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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.

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At least 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Graphite/epoxy composite stiffened panel fabrication development

This report describes the manufacturing development procedures used to fabricate a series of carbon/epoxy panels with integrally molded stiffeners. Panel size was started at 6 inches by 18 inches and one stiffener and increased to 30 inches by 60 inches and six integral stiffeners. Stiffener concepts were optimized for minimum weight (or mass) to carry stress levels from 1500 lbs/inch to 25,000 lbs/inch compression load. Designs were created and manufactured with a stiffener configuration of integrally molded hat, J, I, sine wave I, solid blade, and honeycomb blade shapes. Successful and unsuccessful detail methods of tooling, lay-up methods, and bagging methods are documented. Recommendations are made for the best state-of-the-art manufacturing technique developed for type of stiffener construction.

Palmer, R. J.↗
NASA NTRS1985

Encapsulation Processing and Manufacturing Yield Analysis

Evaluation of the ethyl vinyl acetate (EVA) encapsulation system is presented. This work is part of the materials baseline needed to demonstrate a 30 year module lifetime capability. Process and compound variables are both being studied along with various module materials. Results have shown that EVA should be stored rolled up, and enclosed in a plastic bag to retard loss of peroxide curing agents. The TBEC curing agent has superior shelf life and processing than the earlier Lupersol-101 curing agent. Analytical methods were developed to test for peroxide content, and experimental methodologies were formalized.

Willis, P.↗
NASA NTRS1985

High Weber number SMD correlations for pressure atomizers

Recently acquired experimental data are presented which reveal that, for Weber number (We) greater than 10.0, the atomization from simplex pressure atomizers is significantly greater than would be predicted from previously derived Sauter mean diameter (SMD) correlations. A different SMD correlation is required to accurately predict the experimental data. Below We of about 10.0, the atomization is dominated by inertial forces and bag-type breakup results. Above We of about 10.0, shear-type breakup occurs and results in a very fine spray which can accurately be predicted using a quadratic expression in Delta P. The correlation is extended to include fuel property effects, and SMD is found to vary linearly with fuel surface tension, while the influence of the fuel viscosity is not apparent.

Kennedy, J. B.↗
NASA NTRS1986

A fundamental problem in determining functional residual capacity or residual volume

To measure a lung volume that is not directly accessible, one often follows dilution of a single-gas tracer, present initially only in the lung or in a rebreathing bag. The final volume available to the tracer is assumed to be the sum of the two initial components. Since O2 is taken up and CO2 is eliminated during the few breaths required for mixing, the total volume changes. The error in lung volume due to this volume change can exceed 10 pct. Theoretical and experimental data is presented to demonstrate the effect of CO2 and O2 exchange. A general equation, based on N2 and Ar, which allows one to circumvent the problems created by these fluxes is introduced. The pitfall of the back-extrapolation approach for a single tracer is shown.

Boutellier, U.↗
NASA NTRS1987

Measuring Leakage From Large, Complicated Machinery

Test chamber improvised from large bag. Cumulative sizes of leaks in large, complicated machinery measure with relatively simple variation of helium leak-checking technique. When used to check Space Shuttle main engine, new technique gave repeatable and correct results within 0.5 stdin.3/min (1.4 x 10 negative to the seventh power stdm3/s).

Bottemiller, S.↗
NASA NTRS1987

Applying Tape in Vacuum or Air

Cost and complexity reduced. Device applies adhesive second-surface-mirror tape to flat surfaces. Use of device replaces previous application of tape by time-consuming and labor-intensive procedure of autoclaving in vacuum bags.

Downs, Karyn S.↗
NASA NTRS1987

Filament-Winding Technique for Concave Parts

Dummy mold and vacuum bagging yield accurate part girth. Proposed method of filament winding facilitates accurate fabrication of fiber/matrix composite parts having closed sections with concave surfaces. Parts laid up by hand now wound with filaments; reducing time and cost of fabrication and improving quality of parts.

Carter, Donald↗
NASA NTRS1986

Radiocarbon tracer measurements of atmospheric hydroxyl radical concentrations

The usefulness of the C-14 tracer in measurements of atmospheric hydroxyl radical concentration is discussed. The apparatus and the experimental conditions of three variations of a radiochemical method of atmosphere analysis are described and analyzed: the Teflon bag static reactor, the flow reactor (used in the Wallops Island tests), and the aircraft OH titration reactor. The procedure for reduction of the aircraft reactor instrument data is outlined. The problems connected with the measurement of hydroxyl radicals are discussed. It is suggested that the gas-phase radioisotope methods have considerable potential in measuring tropospheric impurities present in very low concentrations.

Campbell, M. J.↗
NASA NTRS1986

The pultrusion process for structures on advanced aerospace transportation systems

The pultrusion process, which has the potential for use in the manufacture of structures for aerospace hardware, is described. In this process, reinforcing fibers are pulled continuously through a resin system for wetting and subsequently through a heated die for polymerization. By using this process, fabrication of very long lengths of high strength, lightweight structures with consistently high quality for aerospace applications is possible. The more conventional processes involve hand lay-up, vacuum bagging, autoclaving or oven curing techniques such that lengths of structural elements produced are limited by the lengths of autoclaves or curing ovens. Several types of developmental structural elements are described in which fiberglass, aramid, graphite, and hybrid fiber systems have been used as reinforcements in an epoxy matrix and their flexural properties compared. Reinforcement fibers having tailor-made orientations which achieve tailor-made strength in the pultrusions are described. The potential aerospace applications for the pultruded products are described with advantages cited over conventional hand lay-up methods.

Wilson, Maywood L.↗
NASA NTRS1987

Trickle water and feeding system in plant culture and light-dark cycle effects on plant growth

Rockwool, as an inert medium covered or bagged with polyethylene film, can be effectively used for plant culture in space stations. The most important machine is the pump adjusting the dripping rate in the feeding system. Hydro-aeroponics may be adaptable to a space laboratory. The shortening of the light-dark cycles inhibits plant growth and induces an abnormal morphogenesis. A photoperiod of 12 hr dark may be needed for plant growth.

Takano, T.↗
NASA NTRS1986

The RP-2 sailplane

The all-composite design and fabrication methodology employed by Rensselaer Polytechnic Intitute's 'CAPGLIDE' program in producing such sailplanes as the RP-2 is discussed. The RP-2's production methods, which furnish hands-on experience for the students enrolled in the program, encompass wet lay-up and vacuum bag procedures, as well as autoclave curing of prepreg parts employing graphite, kevlar, and glass fiber reinforcements. Epoxy resins are the primary matrix materials, and are used in conjunction with polymer foams for the sandwich panel elements of the sailplane structure.

Winckler, Steven↗
NASA NTRS1989

Automatic Sprout Grower

Self-contained seed-sprouting system provides environment for sprouting seeds quickly and easily. Sprouting container standard 6-oz package for dehydrated food and drink mixes in Space Shuttle. About 4 g of dry alfalfa or radish seeds vacuum-sealed in each cup, like freeze-dried foods. Sixteen cups suspended in tray. Air-and-water inlet tube links each cup to system of tubes and solenoid valves alternately furnish air and water and remove stale air. Peristaltic pump supplies water from vinyl medical-fluid bag. Small diaphragm pump supplies and exhausts air. Small circuit board times movements of air and water. Kit offers advantages to home gardeners. Apartment dwellers use it for steady production of homegrown sprouts even though they have no garden space.

Sauer, Richard L.↗
NASA NTRS1989

Electrostatic charging of spacecraft in response to electron beam injection

Electron beam injections from spacecraft now constitute a major activity in space research. Here, the charging level of a conducting surface when an electron beam is injected from it is investigated. Injections into both vacuum and an ambient plasma are considered. When a Maxwellian beam is injected into vacuum, the surface changes to a potential much greater than the average beam energy. The dependence of this excess is examined by considering beams with water-bag types of velocity distribution functions in which no electron has a velocity V(max) above a certain value. The electric field distribution in the electron sheath near the surface is determined by the pressure distribution. Thus, the surface potential is determined not only by V(max) but by all the beam parameters. The ambient plasma reduces the charging level and causes an oscillation in the surface potential. The oscillation frequency is the electron-plasma frequency associated with the ambient plasma.

Singh, Nagendra↗
NASA NTRS1987

Low cost tooling material and process for graphite and Kevlar composites

An Extruded Sheet Tooling Compound (ESTC) was developed for use in quickly building low cost molds for fabricating composites. The ESTC is a very highly mineral-filled resin system formed into a 6 mm thick sheet. The sheet is laid on the pattern, vacuum (bag) is applied to remove air from the pattern surface, and the assembly is heat cured. The formed ESTC is then backed and/or framed and ready for use. The cured ESTC exhibits low coefficient of thermal expansion and maintains strength at temperatures of 180 to 200 C. Tools were made and used successfully for: Compression molding of high strength epoxy sheet molding compound, stamping of aluminum, resin transfer molding of polyester, and liquid resin molding of polyester. Several variations of ESTC can be made for specific requirements. Higher thermal conductivity can be achieved by using an aluminum particle filler. Room temperature gel is possible to allow use of foam patterns.

Childs, William I.↗
NASA NTRS1988

Initial blood storage experiment

The possibility of conducting experiments with the formed elements of the blood under conditions of microgravity opens up important opportunities to improve the understanding of basic formed element physiology, as well as, contribution to improved preservation of the formed elements for use in transfusion. The physiological, biochemical, and physical changes of the membrane of the erythrocyte, platelet, and leukocyte was studied during storage under two specific conditions: standard blood bank conditions and microgravity, utilizing three FDA approved plastic bags. Storage lesions; red cell storage on Earth; platelet storage on Earth; and leukocyte storage Earth were examined. The interaction of biomaterials and blood cells was studied during storage.

Surgenor, Douglas MACN.↗
NASA NTRS1990

Pressure and current balance conditions during electron beam injections from spacecraft

Electrostatic charging level of a conducting surface in response to injections of electron beams into space plasma is investigated by means of one-dimensional Vlasov code. Injections of Maxwellian beams into a vacuum shows that the surface can charge up to an electric potential phi sub s greater than W sub b, where W sub b is the average electron beam energy. Since Maxwellian beams have extended trails with electrons having energies greater than W sub b, it is difficult to quantify the charging level in terms of the energies of the injected electrons. In order to quantitatively understand the charging in excess of W sub b, simulations were carried out for water-bag types of beam with velocity distribution functions described by f(V) = A for V sub min approx. less than V approx. less than V sub max and f(V) = O otherwise, where A is a constant making the normalized beam density unity. It is found that V sub max does not directly determine the charging level. The pressure distribution in the electron sheath determines the electric field distribution near the surface. The electric field in turn determines the electrostatic potential of the vehicle. The pressure distribution is determined by the beam parameters such as the average beam velocity and the velocity spread of the beam.

Hwang, K. S.↗
NASA NTRS1991

Aft segment dome-to-stiffener factory joint insulation void elimination

Since the detection of voids in the internal insulation of the dome-to-stiffener factory joint of the 15B aft segment, all aft segment dome-to-stiffener factory joints were x-rated and all were found to contain voids. Using a full-scale process simulation article (PSA), the objective was to demonstrate that the proposed changes in the insulation layup and vacuum bagging processes will greatly reduce or eliminate voids without adversely affecting the configuration of performance of the insulation which serves as a primary seal over the factory joint. The PSA-8 aft segment was insulated and cured using standard production processes.

Jensen, S. K.↗
NASA NTRS1991

Lightning protection design and testing of an all composite wet wing for the Egrett

The Egrett aircraft has an all composite wing comprising CFC(carbon fiber composite)/Nomex sandwich skins, full length CFC main spar caps, and GFRP (glass fiber reinforced plastics) main and auxiliary spar webs. It also has short inboard CFC auxiliary spar caps. It has fine aluminum wires woven into the surface for protection. It has an integral fuel tank using the CFC/Nomex skins as the upper and lower tank walls, and lies between the forward auxiliary spar and the forward of the two main spar webs. The fuel tank is not bagged, i.e., it is in effect a wet wing tank. It has conventional capacitive type fuel gauging. The aircraft was cleared to IFR standards and so required full lightning protection and demonstration that it would survive the lightning environment. The lightning protection was designed for the wing (and also for the remainder of the aircraft). An inner wing test samples (which included a part of the fuel tank) were tested as part of the proving program. The protection design and the testing process are described. The intrinsic structural features are indicated that improve lightning protection design and which therefore minimize the weight and cost of any added lightning protection components.

Burrows, B. J. C.↗