Theory and Application of the Equivalent System Mass Metric

Levri, Julie A.; Vaccari, David A.; Drysdale, Alan

doi:10.4271/2000-01-2395

Cited by 64 publications

(36 citation statements)

References 6 publications

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“…ESM also assumes that the technologies meet identical reliability and technical requirements, "Comparison of systems or subsystems with ESM is only suitable where the systems or subsystems satisfy identical requirements, including levels of safety and reliability." 2 Other technology and architecture developers have struggled with these same limitations in evaluating state-ofthe-art alongside promising technologies, "ESM is the sum of real masses and mass penalties for cost factors judged to be significant for life support: volume, power, cooling, manpower, and logistics.... Thus it does not consider flight readiness (TRL) nor requirements options.…”

Section: Sustainable Eclss Conceptsmentioning

confidence: 99%

“…If this is the case, the researcher's expertise on the matter may then be used to make reasonable adjustments in ESM in order to compare technologies. , 2 Therefore, ESM inherently relies on the technology developers to provide candid input on reliability, and requires operational experience to evaluate failures. ESM has no mechanism to compare technologies at different Technology Readiness Levels (TRL), and as such currently has limited capability to allow the evaluation of a range of potential technologies.…”

Section: Sustainable Eclss Conceptsmentioning

confidence: 99%

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Developing Sustainable Life Support System Concepts

Thomas

2010

40th International Conference on Environmental Systems

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Sustainable spacecraft life support concepts may allow the development of more reliable technologies for long duration space missions. Currently, life support technologies at different levels of development are not well evaluated against each other, and evaluation methods do not account for long term reliability and sustainability of the hardware. This paper presents point-of-departure sustainability evaluation criteria for life support systems, that may allow more robust technology development, testing and comparison. An example sustainable water recovery system concept is presented. L IntroductionSustainability is the capacity to endure. Long duration spaceflight, as anticipated for Moon and Mars missions, will require hardware that is less prone to failure and generally more rigorous and sustainable than the current stateof-the-art. Sustainable Environmental Control and Life Support Systems (SECLSS) may be developed to function for long periods of time in harsh environments, with limited maintenance and resupply. Water recovery, air revitalization, habitation, food and power systems may benefit from considering sustainability a design goal.The SECLSS project is designed to develop rough life support system architectures, evolve technology concepts, and collaborate with NASA partners to consider long term sustainability as a design driver for life support systems. One example application requiring innovation is wastewater management ; wherein wastewater fouling is accommodated by the design of the fluid mana gement hardware. This paper provides an overview of the SECLSS project concept and proposed sustainability evaluation criteria for ECLSS technologies, and details a preliminary example technology for water recovery on the lunar outpost. II. BackgroundA long-terns lunar outpost will require sustainable life support technologies that are capable of functioning for years with minimum resupply and maintenance. While life support resources such as grater and air will remain in short supply, the availability of gravity, energy, and natural resources on the lunar surface allow for innovation in the design of outpost technologies, potentially including the adoption of terrestrial technologies previously not feasible for short duration microgravity flight.As missions become extended in duration and move toward more self-reliant operations, new demands are placed on the life support system design. Thus far, all indications have suggested that the lunar outpost water recovery systems will be evolved from current spacecraft technologies, including urine pretreatment and distillation'. However, these technologies were developed for microgravity compatibility, and may carry undesirable fouling and failure mode heritage from this environment. For example, it is well recognized that water handling systems used in a spacecraft are prone to failure caused by biofouling and mineral scaling, which can clog mechanical systems and degrade the performance of capillary-based technologies. The recent challenges with the Urine Proc...

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Section: Sustainable Eclss Conceptsmentioning

confidence: 99%

Section: Sustainable Eclss Conceptsmentioning

confidence: 99%

Developing Sustainable Life Support System Concepts

Thomas

2010

40th International Conference on Environmental Systems

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“…Food processing labor and food preparation labor are calculated and separately assigned to the processing costs of ingredients and the preparation cost of recipes, respectively. The ESM cost estimation procedures used are outlined in (6,10).…”

Section: Model For Current Studymentioning

confidence: 99%

“…ESM accounting of plans for space missions allows for the comparison among different life support system options using a single unit of measure: the ESM of the option (6,10). The ESM cost of labor [kg/work hour] will depend on the ESM of the life support system, the number of hours in a standard workweek and other life support demands on crew time.…”

Section: Introductionmentioning

confidence: 99%

Work Measurement for Estimating Food Preparation Time of a Bioregenerative Diet

Olabi

Hunter²,

Jackson³

et al. 2003

habitation (elmsford)

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During space missions, such as the prospective Mars mission, crew labor time is a strictly limited resource. The diet for such a mission (based on crops grown in a bioregenerative life support system) will require astronauts to prepare their meals essentially from raw ingredients. Time spent on food processing and preparation is time lost for other purposes. Recipe design and diet planning for a space mission should therefore incorporate the time required to prepare the recipes as a critical factor. In this study, videotape analysis of an experienced chef was used to develop a database of recipe preparation time. The measurements were highly consistent among different measurement teams. Data analysis revealed a wide variation between the active times of different recipes, underscoring the need for optimization of diet planning. Potential uses of the database developed in this study are discussed and illustrated in this work.

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“…The cost of a bioregenerative diet depends on a number of factors, the most important of which are lighting technology, crop productivity and crew labor (10,18). The cost of bioregenerative space diets is usually calculated in equivalent system mass (ESM) units (4,15), as it is in this study. Economic studies of the effect of design choices on the cost of components of a bioregenerative life support space diet and the interactions between them are potentially very useful in the planning of a life support system in planetary missions.…”

Section: Introductionmentioning

confidence: 99%

Optimized Bioregenerative Space Diet Selection With Crew Choice

Vicens

Wang²,

Olabi

et al. 2003

habitation (elmsford)

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Previous studies on optimization of crew diets have not accounted for choice. A diet selection model with crew choice was developed. Scenario analyses were conducted to assess the feasibility and cost of certain crew preferences, such as preferences for numerous-desserts, high-salt, and high-acceptability foods. For comparison purposes, a no-choice and a random-choice scenario were considered.The model was found to be feasible in terms of food variety and overall costs.The numerous-desserts, high-acceptability, and random-choice scenarios all resulted in feasible solutions costing between 13.2 and 17.3 kg ESM/person-day.Only the high-sodium scenario yielded an infeasible solution. This occurred when the foods highest in salt content were selected for the crew-choice portion of the diet. This infeasibility can be avoided by limiting the total sodium content in the crew-choice portion of the diet. Cost savings were found by reducing food variety in scenarios where the preference bias strongly affected nutritional content.

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Theory and Application of the Equivalent System Mass Metric

Cited by 64 publications

References 6 publications

Developing Sustainable Life Support System Concepts

Developing Sustainable Life Support System Concepts

Work Measurement for Estimating Food Preparation Time of a Bioregenerative Diet

Optimized Bioregenerative Space Diet Selection With Crew Choice

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