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A long-duration lunar outpost will rely entirely upon imported or preserved foods to sustain the crew during early Lunar missions. Fresh, perishable foods (e.g. salad crops) would be consumed by the crew soon after delivery by the re-supply missions, and can provide a supplement to the diet rich in antioxidants (bioprotectants) that would serve as a countermeasure to radiation exposure. Although controlled environment research has been carried out on the growth of salad crops under a range of environmental conditions, there has been no demonstration of sustainable production in a flight-like system under conditions that might be encountered in space. Several fundamental challenges that must be overcome in order to achieve sustained salad crop production under the power, volume and mass constraints of early Lunar outposts include; growing multiple species, sustaining productivity through multiple plantings, and minimizing time for crew operations.

The establishment of a human-tended lunar base requires an autonomous bioregenerative life support system. Bioregeneration within a Lunar Engineered Closed/Controlled EcoSystem (LECCES) can be realized by integrating humans, plants, animals, and waste treatment subsystems. This integration incorporates physical/chemical and biological waste treatment processes that minimize resupply requirements from Earth. A LECCES top-level system integration model is developed based on human metabolic massflow requirements. The proposed model is presented and its components are discussed.

The challenge of food provision in a human-tended Lunar/Martian base necessitates the development of stable, nutritious and palatable foods from limited plant sources. The ability to safely prepare and store a wide variety of foods having physiological and psychological acceptability, with a limited number of starting materials, plays a prime role in the success of long-term missions. Since wheat has been proposed as one of the major crops to be grown on space outposts, this project focuses on identifying novel ways to process food products from wheat under vacuum conditions. Vacuum has not been sufficiently exploited for food processing, and space vacuum can be capitalized for selected food processes. Two techniques currently under investigation are vacuum baking and extrusion. Vacuum oven baking minimizes the need for extensive proofing and/or chemical leavening and decreases preparation time.

Light-emitting diodes (LEDs) represent an innovative artificial lighting source with several appealing features specific for supporting plants, whether on space-based transit vehicles or planetary life support systems. Appropriate combinations of red and blue LEDs have great potential for use as a light source to drive photosynthesis due to the ability to tailor irradiance output near the peak absorption regions of chlorophyll. This paper describes the importance of far-red radiation and blue light associated with narrow-spectrum LED light emission. In instances where plants were grown under lighting sources in which the ratio of blue light (400–500 nm) relative to far-red light (700–800 nm) was low, there was a distinct leaf stretching or broadening response. This photomorphogenic response sanctioned those canopies as a whole to reach earlier critical leaf area indexes (LAI) as opposed to plants grown under lighting regimes with higher blue:far-red ratios.

Growth Temperatures And Lighting Intensity Are Key Factors That Directly Impact The Design, Engineering, And Horticultural Practices Of Sustainable Life-Support Systems For Future Long-Term Space Missions. The Effects Of Exposure Of Lettuce (Cv. Flandria), Radish (Cv. Cherry Bomb Ii). And Green Onion (Cv. Kinka) Plants To Controlled Environment Temperatures (Constant Day/Night Temperature Of 22, 25, Or 28 °C) And Lighting Intensities (8.6, 17.2, Or 25.8 Mol M−2 D−1 Photosynthetic Photon Flux [Ppf]) At Elevated Co2 (1200 µMol Mol−1) Was Investigated To Ascertain Overall Yield Responses. Following 35 Days Growth, The Yields Of Lettuce Indicated That Increasing The Growing Temperature From 22 To 28°C Slightly Increased The Edible Fresh Mass Of Individual Plants. However, Even Though Lettuce Plants Grown Under High Ppf Had The Highest Fresh Mass, The Resultant Increase In The Incidence And Severity Of Tipburn Reduced The Overall Quality Of The Lettuce Head.

Engineering strategies for advanced life support systems to be used on Lunar and Mars bases involve a wide spectrum of approaches. These range from purely physical-chemical life support strategies to purely biological approaches. Within the context of biological based systems, a bioengineered system can be devised that would utilize the metabolic mechanisms of plants to control the rates of CO2 uptake and O2 evolution (phytosynthesis) and water production (transpiration). Such a mechanism of external engineering control has become known as “throttling”. Research conducted at the John F. Kennedy Space Center's Controlled Ecological Life Support System Breadboard Project has demonstrated the potential of throttling these fluxes by changing environmental parameters affecting the plant processes. Among the more effective environmental throttles are: light and CO2 concentration for controlling the rate of photosynthesis and humidity and CO2 concentration for controlling transpiration.

Conversion of lunar regolith into a plant growth medium is crucial to the development of a regenerative life support system for a lunar base. Plants, which are the core of such a system, are a source of food and oxygen for humans and a sink for carbon dioxide and other wastes. Because of the the shortage of lunar regolith, simulants were used for examining its suitability for plant growth. Dissolution studies of Minnesota Lunar Simulant (MLS), a prepared finely-ground basalt, were conducted to measure solution species, to assess the levels of plant nutrients and toxic elements, and to identify the minerals controlling these levels. MLS weathered in shaker flasks over a 150 d period yielded basic solutions of pH near 9.0 buffered by calcite. Most elemental concentrations were within the range for typical alkaline terrestrial soil solutions.

Exploration of the Moon is the most crucial and decisive step toward human expansion into the vast reaches of space. The Moon is the natural and ideal testbed for determining human capability to survive, function, expand and settle into the space environment. Scientific studies, astronomic observations, and exploitation and utilization of space resources culminating in the establishment of a self-sufficient permanently human-tended lunar base are the goals of lunar exploration. Four development stages in the evolutionary exploration of the Moon are suggested: (1) exploratory; (2) pioneering; (3) outpost; and (4) base. Overall goals and specific objectives, functional requirements, construction conditions, and life support systems requirements needed in each stage are identified.

Long-term human missions in space, establishment of a human-tended lunar base and of a Martian base requires an autonomous life support system. An Engineered Closed/Controlled Ecosystem (ECCES) can provide autonomy by integrating a human module with support plant and animal modules and waste treatment subsystems. Integration of physical/chemical and biological waste treatment subsystems can lead to a viable and operational bioregenerative system through minimizing resupply requirements from Earth. Life support requirements of the human module “drive” the design and operation an ECCES. A top-level diagram for an ECCES was developed based on the human module requirements. The proposed top-level diagram is presented and its components are discussed.

Conversion of lunar regolith into a plant growth medium is crucial to the development of a regenerative life support system for a lunar base. Simulants must be used to study weathering processes and to develop procedures for the conversion of lunar regolith into a suitable plant growth medium because of the shortage of actual lunar materials. Dissolution studies have been conducted for Johnson Space Center Lunar Simulant-1 (JSCLS-1) to assess levels of plant nutrients and toxic elements. Weathering in water for 150 4 in the presence of atmospheric oygen and carbon dioxide, yielded alkaline solutions with pH near 8.8. Concentrations of most plant nutrients were at levels normally considered acceptable for plant growth. However, nitrogen was deficient, and phosphorus was present at levels typical of unfertilized soils. DTPA extracts indicated possible manganese and zinc deficiencies. Solution metals were at concentrations far below those generally harmful to plants.

As space missions become longer in duration, the need to recycle waste into useful compounds rises dramatically. This problem can be addressed through the integration of human and plant modules in an ecological life support system. One of the waste streams leaving the human module is urine. In addition to the reclamation of water from urine, recovery of the nitrogen is important because it can be used as a nutrient for the plant module. A 3-step biological process for the conversion of nitrogenous waste (urea) to resource (nitrate) is proposed. Mathematical modeling was used to investigate the bioreactor system, with the goal of maximizing the ratio of performance to volume and energy requirements. Calculations show that separation of the two microbial conversions into two steps requires a smaller total reactor volume than combining them in a single bioreactor.

Closed ecological life support systems incorporating plants represent the only potential for achieving self-sufficiency in an extraterrestrial biosphere. A model of input/output metabolic mass flow rates for a plant module in an Engineered Closed/Controlled EcoSystem is presented. Wheat crop was chosen as a case study for modeling metabolic mass flow rates. Coefficients for the mass flow rates, for each metabolic element, are determined per unit area of wheat production. The coefficients are utilized to compute the area of edible biomass production necessary to accommodate human food requirements. This model for computing metabolic mass flow rates can be applied for any crop under specified growing conditions.

A BRIC (Biological Research In a Canister) experiment to investigate the effects of reduced gravity at the molecular level using Arabidopsis has been initiated. To ensure an efficient BRIC experiment, a series of ground-based studies have been conducted. These studies were designed to determine: 1) the ideal seed density to obtain enough plant tissue from a single canister; 2) optimum germination surface for tissue recovery after freezing in liquid nitrogen; 3) yield and quality of mRNA from small amounts of tissue; 4) time point to freeze the seedlings; and 5) changes in gene expression that may be caused by stresses during launch.

Five potato (Solanum tuberosum L.) leaf cuttings were flown on STS-73 in late October, 1995 as part of the 16-day USML-2 mission. Pre-flight studies were conducted to study tuber growth, determine carbohydrate concentrations and examine the developing starch grains within the tuber. In these tests, tubers attained a fresh weight of 1.4 g tuber-1 after 13 days. Tuber fresh mass was significantly correlated to tuber diameter. Greater than 60% of the tuber dry mass was starch and the starch grains varied in size from 2 to 40 mm in the long axis. For the flight experiment, cuttings were obtained from seven-week-old Norland potato plants, kept at 5°C for 12 hours then planted into arcillite in the ASTROCULTURE™ flight hardware. The flight package was loaded on-board the orbiter 22 hours prior to launch.

A research project has begun to identify the best cultivar for strawberry production as part of an advanced life support system for space. For the cultivar trials, hydroponic systems will be used, so the plants can be grown optimally under controlled environmental conditions and without water stress. The objectives of this project were to determine changes in nutrient solution characteristics, specifically dissolved oxygen (DO), electrical conductivity (EC), hydrogen ion concentration (pH), and temperature, versus four different flow rates (0.5, 1.0, 2.0, and 3.6 L·min−1) at fixed distances in the hydroponic channel with and without media. Three media treatments were used: 1) no media, 2) arcillite, and 3) perlite. The results showed that the highest flow rate (i.e., 3.6 L min−1) exhibited the most uniform conditions of all nutrient solution characteristics and for each of the media treatments over the 7.92 m length of channel.