558 research outputs found
Design of multilayer insulation systems
Analytical models for insulation system heat transfer studies the types of materials best suited for a near solar environment. This multilayer insulation system for spacecraft can operate at temperatures in the 300 to 700 degree K range
Development of techniques and associated instrumentation for high temperature emissivity measurements Quarterly progress report, 30 Sep. - 31 Dec. 1970
Emittance measurement techniques for space shuttle materials in high temperature environmental simulatio
Development of techniques and associated instrumentation for high temperature emissivity measurements
The calibrating and testing procedures for the radiometric emittance measurement apparatus are described. Test results are given for the NBS platinum-rhodium standard (SRM No. 1409), the NBS oxidized Kanthal standard, and the oxidized Rene 41 materials. Results indicate that with the platinum-rhodium standard the measurement system compared with the NBS data to within 0.02 for both total and spectral normal emitttance. Data from the Kanthal strip was consistently higher than NBS values. For oxidized Rene 41, no significant changes in as prepared emittance was observed. The emittance was stable for temperatures up to 1150 K
Thermal performance of multilayer insulations Interim report
Heat flux and optical property measurement for multilayer insulatio
Invasive bacterial infections in Gambians with sickle cell anaemia in an era of widespread Pneumococcal and Haemophilus influenzae type B vaccination
Background: There is relatively little data on the aetiology of bacterial infections in patients with sickle cell anaemia (SCA) in West Africa, and no data from countries that have implemented conjugate vaccines against both Streptococcus pneumoniae and Haemophilus influenzae type b (Hib). Methods: We conducted a retrospective analysis of SCA patients admitted to the Medical Research Council Unit, The Gambia during a five-year period when there was high coverage of Hib and Pneumococcal conjugate vaccination. We evaluated 161 admissions of 126 patients between April 2010 and April 2015. Results: Pathogenic bacteria were identified in blood cultures from 11 of the 131 admissions that had cultures taken (8.4%, 95% CI 4.5-14.1%). The most frequent isolate was Salmonella Typhimurium (6/11; 54.5%), followed by Staphylococcus aureus (2/11; 18.2%) and other enteric Gram-negative pathogens (2/11; 18.2%) and there was one case of H. influenzae non-type b bacteraemia (1/11; 9.1%). There were no episodes of bacteraemia caused by S. pneumoniae or Hib. Conclusions: The low prevalence of S. pneumoniae and Hib, and the predominance of non-typhoidal Salmonella as a cause of bacteraemia suggest the need to reconsider optimal antimicrobial prophylaxis and the empirical treatment regimens for patients with SCA
Conceptual design and analysis of orbital cryogenic liquid storage and supply systems
A wide variety of orbital cryogenic liquid storage and supply systems are defined in NASA and DOD long-range plans. These systems include small cooling applications, large chemical and electrical orbit transfer vehicles and supply tankers. All have the common requirements of low-g fluid management to accomplish gas-free liquid expulsion and efficient thermal control to manage heat leak and tank pressure. A preliminary design study was performed to evaluate tanks ranging from 0.6 to 37.4 cu m (22 to 1320 cu ft). Liquids of interest were hydrogen, oxygen, methane, argon and helium. Conceptual designs were generated for each tank system and fluid dynamic, thermal and structural analyses were performed for Shuttle compatible operations. Design trades considered the paradox of conservative support structure and minimum thermal input. Orbital performance and weight data were developed, and a technology evaluation was completed
Radiative properties of advanced spacecraft heat shield materials
Experimental results are presented to show the effects of simulated reentry exposure by convective heating and by radiant heating on spectral and total emittance of statically oxidized Inconel 617 and Haynes HS188 superalloys to 1260 K and a silicide coatea (R512E) columbium 752 alloy to 1590 K. Convective heating exposures were conducted in a supersonic arc plasma wind tunnel using a wedge-shaped specimen configuration. Radiant tests were conducted at a pressure of .003 atmospheres of dry air at a flow velocity of several meters per second. Convective heating specimens were subjected to 8, 20, and 38 15-min heating cycles, and radiant heating specimens were tested for 10, 20, 50, and 100 30-min heating cycles. Changes in radiative properties are explained in terms of changes in composition resulting from simulated reentry tests. The methods used to evaluate morphological, compositional and crystallographic changes include: Auger electron spectroscopy; scanning electron microscopy; X-ray diffraction analysis; and electron microprobe analysis
Phylogenetic considerations for predicting the host range of Ustilago sporoboli-indici, a potential biological control agent for Sporobolus species in Australia
The ribosomal DNA internal transcribed spacer region was amplified and sequenced from a selection of specimens of the Sporobolus smut Ustilago sporoboli-indici. Phylogenetic comparison with other Ustilago and Sporisorium species revealed strong support for an evolutionary radiation of Ustilago species infecting the Chloridoideae and Pooideae, of which U. sporoboli-indici forms a major lineage. Comparisons are made with other groups of plant pathogenic fungi, and it is concluded that phylogenetic analyses of potential biocontrol agents are useful for identifying pathogens that are derived from evolutionary lineages that parasitize a wide range of unrelated plants. Such pathogens are less desirable as biocontrol agents as they may have a greater likelihood of infecting plants outside their normal host ranges
Study of methane fuel for subsonic transport aircraft
The cost and performance were defined for commercial transport using liquid methane including its fuel system and the ground facility complex required for the processing and storage of methane. A cost and performance comparison was made with Jet A and hydrogen powered aircraft of the same payload and range capability. Extensive design work was done on cryogenic fuel tanks, insulation systems as well as the fuel system itself. Three candidate fuel tank locations were evaluated, i.e., fuselage tanks, wing tanks or external pylon tanks
Evacuated load-bearing high performance insulation study
A light weight, vacuum jacketed, load bearing cryogenic insulation system was developed and tested on a 1.17-m (46-in.) spherical test tank. The vacuum jacket consists of 0.08 mm (0.003 in.) thick 321 stainless steel formed into a wedge design that allows elastic jacket movements as the tank shrinks (cools) or expands (warms up or is pressurized). Hollow glass spheres, approximately 80 micrometers in diameter with a bulk density of 0.069 g/cc (4.3 lb cubic foot), provide the insulating qualities and one atmosphere load bearing capability required. The design, fabrication, and test effort developed the manufacturing methods and engineering data needed to scale the system to other tank sizes, shapes, and applications. The program demonstrated that thin wall jackets can be formed and welded to maintain the required vacuum level of .013 Pa yet flex elastically for multiple reuses. No significant shifting or breakage of the microspheres occurred after 13 simulated Space Tug flight cycles on the test tank and a hundred 1 atmosphere load cycles in a flat plate calorimeter. The test data were then scaled to the Space Tug LO2 and LH2 tanks, and weight, thermal performance, payload performance, and costs were compared with a helium purged multilayer insulation system
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