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Equivalent System Mass (ESM) is the basis of the Advanced Life Support Research and Technology Development metric for measurement of progress of the Advanced Life Support (ALS) Project under the Advanced Human Support Technology (AHST) Program. ESM may be used to evaluate a system or technology based upon its mass, volume, power, cooling and manpower requirements. The ESM metric as defined in the ALS Research and Technology Development Metric Baseline is International Space Station (ISS) technology ESM divided by the ALS technology ESM for a specified mission. This paper discusses various theoretical and practical issues behind application of ESM to systems as well as to individual technologies. Difficulties that might be encountered by researchers in application of the metric are addressed. It is crucial that ALS researchers be proficient in assessing technologies and/or systems of interest with ESM, to minimize the chance of misapplication of the approach.

The development of a mathematical model that adequately captures and describes the interactions among the various system components is critical to the understanding and control of physical, chemical or biological phenomena. This often involves developing a multivariate model that will be used to forecast future events. Once the model has been proposed, it must be validated to check its adequacy in terms of its ability to forecast future events. However, such empirical models are subject to a number of pitfalls including overfitting, chance correlation, extrapolation, and lack of parsimony. In this paper, we describe the application of techniques to avoid these problems. The techniques described here are stratified data sampling, cross-validation, summed independent variables, and the use constraints to model complexity.

Nutrient recovery and biodegradation of inedible biomass is an integral part of an Advanced Life Support (ALS) system for space travel. This study investigates the mineralization and nitrogen recovery of hydroponically grown crops, namely, tomato, peanut, wheat and a 50:50 mixture of peanut and wheat. Shaker flask studies were conducted under various growth conditions of temperature and incubation times utilizing activated sludge and Phanerochaete chrysosporium (P. chrysosporium) inocula. Incubation temperature ranged from 25°C to 60°C and the flasks were monitored for nutrient recovery and solids reduction at 16, 32, 64 and 128 days. For the activated sludge systems, overall solids destruction during the 128 days of incubation ranged from 56% to 60% for the crops investigated. Similar results were found for the fungal systems indicating no substantial degradation enhancement.

Micronutrient recovery was investigated in two microbial systems, activated sludge and Phanerochaete chrysosporium (P. chrysosporium). Hydroponically grown crops, namely, tomato, peanut, wheat and a 50:50 mixture of peanut and wheat were used in the study. The experiments were conducted in shaker flasks on a 1% solids basis at 25°C for all crops and at 25°C, 40°C, 50°C and 60°C for tomato plant material. The micronutrient content of the leachate was determined initially and after 16, 32, 64, and 128 days of incubation. In order to determine the extent and rate of micronutrient release during the initial stages of incubation, when most of the solids degradation occurs, two separate experiments were conducted in batch reactors for 16 days. The micronutrient content of the batch reactor leachate was monitored on a daily basis. Micronutrients assessed included boron, manganese, iron, magnesium, zinc, copper, calcium, phosphorus and potassium.

Few data are available on biodegradation rates of materials over the long-term (more than 30 days). This information is necessary to conduct trade studies (studies used to make selections between alternatives) comparing various degrees of biodegradation versus combining biodegradation with incineration for advanced life support (ALS) systems. This paper describes the extreme case in which solids are degraded only by biodegradation. Data on biodegradation of insoluble solids from inedible parts of tomato plants are fitted to single and double exponential decay models to obtain half-life estimates for these materials. The data were obtained from batch experiments of material degradation over a 128-day period using mixed microbial cultures including activated sludge and an inoculum of Phanaerochaete Chrysosporium, a fungus known for its ability to degrade lignin.

The use of air treatment biofilters for the control of trace air contaminants in advanced life support (ALS) systems is currently being investigated by the Waste Processing and Resource Recovery team of the New Jersey - NSCORT (NASA Specialized Center of Research and Training). Ammonia (NH3) was selected as a model compound because it presents special challenges to the sustained operation of a biofilter; additionally, ammonia' is a contaminant of concern to ALS. The special challenges that NH3 removal presents to biofilter operation are due to (dynamic changes in the biodegradation environment which result from the accumulation of ammonia and its metabolic (biotransformation) products. This accumulation degrades the quality of the environment eventually limiting and eliminating the desired biological activity. This paper contains inform&ion on the development of a mathematical model for a nitrifying biofilter.