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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 145 records · Page 8

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NASA NTRS1980

High-speed data link for moderate distances and noisy environments

A full duplex, high speed data link is described which comprises identical modules at each site for communication over coaxial cables. Each module having a digital frequency modulation (DFM) transmitter with an first-in-first-out (FIFO) data buffer for data from a digital system to be transmitted over a cable and a receiver with an FIFO data buffer for data received for a digital system at the other end of the cable. Data words are preceded by a sync word which enables the receiver. Every word transmitted, including the sync word is stored in the FIFO data buffer. This arrangement using FIFO buffers allows for asynchronous transmission of data with receipt of the data beginning with the very first bit of the sync word.

Sievers, M. W.↗

NASA NTRS1980

An experimental, low-cost, silicon-aluminide high-temperature coating for superalloys

An evaluation of a duplex silicon-slurry/aluminide coating is presented. The coating is cyclically tested in Mach 1 combustion gases for oxidation and thermal fatigue resistance at 1093 C and in Mach 0.3 gases for hot-corrosion resistance at 900 C. The base metal superalloys are ViA and B-1900. The coated B-1900 specimens performed much better in oxidation than similar specimens coated with aluminides and almost as well as the more expensive Pt-Al and MCrAlY (where M is Ni and/or Co) coatings deposited by the physical vapor deposition process. The coating also provided good hot corrosion protection. Metallographic, X-ray, and electron microprobe studies are used to characterize the coating, determine failure mechanisms, and study some of the changes due to exposure.

Young, S. G.↗

NASA NTRS1980

A digitally implemented communications experiment utilizing the communications technology satellite, Hermes

Developments which will reduce the costs associated with the distribution of satellite services are considered with emphasis on digital communication link implementation. A digitally implemented communications experiment (DICE) which demonstrates the flexibility and efficiency of digital transmission of television video and audio, telephone voice, and high-bit-rate data is described. The utilization of the DICE system in a full duplex teleconferencing mode is addressed. Demonstration teleconferencing results obtained during the conduct of two sessions of the 7th AIAA Communication Satellite Systems Conference are discussed. Finally, the results of link characterization tests conducted to determine (1) relationships between the Hermes channel 1 EIRP and DICE model performance and (2) channel spacing criteria for acceptable multichannel operation, are presented.

Jackson, H. D.↗

NASA NTRS1980

An experimental, low-cost, silicon-aluminide high-temperature coating for superalloys

A duplex silicon-slurry/aluminide coating has been developed and cyclically tested in Mach 1 combustion gases for oxidation and thermal fatigue resistance at 1093 C and Mach 0.3 gases and hot-corrosion resistance at 900 C. The base-metal superalloys were VIA and B-1900. The coated B-1900 specimens were found to perform much better in oxidation than similar specimens coated with aluminides, and almost as well as the more expensive Pt-Al and MCrAlY (where M is Ni and/or Co) coatings deposited by the physical vapor deposition process. The coatings also provided good hot-corrosion protection.

Young, S. G.↗

NASA NTRS1980

Evaluation of present-day thermal barrier coatings for industrial/utility applications

Atmospheric burner rig tests have been conducted to evaluate the corrosion resistance of present-day thermal barrier coatings. The coatings are primarily plasma-sprayed and zirconia-based. Both duplex and graded coating systems were tested at a gas temperature of 2100 F and metal temperatures that range from 1475 F to 1650 F. The fuels ranged from clean GT No. 2 to that doped with impurity levels which simulate water-washed residual fuels. Results to date suggest that liquid sulfate condensates play an important role in the coating degradation mechanisms, whereas the role of vanadium and its salts is less clear.

Bratton, R. J.↗

NASA NTRS1980

Preliminary interface revision notice SD-152C update of section 8.3 of ICD 2-19001 for detached payloads

The payload interrogator provides full duplex communication between the orbiter and detached payloads. This capability includes transmission of commands to and the reception of telemetry data from such payloads. Both NASA (STDN and DSN) and DOD (SGLS) transmit/receive frequency pairs are available. In addition to two way RF communication, Ku band rendezvous radar is also available. The radar skin-tracks targets in the passive mode or actively tracks transponder equipped payloads. Characteristics referring to those orbiter avionics characteristics of which the payloads must be cognizant and requirements referring to specifications placed upon payload communication equipment are discussed.

Source record↗

NASA NTRS1981

Definition, analysis and development of an optical data distribution network for integrated avionics and control systems

The potential and functional requirements of fiber optic bus designs for next generation aircraft are assessed. State-of-the-art component evaluations and projections were used in the system study. Complex networks were decomposed into dedicated structures, star buses, and serial buses for detailed analysis. Comparisons of dedicated links, star buses, and serial buses with and without full duplex operation and with considerations for terminal to terminal communication requirements were obtained. This baseline was then used to consider potential extensions of busing methods to include wavelength multiplexing and optical switches. Example buses were illustrated for various areas of the aircraft as potential starting points for more detail analysis as the platform becomes definitized.

Burns, R. R.↗

NASA NTRS1980

Thermal barrier coatings for superalloys

The current status of ceramic thermal barrier coatings for protection of turbine airfoil components is reviewed. Test results for an early duplex coating system ZrO2-12% Y2O3/Ni-16% Cr-6% Al-0.6% Y, improved system ZrO2-8% Y2O3/Ni-17% Cr-5% Al-0.35% Y, and air/fuel impurity tolerant systems based on ZrO2-8% Y2O3, 2CaO-SiO2, and a MgO-NiCrAlY cermet are discussed. Preliminary test results at 800 C for a graded ZrO2-8% Y2O3/Ni-20% Cr-11% Al-0.4% Y coating system show that the coating can survive at least 500 hr in the presence of 50 ppm V plus other fuel contaminants and additives.

Miller, R. A.↗

NASA NTRS1982

Legal education at sea via ATS-1. An evaluation of the T/S Golden Bear experiment

A course in maritime law was provided via ATS satellite to law students onboard ship. Classes were received while the ship was on the open seas and in the various ports visited. A half duplex audio channel provided the primary communication mode. All participants judged this pilot study to be extremely useful. Students were able to pursue their course work and to have the benefits of research guidance from academic advisors, while gaining practical, hands on experience at sea.

Connors, M. M.↗

NASA NTRS1982

Advanced ceramic coating development for industrial/utility gas turbines

A program was conducted with the objective of developing advanced thermal barrier coating (TBC) systems. Coating application was by plasma spray. Duplex, triplex and graded coatings were tested. Coating systems incorporated both NiCrAly and CoCrAly bond coats. Four ceramic overlays were tested: ZrO2.82O3; CaO.TiO2; 2CaO.SiO2; and MgO.Al2O3. The best overall results were obtained with a CaO.TiO2 coating applied to a NiCrAly bond coat. This coating was less sensitive than the ZrO2.8Y2O3 coating to process variables and part geometry. Testing with fuels contaminated with compounds containing sulfur, phosphorus and alkali metals showed the zirconia coatings were destabilized. The calcium titanate coatings were not affected by these contaminants. However, when fuels were used containing 50 ppm of vanadium and 150 ppm of magnesium, heavy deposits were formed on the test specimens and combustor components that required frequent cleaning of the test rig. During the program Mars engine first-stage turbine blades were coated and installed for an engine cyclic endurance run with the zirconia, calcium titanate, and calcium silicate coatings. Heavy spalling developed with the calcium silicate system. The zirconia and calcium titanate systems survived the full test duration. It was concluded that these two TBC's showed potential for application in gas turbines.

Vogan, J. W.↗

NASA NTRS1982

Molecular structure of r/GCG/d/TATACGC/ - A DNA-RNA hybrid helix joined to double helical DNA

The molecule r(GCG)d(TATACGC) is self-complementary and forms two DNA-RNA hybrid segments surrounding a central region of double helical DNA; its molecular structure has been solved by X-ray analysis. All three parts of the molecule adopt a conformation which is close to that seen in the 11-fold RNA double helix. The conformation of the ribonucleotides is partly determined by water molecules bridging between the ribose O2' hydroxyl group and cytosine O2. The hybrid-DNA duplex junction contains no structural discontinuities. However, the central DNA TATA sequence has some structural irregularities.

Wang, A. H.-J.↗

NASA NTRS1983

Development of strain tolerant thermal barrier coating systems, tasks 1 - 3

Insulating ceramic thermal barrier coatings can reduce gas turbine airfoil metal temperatures as much as 170 C (about 300 F), providing fuel efficiency improvements greater than one percent and durability improvements of 2 to 3X. The objective was to increase the spalling resistance of zirconia based ceramic turbine coatings. To accomplish this, two baseline and 30 candidate duplex (layered MCrAlY/zirconia based ceramic) coatings were iteratively evaluated microstructurally and in four series of laboratory burner rig tests. This led to the selection of two candidate optimized 0.25 mm (0.010 inch) thick plasma sprayed partially stabilized zirconia ceramics containing six weight percent yttria and applied with two different sets of process parameters over a 0.13 mm (0.005 inch) thick low pressure chamber sprayed MCrAlY bond coat. Both of these coatings demonstrated at least 3X laboratory cyclic spalling life improvement over the baseline systems, as well as cyclic oxidation life equivalent to 15,000 commercial engine flight hours.

Anderson, N. P.↗

NASA NTRS1984

Computer studies of hybrid-slotted working sections with minimum interference at subsonic speeds

A series of computations on tunnel boundary-interference effects for hybrid-slotted working sections was performed using the WALINT code. The slots were modeled as lines of porosity with linear crossflow characteristics. The basic shape evaluated was for a rectangular section with height-to-width ratio = 0.835 and its companion in the duplex mode (half model testing) with height-to-width ratio = 0.6. A best overall basic configuration was determined with seven slots on each wall with open area ratio on each wall of 17.5%. For both full-span and half-model testing, the optimum solution required closing all but two slots on each of the half-walls parallel to the plane of the wing (equivalent to four slots on the full floor and ceiling). The results are presented here for the best configurations and are shown to be within the figure-of-merit range of + or - 0.04 in upwash, and + or - 0.1 in curvature for the Mach number range 0.6 to 0.85. Blockage effects are shown to be small.

Steinle, F. W., Jr.↗

NASA NTRS1984

Carbides in iron-rich Fe-Mn-Cr-Mo-Al-Si-C systems

The optimization of high carbon iron-base superalloy properties with duplex microstructure gamma + M7C3 carbide requires analysis in the context of a seven-component system. Data are first provided here for the Fe-Mn-Cr-Mo-C quinary system, at 30 at. pct carbon. A characterization of competing carbides, according to a pseudoternary phase diagram at 35 wt pct iron, is made from isothermal sections. It is noted that while M7C3 and M3C carbides' occurrences are respectively favored at the Cr and Mn corners, the M2C carbide and molybdenum cementite are predominant with increasing amounts of Mo. Lattice parameters are reported for the various carbides.

Lemkey, F. D.↗

NASA NTRS1984

ARQ schemes for data transmission in mobile radio systems

The problem of providing data communications over a land mobile radio channel is considered, taking into account error detection combined with retransmission on request as a means of obtaining reliability in digital data transmission. The considered systems are referred to as automatic RQ (repeat-request) or ARQ. It is pointed out that the distinguishing features of a land mobile radio (LMR) system, as far as the ARQ protocol is concerned, are a frequency or pair of frequencies shared by a large population of half-duplex users which cannot transmit and receive simultaneously. A description is presented of those variations of ARQ which are adaptable to an LMR system. A new channel model for a fading LMR channel is developed, and several ARQ protocols and some new protocol combinations are described. The relationships are developed for a description of the various protocols in terms of channel failure probabilities. Undetected error probabilities are developed and compared.

Comroe, R. A.↗

NASA NTRS1986

Plasma-Sprayed Coatings on Porous Surfaces

Need for combining benefits of duplex thermal-barrier coatings with film cooling on gas-turbine vanes and blades stimulated development of improved method for plasma spraying these coatings. Method reduces blocking of holes by plasma-sprayed material and at same time reduces base-metal oxidation during coating operation. Features provide potential for increased engine efficiency and power, reduced fuel consumption, use of less costly materials or construction procedures, and extended life and durability.

Leibert, C. H.↗

NASA NTRS1983

Analytical redundancy management mechanization and flight data analysis for the F-8 digital fly-by-wire aircraft flight control sensors

The details are presented of an onboard digital computer algorithm designed to reliably detect and isolate the first failure in a duplex set of flight control sensors aboard the NASA F-8 digital fly-by-wire aircraft. The algorithm's successful flight test program is summarized, and specific examples are presented of algorithm behavior in response to software-induced signal faults, both with and without aircraft parameter modeling errors.

Deckert, J. C.↗

NASA NTRS1984

Advanced information processing system

Design and performance details of the advanced information processing system (AIPS) for fault and damage tolerant data processing on aircraft and spacecraft are presented. AIPS comprises several computers distributed throughout the vehicle and linked by a damage tolerant data bus. Most I/O functions are available to all the computers, which run in a TDMA mode. Each computer performs separate specific tasks in normal operation and assumes other tasks in degraded modes. Redundant software assures that all fault monitoring, logging and reporting are automated, together with control functions. Redundant duplex links and damage-spread limitation provide the fault tolerance. Details of an advanced design of a laboratory-scale proof-of-concept system are described, including functional operations.

Lala, J. H.↗