Rhenium Prevents Corrosion
Rhenium layer inside carbon-composite thrust chamber prevents corrosion when liquid fluorine/hydrazine rocket engine is fired. Liner also eliminates erosion of solid propellant carbon nozzels.
Appel, M. A.↗
SEARCH · Search NASA
Results for “preventative”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Preventing Moisture Damage To Solar Panels
Encapsulating photovoltaic solar cells with polysulfonated membrane prevents moisture damage to cells. Gases escape through vents before damage can occur.
Laue, E. G.↗
Radio frequency selection and interference prevention
The bands available for deep-space communications, and the choice of particular mission frequencies are discussed. The more general susceptibility of deep-space Earth stations to various kinds of interference is then presented. An associated topic is the development of protection criteria that specify maximum allowable levels of interference. Next, the prediction of interference from near-Earth satellites is described, with particular emphasis on the problems and uncertainties of such predictions. Finally, a brief description of other activities aimed at the prevention or avoidance of interference to deep-space radio communications is given.
Degroot, N. F.↗
Evaluation of a Reverse Gradient Garment for prevention of bed-rest deconditioning
A Reverse Gradient Garment (RGG) was used to intermittently induce venous pooling in the extremities of a magnitude similar to that seen in going from a lying to standing position during the course of a 15-d period of horizontal bed rest. Venous pooling failed to improve bed-rest-induced losses in +2.5 Gz and +3.0 Gz centrifugation tolerance or to prevent increased heart-rate responses to lower-body negative pressure (LBNP). Four subjects served as controls, four were treated. Tests during the 7-d recovery period showed fluid/electrolyte and body composition values to have returned to pre-bed-rest levels with continued depression of acceleration tolerance times (56% decreased at +2.5 Gz and 74% decreased at +3.0 Gz compared to pre-bed-rest levels) and exaggerated blood insulin response on glucose tolerance testing (blood insulin for treated group increased 95% at 1 h before bed rest and 465% during recovery). This study demonstrates that the physiologic changes after bed rest persist for significant periods of time. Acceleration tolerance time proved to be a sensitive test for the deconditioning process.
Sandler, H.↗
Design for prevention of acoustic fatigue
It is pointed out that new noise prediction methods and acoustic life estimation methods have matured to the point where they can be combined into a unified engineering procedure. "Life derivatives" can be extracted from parametric charts to furnish design data for preventing acoustic fatigue. The acoustic fatigue life is shown to be sensitive to the damping ratio through the use of life derivatives. The localized nature of propeller noise can be quantified with an "isodecibel" contour diagram.Even though the peak sound pressure level may be high, the directional derivatives show the noise decay rates with distance. Acoustic fatigue design is discussed from the overall design methodology and is shown to be similar to other structural design problems. While nonlinearities present a formidable design engineering problem, they are manageable by proven semi-empirical techniques. For new design problems, it is imperative to determine whether the data base completely spans the design variables.
Smith, H. W.↗
An appraisal of the value of vitamin B12 in the prevention of motion sickness
It has been suggested that vitamin B12 given by intramuscular injection can significantly reduce the occurrence of motion sickness in susceptible individuals (Banks, 1980). Since it is known that B12 influences the metabolism of histidine and choline, dietary precursors to neurotransmitters with established roles in motion sickness, an experimental evaluation has been undertaken of the efficacy of B12 in the prevention of motion sickness induced by controlled coriolis simulation. Subjects executed standardized head movements at successively higher rpm until a malaise III endpoint was reached. Following two baseline tests with this motion stressor, subjects received a B12 injection, a second injection two weeks later, and a final motion sickness test three weeks later. No significant differences in the susceptibility to motion sickness were noted after B12.
Kohl, R. L.↗
Preventing Fires in Cryogenic Oxidizer Lines
Friction and compression induced ignition prevented by heat-dissipation layer. Thin layer of copper placed inside surfaces of pipes and other parts in contact with flowing liquid oxygen, fluorine, or other oxidizers. Copper layer of only 0.001 to 0.005 inch (0.0254 to 0.127 mm) ensures heat away from hotspots thereby discouraging ignition. Copper layer increases oxygen ignition threshold of pipe by 5 to 20 times.
Wagner, W. R.↗
The Flight Test of an Automatic Spin Prevention System
The paper describes the flight testing of the Spin Prevention and Incidence Limiting System (SPILS) now fitted to the Tornado aircraft. The trial was carried out in parallel with the conventional stalling and spinning trial and the special aircraft equipment and test procedures were common to both trials for much of the time. The use of telemetry was of particular importance to the conduct of the trial and is considered in some detail. The paper then describes the SPILS flight testing, with and without stores, and describes the reasons for the control law modifications required to "fine tune" the performance of the system. In conclusion, consideration is given to the lessons learned from the flight trial.
P S Butcher↗
Transdermal scopolamine in the prevention of motion sickness - Evaluation of the time course of efficacy
This study evaluated the time course of efficacy of transdermal scopolamine in the prevention of motion sickness induced by exposure to coriolis stimulation in a rotating chair. We measured levels of efficacy, quantified side effects and symptoms, and determined inter- and intra-subject variability following use of transdermal scopolamine. The response to transdermal scopolamine was highly variable, although overall we recorded a 40 percent improvement in test scores 16-72 h after application of the transdermal system. This variability could not be explained solely by the levels of scopolamine present in the blood. The improvement was not due to the artifactual repression by scopolamine of selected symptoms of motion sickness. An unexpectedly high incidence of side effects was reported. It was concluded that the therapeutic use of transdermal scopolamine be evaluated individually and that individuals be cautioned that subsequent usage may not always be effective.
Homick, J. L.↗
Prevention of metabolic alterations caused by suspension hypokinesia in leg muscles of rats
Rats were subjected to tail-cast suspension hypokinesia for 6 days with one leg immobilized in dorsal flexion by casting. Control animals were also tail-casted. The soleus, gastrocnemius and plantaris muscles of uncasted hypokinetic legs were smaller than control muscles. Dorsal flexion prevented atrophy of these muscles and caused the soleus to hypertrophy. The anterior muscles were unaffected by hypokinesia. The smaller size of the soleus of the uncasted leg relative to the dorsal flexed and weight bearing limbs correlated with slower protein synthesis and faster proteolysis. The capacity of this muscle to synthesize glutamine (gln), which carries nitrogenous waste from muscle was also measured. Although tissue homogenates showed higher activities of gln synthetase, the rate of de novo synthesis was not altered in intact muscle but the tissue ratio of gln/glutamate was decreased. Glutamate and ATP were not limiting for gln synthesis, but availability of ammonia may be a limiting factor for this process in hypokinesia.
Tischler, M. E.↗
Moisture absorption characteristics of the Orbiter thermal protection system and methods used to prevent water ingestion
The Space Shuttle Orbiter's silica tile Thermal Protection System (TPS) is beset by the moisture absorption problems inherently associated with low density, highly porous insulation systems. Attention is presently given to the comparative success of methods for the minimization and/or prevention of water ingestion by the TPS tiles, covering the development of water-repellent agents and their tile application techniques, flight test program results, and materials improvements. The use of external films for rewaterproofing of the TPS tiles after each mission have demonstrated marginal to unacceptable performance. By contrast, a tile interior waterproofing agent has shown promise.
Schomburg, C.↗
Spacecraft contamination: Sources and prevention; Thermophysics Conference, 18th, Montreal, Canada, June 1-3, 1983, Selected Papers
Results of current research in the field of spacecraft contamination are presented. An overview of the various sources of contamination is given, showing the many and diverse mechanisms associated with the degradation of thermal and optical performance of spacecraft surfaces and optics. Some of the causes of contamination are discussed, including spallation of foam insulation on cryogenic fuel tanks, dispersion of particle contamination about a spacecraft, particle contamination of optical sensors, and the influence of the location of venting systems. Contamination prevention is addressed. Infrared transmittance and infrared optical properties of contaminants are considered along with the effects and properties of mixtures of exhaust species, of plume boundary layer flow, and of the contamination associated with bipropellant attitude control thrusters proposed for the Galileo spacecraft. Also discussed are: degradation of 'clean' thermal control surfaces over four years in orbit, in-orbit measurement of solar absorptance, and contamination from postfire efflux of a solid-propellant rocket motor.
Roux, J. A.↗
Practical preventive reliability using matrix forms
This paper describes a practical new tool to improve the reliability of equipment. It uses a matrix form to help monitor anticipated component faults precisely. The tool provides the practical measures necessary to generate matrix tables that accurately display all causes of failure and all planned programmatic analyses, tests, processes, and inspections. When completed, the matrix tables give users in-depth visibility of the degree of protection against component failure that is provided by the program's preventive measure plans. The matrix form is an excellent technique for tracking, and thereby influencing, the reliability of nonelectronic spacecraft subsystems or components. No electronic applications have been tried, but the procedure can be useful in the electronics field, e.g., in integrated circuit production planning, and perhaps in process control, inspection or test lines for other electronic components. The drawing of forms, and the recording/manipulation of the data can be computerized.
Johnson, S. A.↗
Space Shuttle ice prevention studies
Turbojet engine exhausts are being considered for the prevention of ice formation on the Space Shuttle External Tank (ET) when cryogenic propellants are loaded. The ice could dislodge and damage the Thermal Protection System tiles of the Shuttle Orbiter. An oil flow visualization technique was developed to quickly and inexpensively study the flowfields created by jet exhausts. The procedure can also determine the influence of geometry, jet exhausts, and wind conditions on the size and location of flow regions. A black tempra and kerosene mixture was applied to an ET model; the wind tunnel and jet flow were started; and when they stopped the flow patterns were photographed to determine which parameters had the greatest influence on the flowfields.
Porteiro, J. L. F.↗
Preventing Delamination of Silverized FEP Films
Edge treatment inhibits attack by moisture. New technique prevents delamination by sealing edges where delamination starts. Samples of aluminum/FEP/silver laminate survive humidity tests and other environmental tests when edges of layers are covered by epoxy bead. Untreated laminates, in contrast, deteriorated seriously during such tests.
Domnikov, L.↗
Corrosion and corrosion prevention in gas turbines
The conditions governing the corrosion behavior in gas turbines are surveyed. Factors such as temperature, relative humidity, the presence of sulfur and nitrogen dioxide, and fuel quality are discussed. Electromechanical corrosion at relatively low temperature in compressors; oxidation; and hot corrosion (sulfidation) at high temperature in turbines are considered. Corrosion prevention by washing and rinsing, fueld additives, and corrosion resistant materials and coatings are reviewed.
Mom, A. J. A.↗
Pyrotechnic system failures: Causes and prevention
Although pyrotechnics have successfully accomplished many critical mechanical spacecraft functions, such as ignition, severance, jettisoning and valving (excluding propulsion), failures continue to occur. Provided is a listing of 84 failures of pyrotechnic hardware with completed design over a 23-year period, compiled informally by experts from every NASA Center, as well as the Air Force Space Division and the Naval Surface Warfare Center. Analyses are presented as to when and where these failures occurred, their technical source or cause, followed by the reasons why and how these kinds of failures persist. The major contributor is a fundamental lack of understanding of the functional mechanisms of pyrotechnic devices and systems, followed by not recognizing pyrotechnics as an engineering technology, insufficient manpower with hands-on experience, too few test facilities, and inadequate guidelines and specifications for design, development, qualification and acceptance. Recommendations are made on both a managerial and technical basis to prevent failures, increase reliability, improve existing and future designs, and develop the technology to meet future requirements.
Bement, Laurence J.↗
Gravitational haemodynamics and oedema prevention in the giraffe
The question of how giraffes avoid pooling of blood and tissue fluid (edema) in dependent tissues of their extremities is addressed. As monitored by radiotelemetry, the blood and tissue fluid pressures that govern transcapillary exchange vary greatly with exercise. These pressures, combined with a tight skin layer, move fluid upward against gravity. The skin thus functions like a natural antigravity suit. Other mechanisms that prevent edema include precapillary vasoconstriction and low permeability of capillaries to plasma proteins.
Hargens, Alan R.↗