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At least 379 records · Page 21

Program Analyzes Spacecraft/Ground Radio Links

A versatile computer program analyzes the link-design control table necessary for designing the telecommunication subsystem of a spacecraft in orbit around the Earth or on a deep-space mission. The program helps to calculate all the important parameter values for spacecraft-to-ground telemetry links and ground-to-spacecraft command links. The program also enables the design of turn-around ranging and one-way ranging links, which are very useful for determining the positions of spacecraft and for satisfying various other operational needs. The user can specify several aspects of spacecraft telecommunication-subsystem design, including the nature of the antenna (paraboloidal reflector, patch, dipole, etc.), the power-amplifier rating, and the link data rate. The program enables the use of comparative design procedures and includes an extensive database on the capabilities, attributes, and costs of commercially available telecommunications equipment. Hence, the program can also perform cost analyses. The software includes an extensive ground-station database, so that link design can be carried out using different ground stations in a comparative process in an effort to select the best design. The output of the program is in the form of graphs as well as numbers.

Lansing, Faiza↗

The development of a stepped frequency microwave radiometer and its application to remote sensing of the Earth

The design, development, application, and capabilities of a variable frequency microwave radiometer are described. This radiometer demonstrated the versatility, accuracy, and stability required to provide contributions to the geophysical understanding of ocean and ice processes. A closed-loop feedback method was used, whereby noise pulses were added to the received electromagnetic radiation to achieve a null balance in a Dicke switched radiometer. Stability was achieved through the use of a constant temperature enclosure around the low loss microwave front end. The Dicke reference temperature was maintained to an absolute accuracy of 0.1 K using a closed-loop proportional temperature controller. A microprocessor based digital controller operates the radiometer and records the data on computer compatible tapes. This radiometer exhibits an absolute accuracy of better than 0.5 K when the sensitivity is 0.1 K. The sensitivity varies between 0.0125 K and 1.25 K depending upon the bandwidth and integration time selected by the digital controller. Remote sensing experiments were conducted from an aircraft platform and the first radiometeric mapping of an ocean polar front; exploratory experiments to measure the thickness of lake ice; first discrimination between first year and multiyear ice below 10 GHz; and the first known measurements of frequency sensitive characteristics of sea ice.

Harrington, R. F.↗

Attached shuttle payload carriers: Versatile and affordable access to space

The shuttle has been primarily designed to be a versatile vehicle for placing a variety of scientific and technological equipment in space including very large payloads; however, since many large payloads do not fill the shuttle bay, the space and weight margins remaining after the major payloads are accommodated often can be made available to small payloads. The Goddard Space Flight Center (GSFC) has designed standardized mounting structures and other support systems, collectively called attached shuttle payload (ASP) carriers, to make this additional space available to researchers at a relatively modest cost. Other carrier systems for ASP's are operated by other NASA centers. A major feature of the ASP carriers is their ease of use in the world of the Space Shuttle. ASP carriers attempt to minimized the payload interaction with Space Transportation System (STS) operations whenever possible. Where this is not possible, the STS services used are not extensive. As a result, the interfaces between the carriers and the STS are simplified. With this near autonomy, the requirements for supporting documentation are considerably lessened and payload costs correspondingly reduced. The ASP carrier systems and their capabilities are discussed in detail. The range of available capabilities assures that an experimenter can select the simplest, most cost-effective carrier that is compatible with his or her experimental objectives. Examples of payloads which use ASP basic hardware in nonstandard ways are also described.

Source record↗

ASpect: A new spectrum and line analysis package for IRAF

We examined several publicly available spectral analysis software packages looking for one with enough functionality and versatility to meet the analysis needs of astronomers during the next decade. None of those examined can satisfactorily support the wide variety of panchromatic science programs that are now becoming possible. Furthermore, we concluded that none of these packages can be simply modified to include critical functions because of their original (limited) designs. During the next two years we will write a new spectral analysis package, ASpect, that will incorporate the latest analysis techniques for astronomical spectra in all wavelength domains. The ASpect package has several functional requirements. It must operate on spectra from a wide variety of ground-based and space-based instruments spanning wavelengths from radio to gamma rays. It must accommodate non-linear dispersion relations. It must provide a variety of functions, individually or in combination, with which to fit spectral features and the continuum. It is vitally important that known bad data be masked and that, uncertainties be propagated throughout the calculations in order for astronomers to evaluate the reliability of results. Finally, this new package must provide a powerful, intuitive graphical user interface to handle the burden of data input/output (I/O), on-line 'help,' selection of relevant features for analysis, plotting and graphical interaction, and data base management--all in a comprehensible environment. We anticipate that ASpect will take the form of an external package in IRAF (such as the NOAO and STSDAS packages) and will be layered upon the IRAF virtual Operating System to make it available on as many platforms as possible, while making it resistant to changes in operating systems and compilers. Our choice of IRAF is motivated by its portability, its wide use within the astronomical community, and its rich set of existing user applications.

Hulbert, S. J.↗

Near-term Persistent Platform Orbital Testbed: Three Candidate Architecture Options

On-orbit Servicing, Assembly, and Manufacturing (OSAM) will revolutionize the space industry by transforming the concept of operations of space systems and enabling new, radically different system implementations. These new implementations will benefit from a novel persistent asset design paradigm which focuses on evolvable designs that are tailored to the operational environment, not the launch environment. In addition, the ability to launch sub-systems independently enable future persistent assets to economically expand in capability and size, achieving cost effective and productive operations lasting for decades like terrestrial observatories. With few exceptions (International Space Station, Hubble Space Telescope, Mission Extension Vehicle customers), current space systems are not visited once they are operational. Leveraging emerging low cost commercial launch provides the ability to repeatedly and routinely revisit space systems. Thus, revolutionary new approaches for space system design are possible, creating completely new opportunities for small businesses and accelerating the growth of already established space industries. To usher in the revolutionary new operational paradigm, two things are needed. First, to build confidence in the technology and new paradigm, there must be a leading example, a bellwether persistent asset, that demonstrates the reliability and maturity of the new persistent asset paradigm (where repeated visits are common). Second, in order to rapidly advance and validate OSAM capabilities, an efficient means is required to conduct tests in the space environment. A persistent platform testbed satisfies both these needs. The space environment exhibits a plethora of characteristics that are difficult and costly to accurately simulate for a full system in a terrestrial laboratory, such as near zero gravity, a wide range of ionizing radiation types, atomic oxygen, and micro-meteoroids and space debris traveling at high velocity. In addition, since persistent assets range in mass from a few grams to several metric tons, it is difficult to accurately simulate interactions between these systems and visiting vehicles (that also exhibit a wide range of varying masses and capabilities). These interactions include the transmission of forces and/or exchanging mass (in the form of instruments, fuel, robotic assets, etc.). Thus, a rapid, versatile and cost efficient in-space testing capability that includes a persistent test platform and a surrounding in-space test zone is needed to mature technologies through experimentation. The testbed can provide common services, such as: power, thermal control, vibration isolation, data transmission between experiments and terrestrial experimenters, station-keeping, pointing, and robotic agents that can be leveraged by customer experiments. The onboard robotic agents can be used to provide payload handling services, such as: assembly, change out or upgrade, relocation, connecting/disconnecting utilities, inspection, repair or servicing, etc. Since the persistent platform cost will be amortized over many hosted payloads, its services can eventually be offered at a price much lower than if one were to design a unique and dedicated spacecraft and mission for those few experiments. The key to achieving an effective testbed is providing efficient cost effective access and infrastructure to a variety of commercial, academic and government customers coupled with extensibility, in the capability of an individual persistent platform test bed or replication of the test bed in a different operational regime. Three potential options for implementing a test bed were developed and evaluated in this study.

Persistent Platform↗

Near-term Persistent Platform Orbital Testbed: Three Candidate Architecture Options

On-orbit Servicing, Assembly, and Manufacturing (OSAM) will revolutionize the space industry by transforming the concept of operations of space systems and enabling new, radically different system implementations. These new implementations will benefit from a novel persistent asset design paradigm which focuses on evolvable designs that are tailored to the operational environment, not the launch environment. In addition, the ability to launch sub-systems independently enable future persistent assets to economically expand in capability and size, achieving cost effective and productive operations lasting for decades like terrestrial observatories. With few exceptions (International Space Station, Hubble Space Telescope, Mission Extension Vehicle customers), current space systems are not visited once they are operational. Leveraging emerging low cost commercial launch provides the ability to repeatedly and routinely revisit space systems. Thus, revolutionary new approaches for space system design are possible, creating completely new opportunities for small businesses and accelerating the growth of already established space industries. To usher in the revolutionary new operational paradigm, two things are needed. First, to build confidence in the technology and new paradigm, there must be a leading example, a bellwether persistent asset, that demonstrates the reliability and maturity of the new persistent asset paradigm (where repeated visits are common). Second, in order to rapidly advance and validate OSAM capabilities, an efficient means is required to conduct tests in the space environment. A persistent platform testbed satisfies both these needs. The space environment exhibits a plethora of characteristics that are difficult and costly to accurately simulate for a full system in a terrestrial laboratory, such as near zero gravity, a wide range of ionizing radiation types, atomic oxygen, and micro-meteoroids and space debris traveling at high velocity. In addition, since persistent assets range in mass from a few grams to several metric tons, it is difficult to accurately simulate interactions between these systems and visiting vehicles (that also exhibit a wide range of varying masses and capabilities). These interactions include the transmission of forces and/or exchanging mass (in the form of instruments, fuel, robotic assets, etc.). Thus, a rapid, versatile and cost efficient in-space testing capability that includes a persistent test platform and a surrounding in-space test zone is needed to mature technologies through experimentation. The testbed can provide common services, such as: power, thermal control, vibration isolation, data transmission between experiments and terrestrial experimenters, station-keeping, pointing, and robotic agents that can be leveraged by customer experiments. The onboard robotic agents can be used to provide payload handling services, such as: assembly, change out or upgrade, relocation, connecting/disconnecting utilities, inspection, repair or servicing, etc. Since the persistent platform cost will be amortized over many hosted payloads, its services can eventually be offered at a price much lower than if one were to design a unique and dedicated spacecraft and mission for those few experiments. The key to achieving an effective testbed is providing efficient cost effective access and infrastructure to a variety of commercial, academic and government customers coupled with extensibility, in the capability of an individual persistent platform test bed or replication of the test bed in a different operational regime. Three potential options for implementing a test bed were developed and evaluated in this study.

Persistent Platform↗

Single shot demountable self-contained He-3 refrigerator

The present investigation is concerned with the development of a self-contained demountable He-3 refrigerator which greatly increases the versatility of a cold-plate-style helium Dewar. The refrigerator is controlled by a single heater. The considered design makes it possible to achieve a temperature of 0.27 K without costly or time-consuming modifications to the Dewar. An example for an employment of a temperature of less than 1 K in space is related to the study of the critical behavior of He-3/He-4 mixtures in the absence of gravitational mixing. This requires a temperature of 0.87 K. Such low temperatures can also be utilized in the space operation of infrared telescopes. Attention is given to details of system design, the operating principles, and aspects of performance.

Kittel, P.↗

X-ray emission-line spectra of photoionized plasmas - Density sensitivity of the Fe L-shell series

The circumsource environments of accretion-powered X-ray sources are likely to support relatively dense (greater than 10 exp 11/cu cm) photoionized X-ray emission-line regions. The Fe L-shell ions provide a versatile class of plasma diagnostics in this regime, their multielectron structures resulting in diverse spectral phenomena. Attention is given to the spectral response of Fe L-shell ions to variations in electron density over the range 10 exp 11 to 10 exp 16/cu cm. It is found that density-sensitive line ratios exist in the wavelength interval 12-17 A for the ions Fe XVII-XXI. The prominent role of radiative recombination in the population kinetics distinguishes the density-sensitive Fe lines in photoionized plasmas from those which operate in coronal equilibrium plasmas. The results of detailed atomic modeling of these ions are presented and applications to spectroscopic observations of accretion-driven X-ray sources are discussed.

Liedahl, Duane A.↗

Orbital spacecraft consumables resupply

The capability to replenish spacecraft, satellites, and laboratories on-orbit with consumable fluids provides significant increases in their cost and operational effectiveness. Tanker systems to perform on-orbit fluid resupply must be flexible enough to operate from the Space Transportation System (STS), Space Station, or the Orbital Maneuvering Vehicle (OMV), and to accommodate launch from both the Shuttle and Expendable Launch Vehicles (ELV's). Resupply systems for storable monopropellant hydrazine and bipropellants, and water have been developed. These studies have concluded that designing tankers capable of launch on both the Shuttle and ELV's was feasible and desirable. Design modifications and interfaces for an ELV launch of the tanker systems were identified. Additionally, it was determined that modularization of the tanker subsystems was necessary to provide the most versatile tanker and most efficient approach for use at the Space Station. The need to develop an automatic umbilical mating mechanism, capable of performing both docking and coupler mating functions was identified. Preliminary requirements for such a mechanism were defined. The study resulted in a modular tanker capable of resupplying monopropellants, bipropellants, and water with a single design.

Dominick, Sam M.↗

A finite-element-based perturbation model for the rotordynamic analysis of shrouded pump impellers: Part 1: Model development and applications

This study concerns the rotor dynamic characteristics of fluid-encompassed rotors, with special emphasis on shrouded pump impellers. The core of the study is a versatile and categorically new finite-element-based perturbation model, which is based on a rigorous flow analysis and what we have generically termed the 'virtually' deformable finite-element approach. The model is first applied to the case of a smooth annular seal for verification purposes. The rotor excitation components, in this sample problem, give rise to a purely cylindrical, purely conical, and a simultaneous cylindrical/conical rotor whirl around the housing centerline. In all cases, the computed results are compared to existing experimental and analytical data involving the same seal geometry and operating conditions. Next, two labyrinth-seal configurations, which share the same tooth-to-tooth chamber geometry but differ in the total number of chambers, were investigated. The results, in this case, are compared to experimental measurements for both seal configurations. The focus is finally shifted to the shrouded-impeller problem, where the stability effects of the leakage flow in the shroud-to-housing secondary passage are investigated. To this end, the computational model is applied to a typical shrouded-impeller pump stage, fabricated and rotor dynamically tested by Sulzer Bros., and the results compared to those of a simplified 'bulk-flow' analysis and Sulzer Bros.' test data. In addition to assessing the computed rotor dynamic coefficients, the shrouded-impeller study also covers a controversial topic, namely that of the leakage-passage inlet swirl, which was previously cited as the origin of highly unconventional (resonance-like) trends of the fluid-exerted forces. In order to validate this claim, a 'microscopic' study of the fluid/shroud interaction mechanism is conducted, with the focus being on the structure of the perturbed flow field associated with the impeller whirl. The conclusions of this study were solidified by the outcome of a numerical-certainty exercise, where the grid dependency of the numerical results is objectively examined. The final phase of the shrouded-impeller investigation involves the validation of a built-in assumption, in all other perturbation models, whereby single-harmonic tangential distributions of all the flow thermophysical properties are imposed. The last phase of the investigation course is aimed at verifying the fine details of the perturbed flow field in light of recent set of detailed LDA measurements in a smooth annular seal. Grid dependency of the fluid-induced forces is also investigated, and specific recommendations are made.

Baskharone, Erian A.↗

A next-generation mapping spectrometer

Operational and design characteristics for a remote sensing instrument for aircraft and orbital use are defined. The ideal instrument would be based around two-dimensional detector arrays, silicon for the visible and very-near infrared (0.4 to 1.0 microns) and InSb or PbS for the rest of the near-infrared (out to about 2.6 microns). Spectral information would be dispersed along one axis. Thus one exposure or frame would simultaneously record a full spectrum for each pixel in a row perpendicular to the ground track. The instrument should be smart and versatile, with extensive pre-processing capability programmable from the ground. Spatial and spectral resolution, signal to noise radio, data precision, and calibration and atmospheric corrections are also discussed.

Singer, R. B.↗

A Versatile Planetary Radio Science Microreceiver

We have developed a low-power. programmable radio "microreceiver" that combines the functionality of two science instruments: a Relative Ionospheric Opacity Meter (riometer) and a swept-frequency, VTF/HF radio spectrometer. The radio receiver, calibration noise source, data acquisition and processing, and command and control functions are all contained on a single circuit board. This design is suitable for miniaturizing as a complete flight instrument. Several of the subsystems were implemented in a field-programmable gate array (FPGA), including the receiver detector, the control logic, and the data acquisition and processing blocks. Considerable efforts were made to reduce the power consumption of the instrument, and eliminate or minimize RF noise and spurious emissions generated by the receiver's digital circuitry. A prototype instrument was deployed at McMurdo Station, Antarctica, and operated in parallel with a traditional riometer instrument for approximately three weeks. The attached paper (accepted for publication by Radio Science) describes in detail the microreceiver theory of operation, performance specifications and test results.

Fry, Craig D.↗

Foam For Filtering

Like nature's honeycomb, foam is a structure of many-sided cells, apparently solid but actually only three percent material and 97 percent air. Foam is made by a heat-producing chemical reaction which expands a plastic material in a manner somewhat akin to the heat-induced rising of a loaf of bread. The resulting structure of interconnected cells is flexible yet strong and extremely versatile in applicati6n. Foam can, for example, be a sound absorber in one form, while in another it allows sound to pass through it. It can be a very soft powder puff material and at the same time a highly abrasive scrubber. A sampling of foam uses includes stereo speaker grilles, applying postage meter ink, filtering lawnmower carburetor air; deadening noise in trucks and tractors, applying cosmetics, releasing fabric softener and antistatic agents in home clothes dryers, painting, filtering factory heating and ventilating systems, shining shoes, polishing cars, sponge-mopping floors, acting as pre-operative surgical scrubbers-the list is virtually limitless. The process by which foam is made produces "windows," thin plastic membranes connecting the cell walls. Windowed foam is used in many applications but for certain others-filtering, for example-it is desirable to have a completely open network. Scott Paper Company's Foam Division, Chester, Pennsylvania, improved a patented method of "removing the windows," to create an open structure that affords special utility in filtering applications. NASA technology contributed to Scott's improvement.

Source record↗

The Advanced Geared Turbofan 30,000 lbf – electrified (AGTF30-e): A Virtual Testbed for Electrified Aircraft Propulsion Research

Electrified Aircraft Propulsion (EAP) is a growing topic of research with the potential to shape the future of commercial air travel. Here, detailed mathematical models serve an essential role in developing understanding and evaluating different technologies and design concepts. The Advanced Geared Turbofan 30,000 lbf – electrified (AGTF30-e) is an open-source software package developed by the National Aeronautics and Space Administration (NASA). The AGTF30-e provides a realistic propulsion system model of a conceptual electrified advanced geared turbofan engine suitable for propelling a single-aisle commercial aircraft. Included with the engine model is a controller that provides representative dynamic performance across a full operating envelop. The model is meant to facilitate research studies and promote collaboration. It is envisioned for use in concept exploration studies, technology impact studies, and dynamics and controls studies. The engine model can be run in various modes of operation including boost and power extraction. It also has options for other electrification features and methods for engine shaft and electric machine integration. This paper documents the AGTF30-e and illustrates its use through various simulation scenarios.

AGTF30-e↗

II. Aerodynamic research relative to variable-sweep multimission aircraft

The development of a multimission military aircraft would be highly desirable both from the standpoint of easing the strain on the national budget by reducing the number of aircraft types and of providing versatility which would increase the effectiveness of the aircraft in the performance of a given mission. Some of the capabilities which might be required of such an aircraft are shown in figure 1 along with their respective aerodynamic and configuration requirements. The first three capabilities are grouped together since they all require good subsonic characteristics. The first, a long loiter capability for combat air patrol and the second, a long ferry range for efficient aircraft deployment both require a high subsonic lift-drag ratio. The third capability, STOL, is desirable for carrier and short-field operation and requires the development of high lift. All three of these capabilities can best be obtained with a high-aspect-ratio wing having a large span and a low-sweep angle. The fourth capability is that of a high-altitude supersonic attack or intercept and requires a high lift-drag ratio at supersonic speeds which dictates a rather slender configuration with a moderate-span wing which is either very thin or highly swept. The fifth capability listed in figure 1 is that of a low-altitude high-speed attack that would increase the probability of long-range penetration of antiaircraft defenses. The high dynamic pressures encountered on the deck at high speeds require a low-lift-curve slope to reduce the gust-induced normal accelerations, and low friction and wave drag (drag due to lift is insignificant at high dynamic pressures) to assure sufficient speed and range. In order to best satisfy these requirements, a slender aircraft having little or no wing is required. It is apparent from figure 1 that these five capabilities are highly incompatible and that an efficient multimission aircraft will require a means of varying its aerodynamic characteristics. This can be best accomplished with some type of variable-wing geometry. There are, of course, several types of variable wing geometry. However, in view of the extremely large variations in wing span desired, variable wing sweep, as indicated In the lower right sketch of figure 1, appears to provide the best method. The Langley Research Center of the National Aeronautics and Space Administration has therefore initiated a research program to provide the aerodynamic information needed for the development of a variable-sweep multimission military aircraft, and it is the purpose of this paper to briefly describe some of the results of this program.

Military aircraft↗

The Advanced Geared Turbofan 30,000 lb f – electrified (AGTF30-e): A Virtual Testbed for Electrified Aircraft Propulsion Research

Electrified Aircraft Propulsion (EAP) is a growing topic of research with the potential to shape the future of commercial air travel. Here, detailed mathematical models serve an essential role in developing understanding and evaluating different technologies and design concepts. The Advanced Geared Turbofan 30,000 lb f – electrified (AGTF30-e) is an open-source software package developed by the National Aeronautics and Space Administration (NASA). The AGTF30-e provides a realistic propulsion system model of a conceptual electrified advanced geared turbofan engine suitable for propelling a single-aisle commercial aircraft. Included with the engine model is a controller that provides representative dynamic performance across a full operating envelop. The model is meant to facilitate research studies and promote collaboration. It is envisioned for use in concept exploration studies, technology impact studies, and dynamics and controls studies. The engine model can be run in various modes of operation including boost and power extraction. It also has options for other electrification features and methods for engine shaft and electric machine integration. This paper documents the AGTF30-e and illustrates its use through various simulation scenarios.

AGTF30-e↗

Requirements and Development of an Acceleration Measurement System for International Space Station Microgravity Science Payloads

The International Space Station is being developed by NASA and international partners as a versatile user platform to allow long term on-orbit investigations of a variety of scientific and technology arenas. In particular, scientific studies are planned within a research class known as microgravity science in areas such as biotechnology, combustion, fluid physics, and materials sciences. An acceleration measurement system is in development to aid such research conducted in the on-orbit conditions of apparent weightlessness. This system provides a general purpose acceleration measurement capability in support of these payloads and investigators. Such capability allows for systematic study of scientific phenomena by obtaining information regarding the local accelerations present during experiment operations. Preparations for implementing this flight measurement system involves two distinct stages: requirements development prior to initiating the design activity, and the design activity itself. This paper defines the requirements definition approach taken, provides an overview of the results of the requirements phase, and outlines the initial design considerations being addressed for this measurement system. Some preliminary engineering approaches are also described.

Sutliff, Thomas J.↗

A versatile ground data display system for Spacelab experiments

A microprocessor-based data capture and display system suited to the needs of many Spacelab experimenters is described. Although developed specifically for the needs of the FAUST UV astronomy telescope, several features of the system may make it attractive to other groups who need to interact with their Spacelab data in real or near-real time. The display system captures data from the serial data stream originating in the Spacelab experiment computer input/output (ECIO) data channel, and can reformat and display several hundred variables per second in real time. The system offers a combination of CRT display and analog paper strip-chart output. A facility is also provided for simultaneously creating floppy-disk records of short segments of data according to prearranged criteria, to allow detailed examination of critical events in the operation of the experiment. The simplicity, economy, reliability, and flexibility of the display system suggest its use for monitoring a variety of low- and medium-data-rate Spacelab experiments.

Werthimer, D.↗