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Plant growth chambers, whether designed for Earth or space applications, should provide the basic means for supporting healthy plant growth of almost any species. These chambers typically satisfy species- and age-specific light, atmosphere composition, water and nutrient requirements. Engineering solutions to satisfy these basic requirements in different plant chambers may vary widely, and each species or each experimental protocol may need individual testing and adaptation of the supporting hardware and science protocols. This paper will summarize the design trades, tests and evaluation experiments conducted to ensure proper hardware functionality and proper hardware / lifeware compatibility for the desired experimental protocols in space.

Aeroponics is the process of growing plants in an air/mist environment without the use of soil or an aggregate media. Aeroponics has contributed to advances in several areas of study including root morphology, nutrient uptake, drought and flood stress, and responses to variations in oxygen and/or carbon dioxide root zone concentrations. The adaptability of the aeroponic process that has benefited researchers makes its application to spaceflight plant growth systems appealing. Greater control of growth parameters permits a greater range of crop performance throttling and the elimination of aggregates or common growth substrates lowers system mass, lessens disease propagation between plants, and can decrease the required crew time for both planting and harvesting.

An event in which electronic insulation consisting of polytetrafluoroethylene undergoes thermodegradation on the Space Station Freedom is considered experimentally and theoretically from the initial chemistry and convective transport through pulmonary deposition in humans. The low-gravity environment impacts various stages of event simulation. Vapor-phase and particulate thermodegradation products were considered as potential spacecraft contaminants. A potential pathway for the production of ultrafine particles was identified. Different approaches to the simulation and prediction of contaminant transport were studied and used to predict the distribution of generic vapor-phase products in a Space Station model.

The Autonomous Garden Pod (AG-Pod) is a modular crop production system that can lower the equivalent system mass (ESM) for bioregenerative life support systems. AG-Pod combines existing technologies, many of which are at the technology readiness level (“TRL”) 8 or 9, into a flight-ready system adaptable to many needs from Space Station microgravity plant research to interplanetary transit and planetary surface food production systems. The plant-rated module resides external to the spacecraft pressurized volume and can use natural direct solar illumination. This reduces the ESM of crop production systems by eliminating the use of spacecraft internal pressurized volume and by reducing power and heat rejection resources that would be needed for full artificial lighting. However, lowering of the crop production ESM is also achieved from the use of lightweight structures including composite and inflatable technology.

PGBA, a plant growth facility developed for commercial space biotechnology research, successfully grew a total of 50 plants (6 species) during 10 days aboard the Space Shuttle Endeavor (STS-77), and has reflown aboard the Space Shuttle Columbia (STS-83 for 4 days and STS-94 for 16 days) with 55 plants and 10 species. The PGBA life support system provides atmospheric, thermal, and humidity control as well as lighting and nutrient supply in a 33 liter microgravity plant growth chamber. The atmosphere treatment system removes ethylene and other hydrocarbons, actively controls CO2 replenishment, and provides passive O2 control. Temperature and humidity are actively controlled.

In order to assess the robustness of a Spacecraft Life Support System (LSS) design based on average performance values, criteria such as stability and controllability must be considered under variable and peak system loads. The Exploration Group at the Technische Universität München (TUM) is developing the “Virtual Habitat” computational tool (V-HAB) for exactly this type of investigation. In order to characterize the relative level of confidence for a complex model such as this, a generalized metric was defined which is able to indicate an incremental Model Confidence Level (MCL) throughout the model development process. This paper describes a proposed metric for systematically rating and describing the level of model development, created for and based on the V-HAB simulation.

Accurate root zone moisture control in microgravity plant growth systems is problematic. With gravity, excess water drains along a vertical gradient, and water recovery is easily accomplished. In microgravity, the distribution of water is less predictable and can easily lead to flooding, as well as anoxia. Microgravity water delivery systems range from solidified agar, water-saturated foams, soils and hydroponics soil surrogates including matrix-free porous tube delivery systems. Surface tension and wetting along the root substrate provides the means for adequate and uniform water distribution. Reliable active soil moisture sensors for an automated microgravity water delivery system currently do not exist. Surrogate parameters such as water delivery pressure have been less successful.

Until now, NASA's space water reuse research program has not considered the transport of water borne infectious enteric viruses; however, viral diseases probably are a significant concern in long duration space missions. To simplify monitoring and prediction of pathogen distribution, model indicator strains historically have been used. In this research, the male specific RNA coliphage MS-2 is used as a model of enteric viruses due to their similar size and biochemical composition. Inactivation of some water borne enteric viruses by iodine has previously been characterized. In this paper, iodine inactivation of the model coliphage MS-2 in buffered water is compared with earlier bench-scale disinfection survival data and with survival in iodinated simulated shower water used in a test water recycling system.

Iodine is being considered for disinfection of recycled hygiene and potable water in Space Station Freedom. Like chlorine, the halogen iodine can form disinfection by-products (DBPs) when used as a disinfectant in waters with dissolved or colloidal organic compounds. Recycled shower and laundry wastewater, urine and condensate from the space cabin atmosphere all have large amounts of dissolved and colloidal organic compounds and may generate iodinated DBP's which can be toxic to humans. We have investigated the formation of iodinated DBP's (IDP's) in model compounds typical of shower wastewater and condensate. The selection of these model compounds and flask experiments to test for IDP formation have been described. Methods for reaction, extraction and analysis for IDP's also have been developed. We have tentatively identified likely organic precursors from recycled water and several iodinated organic compounds formed during the reaction with iodine.

The efficiency and robustness of pilot-automation interaction is a function of the volume of memorized action sequences required to use the automation to perform mission tasks. This paper describes a model of pilot cognition for the evaluation of the cognitive usability of cockpit automation. Five common cockpit automation design errors are discussed with examples.

P-MASS, the Plant-Module for Autonomous Space Support, is designed to support and provide life support for a variety of plants, algae and bacteria in low earth orbit during the maiden flight of COMET-1. The first launch is scheduled for early 1993. With a nominal mission duration of 30 days in microgravity, P-MASS will bridge the gap between the shorter duration experiments possible onboard the NSTS Space Shuttle (approximately 14 days) and the future Space Station Freedom for space biology applications. Environmental data and video images are collected, stored onboard and downlinked daily. In addition, the payload and all specimens will be returned for ground analysis with the recovery system (reentry capsule). P-MASS is designed within a payload envelope of 0.28 x 0.22 x 0.32 m (19.71) and a mass of approximately 20 kg. A total of 115 Watt electric power is available continuously for the Plant-Module (60 W lighting, 40 Watt cooling, 15 W housekeeping).

Water reuse is essential for long duration space missions. However, water recycle systems also provide a habitat for microorganisms and allow accumulation of chemical compounds which may be acutely or chronically toxic to mission crew members. Contaminant fate and accumulation in closed-loop water recycle systems is being investigated at the University of Colorado and Martin Marietta as part of the activities of the Center for Space Environmental Health (CSEH), a NASA Specialized Center of Research and Training (NSCORT). The water contaminant distribution research uses a scaled-down physical model of a water (shower, laundry, urine and/or condensate) recycle system to analyze for and model four “indicator” contaminants: viruses and bacteria, nitrogen species, and selected organic and inorganic compounds. The water recycle test bed is comprised of five or more individual water treatment processes linked in a closed loop, and spiked with chemical and biological contaminants.

The Biological Wastewater Processor Experiment Definition team is performing the preparatory ground research required to define and design a mature space flight experiment. One of the major outcomes from this work will be a unit-gravity prototype design of the infrastructure required to support scientific investigations related to microgravity wastewater bioprocessing. It is envisioned that this infrastructure will accommodate the testing of multiple bioprocessor design concepts in parallel as supplied by NASA, small business innovative research (SBIR), academia, and industry. In addition, a systematic design process to identify how and what to include in the space flight experiment was used.

It is well known that selection of the pressure/oxygen ratio for a human space habitat is a critical decision for the well-being and mission performance of astronauts. It has also been noted how this ratio affects the requirement for pre- and post-breathing and the type and flexibility of EVA/EHA astronaut suits. However, little attention has been paid to how these issues interact with various mission design strategies. Using the first manned mission to Mars as a baseline mission, we have separated the mission into its component parts as it relates to habitat type (i.e., the Earth-Mars interplanetary vehicle, the ascent/descent vehicle, the base, human rover vehicles, etc.) and have determined the oxygen resupply requirements for each part as they reflect a mission design strategy. These component parts form a matrix where duration of stay, loss of oxygen due to leakage and usage, and oxygen resupply needs are calculated.