Goudarzi, S. and A.J. Both. 2004. Accounting for performance decrements in crew time calculations for space missions. SAE Technical Paper No. 2004-ICES-215.
Abstract
Equivalent
System Mass (ESM) is a metric used in Advanced Life Support (ALS) studies to
evaluate and compare life support system technologies. Previous crew time ESM
calculations considered only the amount of crew time required to perform a
particular task without any interventions (stress events), i.e., they calculated
static crew time. However, variations in time spent on operating and maintaining
a life support system may occur due to performance fluctuations of the crew
caused by a range of stress events experienced. Simulated crew performance
calculations appear to suggest that crew time varies based on how each
crewmember deals with stress events. Assigning a variable that accounts for such
variation in crew time can be used in the crew selection process and for crew
management strategies to better deal with inevitable stress events.
Kang, S. and A.J. Both. 2002. A management information
system for food nutritional analysis and biomass production in an advanced life
support system. Journal of Life Support and
Biosphere Science 8(3/4):191-197. NJAES Paper No. D-70501-03-02.
Abstract
A
management information system (MIS), including a database management system
(DBMS) and a decision support system (DSS), was developed to dynamically analyze
the variable nutritional content of foods grown and prepared in an Advanced Life
Support System (ALSS) such as required for long-duration space missions.
The DBMS was designed around the known nutritional content of a list of
candidate crops and their prepared foods. The DSS was designed to determine the
composition of the daily crew diet based on crop and nutritional information
stored in the DBMS. Each of the selected food items was assumed to be harvested
from a yet-to-be designed ALSS biomass production subsystem and further prepared
in an accompanying food preparation subsystems. The developed DBMS allows for
the analysis of the nutrient composition of a sample 20-day diet for future
Advanced Life Support missions and is able to determine the required quantities
of food needed to satisfy the crews daily consumption. In addition, based on
published crop growth rates, the DBMS was able to calculate the required size of
the biomass production area needed to satisfy the daily food requirements for
the crew. Results from this study can be used to help design future Advanced
Life Support Systems for which the integration of various subsystems, e.g.,
biomass production, food preparation and consumption, and waste processing, is
paramount for the success of the mission.
Mears, D.R. and A.J. Both. 2002. A positive pressure ventilation system with insect screening for tropical and subtropical greenhouse facilities. Acta Horticulturae 578:125-132. NJAES Paper No. P-03130-06-01.
Abstract
The use of screening to reduce insect
entry into greenhouses is becoming a common practice, particularly in commercial
production facilities in warmer climates with larger insect populations.
Effective insect screening can reduce the use of pesticides, potentially saving
money, and thus reducing the chance for environmental pollution. In an era of
increasing public environmental awareness and insistence for more stringent
regulatory control, non-chemical means of crop protection are increasing in
importance. The prevention of movement of any insects into or out of quarantine
greenhouse facilities has long been a major consideration in their design.
Recent advances in quarantine greenhouse design have provided a basis for
improving the designs adopted for commercial greenhouse operations. The most
common screening systems for mechanically ventilated greenhouses, with exhaust
fans, involve the application of screening at the air inlet only. Attempts to
screen naturally ventilated greenhouses generally result in undesirably high air
temperatures, in part because effective systems must screen both inlets and
outlets, effectively doubling the airflow resistance.
A
positive pressure ventilation system with insect screening can offer several
advantages over standard exhaust systems. A positive pressure ventilation system
should maintain high enough internal greenhouse air pressures that outgoing air
velocities through open doors or other openings in the structure exceed the
flying speed of the insects of concern. Such a system should be more effective
in excluding insects than an exhaust system, which tends to draw insects in
through any openings. In a properly designed positive pressure ventilation
system, insect exclusion can be achieved with only one application of screening
at the air inlet. Doorways and any possible small openings in the greenhouse
glazing will not provide easy entry points for insects. This concept is
particularly attractive for use in warmer climates and in tropical or
subtropical areas where modest airflow rates can be used to maintain positive
internal greenhouse air pressures throughout the entire day and night.
Goudarzi,
S., J. Cavazzoni, and A.J. Both. 2002. Dynamic modeling of crew performance for
long duration space missions. Presented at the 32nd International
Conference on Environmental Systems, July 15-18, San Antonio, Texas. SAE
Technical Paper No. 02ICES-196. NJAES Paper No. H-70501-01-02.
Abstract
Long
duration space mission crews will have to perform
a myriad of tasks under extreme conditions for exploratory and settlement
missions. The primary goal for any
mission is the achievement of specific scientific endeavors and the maintenance
of a safe crew environment. Stressors
such as isolation, confinement, microgravity, extraneous work schedules, and
crew heterogeneity are examples of elements that may alter the consistency of
crew performance. It is critical to predict the
influence of such stressors on crew performance for designing successful and
safe mission scenarios. In order to
assist in the future planning of long duration space missions, the Systems
Integration, Modeling and Analysis team of the NJ-NSCORT has developed an
interactive top-level model of an Advanced Life Support System (ALSS).
Specifically, this dynamic ALSS model consists of a biomass production
unit, a food-processing unit, a waste processing and resource recovery unit, and
a crew model that defines human requirements.
The crew model, which had previously been developed as a simple tool to
examine physical requirements such as calorie intake and oxygen consumption
based upon habitat conditions and specific human characteristics, has now been
expanded to include physiological and psychological stressors to better
determine overall crew performance. This expanded crew model will aid in
estimating crew time requirements more effectively for varying mission
scenarios, and may be used for evaluating how planned and random external and
internal events affect crew performance.
Both,
A.J., D.E. Ciolkosz, and L.D. Albright. 2002. Evaluation of light uniformity
underneath supplemental lighting systems. Acta Horticulturae 580:183-190.
Abstract
The use of supplemental
lighting systems is increasing as more growers become interested in shortening
the time needed for their crops to reach maturity, and/or in continuous plant
production throughout the winter season. The installation and operation of
supplemental lighting systems can add significantly to the overall energy
requirement of a greenhouse operation. Obviously, the selection of energy
efficient luminaires is an important design consideration. In addition, a high
degree of light uniformity is required for consistent plant production
throughout the growing area. Sometimes, different design criteria are used to
characterize the light distribution in plant production facilities. Several of
these design criteria are discussed in this study. Other times, the design of
supplemental lighting systems for plant production facilities is optimized with
the help of sophisticated computer software programs. Depending on the
dimensions and characteristics of the plant production area, the available
luminaire mounting height, the average height of the crop, and the number and
placement of the particular luminaires selected, the software calculates the
resulting light intensity and uniformity. Or, based on the desired light
intensity, it calculates the required number and placement of the selected
luminaires. In this study, the usefulness of light uniformity criteria and
design software is demonstrated. These design tools can help improve or evaluate
light uniformity either during the design phase, or after installation of a
lighting system.
Kang,
S., K.C. Ting, and A.J. Both. 2001. Systems studies and modeling of advanced
life support systems. Agricultural and Biosystems Engineering 2(2):41-49. NJAES
Paper No. P-70501-17-01.
Abstract
Advanced Life Support Systems (ALSS) are being studied to
support human life during long-duration space missions. ALSS can be categorized
into four subsystems: Crew, Biomass Production, Food Processing and Nutrition,
Waste Processing and Resource Recovery. The System Studies and Modeling (SSM)
team of New Jersey-NASA Specialized Center of Research and Training (NJ-NSCORT)
has facilitated and conducted analyses of ALSS to address systems level issues.
The underlying concept of the SSM work is to enable the effective utilization of
information to aid in planning, analysis, design, management, and operation of
ALSS and their components. Analytical tools and computer models for ALSS
analyses have been developed and implemented for value-added information
processing. The results of analyses have been delivered through the internet for
effective communication within the advanced life support (ALS) community.
Several modeling paradigms have been explored by developing tools for use in
systems analysis. They include object-oriented approach for top-level models,
procedural approach for process-level models, and application of commercially
available modeling tools such as MATLABź/Simulinkź.
Every paradigm has its particular applicability for the purpose of modeling
work. An overview is presented of the systems studies and modeling work
conducted by the NJ-NSCORT SSM team in its efforts to provide systems analysis
capabilities to the ALS community. The experience gained and the analytical
tools developed from this work can be extended to solving problems encountered
in general agriculture.
Ciolkosz,
D.E., A.J. Both, and L.D. Albright. 2001. Selection and placement of greenhouse
luminaires for uniformity. Applied Engineering in Agriculture 17(6):875-882.
Abstract
Design considerations regarding the effects of luminaire selection and layout on light level uniformity were examined in this study. Flux transfer computer simulations were utilized to determine the effect of luminaire selection and spacing on uniformity in the center, as well as near the perimeter, of a greenhouse. Two design parameters - the spacing ratio (luminaire spacing-to mounting height ratio divided by the spacing criterion) and the area ratio (greenhouse area per luminaire divided by spacing criterion squared times mounting height squared) - were developed and investigated as possible indicators of light level uniformity. Uniformity at the center of the greenhouse was found to be a function of the area ratio of the lighting design. This information can be used to determine the maximum allowable spacing to achieve a desired uniformity level at the center of the greenhouse. Staggered square layouts of luminaires do not give improved uniformity over regular square layouts, but staggered rectangular layouts were more uniform than regular rectangular layouts. Light uniformity near the perimeter of a greenhouse improves as luminaires are added to the perimeter, with an optimum perimeter spacing depending on the mounting height and overall greenhouse spacing of the luminaires.
Abstract
Lettuce growth data are presented that show the importance of the daily light integral for predictable vegetative growth. Dry mass accumulation is shown to be proportional to the light integral, and a consistent daily light integral is proposed to be central to consistent production. Supplemental lighting control rules are defined and described and a computer implementation is used in conjunction with ten years of hourly weather data to test (by simulation) adequacy of the rules to control supplemental lights and movable shades in greenhouses to achieve a consistent daily integral of Photosynthetically Active Radiation (PAR), mol-m-2-day-1, on days of either insufficient or excess solar irradiation, which are most days. The rules require neither historical data bases of weather characteristics nor daily weather forecasts. Control decisions are suggested to be made hourly, based on the current days accumulating solar PAR integral inside the greenhouse. The model is sensitive to time-of-day electrical rates, changing seasons, weather, greenhouse and component characteristics, and greenhouse location (latitude and longitude). The rules contain parameters with values suggested for northeastern United States solar conditions but which may be adjusted for local solar climates that are significantly different.
Abstract
The design and operation of a floating hydroponic system are described. The nutrient solution temperature and dissolved oxygen concentration in this hydroponic system were maintained with two simple control mechanisms. During a 24 day growth trial with lettuce (Lactuca sativa L., cv Vivaldi), nutrient solution temperature was controlled to 24 ± 0.3șC and the dissolved oxygen concentration to 8.4 ± 0.2 mg-L-1. Measurements of shoot fresh and dry mass as well as root dry mass of plants aged from 11 to 35 days after sowing were taken. Desired nutrition and pH levels in this closed recirculation system were maintained manually. Greenhouse air temperature and daily integrated light level were precisely maintained at consistent levels throughout the experiment. Example data of plant response showed a rapid decline in root-shoot ratio shortly after transplant, followed by a gradual decline towards final harvest (35 days after sowing). Root-shoot ratio at final harvest was 10%. Percentage of shoot dry matter declined steadily from 8% at transplant to 4% at final harvest. Results showed an improved environment control can result in highly uniform plant production.
Abstract
Growth equations may be relatively general and describe plant dry mass accumulation based on data representing wide ranges of environment parameter values or they may be narrow and apply only to limited ranges. This paper proposes an empirical approach of the second type, a method to derive, by regression growth functions that can be readily implemented on control computers to improve (or attempt to optimize) growth within a narrow range of growing conditions. The method assumes plant vegetative growth may be predicted by two separable functions, which combine by multiplication. One function is based on environmental conditions (air temperature, CO2 concentration, light integral, and nutrient solution nitrate concentration, but not root zone temperature). The other function has two parameters, root zone temperature and time. Three data sets of hydroponic lettuce vegetative growth data are analyzed using the method. In each case, converting the original data to dimensionless form permitted the data to be expressed using a single, simple equation that described the original data relatively well.
Abstract
Tipburn, a physiological disorder of lettuce, has been linked to insufficient evapotranspiration (ET). Better understanding of ET in greenhouse lettuce crops may be useful as a management tool to control tipburn. A regression model is presented to characterize ET from greenhouse lettuce (Lactuca sativa L., cv. "Vivaldi") based on data from twelve crops grown in a nutrient film technique (NFT) system. Several CO2 concentrations and daily light integrals were applied to the lettuce crops and the resulting daily ET integrals were measured. A regression model was derived for daily ET as a function of growth rate and the resulting daily and cumulative ET values were calculated and compared to measured values. ET rate was found to vary linearly with growth rate (R sq. (adj) = 0.63) but higher CO2 levels were associated with lesser values of the slope of the relationship. Modeled and measured data were in good agreement even though relative humidity was not included in the model. An equation is presented that may be useful to calculate daily ET targets that must be achieved to prevent tipburn in hydroponic lettuce.
Abstract
Butterhead lettuce (Lactuca sativa L., cv. Ostinata) was used to study lettuce production at varied shoot (air) and root (pond) temperatures. A floating hydroponic system was used to study the influence of pond temperature on lettuce growth for 35 days. Pond water temperature set points of 17, 24 and 31șC were used at air temperatures of 17/12, 24/19, and 31/26șC (day/night). Pond temperature affected plant dry mass, and air temperature significantly affected growth over time. Maximum dry mass was produced at the 24/24șC (air/pond temperature) treatment. Final dry mass at the 31/24șC treatment did not differ significantly from the 24/24șC treatment. The 24șC pond treatment maintained market quality lettuce head production in 31șC air. Using optimal pond temperature, lettuce production was deemed acceptable at a variety of air temperatures outside the normal range, and particularly at high air temperatures.
Abstract
The interaction between daily integrated photosynthetically active radiation (PAR) and elevated aerial CO2 concentration was studied during plant growth experiments with leaf lettuce (Lactuca sativa L., cv. Vivaldi) grown in a nutrient film technique system in a greenhouse. Accurate control of all environment parameters (except relative humidity) and four identical greenhouse sections constituted the experimental setup. Supplemental lighting (high pressure sodium lamps) was used to provide additional PAR to the lettuce on days when too little sunlight was available to reach the required daily light integral. Two experiments with four treatments each were performed to investigate six integrated PAR/CO2 concentration combinations: 11/1500, 12/1250, 13/1000, 14/750, 15/530, and 16/400 (mol-m-2-d-1/”mol-mol-1). The target integrated PAR levels were accurately maintained during each treatment but the two highest CO2 concentrations could not consistently be maintained because periodic ventilation was required for accurate temperature control. Lettuce plants were grown for 24 days under these conditions after being grown in a growth room under optimum conditions for 11 days. Periodic harvests during the greenhouse growing phase provided shoot dry-mass data. Shoot fresh-mass and number of leaves per plant were determined at the final harvest 35 days after seeding. Plant growth under the six different treatments was virtually identical and resulted in an average shoot fresh-mass of 190 g with a dry matter percentage of 3.7%. The results of the described experiments show a flexible management strategy regarding daily integrated PAR level and aerial CO2 concentration can be employed for the most economical lettuce production.
Abstract
The PPFi (instantaneous photosynthetic photon flux, in ”mol-m-2-s-1) output and electric energy consumption of nine different 400 watt high pressure sodium (HPS) luminaires were measured at six mounting heights from 0.5 to 3.0 m in 0.5 m increments. Differences in luminaire efficacy and PPFi distribution patterns were found, but too few luminaires were tested to reach statistically valid conclusions. The most efficient luminaire proved 25% more energy efficient than the least efficient luminaire. PPFi data from one of the luminaires tested was used to design a research greenhouse, which required uniform PPFi distribution patterns at various PPFi levels.
Abstract
Bibb lettuce (Lactuca sativa L., cv. Ostinata) was grown in peat-vermiculite plugs placed in a recirculating hydroponic (NFT) system. Supplemental lighting was used to reach different PPFtarget levels in each of 35 treatments. A second order exponential polynomial was developed to predict dry weight (DW) accumulation for PPFtarget levels between 8 and 22 mol-m-2-d-1. Little difference in DW production was noted between lettuce grown under daytime and nighttime lighting. Tipburn was prevented using a fan blowing greenhouse air vertically down onto the lettuce plants. Marketable (150 g fresh weight) lettuce heads were produced in 24 days after transplant while receiving an average PPFintegral of 17 mol-m-2-d-1.
Abstract
A new high intensity electrodeless light source, powered by two microwave generating units, was evaluated and compared with fluorescent and air- and water- cooled high pressure sodium (HPS) lamps. Radiation measurements were taken in the following wavebands: 400-700 nm (photosynthetically active radiation or PAR), 700-800 nm (far red), 800-2,800 nm (near infrared) and 2,800-50,000 nm (far infrared), for all four light sources. The distribution of the radiation output of the microwave lamp over the various wavebands closely resembled the output of a water-cooled HPS lamp, although the microwave lamp was capable of delivering much higher light intensities. The relatively small amount of radiation emitted in the infrared waveband makes the microwave lamp a promising light source for plant irradiation in growth rooms (phytotrons).
Abstract
Primed spinach (Spinacia oleracea L., cv. Nordic) seed was started in rockwool slabs in a growth room for eight days before the seedlings were transplanted into a controlled environment greenhouse equipped with five identical, but separate, NFT systems. The day and night temperatures in the greenhouse were maintained at 24 and 18șC, respectively, with the daytime starting at 06:00 and ending at 22:00 hr. A photoperiod of 16 hrs was maintained, to prevent early bolting, and different target daily integrated light levels (PPF, in mol-m-2-d-1) were studied to observe dry weight production. HPS lamps were used as the supplemental light source. Thirty-three days after seeding a final harvest was performed. Using the expolinear growth equation, dry weight production can be predicted based solely on target daily integrated light levels. Total chlorine residuals in the nutrient solution higher than 1 ppm were observed to be toxic. Root disease (rot) in the plant crown was found to be caused by Fusarium. Several remedies, including three biofungicides and potassium silicate, were tried but none proved to be consistently successful.
Abstract
Lettuce growth experiments were carried out to study the effect of sub- and super-saturated dissolved oxygen (DO) concentrations on the growth in floating hydroponic systems. The hydroponic systems had the pure O2 and N2 gas supply apparatus with a precise DO control. The system made it easy to increase DO concentration higher than the saturated level. Lettuce plants of Day 11 were grown until Day 35 under various DO concentrations: sub-saturated, saturated, and super-saturated concentrations. There was no significant differences in fresh weight, shoot and root dry weights among the DO concentrations: 2.1 (25% of the saturated at 24șC), 4.2 (50%), 8.4 (saturated), and 16.8 (200%) mg/L. The critical level for lettuce growth was considered to be lower than 2.1 mg/L. Neither root damage nor delay of shoot growth was observed at any of the studied DO concentrations. From the results, it can be concluded that the designed DO control system is a practical and economical method to maintain an optimum DO concentration for lettuce production in floating hydroponics.