Accumulation and effect of volatile organic compounds in closed life support systems.

Bioregenerative life support systems (BLSS) being considered for long duration space missions will operate with limited resupply and utilize biological systems to revitalize the atmosphere, purify water, and produce food. The presence of man-made materials, plant and microbial communities, and human activities will result in the production of volatile organic compounds (VOCs). A database of VOC production from potential BLSS crops is being developed by the Breadboard Project at Kennedy Space Center. Most research to date has focused on the development of air revitalization systems that minimize the concentration of atmospheric contaminants in a closed environment. Similar approaches are being pursued in the design of atmospheric revitalization systems in bioregenerative life support systems. in a BLSS one must consider the effect of VOC concentration on the performance of plants being used for water and atmospheric purification processes. In addition to phytotoxic responses, the impact of removing biogenic compounds from the atmosphere on BLSS function needs to be assessed. This paper provides a synopsis of criteria for setting exposure limits, gives an overview of existing information, and discusses production of biogenic compounds from plants grown in the Biomass Production Chamber at Kennedy Space Center.     

Performance and reliability of the NASA Biomass Production Chamber.

The Biomass Production Chamber (BPC) at the Kennedy Space Center is part of the Controlled Ecological Life Support System (CELSS) Breadboard Project. Plants are grown in a closed environment in an effort to quantify their contributions to the requirements for life support. Performance of this system is described. Also, in building this system, data from component and subsystem failures are being recorded. These data are used to identify problem areas in the design and implementation. The techniques used to measure the reliability will be useful in the design and construction of future CELSS. Possible methods for determining the reliability of a green plant, the primary component of a CELSS, are discussed.     

Improvements in the re-flight of spaceflight experiments on plant tropisms

In order to effectively study phototropism, the directed growth in response to light, we performed a series of experiments in microgravity to better understand light response without the “complications” of a 1-g stimulus. These experiments were named TROPI (for tropisms) and were performed on the European Modular Cultivation System (EMCS), a laboratory facility on the International Space Station (ISS). TROPI-1 was performed in 2006, and while it was a successful experiment, there were a number of technical difficulties. We had the opportunity to perform TROPI-2 in 2010 and were able to optimize experimental conditions as well as to extend the studies of phototropism to fractional gravity created by the EMCS centrifuge. This paper focuses on how the technical improvements in TROPI-2 allowed for a better experiment with increased scientific return. Major modifications in TROPI-2 compared to TROPI-1 included the use of spaceflight hardware that was off-gassed for a longer period and reduced seed storage (less than 2 months) in hardware. These changes resulted in increased seed germination and more vigorous growth of seedlings. While phototropism in response to red illumination was observed in hypocotyls of seedlings grown in microgravity during TROPI-1, there was a greater magnitude of red-light-based phototropic curvature in TROPI-2. Direct downlinking of digital images from the ISS in TROPI-2, rather than the use of analog tapes in TROPI-1, resulted in better quality images and simplified data analyses. In TROPI-2, improved cryo-procedures and the use of the GLACIER freezer during transport of samples back to Earth maintained the low temperature necessary to obtain good-quality RNA required for use in gene profiling studies.     

NASA's Biomass Production Chamber: a testbed for bioregenerative life support studies.

The Biomass Production Chamber (BPC) located at Kennedy Space Center, FL, USA provides a large (20 m2 area, 113 m3 vol.), closed environment for crop growth tests for NASA's Controlled Ecological Life Support System (CELSS) program. Since the summer of 1988, the chamber has operated on a near-continuous basis (over 1200 days) without any major failures (excluding temporary power losses). During this time, five crops of wheat (64-86 days each), three crops of soybean (90 to 97 days), five crops of lettuce (28-30 days), and four crops of potato (90 to 105 days were grown, producing 481 kg of dry plant biomass, 196 kg edible biomass, 540 kg of oxygen, 94,700 kg of condensed water, and fixing 739 kg of carbon dioxide. Results indicate that total biomass yields were close to expected values for the given light input, but edible biomass yields and harvest indices were slightly lower than expected. Stand photosynthesis, respiration, transpiration, and nutrient uptake rates were monitored throughout growth and development of the different crops, along with the build-up of ethylene and other volatile organic compounds in the atmosphere. Data were also gathered on system hardware maintenance and repair, as well as person-hours required for chamber operation. Future tests will include long-term crop production studies, tests in which nutrients from waste treatment systems will be used to grow new crops, and multi-species tests.     

Spaceflight hardware allowing unilateral irradiation and chemical fixation in petri dishes.

To accommodate a spaceflight experiment with moss (SPM), experiment-unique equipment (EUE) was developed by engineers at Kennedy Space Center. The hardware allows sterile culture for an extended period of time in commercial petri dishes, lateral illumination of each culture with light of a specific wavelength (660 nm; other wavelengths are possible) and a range of intensities (0.05-5 micromoles photons m-2 s-1), incubation in complete darkness, and chemical fixation to terminate the experiment under conditions of microgravity. The use of a fixative required triple containment to protect the astronaut crew. An external panel on the experiment container allowed the timing of illumination and fixation to be controlled by the crew. Light quality is provided by light emitting diodes (LEDs) that are located in the lid of the outer container, the BRIC (Biological Research In Canisters)-LED. Each canister accommodates 6 Petri Dish Fixation Units (PDFUs), and each PDFU holds one 6 cm petri dish. All components are autoclavable. LED illumination is piped through a transparent glass rod. Each PDFU contains fixative in a reservoir that is released by the depression of an actuator. This hardware performed well during its first flight, the 16-day STS-87 mission in Nov./Dec., 1997 as part of the Collaborative USA and Ukrainian Experiment (CUE). It supported vigorous and sterile moss growth, cells were maintained in position and were well-fixed, and there was a vigorous and consistent response to light. Although here used for moss, in future flight experiments this unique new hardware can be used for many types of organisms normally grown in petri dishes, with or without a requirement for illumination.     

Use of biologically reclaimed minerals for continuous hydroponic potato production in a CELSS.

Plant-derived nutrients were successfully recycled in a Controlled Ecological Life Support System (CELSS) using biological methods. The majority of the essential nutrients were recovered by microbiologically treating the plant biomass in an aerobic bioreactor. Liquid effluent containing the nutrients was then returned to the biomass production component via a recirculating hydroponic system. Potato (Solanum tuberosum L.) cv. Norland plants were grown on those nutrients in either a batch production mode (same age plants on a nutrient solution) or a staggered production mode (4 different ages of plants on a nutrient solution). The study continued over a period of 418 days, within NASA Breadboard Project's Biomass Production Chamber at the Kennedy Space Center. During this period, four consecutive batch cycles (104-day harvests) and 13 consecutive staggered cycles (26-day harvests) were completed using reclaimed minerals and compared to plants grown with standard nutrient solutions. All nutrient solutions were continually recirculated during the entire 418 day study. In general, tuber yields with reclaimed minerals were within 10% of control solutions. Contaminants, such as sodium and recalcitrant organics tended to increase over time in solutions containing reclaimed minerals, however tuber composition was comparable to tubers grown in the control solutions.     

Soybean cultivation for Bioregenerative Life Support Systems (BLSSs): The effect of hydroponic system and nitrogen source

Soybean [Glycine max (L.) Merr.] is one of the plant species selected within the European Space Agency (ESA) Micro-Ecological Life Support System Alternative (MELiSSA) project for hydroponic cultivation in Biological Life Support Systems (BLSSs), because of the high nutritional value of seeds. Root symbiosis of soybean with Bradirhizobium japonicum contributes to plant nutrition in soil, providing ammonium through the bacterial fixation of atmospheric nitrogen. The aim of this study was to evaluate the effects of two hydroponic systems, Nutrient Film Technique (NFT) and cultivation on rockwool, and two nitrogen sources in the nutrient solution, nitrate (as Ca(NO₃)₂ and KNO₃) and urea (CO(NH₂)₂), on root symbiosis, plant growth and seeds production of soybean. Plants of cultivar ‘OT8914’, inoculated with B. japonicum strain BUS-2, were grown in a growth chamber, under controlled environmental conditions.     

Antioxidant capacity reduced in scallions grown under elevated CO2 independent of assayed light intensity

Long-duration manned space missions mandate the development of a sustainable life support system and effective countermeasures against damaging space radiation. To mitigate the risk of inevitable exposure to space radiation, cultivation of fresh fruits and vegetables rich in antioxidants is an attractive alternative to pharmacological agents. However it has yet to be established whether antioxidant properties of crops can be preserved or enhanced in a space environment where environmental conditions differ from that which plants have acclimated to on earth. Scallion (Allium fistulosum) rich in antioxidant vitamins C and A, and flavonoids was used as a model plant to study the impact of a range of CO₂ concentrations and light intensities that are likely encountered in a space habitat on food quality traits. Scallions were hydroponically grown in controlled environmental chambers under a combination of 3 CO₂ concentrations of 400, 1200 and 4000 μmol mol⁻¹ and 3 light intensity levels of 150, 300, 450 μmol m⁻² s⁻¹. Total antioxidant activity (TAA) of scallion extracts was determined using a radical cation scavenging assay. Both elevated CO₂ and increasing light intensity enhanced biomass accumulation, but effects on TAA (based on dry weight) differed. TAA was reduced for plants grown under elevated CO₂, but remained unchanged with increases in light intensity. Elevated CO₂ stimulated greater biomass production than antioxidants, while an increase in photosynthetic photo flux promoted the synthesis of antioxidant compounds at a rate similar to that of biomass. Consequently light is a more effective stimulus than CO₂ for antioxidant production.     

Community metabolism of aquatic Closed Ecological Systems: Effects of nitrogen sources

To investigate the effect of nitrogen sources on Closed Ecological Systems (CESs), three nitrogen sources (NaNO₃, sodium nitrate; NH₄Cl, ammonium chloride; and NH₄NO₃, ammonium nitrate) were each tested in freshwater CESs consisting of a chemically defined medium, three species of green algae (Ankistrodesmus, Scenedesmus, and Selenastrum), the grazer Daphnia magna, and associated microbes, under 12 h light/12 h dark cycles. It had been hypothesized that the development of high pH in earlier CESs was the result of nitrate utilization, and that ammonium might result in acid conditions, while ammonium nitrate might result in more moderate pH. The three nitrogen sources supported similar densities of algae (estimated by in vivo fluorescence) and similar Daphnia populations. The experiments showed that pH levels rapidly increased when grazers were absent or at low abundances irrespective of the nitrogen source. Consequently, it is hypothesized that carbon cycles, rather than nitrogen sources, are responsible for the pH dynamics. Oxygen diurnal (light:dark) cycles tended to come into balance more quickly than pH. It may be more feasible to convert O₂ data to energy units (using “oxycalorific” values) than CO₂ data since CO₂ dynamics may include other chemical reactions than just photosynthesis and respiration. The feasibility of sustaining grazer populations for at least several weeks in small, simple CESs was demonstrated, along with the ability to monitor algae-grazer dynamics, and the recording of O₂ and pH measurements.     

NASA's Space Life Sciences Training Program.

The Space Life Sciences Training Program (SLSTP) is an intensive, six-week training program held every summer since 1985 at the Kennedy Space Center (KSC). A major goal of the SLSTP is to develop a cadre of qualified scientists and engineers to support future space life sciences and engineering challenges. Hand-picked, undergraduate college students participate in lectures, laboratory sessions, facility tours, and special projects: including work on actual Space Shuttle flight experiments and baseline data collection. At NASA Headquarters (HQ), the SLSTP is jointly sponsored by the Life Sciences Division and the Office of Equal Opportunity Programs: it has been very successful in attracting minority students and women to the fields of space science and engineering. In honor of the International Space Year (ISY), 17 international students participated in this summer's program. An SLSTP Symposium was held in Washington D.C., just prior to the World Space Congress. The Symposium attracted over 150 SLSTP graduates for a day of scientific discussions and briefings concerning educational and employment opportunities within NASA and the aerospace community. Future plans for the SLSTP include expansion to the Johnson Space Center in 1995.     

Theoretical and practical considerations for staggered production of crops in a BLSS.

A functional Bioregenerative Life Support System (BLSS) will generate oxygen, remove excess carbon dioxide, purify water, and produce food on a continuous basis for long periods of operation. In order to minimize fluctuations in gas exchange, water purification, and yield that are inherent in batch systems, staggered planting and harvesting of the crop is desirable. A 418-d test of staggered production of potato cv. Norland (26-d harvest cycles) using nutrients recovered from inedible biomass was recently completed at Kennedy Space Center. The results indicate that staggered production can be sustained without detrimental effects on life support functions in a CELSS. System yields of H2O, O2 and food were higher in staggered than batch plantings. Plants growing in staggered production or batch production on "aged" solution initiated tubers earlier, and were shorter than plants grown on "fresh" solution. This morphological response required an increase in planting density to maintain full canopy coverage. Plants grown in staggered production used available light more efficiently than the batch planting due to increased sidelighting.     

The performance of KSC Fixation Tubes with RNALater for orbital experiments: A case study in ISS operations for molecular biology

Molecular biology experiments on the International Space Station (ISS) continue to face challenges of sample harvesting and sample return to earth for post flight analysis; however, the use of Kennedy Space Center Fixation Tubes filled with RNALater has proven to be a robust solution to many of these challenges. While it is clear that one direction of future spaceflight experimentation may be towards enhanced on-orbit analytical capabilities, the rapid progress of earth-bound analytical capacity dictates that facile return of molecular biology samples from the ISS will continue to be a mainstay of space life sciences research and flight operations. In this paper we present a case study of the successful performance of KFTs and RNALater over a broad set of operational conditions of ascent configuration, on-orbit experiment use, on-orbit storage and sample return configurations that are unique to ISS current operations and constraints. We also provide observations on performance limits and discuss deployment opportunities and scenarios that are consistent with continued successful ISS molecular biology experimentation.     

Contribution of satellite laser ranging to combined gravity field models

In the framework of satellite-only gravity field modeling, satellite laser ranging (SLR) data is typically exploited to recover long-wavelength features. This contribution provides a detailed discussion of the SLR component of GOCO02S, the latest release of combined models within the GOCO series. Over a period of five years (January 2006 to December 2010), observations to LAGEOS-1, LAGEOS-2, Ajisai, Stella, and Starlette were analyzed. We conducted a series of closed-loop simulations and found that estimating monthly sets of spherical harmonic coefficients beyond degree five leads to exceedingly ill-posed normal equation systems. Therefore, we adopted degree five as the spectral resolution for real data analysis. We compared our monthly coefficient estimates of degree two with SLR and Gravity Recovery and Climate Experiment (GRACE) time series provided by the Center for Space Research (CSR) at Austin, Texas. Significant deviations in C₂₀ were noted between SLR and GRACE; the agreement is better for the non-zonal coefficients. Fitting sinusoids together with a linear trend to our C₂₀ time series yielded a rate of (−1.75 ± 0.6) × 10⁻¹¹/yr; this drift is equivalent to a geoid change from pole to equator of 0.35 ± 0.12 mm/yr or an apparent Greenland mass loss of 178.5 ± 61.2 km³/yr. The mean of all monthly solutions, averaged over the five-year period, served as input for the satellite-only model GOCO02S. The contribution of SLR to the combined gravity field model is highest for C₂₀, and hence is essential for the determination of the Earth’s oblateness.     

Selection and hydroponic growth of potato cultivars for bioregenerative life support systems

As part of the ESA-funded MELiSSA program, Ghent University and the Université catholique de Louvain investigated the suitability, growth and development of four potato cultivars in hydroponic culture under controlled conditions with the aim to incorporate such cultivation system in an Environmental Control and Life Support System (ECLSS). Potato plants can fulfill three major functions in an ECLSS in space missions: (a) fixation of CO₂ and production of O₂, (b) production of tubers for human nutrition and (c) production of clean water after condensation of the water vapor released from the plants by transpiration. Four cultivars (Annabelle, Bintje, Desiree and Innovator) were selected and grown hydroponically in nutrient film technique (NFT) gullies in a growth chamber under controlled conditions. The plant growth parameters, tuber harvest parameters and results of tuber nutritional analysis of the four cultivars were compared. The four potato cultivars grew well and all produced tubers. The growth period lasted 127 days for all cultivars except for Desiree which needed 145 days. Annabelle (1.45 kg/m²) and Bintje (1.355 kg/m²) were the best performing of the four cultivars. They also produced two times more tubers than Desiree and Innovator. Innovator produced the biggest tubers (20.95 g/tuber) and Desiree the smallest (7.67 g/tuber). The size of Annabelle and Bintje potatoes were intermediate. Bintje plants produced the highest total biomass in term of DW. The highest non-edible biomass was produced by Desiree, which showed both the highest shoot and root DW. The manual length and width measurements were also used to predict the total tuber mass. The energy values of the tubers remained in the range of the 2010 USDA and Souci-Fachmann-Kraut food composition databases. The amount of Ca determined was slightly reduced compared to the USDA value, but close to the Souci-Fachmann-Kraut value. The concentration of Cu, Zn and P were high compared to both databases.     

Operations of a spaceflight experiment to investigate plant tropisms

Plants will be an important component in bioregenerative systems for long-term missions to the Moon and Mars. Since gravity is reduced both on the Moon and Mars, studies that identify the basic mechanisms of plant growth and development in altered gravity are required to ensure successful plant production on these space colonization missions. To address these issues, we have developed a project on the International Space Station (ISS) to study the interaction between gravitropism and phototropism in Arabidopsis thaliana. These experiments were termed TROPI (for tropisms) and were performed on the European Modular Cultivation System (EMCS) in 2006. In this paper, we provide an operational summary of TROPI and preliminary results on studies of tropistic curvature of seedlings grown in space. Seed germination in TROPI was lower compared to previous space experiments, and this was likely due to extended storage in hardware for up to 8 months. Video downlinks provided an important quality check on the automated experimental time line that also was monitored with telemetry. Good quality images of seedlings were obtained, but the use of analog video tapes resulted in delays in image processing and analysis procedures. Seedlings that germinated exhibited robust phototropic curvature. Frozen plant samples were returned on three space shuttle missions, and improvements in cold stowage and handing procedures in the second and third missions resulted in quality RNA extracted from the seedlings that was used in subsequent microarray analyses. While the TROPI experiment had technical and logistical difficulties, most of the procedures worked well due to refinement during the project.     

Influence of the interaction between light intensity and CO2 concentration on productivity and quality of spinach (Spinacia oleracea L.) grown in fully controlled environment

The effects of the factorial combination of two light intensities (200 and 800 μmol m⁻² s⁻¹) and two CO₂ concentrations (360 and 800 ppm) were studied on the productivity and nutritional quality of spinach (Spinacia oleracea L.) grown under controlled environment. After 6 weeks within a growth chamber, spinach plants were sampled and analyzed for productivity and quality. There were no statistically significant interactions between the effects of light and CO₂ for all of the variables studied, except for the nitrate and oxalic acid content of the leaves. High light and high CO₂ independently one from the other, promoted spinach productivity, and the accumulation of ascorbic acid, while their interactive effect limited the accumulation of nitrate and oxalic acid in the spinach leaves. The results highlight the importance of considering the effects of the interaction among environmental variables on maximizing production and the nutritional quality of the food when cultivating and modeling the plant response in controlled environment systems such as for bioregenerative life support.