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Radmer, R.

Publications and source records attributed to Radmer, R..

12 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Biomass recycle as a means to improve the energy efficiency of CELSS algal culture systems

Algal cultures can be very rapid and efficient means to generate biomass and regenerate the atmosphere for closed environmental life support systems. However, as in the case of most higher plants, a significant fraction of the biomass produced by most algae cannot be directly converted to a useful food product by standard food technology procedures. This waste biomass will serve as an energy drain on the overall system unless it can be efficiently recycled without a significant loss of its energy content. Experiments are reported in which cultures of the alga Scenedesmus obliquus were grown in the light and at the expense of an added carbon source, which either replaced or supplemented the actinic light. As part of these experiments, hydrolyzed waste biomass from these same algae were tested to determine whether the algae themselves could be made part of the biological recycling process. Results indicate that hydrolyzed algal (and plant) biomass can serve as carbon and energy sources for the growth of these algae, suggesting that the efficiency of the closed system could be significantly improved using this recycling process.

Radmer, R.↗
NASA NTRS1987

Algal culture studies for CELSS

Microalgae are well-suited as a component of a Closed Environmental Life Support System (CELSS), since they can couple the closely related functions of food production and atmospheric regeneration. The objective was to provide a basis for predicting the response of CELSS algal cultures, and thus the food supply and air regeneration system, to changes in the culture parameters. Scenedesmus growth was measured as a function of light intensity, and the spectral dependence of light absorption by the algae as well as algal respiration in the light were determined as a function of cell concentration. These results were used to test and confirm a mathematical model that describes the productivity of an algal culture in terms of the competing processes of photosynthesis and respiration. The relationship of algal productivity to cell concentration was determined at different carbon dioxide concentrations, temperatures, and light intensities. The maximum productivity achieved by an air-grown culture was found to be within 10% of the computed maximum productivity, indicating that CO2 was very efficiently removed from the gas stream by the algal culture. Measurements of biomass productivity as a function of cell concentration at different light intensities indicated that both the productivity and efficiency of light utilization were greater at higher light intensities.

Radmer, R.↗
NASA NTRS1986

An analysis of the productivity of a CELSS continuous algal culture system

One of the most attractive aspects of using algal cultures as plant components for a Closed Ecological Life Support Systems (CELSS) is the efficiency with which they can be grown. Although algae are not necessarily intrinsically more efficient than higher plants, the ease which they can be handled and manipulated (more like chemical reagents than plants), and the culturing techniques available, result in much higher growth rates than are usually attainable with higher plants. Furthermore, preliminary experiments have demonstrated that algal growth and physiology is not detectable altered in a microgravity environment, (1) whereas the response of higher plants to zero gravity is unknown. In order to rationally design and operate culture systems, it is necessary to understand how the macroparameters of a culture system, e.g., productivity, are related to the physiological aspects of the algal culture. A first principles analysis of culture system is discussed, and a mathematical model that describes the relationship of culture productivity to the cell concentration of light-limited culture is derived. The predicted productivity vs cell concentration curve agrees well with the experimental data obtained to test this model, indicating that this model permits an accurate prediction of culture productivity given the growth parameters of the system.

Radmer, R.↗
NASA NTRS1986

Do the higher oxidation states of the photosynthetic O2-evolving system contain bound H2O?

A modified mass spectrometer was used to determine whether the higher oxidation states of the photosynthetic O2-evolving system contain substrate water that is not freely exchangeable with the external medium. Our data indicated that the higher oxidation states contain no appreciable bound, non-exchangeable H2O. This suggests that H2O oxidation takes place via a rapid, concerted, all-or-none mechanism rather than by a mechanism involving stable, partially oxidized, H2O-derived intermediates. These findings set definite constraints on possible mechanisms of O2 evolution.

NASA Discipline Life Support Systems↗
NASA NTRS1984

Algal culture studies related to a closed ecological life support system

Studies on the steady-state long-term (4 month) culture of Scenedesmus obliquus algae, maintained in an annular air-lift column operated as a turbidostat, were carried out to evaluate the life-supporting possibilities of this system. Chlorophyll production and cell number as functions of the dry weight were linear at constant illumination. Productivity (measured as the product of dry weight, mg/ml, and the growth rate, ml/hr) vs. dry weight rose linearly until the cell density reached a level at which light became limiting (89 percent absorption of the photosynthetically active radiation). In the initial, linear portion of the curve, the productivity was limited by cell growth at the given light intensity. The maximum dilution rate of the system corresponded to the doubling time of 13.4 hr, about half the maximum rate, with a productivity of 80 percent of the maximum theoretical productivity. The high light utilization efficiencies were contributed by the low (10 percent of full sunlight) incident intensities.

Radmer, R.↗
NASA NTRS1984

Problems associated with the utilization of algae in bioregenerative life support systems

A workshop was conducted to identify the potential problems associated with the use of microalgae in biorregenerative life support systems, and to identify algae rlated research issues that must be addressed through space flight experimentation. Major questions to be resolved relate to the choice of algal species for inclusion in a bioregenerative life support system, their long term behavior in the space environment, and the nature of the techniques required for the continuous growth of algae on the scale required. Consideration was given to the problems associated with the conversion of algal biomass into edible components. Specific concerns were addressed and alternative transformation processes identified and compared. The workshop identified the following major areas to be addressed by space flight experimentation: (1) long term culture stability, (2) optimal design of algal growth reactors, and (3) post growth harvesting and processing in the space environment.

Averner, M. M.↗
NASA NTRS1984

Algal culture studies related to a Closed Ecological Life Support System (CELSS)

In many respects, algae would be the ideal plant component for a biologically based controlled life support system, since they are eminently suited to the closely coupled functions of atmosphere regeneration and food production. Scenedesmus obliquus and Spirulina platensis were grown in three continuous culture apparatuses. Culture vessels their operation and relative merits are described. Both light and nitrogen utilization efficiency are examined. Long term culture issues are detailed and a discussion of a plasmid search in Spirulina is included.

Radmer, R.↗
NASA NTRS1976

A versatile system for biological and soil chemical tests on a planetary landing craft. II - Hardware development

A system has been under development which is designed to seek remotely for clues to life in planetary soil samples. The basic approach is a set of experiments, all having a common sensor, a gas analysis mass spectrometer which monitors gas composition in the head spaces above sealed, temperature controlled soil samples. Versatility is obtained with up to three preloaded, sealed fluid injector capsules for each of eleven soil test cells. Tests results with an engineering model has demonstrated performance capability of subsystem components such as soil distribution, gas sampling valves, injector mechanisms, temperature control, and test cell seal.

Martin, J. P.↗
NASA NTRS1976

Unified Mars detection system

A life-detection system is described which is designed to detect and characterize possible Martian biota and to gather information about the chemical environment of Mars, especially the water and amino acid contents of the soil. The system is organized around a central mass spectrometer that can sensitively analyze trace gases from a variety of different experiments. Some biological assays and soil-chemistry tests that have been performed in the laboratory as typical experiment candidates for the system are discussed, including tests for soil-organism metabolism, measurements of soil carbon contents, and determinations of primary aliphatic amines (amino acids and protein) in soils. Two possible test strategies are outlined, and the operational concept of the detection system is illustrated. Detailed descriptions are given for the mass spectrometer, gas inlet, incubation box, test cell modules, seal drive mechanism, soil distribution assembly, and electronic control system.

Martin, J. P.↗
NASA NTRS1976

Energy requirements of a biosphere

The question is considered of whether a biosphere similar to that on earth could exist in the region of the outer planets, where relatively little light is available for photosynthetic processes. The type of photosynthesis most abundant on earth is discussed along with light conversion in photosynthesis, the light-harvesting system in plants, photosynthetic efficiency, and carbon production in nature. The dynamic range of metabolic rates is examined, and photosynthesis in anaerobic organisms is described. It is suggested that organisms having very large photosynthetic pigment units would thrive in the light intensities prevailing on Titan and that the surface of Titan might well be able to maintain a biosphere driven by oxygen-generating photosynthesis.

Kok, B.↗
NASA NTRS1971

Photoactivation of the manganese catalyst of O2 evolution. II A two-quantum mechanism.

A kinetic analysis is presented of the data obtained in previously described kinetic experiments relating to the photoactivation of the Mn complex required for photosynthetic O2 evolution. The results obtained from the computer simulation of the derived kinetic model compare favorably with the experimentally derived values. They also suggest that photoactivation can be rationalized in terms of a two-quantum process.

Radmer, R.↗