mission or to establish and support a long term base. The later lunar sorties described in the ESAS have longer duration and use rovers not provided earlier, so they are more cost-effective in surface exploration. The planned permanent lunar base provides one-sixth the cost per EVA hour and a thirty percent lower cost per kilometer of explorable distance, but exploration is limited to a single site. There is an important trade-off between the number of different sites explored and the total time spent in surface exploration.

The least expensive life support for brief human missions is direct supply of all water and oxygen from Earth without any recycling. The currently most advanced human life support system was designed for the International Space Station (ISS) and will use physicochemical systems to recycle water and oxygen. This paper compares physicochemical to direct supply air and water life support systems using Equivalent Mass (EM). EM breakeven dates and EM ratios show that physicochemical systems are more cost effective for longer mission durations.

This paper considers the design of a life support system for transit to Mars and return to Earth. Because of the extremely high cost of launching mass to Mars, the Mars transit life support system must minimize the amount of oxygen, water, and food transported. The three basic ways to provide life support are to directly supply all oxygen and water, or to recycle them using physicochemical equipment, or to produce them incidentally while growing food using crop plants. Comparing the costs of these three approaches shows that physicochemical recycling of oxygen and water is least costly for a Mars transit mission. The long mission duration also requires that the Mars transit life support system have high reliability and maintainability. Mars transit life support cannot make use of planetary resources or gravity. It should be tested in space on the International Space Station (ISS).

How much integrated system level test should be performed on a spacecraft before it is launched? Although sometimes system test is minimized, experience shows that systems level testing should be thorough and complete. Reducing subsystem testing is a less dangerous way to save cost, since it risks finding problems later in system test, while cutting systems test risks finding them even later on orbit. Human-rated spacecraft test planning is informal, subjective, and inconsistent, and its extent is often determined by the decision maker's risk tolerance, decision-making style, and long-term or short-term view. Decisions on what to test should be guided by an overall mission cost-benefit analysis, similar to the risk analysis used to guide development efforts.

This work presents a simple and useful project process model. The project model directly shows how a few basic parameters determine project duration and cost and how changes in these parameters can improve them. Project cost and duration can be traded-off by adjusting the work rate and staffing level. A project's duration and cost can be computed on the back of an envelope, with an engineering calculator, or in a computer spreadsheet. The project model can be simulated dynamically for further insight. The project model shows how and why projects can greatly exceed their expected duration and cost. Delays and rework requirements may create work feedback loops that increase cost and schedule in non-proportional and non-intuitive ways.

The Environmental Control and Life Support (ECLS) requirements to reach the International Space Station (ISS), the Moon, and Mars as part of the Vision for Space Exploration (VSE) are similar to the earlier ECLS requirements for Apollo, Space Shuttle, and ISS. It seems reasonable that the VSE life support designs will develop in the same way. The ECLS for spacecraft to reach ISS and the Moon can use the Shuttle and Apollo approaches. However, the long duration ECLS for the Moon base should be the same as for Mars, because the Moon will be the testbed for Mars. The ECLS for Mars could be similar to that of ISS, but it should be redesigned to incorporate lessons learned, to take advantage of twenty years technical progress, and to respond to the much more difficult launch mass and reliability requirements for Mars.

This paper considers the possible current and future distribution of technical civilizations in our galaxy. Either we are the only technical civilization in the galaxy or there are others. Humanity will spread through the galaxy or not. If there are other technical civilizations, we may become aware of them or not, interact with them or not. Although we do not know the actual situation, there are only a few distinct possibilities. Thinking logically about the galactic future of the human race does not require that we know what the galaxy contains or how it will develop, only that we consider all the possible alternatives. This paper describes and develops models of the current distribution and possible future spread of technical civilizations in the galaxy.

Popular depictions of space exploration as well as government life support research programs have long assumed that future planetary bases would rely on small scale, closed ecological systems with crop plants producing food, water, and oxygen and with bioreactors recycling waste. In actuality, even the most advanced anticipated human life support systems will use physical/ chemical systems to recycle water and oxygen and will depend on food from Earth. This paper compares bioregenerative and physical/chemical life support systems using Equivalent System Mass (ESM), which gauges the relative cost of hardware based on its mass, volume, power, and cooling requirements. Bioregenerative systems are more feasible for longer missions, since they avoid the cost of continually supplying food.

This paper considers system design and technology selection for the crew air and water recycling systems to be used in long duration human space exploration. The ultimate objective is to identify the air and water technologies likely to be used for the vision for space exploration and to suggest alternate technologies that should be developed. The approach is to conduct a preliminary systems engineering analysis, beginning with the Air and Water System (AWS) requirements and the system mass balance, and then to define the functional architecture, review the current International Space Station (ISS) technologies, and suggest alternate technologies.

The purpose of NASA's Research and Development (R&D) programs is to provide advanced human support technologies for the Exploration Systems Mission Directorate (ESMD). The new technologies must be sufficiently attractive and proven to be selectable for future missions. This requires identifying promising candidate technologies and advancing them in technology readiness until they are likely options for flight. The R&D programs must select an array of technology development projects, manage them, and either terminate or continue them, so as to maximize the delivered number of potentially usable advanced human support technologies. This paper proposes an effective project selection methodology to help manage NASA R&D project portfolios.

NASA requires continuous risk management for all programs and projects. The risk management process identifies risks, analyzes their impact, prioritizes them, develops and carries out plans to mitigate or accept them, tracks risks and mitigation plans, and communicates and documents risk information. Project risk management is driven by the project goal and is performed by the entire team. Risk management begins early in the formulation phase with initial risk identification and development of a risk management plan and continues throughout the project life cycle. This paper describes a risk management approach that is suggested for use in NASA's Human Support Research and Technology (HSRT).

Systems engineering is largely the analysis and planning that support the design, development, and operation of systems. The most common application of systems engineering is in guiding systems development projects that use a phased process of requirements, specifications, design, and development. This paper investigates how systems engineering techniques should be applied in research and technology development programs for advanced space systems. These programs should include anticipatory engineering of future space flight systems and a project portfolio selection process, as well as systems engineering for multiple development projects.

Future space life support systems may use crop plants to grow most of the crew’s food. A harvest failure can reduce the food available for future consumption. If the previously stored food is insufficient to last until the next harvest, the crew may go hungry. This paper considers how the overall food supply system should be designed to cope with food production failures. The food supply system for a mission will use grown food, or stored food, or both. The optimum food supply mix depends on the costs and failure probabilities of stored and grown food. A simple food system model assumes that either we obtain the nominal harvest or a failure occurs and no food is harvested. Given the probability that any particular harvest fails, it is easy to compute the expected number of failures and the total food shortfall over a mission.

This paper describes engineering rules of thumb for life support system design. One general design rule is that the longer the mission, the more the life support system should use regenerable technologies and recycling. A more specific rule is that, if plants supply more than about half the food, the plants will provide all the oxygen needed by the crew. There are many such design rules that can help in planning the analysis of life support systems or in assessing design concepts. These rules typically describe the results of steady state, “back of the envelope,” trade-off calculations. They are useful in suggesting plausible candidate life support system designs or approaches. Life support system engineers should consider the basic design rules and make quick steady state calculations as a guide before doing detailed design.