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The functional dependence of acceleration-induced burning-rate augmentation on the magnitude and orientation of the acceleration vector was determined for an aluminized composite propellant by using a slab motor mounted at various angles on a centrifuge. The rate augmentation was strongly dependent on the orientation of the acceleration vector with respect to the burning propellant surface.
A previous investigation indicated that combustion efficiency of low burning-rate propellants could be improved if the aluminum fuel was replaced by aluminum particles coated with a magnesium-aluminum eutectic alloy (ALCAL). The purpose of the present investigation was to evaluate the possibility of improving the combustion efficiency of these propellants by admixing the eutectic with the aluminum rather than coating the aluminum. Tests of three propellants similar in every respect except for the metal fuel were conducted in test motors with 4.54 kg (10 lbm) of propellant. The first propellant used aluminum fuel; the second contained aluminum admixed with magnesium-aluminum eutectic; the third used ALCAL. The test results show the the admixed fuel gave better low burning-rate combustion efficiency than the other two. The test results also showed that the ALCAL was deficient in that much, if not all, of the coating material could be found as the fine particles in a bimodal mix of aluminum and eutectic. The combustion efficiency of low burning-rate aluminized propellants can be significantly improved by mixing a small amount of magnesium-aluminum alloy with the aluminum fuel.
A microwave Doppler shift technique was developed for measuring the dynamic bulk modulus of dielectric materials such as solid propellants. The system has a demonstrated time resolution on the order of milliseconds and a theoretical spatial resolution of a few microns. Accuracy of the technique is dependent on an accurate knowledge of the wavelength of the microwave in the sample being tested. Such measurement techniques are discussed. Preliminary tests with two solid propellants, one non-aluminized and one containing 16% aluminum, yielded reasonable, reproducible results. It was concluded that with refinements the technique holds promise as a practical means for obtaining accurate dynamic bulk modulus data over a variety of transient conditions.
Experiments were performed to critically demonstrate the effects of diffusion on the aluminum depletion and degradation of NiAl coatings on superalloys. Pack aluminized IN 100 and Mar-M200 were diffusion annealed in 0.0005 torr vacuum at 1100 C for 300 hours. Aluminum losses due to oxidation and vaporization were minimal. Metallographic and electron microprobe analyses showed considerable interdiffusion of the coating with the substrate, which caused a large decrease in the original aluminum level of the coating. Subsequent cyclic furnace oxidation tests were performed at 1100 C using 1 hour cycles on pre-diffused and as-coated specimens. The pre-diffusion treatment decreased the oxidation protection for both alloys, but more dramatically for IN 100. Identical oxidation tests of bulk NiAl, where such diffusion effects are precluded, showed no signs of degradation at twice the time needed to degrade the coated superalloys.
Fines from a Luna 20 soil sample and from three Apollo 16 deep drill core samples have been analyzed for major-minor element abundances by a combined, semi-micro atomic absorption spectrophotometric and colorimetric method. Both the major element and large ion lithophile trace element abundances in these soils, the first from interior highland sites, are greatly influenced by the very high normative plagioclase content, being distinctly richer in Al and Ca, and poorer in K, P, Cr, Mn, Fe, and Ti, than most bulk soil samples from previous lunar missions. The relatively large compositional variations in the Apollo 16 core can be ascribed almost entirely to decreasing plagioclase with increasing depth. The chemical composition of the Luna 20 soil indicates less plagioclase and less KREEP than in the Apollo 16 soils. A lunar differentiation model is presented in which is made the suggestion that KREEP is the result of a second fusion event in a lunar crust consisting of early feldspathic cumulates and primary aluminous 'liquid.'
Glass compositions in the Luna 20 soil indicate a minor contribution of mare rocks and a major contribution of highly feldspathic highland material. Glasses with the composition of highland basalt (anorthositic gabbro or norite) predominate in a range of highly aluminous glasses. The analyses of minerals in the soil show that the highland rocks have a unique assemblage of minerals that can readily be distinguished from the mineral assemblages of either mare or KREEP basalts. The soils are characterized by abundant anorthitic, low-Fe plagioclase. Highly magnesian orthopyroxenes, pigeonites, and augites are the most prominent pyroxenes. Unlike mare basalt pyroxenes, clinopyroxenes with intermediate Ca values are not abundant, but extreme iron enrichment toward pyroxferroite does occur. Olivines are more abundant than at other sites and are Mg-rich, low in Ca and Cr. Spinels with compositions approaching MgAl2O4 predominate over pleonastes and chromites. Ilmenite and metal are present but not abundant. The mineral compositions are consistent with derivation from a suite of highly feldspathic rocks in which highland basalt compositions predominate.
The objective of this work was to better define the effects of propellant composition variables on the acceleration induced burning-rate augmentation of solid propellants. The rate augmentation of an aluminized propellant at a given acceleration level was found to be a nonlinear inverse function of the reference or static burning rate and not controlled by binder or catalyst type at a given reference rate. A nonaluminized and a low rate double-base propellant exhibited strong transient rate augmentation due to surface pitting resulting from the retention of hot particles on the propellant surface.
Aluminized Mylar film is bonded to polyurethane foam mold; Mylar is then removed, leaving highly reflective coating of aluminum on foam. Mold may be used repeatedly to make mirrors for several optical instruments. Large mirrors of almost any shape may be made singularly or in quantity.
The Jimsphere/Jimsonde system is described and some possible applications of the system for air-sea interface measurements are presented. As space vehicles became larger and more sophisticated, an improved method for obtaining wind profile data had to be found. To satisfy this need the FPS-16 radar/Jimsphere system was developed. The Jimsphere is an aluminized mylar spherical balloon, two meters in diameter. The balloon is under superpressure, and is tracked with a high precision radar system. The development of this detailed wind profile system was started in 1963, and the present design was established in 1964. To improve the system, a program was initiated in 1965 to obtain high resolution temperature data simultaneously with the wind profile data.
A material consisting of ripstop nylon bonded to the Mylar side of aluminized Mylar film was used to construct the first Skylab parasol. The mechanical properties of elongation and tensile strength and the radiative properties of solar absorptance and thermal emittance were measured before and after exposure to simulated solar radiation at intensities of 1.0 and 3.5 solar constants for exposure times as long as 947 hours or 3316 equivalent solar hours. The accelerated testing indicated more severe degradation than was experienced in the real-time test (1 solar constant). The results predicted that this material could have given satisfactory performance throughout the planned lifetime of the Skylab workshop.
An experimental investigation was conducted to determine the thermal effectiveness of an aluminized Mylar-silk net insulation system containing up to 160 layers. The experimentally measured heat flux was compared with results predicted by using (1) a previously developed semi-empirical equation and (2) an effective-thermal-conductivity value. All tests were conducted at a nominal hot-boundary temperature of 294 K (530 R) with liquid hydrogen as the heat sink. The experimental results show that the insulation performed as expected and that both the semi-empirical equation and effective thermal conductivity of a small number of layers were adequate in predicting the thermal performance of a large number of layers of insulation.
Experimental and analytical studies were conducted in order to extend previous knowledge of the thermal performance and gas evacuation characteristics of three selected multilayer insulation (MLI) composites. Flat plate calorimeter heat flux measurements were obtained for 20- and 80- shield specimens using three representative layer densities over boundary temperatures ranging from 39 K (70 R) to 389 K (700 R). Laboratory gas evacuation tests were performed on representative specimens of each MLI composite after initially purging them with helium, nitrogen, or argon gases. In these tests, the specimens were maintained at temperatures between 128 K (230 R) and 300 K (540 R). Based on the results of the laboratory-scale tests, a composite MLI system consisting of 112 unperforated, double-aluminized Mylar reflective shields and 113 water preconditioned silk net spacer pairs was fabricated and installed on a 1.22-m-(4-ft-) diameter calorimeter tank.
A novel apparatus for controlling the temperature of balloon-borne equipment is disclosed, the apparatus serving to utilize the radiant energy emitted by the earth and its atmosphere so as to control the temperature of equipment. The apparatus comprises a housing to be carried aloft by a balloon and defining an enclosure for an instrumentation package. The enclosure includes an upper shield portion as well as a bottom window portion at the base, the bottom window facing the earth below during flight. The upper shield portion is constructed of a material such as aluminized Mylar, which serves to reflect direct sunlight.
A radiometer is described operating in a vacuum under steady state conditions. The front element is an aluminum sheet painted on the outer side with black or other absorptive material of selected characteristics. A thermocouple is bonded to the inner side of the aluminum sheet. That is backed by highly insulative layers of glass fiber and crinkled, aluminized Mylar polyester. Those layers are backed with a sturdy, polyester sheet, and the entire lamination is laced together by nylon cords. The device is highly reliable in that it does not drift out of calibration, and is significantly inexpensive.
The thermal performance of shadow shields, and their support struts, for the thermal protection of cryogenic propellants in a simulated deep-space environment was investigated analytically and experimentally. Very low overall heat-transfer rates were obtained when highly reflective aluminized Mylar shadow shields were used. The thermal interactions between the shields and support struts were investigated with fair to good agreement between the analysis and experimental data. The exterior surface of both fiberglass and titanium struts was coated to reduce the heat input into the test tank. The vacuum level inside the test facility strongly influenced the heat-transfer rates.
Four cast nickel-base superalloys were oxidized at 1000 and 1100 C for times up to 100 hr in static air and a Mach 1 gas stream. The oxidation resistance was judged by weight change, metal thickness loss, depletion-zone formation, and oxide formation and morphology. The alloys which formed mostly nickel aluminate (NiAl2O4) and aluminum oxide (Al2O3) (B-1900, VIA, and to a lesser extent 713C) were more oxidation resistant. Poorer oxidation resistance was associated with the appearance of chromium sesquioxide (Cr2O3) and chromite spinel (738X). Refractory metal content had little effect on oxidation resistance. Refractory metals appeared in the scale as tapiolite (NiM2O6, where M represents the refractory metal). Thermal cycling in static air appeared to supply sufficient data for the evaluation of oxidation resistance, especially for alloys which form oxides of low volatility. For alloys of higher chromium levels with high propensities toward forming a chromium-bearing scale of higher volatility, testing under conditions of high gas velocity is necessary to assess fully the behavior of the alloy.
Solar simulator mirrors were refurbished. Two different refurbishment methods were employed. In the first, the electroformed mirror replica was removed from the casting and replaced with a new mirror replica. In the second, only the aluminized surface, with its protective overcoat, was removed from the mirror and replaced after cleaning of the nickel surface.
Experimental demonstration of the effects of diffusion on aluminum depletion and degradation in NiAl coatings on superalloys. Pack aluminized IN 100 and Mar-M200 were vacuum annealed at 1100 C to allow diffusion to proceed independently of oxidation. As-coated and as-diffused coatings were compared before and after cyclic furnace oxidation at 1100 C. The extent of degradation was judged by specific weight change, metallography, and electron microprobe analyses.