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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.

Stored air and water will be sufficient for Crew Exploration Vehicle visits to the International Space Station and for brief missions to the moon, but an air and water recycling system will be needed to reduce cost for a long duration lunar base and for exploration of Mars. The air and water recycling system developed for the International Space Station is substantially adequate but it has not yet been used in operations and it was not designed for the much higher launch costs and reliability requirements of moon and Mars missions. Significant time and development effort, including long duration testing, is needed to provide a flawless air and water recycling system for a long duration lunar base. It would be beneficial to demonstrate air and water recycling as early as the initial lunar surface missions.

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 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.

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.

New variable environment Modified Energy Cascade (MEC) crop models were developed for all the Advanced Life Support (ALS) candidate crops and implemented in SIMULINK. The MEC models are based on the Volk, Bugbee, and Wheeler Energy Cascade (EC) model and are derived from more recent Top-Level Energy Cascade (TLEC) models. The MEC models were developed to simulate crop plant responses to day-to-day changes in photosynthetic photon flux, photoperiod, carbon dioxide level, temperature, and relative humidity. The original EC model allowed only changes in light energy and used a less accurate linear approximation. For constant nominal environmental conditions, the simulation outputs of the new MEC models are very similar to those of earlier EC models that use parameters produced by the TLEC models. There are a few differences. The new MEC models allow setting the time for seed emergence, have more realistic exponential canopy growth, and have corrected harvest dates for potato and tomato.

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.

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.

The purpose of dynamic modeling and simulation of Advanced Life Support (ALS) systems is to help design them. Static steady state systems analysis provides basic information and is necessary to guide dynamic modeling, but static analysis is not sufficient to design and compare systems. ALS systems must respond to external input variations and internal off-nominal behavior. Buffer sizing, resupply scheduling, failure response, and control system design are aspects of dynamic system design. We develop two dynamic mass flow models and use them in simulations to evaluate systems issues, optimize designs, and make system design trades. One model is of nitrogen leakage in the space station, the other is of a waste processor failure in a regenerative life support system. Most systems analyses are concerned with optimizing the cost/benefit of a system at its nominal steady-state operating point. ALS analysis must go beyond the static steady state to include dynamic system design.

The Advanced Life Support (ALS) project uses Equivalent Mass (EM) to report ALS progress and in technology selection. Life Cycle Cost (LCC) is much more widely used. We develop a new metric, Life Cycle Mass (LCM), from EM and a mass-based LCC model. EM, LCM and Mass (M) alone are compared for technology ranking and progress reporting. These metrics are usually highly correlated and typically produce similar technology rankings and ALS progress metrics. Since M is much simpler than EM or LCM, ALS analysis could use M (Mass) alone for initial technology ranking and for ALS metric reporting.

The decision to develop a particular life support technology or to select it for flight usually depends on the cost to develop and fly it. Other criteria such as performance, safety, reliability, crew time, and technical and schedule risk are considered, but cost is always an important factor. Because launch cost would account for much of the cost of a future planetary mission, and because launch cost is directly proportional to the mass launched, equivalent mass has been used instead of cost to select advanced life support technology. The equivalent mass of a life support system includes the estimated mass of the hardware and of the spacecraft pressurized volume, power supply, and cooling system that the hardware requires. The equivalent mass of a system is defined as the total payload launch mass needed to provide and support the system. An extension of equivalent mass, Equivalent System Mass (ESM), has been established for use in the Advanced Life Support project.

Industrial process control has been dominated by closed architectures and proprietary protocols for the last three decades. In the late 1990’s, the advent of open fieldbus and middleware standards has greatly changed the process control arena. Fieldbus has pushed control closer and closer to the process itself. Middleware standards have exposed real-time process data to higher level software applications. Control systems can now be designed to minimize the reconfiguration costs associated with design changes. How can Advanced Life Support (ALS) benefit from these technologies? We consider designing the control system for the BIO-Plex and evaluate how complex it will be, the effort it will require, and how much it will it cost. Various fieldbus technologies were compared and Foundation Fieldbus was chosen for detailed evaluation. This new fieldbus was integrated with an existing ALS system.

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.

Exobiochemistry is the biochemistry of extraterrestrial life. It describes the potential energy and material basis of extraterrestrial life and is needed to guide the search for alien life. The diverse biochemistry of Earth indicates that a wide range of exobiochemistry is possible on other planets. Any exobiochemistry we discover will probably use the same energy sources as Earth's natural biochemistry - light, biological organic material, and more rarely abiotic chemicals. Extraterrestrial life will be based on familiar chemical principles and so will probably capture, store, and release energy using oxidation-reduction reactions similar to those found on Earth. Any extraterrestrial life must produce some chemical indication of its existence. Useful elements will be concentrated, stored, and recycled, altering their availability and isotopic composition.

Space projects are spectacular, costly, and highly visible. Their occasional failures receive extensive analysis and explanation. This paper reviews studies of failures of crewed and uncrewed missions. The explanations of these space project failures include simple oversight errors, poor project management, complex combinations of unforeseen events, and conceptual flaws that prohibited success. Failures are usually found to be caused by project management errors, based on the reasoning that the project manager and team members had the capability and responsibility to avoid them. These failure causes are well known. Why do so many projects make the same mistakes?

Researchers in astrobiology should develop alternate concepts for the detection of extraterrestrial life. We should search for extraterrestrial ecology, exoecology, as well as for extraterrestrial biology, exobiology. Ecology describes the interactions of living things with their environment. All ecosystems are highly constrained by their environment and conform to well-known and inescapable system design principles. An ecology could exist wherever there is an energy source and living things can employ some method to capture, store, and use the available energy. Terrestrial ecosystems use energy sources including light, organic molecules, and, in thermal vents and elsewhere, simple inorganic molecules. Ecosystem behavior is controlled by matter and energy conservation laws and is described by dynamic systems theory. Typically in an ecosystem different molecules are not in chemical equilibrium and scarce materials are conserved, stored, or recycled.

This study introduces several new concepts for suited EVA astronaut ingress/egress (departure and return) from a pressurized planetary surface habitat, based on use of a rear-entry suit and a suit lock or suitport. We provide insight into key operational aspects and integration issues, as well as the results of a requirements analysis and risk assessment of the concepts. The risk assessment included hazard analysis, hazard mitigation techniques, failure mode assessment, and operational risk assessment. Also included are performance and mass estimates for the egress concepts, and concepts for integration of the egress concepts with potential planetary habitat designs.

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.

Dynamic simulation of the lunar outpost habitat life support was undertaken to investigate the impact of life support failures and to investigate possible responses. Some preparatory static analysis for the Lunar Outpost life support model, an earlier version of the model, and an investigation into the impact of Extravehicular Activity (EVA) were reported previously. (Jones, 2008-01-2184, 2008-01-2017) The earlier model was modified to include possible resupply delays, power failures, recycling system failures, and atmosphere and other material storage failures. Most failures impact the lunar outpost water balance and can be mitigated by reducing water usage. Food solids and nitrogen can be obtained only by resupply from Earth. The most time urgent failure is a loss of carbon dioxide removal capability. Life support failures might be survivable if effective operational solutions are provided in the system design.

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.