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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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Formulation improves compatibility of butyl rubbers with hydrazine while reducing permeation to low levels necessary for prolonged storage in space. This is accomplished by replacing carbon-black filler with inert materials such as hydrated silica or clay. Pressure increases suggest that hydrazine is decomposed only slightly by new type of rubber.
The search for advanced measurement techniques for determining long term compatibility of materials with propellants was conducted in several parts. A comprehensive survey of the existing measurement and testing technology for determining material-propellant interactions was performed. Selections were made from those existing techniques which were determined could meet or be made to meet the requirements. Areas of refinement or changes were recommended for improvement of others. Investigations were also performed to determine the feasibility and advantages of developing and using new techniques to achieve significant improvements over existing ones. The most interesting demonstration was that of the new technique, the volatile metal chelate analysis. Rivaling the neutron activation analysis in terms of sensitivity and specificity, the volatile metal chelate technique was fully demonstrated.
A correlation study was made of the variations of the exospheric temperature extrema with various combinations of the monthly mean and daily values of the 2800 MHz and Ca:2 solar indices. The phase and amplitude of the semi-annual component and the term dependent on Kp were found to remain almost the same for the maximum and minimum temperature. The term dependent on the 27 day component of the solar activity was found to be about four times as large for the diurnal maximum as for the minimum. Measurements at Arecibo have shown that temperature gradient changes at 125 km are consistent with the phase difference between the neutral temperature and density maxima. This is used to develop an empirical model which is compatible with both the satellite measurements and the available incoherent scatter measurements. A main feature of this model is that day length is included as a major model parameter.
Testing has demonstrated the compatibility of the all-silica surface insulation system to a variety of space shuttle orbiter environmental aspects for launch, on-orbit, and special reentry conditions. Among the more important results are the success of the cold soak tests, which indicate the suitability of the foam/bond attachment system with a 2 mm thick foam pad for strain isolation, and the reentry temperature overshoot tests (to 1924 K), which show that this system can tolerate considerable dispersion in reentry heating environment.
The limiting operating temperatures of SiGe thermoelectrics designed for extended operation are set by sublimation process of the elements and by considerations of their compatibility with the surrounding insulating elements. Mass spectrometric Knudsen cell and Langmuir vaporization modes of operation have been utilized in the study of the equilibrium vapor species and in the time evaluation of the sublimation process. Isothermal high-vacuum (1 ntorr) anneals of samples have extended observations to long-time spans. The time variations follow the formation of surface depletion layers due to disproportional rates of sublimation of the various species.
Polyurethanes derived from hydroxy terminated polyperfluoro propylene oxide prepolymers were evaluated as matrix resins for filament wound composites which would be exposed to liquid (and 100% gaseous) oxygen environments. A number of structural modifications were brought about by variations in prepolymer molecular weight, and alternative curing agents which allowed retention of the oxygen compatibility. Although satisfactory performance was achieved at sub-ambient temperatures, the derived composites suffered considerable property loss at ambient or slightly elevated temperatures. To attain overall effectiveness of the composite system, upgrading of the polymer thermomechanical properties must first be achieved.
Electromagnetic interference and field-of-view constraints are identified as the areas of most concern to science on solar electric propulsion space vehicles. Several areas are indicated which more detailed data on the space vehicle environment are needed. In addition, possible means to attain or demonstrate science/space vehicle compatibility are recommended for further iteration between space vehicle design and science payload considerations. The space vehicle design developed by the solar electric propulsion system integration technology effort is used. Two payload sets for comet Encke missions (a slow flyby and a rendezvous), as well as several instruments which are not included in the two payload sets, are analyzed to determine requirements on the space vehicle imposed by the instruments in order to meet their objectives. Environmental requirements for the sets of instruments are developed and compared to both the SEPSIT design criteria and the environment as it is presently understood.
A technique for predicting vehicle misalignment, the relationship of vehicle misalignment to the total vehicle/experiment integration effort, and the methodology used in performing a vehicle/experiment pointing compatibility assessment, are presented. The technique is demonstrated in detail by describing how it was used on the Skylab Program.
The available information on the compatibility of materials with oxygen as applied to the production, transport, and applications experience of high pressure liquid and gaseous oxygen is compiled. High pressure is defined as about 2000 to 3000 psia. Since high pressure projections sometimes can be made from lower pressure data, some low pressure data are also included. Low pressure data are included if they are considered helpful to a better understanding of the behavior at high pressures.
Compatibility measurements were made for aluminum 2219-T87 alloy and titanium 6Al-4V alloy in the presence of liquid fluorine and flox. Results of post test characterization after exposure durations of 61 and 70 weeks are presented. Results of the total test program are analyzed.
A method for the prediction of propellant-material compatibility for periods of time up to ten years is presented. Advanced sensitive measurement techniques used in the prediction method are described. These include: neutron activation analysis, radioactive tracer technique, and atomic absorption spectroscopy with a graphite tube furnace sampler. The results of laboratory tests performed to verify the prediction method are presented.
During the development of a project to estimate wheat production, it became necessary to pull data, corresponding to particular fields in a test site, off an ERTS computer compatible tape. Aerial photographs and topographic maps were on hand for the test site. A method was devised, using an affine transformation, to relate the aerial photographs or topographic maps to the tapes. One can thereby access data on the tape corresponding to regions covered by only a few pixels. The theory can be used for the registration of two tapes for the same area and for the geometric correction of images.
This invention relates to learning decoders for decoding compatible convolutional codes. The decoder decodes signals which have been encoded by a convolutional coder and allows performance near the theoretical limit of performance for coded data systems. The decoder includes a sub-bit shift register wherein the received sub-bits are entered after regeneration and shifted in synchronization with a clock signal recovered from the received sub-bit stream. The received sub-bits are processed by a sub-bit decision circuit, entered into a sub-bit shift register, decoded by a decision circuit, entered into a data shift register, and updated to reduce data errors. The bit decision circuit utilizes stored sub-bits and stored data bits to determine subsequent data-bits. Data errors are reduced by using at least one up-date circuit.
Geostationary maritime satellites, one over the Pacific and one over the Atlantic Ocean, are planned to make available high-speed communications and navigation (position determination) services to ships at sea. A shipboard satellite terminal, operating within the authorized maritime L-band, 1636.5 to 1645.0 MHz, will allow ships to pass voice, teletype, facsimile, and data messages to shore communication facilities with a high degree of reliability. The shore-to-ship link will also operate in the maritime L-band from 1535.0 to 1543.5 MHz. A significant number or maritime/commercial ships are expected to be equipped with an L-band satellite terminal by the year 1980, and so consequently, there is an interest in determining electromagnetic compatibility between the proposed L-band shipboard terminal and existing, on-board, shipboard communications/electronics and electrical systems, as well as determining the influence of shore-based interference sources. The shipboard electromagnetic interference survey described was conducted on-board the United States Line's American Leader class (15,690 tons) commercial container ship, the "American Alliance" from June 16 to 20, 1974. Details of the test plan and measurements are given.
Engine/airframe compatibilities are studied utilizing the advanced supersonic transport point design as the baseline for comparison. Detailed studies of four engines are given. The technical analysis, configuration descriptions, and study results are presented for each of the four specific engines studied.
A series of electromagnetic compatibility (EMC) tests were conducted in May, 1975 in the Soviet Union. The purpose of the EMC tests was to determine the effects of the operating environment of the Soviet aircraft, Soyuz, upon the electrical performance of the USA's cable communications equipment located in Soyuz. The test procedures necessary to check out the cable communications test configuration in preparation for the EMC tests are presented.
An investigation has been conducted in order to assess the impact of magnetic fields generated by the propulsion module upon the scientific instrumentation of the spacecraft as proposed for the mission to comet Encke. It was found that dc magnetic fields could potentially be a threat to the magnetometer experiment, whereas ac fields could affect the plasma wave experiment instrumentation. Studies included a set of measurements, computer simulation, and mathematical analyses. Ways for achieving the compatibility of the propulsion module with science are studied and recommendations advanced.
Results of two experiments involving intercomparisons of rocketsonde measurements of temperature and wind data in the 25 to 80 km altitude region in the CIMO (Commission for Instruments and Methods of Observations) program during September 1973 are reported. Rocketsonde systems used by France, the USSR, the UK, the U.S., and Japan in the two parts of the program (one series of tests at Wallops Island, Va., the other in French Guiana) are described. Wind data were derived from radar tracking of retardation devices and payloads in descent. Day and night temperature differences were examined. The intercomparisons revealed excellent compatibility of the rocketsonde data up to 60 km in wind observations. Some outstanding problems are pointed out.