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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

Analytical Techniques for Assessing Gateway and Other Spacecraft Antenna Line-of-Sight

NASA’s Artemis program is committed to landing the next man and the first woman on the Moon by 2024. A critical piece of infrastructure for the mission, the Gateway will inaugurate a sustainable crewed presence beyond low-Earth orbit in cis-lunar space and serve as a staging point for a lunar landing system. The Near Rectilinear Halo Orbit of the Gateway offers numerous operational benefits in terms of its Earth access via the Orion Multipurpose Crew Vehicle, the degree of lunar visibility and surface access it provides, and favorable conditions for station-keeping. To minimize burns during station-keeping and conserve propellant, the Gateway will continually align itself to a solar pressure equilibrium attitude with the Sun; this is convenient for solar array orientation and power generation, but causes difficulties in terms of communication line-of-sight with the Earth, Moon, and visiting vehicles, which appear to be continually rotating about the Gateway’s local frame. A fixed antenna on the Gateway is continually subject to a moving target and can find itself obstructed by the Gateway’s own geometry frequently if not placed carefully. To understand the performance of either Earth-pointing or Moon-pointing antenna placements for a given Gateway geometry, a transient solar system simulation of the Gateway is used to step through orbital ephemeris data and determine the periods in which line-of-sight to a chosen target is achieved and lost. Antenna placements can be tested in the simulation and optimized to increase the average line-of-sight exposure to the target, while also minimizing the maximum duration cut-out in line-of-sight communication experienced; long durations without a successful communication link could pose threats to operations, safety, and mission success. It may be necessary to deviate from the Gateway’s solar pressure equilibrium attitude for short periods of time in order to continue a successful line-of-sight link to a chosen target. Communication coverage spheres can offer insight into what these necessary attitude adjustments may be and are generated by using a 3D mesh of the Gateway and an implementation of the Möller-Trumbore intersection algorithm. This paper outlines the analytical techniques used to perform such antenna placements on the Gateway, offering examples of how line-of-sight strength can be enhanced with an understanding of the Gateway geometry and attitude constraints. These techniques have had direct impact on the writing of communication requirements for NASA and international partner-owned Gateway elements.

Kennedy, William J.↗
NASA NTRSDate not supplied

2020 International Astronautical Congress Conference Presentation - ANALYTICAL TECHNIQUES FOR ASSESSING GATEWAY AND OTHER SPACECRAFT ANTENNA LINE-OF-SIGHT FOR THE ARTEMIS PROGRAM

NASA’s Artemis program is committed to landing the next man and the first woman on the Moon by 2024. The Gateway, a critical piece of infrastructure for the long-term Artemis mission profiles, will inaugurate a sustainable crewed presence beyond low-Earth orbit in cis-lunar space and serve as a staging point for a lunar landing system. The Near Rectilinear Halo Orbit of the Gateway offers numerous operational benefits in terms of its Earth access via the Orion Multipurpose Crew Vehicle, its degree of Earth and lunar visibility, the versatile surface access it provides, and favorable conditions for station-keeping. To minimize burns during station-keeping and conserve propellant, the Gateway will continually align itself to a solar pressure equilibrium attitude with the Sun; this is convenient for solar array orientation and power generation, but causes difficulties in terms of communication line-of-sight with the Earth, Moon, and visiting vehicles, which appear to be continually rotating about the Gateway’s local frame. A fixed antenna on the Gateway is continually subject to a moving target and can find itself obstructed by the Gateway’s own geometry frequently if not placed carefully. To understand the performance of either Earth-pointing or Moon-pointing antenna placements for a given Gateway geometry, a transient solar system simulation of the Gateway is used to step through orbital ephemeris data and determine the periods in which line-of-sight to a chosen target is achieved and lost. Antenna placements can be tested in the simulation and optimized to increase the average line-of-sight exposure to the target, while also minimizing the maximum duration drop-out in line-of-sight communication experienced; long durations without a successful communication link could pose threats to operations, safety, and mission success. It may be necessary to deviate from the Gateway’s solar pressure equilibrium attitude for short periods of time in order to continue a successful line-of-sight link to a chosen target. Communication coverage spheres can offer insight into what these necessary attitude adjustments may be and are generated by using a 3D mesh of the Gateway and an implementation of the Möller-Trumbore intersection algorithm. This paper outlines the analytical techniques used to perform such antenna placements on the Gateway, offering examples of how line-of-sight strength can be enhanced with an understanding of the Gateway geometry and attitude constraints. These techniques have had direct impact on the writing of communication requirements for NASA and international partner-owned Gateway elements.

Gateway↗
NASA NTRS1992

Equal path, phase shifting, sample point interferometer for monitoring the configuration of surfaces

A system for monitoring the configuration of a surface (e.g., a segmented parabolic surface) using orthogonally placed retroreflectors at sets of points 1, 2, and 3 dispersed throughout the surface with a stationary halfwave plate (HWP) in the front of the one retroreflector at a corner point 3 and a rotating halfwave plate (RHWP) over a source of linearly polarized coherent light, thereby causing the direction of linear polarization to continuously rotate through 360 deg and causing light returned by the retroreflector at point 3 to be continuously phase shifted through 360 deg relative to light returned by retroreflectors at points 1 and 2. The returned light from each set of points 1, 2, and 3 is focused onto a bed-of-nails (BON) phase grating diagonally oriented with respect to the orthogonal orientation of the incident beams from retroreflectors 1, 2, and 3, thereby causing overlap in the light from points 1 and 3 to produce interferometric signals 1,3 and 2,3. Any change in phase of the interferometric signals 1,3 and 2,3 indicates both the magnitude and direction of any change in the position of the retroreflector at point 3 relative to retroreflectors at points 1 and 2.

Manhart, Paul K.↗
NASA NTRS1980

System for slicing silicon wafers

An improved system is described which has at least one endless band saw blade that is characterized by a continuously regenerated cutting edge and is unidirectionally driven along a pair of courses extended in mutual parallelism through a cutting station located near the midportion of the courses. The blade is supported at the cutting station by pairs of guides continuously rotated through less than 360 deg of angular displacement during each cutting operation in order to continuously regenerate the blade supporting surfaces of the guide. Blade wobble is thus substantially eliminated.

Collins, E. R.↗
NASA NTRS1981

Rotative balance of the I.M.F. Lille and associated experimental techniques

The study of aerodynamic effects at high incidence associated with motions of wide amplitude incorporating continuous rotations requires the consideration of coupled effects, which are generally nonlinear, in a formulation of equations of motion. A rotative balance designed to simulate such maneuvers in a windtunnel was created to form a test medium for analytical studies. A general description of the assembly is provided by considering two main ranges of application. The capacities and performance of the assembly are discussed.

Verbrugge, R.↗
NASA NTRS1985

A rotating electrical transfer device

The design, development, and performance characteristics of two roll ring configurations - a roll ring being a device used in transferring electrical energy across a continuously rotating or oscillating interface through one or more flexible rolling contacts, or flexures are described. Emphasis is placed on the design problems and solutions encountered during development in the areas of flexure fatigue, contact electroplating, electrical noise, and control of interface geometry. Also, the present status of each configuration is summarized.

Porter, R. S.↗
NASA NTRS1990

The susceptibility of rhesus monkeys to motion sickness

The susceptibility of rhesus monkeys to motion sickness was investigated using test conditions that are provocative for eliciting motion sickness in squirrel monkeys. Ten male rhesus monkeys and ten male Bolivian squirrel monkeys were rotated in the vertical axis at 150 deg/s for a maximum duration of 45 min. Each animal was tested in two conditions, continuous rotation and intermittent rotation. None of the rhesus monkeys vomited during the motion tests but all of the squirrel monkeys did. Differences were observed between the species in the amount of activity that occurred during motion test, with the squirrel monkeys being significantly more active than the rhesus monkeys. These results, while substantiating anecdotal reports of the resistance of rhesus monkeys to motion sickness, should be interpreted with caution because of the documented differences that exist between various species with regard to stimuli that are provocative for eliciting motion sickness.

Corcoran, Meryl L.↗
NASA NTRS1990

Experimental studies of gastric dysfunction in motion sickness: The effect of gastric and vestibular stimulation on the vagal and splanchnic gastric efferents

The susceptibility of rhesus monkeys to motion sickens was investigated using test conditions that are provocative for eliciting motion sickness in squirrel monkeys. Ten male rhesus monkeys and ten male Bolivian squirrel monkeys were rotated in the vertical axis at 150°/s for a maximum duration of 45 min. Each animal was tested in two conditions, continuous rotation and intermittent rotation. None of the rhesus monkeys vomited during the motion tests but all of the squirrel monkeys did. Differences were observed between the species in the amount of activity that occurred during motion tests, with the squirrel monkeys being significantly more active than the rhesus monkeys. These results, while substantiating anecdotal reports of the resistance of rhesus monkeys to motion sickness, should be interpreted with caution because of the documented differences that exist between various species with regard to stimuli that are provocative for eliciting motion sickness.

Meryl L Corcoran↗
NASA NTRS1975

Rotary plant growth accelerating apparatus

Rotary plant growth accelerating apparatus for increasing plant yields by effectively removing the growing plants from the constraints of gravity and increasing the plant yield per unit of space is described. The apparatus is comprised of cylindrical plant beds supported radially removed from a primary axis of rotation, with each plant bed being driven about its own secondary axis of rotation and simultaneously moved in a planetary path about the primary axis of rotation. Each plant bed is formed by an apertured outer cylinder, a perforated inner cylinder positioned coaxially, and rooting media disposed in the space between. A rotatable manifold distributes liquid nutrients and water to the rooting media through the perforations in the inner cylinders as the plant beds are continuously rotated by suitable drive means.

Dedolph, R. D.↗
NASA NTRS2005

Rotating Rake Turbofan Duct Mode Measurement System

An experimental measurement system was developed and implemented by the NASA Glenn Research Center in the 1990s to measure turbofan duct acoustic modes. The system is a continuously rotating radial microphone rake that is inserted into the duct. This Rotating Rake provides a complete map of the acoustic duct modes present in a ducted fan and has been used on a variety of test articles: from a low-speed, concept test rig, to a full-scale production turbofan engine. The Rotating Rake has been critical in developing and evaluating a number of noise reduction concepts as well as providing experimental databases for verification of several aero-acoustic codes. More detailed derivation of the unique Rotating Rake equations are presented in the appendix.

Sutliff, Daniel L.↗
NASA NTRS2011

Charging and Subsequent Dissipation of a Rover Wheel in the Lunar Polar Regions

As a roving vehicle moves along the lunar surface, electric charge will build up through tribo-charging. This charge collected by the roving object will have a dissipative path to either the surface or the ambient plasma, depending upon which path is most conductive. At the lunar terminator region and into nightside regions, the surface is very cold and becomes a very poor conductor. leaving the plasma as the dominant remediating current for dissipation. However, within lunar craters, even plasma currents become substantially reduced which then greatly increases electric 'dissipation times, This work will involve the advancement of the stepping astronaut charge model, by considering the charging and plasma dissipation of a rolling rover wheel, The objective of this work is to determine the nature of charging and discharging for a rover wheel as it rolls along the cold, plasma-starved lunar polar regions. The rotating wheel accumulates charge via contact electrification (tribo-charging) with the lunar regolith. This tribo-charging is dependent on the composition of the objects in contact, with insulators and conductors charging differently. Given the environmental plasma in the region, we then determine the dissipation time for the wheel to bleed off its excess charge into the surrounding plasma. A model of the rover wheel rotating continuously over a surface regolith within a polar crater has been applied. The environmental plasma has been described previously. We define a new tribo-charging term specifically for the rotating system, with charge levels defined as a function of the wheel size, area in contact with the regolith, regolith particle size distribution, as well as the velocity at which the wheel is turning. We recognize that as charged dust accumulates and sticks to the wheel, this behaves effectively as a new current. Hence, the overall charging of the system should no longer vary linearly. and begin to show signs of saturation, We are devising a dust current term to model this charge-limiting effect, and will present the results in discussion.

Jackson, T. L.↗
NASA NTRS2004

Space Station Power Generation Investigated in Support of the Beta Gimbal Anomaly Resolution

The International Space Station (ISS) is the largest and most complex spacecraft ever assembled and operated in orbit. The first U.S. photovoltaic module, containing two solar arrays, was launched, installed, and activated in early December 2000. After the first week of continuously rotating the U.S. solar arrays, engineering personnel in the ISS Mission Evaluation Room observed higher than expected electrical currents on the drive motor in one of the Beta Gimbal Assemblies (BGA), the mechanism used to maneuver a U.S. solar array (see the on-orbit photograph). The magnitude of the motor currents continued to increase over time on both BGAs, creating concerns about the ability of the gimbals to continue pointing the solar arrays towards the Sun, a function critical for continued assembly of the ISS. The BGA provides two critical capabilities to the ISS: (1) transfer of electrical power across a rotating joint and (2) positioning of the solar arrays. A number of engineering disciplines convened in May 2001 to address this on-orbit hardware anomaly. Over the course of a year, many scenarios were developed and used. Only two are discussed here: parked arrays and dual-angle mode.

Delleur, Ann M.↗
NASA NTRSDate not supplied

Quiet High Speed Fan II (22-inch) Duct Mode Characteristics as Measured by the Rotating Rake Mode Measurement System while Operated in the NASA Glenn 9x15 Low Speed Wind Tunnel

Wind Tunnel test at a tunnel Mach number of 0.10. This was an entry to investigate the effect of “stator clocking” on noise. The fan consisted of a moderately aft swept rotor and an aft swept set of stator vanes. The fan stage consisted of 22 rotor blades, 50 stator vanes, and 10 downstream support struts. A set of stator vanes designed for lower noise was tested as well as a baseline stator vane set. The stator assembly could be rotated several degrees to adjust the clocking angle between the stator vane pack and the strut assembly. All configurations were with a hard wall duct (no acoustic treatment). The NASA Glenn Research Center’s Rotating Rake Mode Measurement System was utilized to obtain a complete map of the acoustic duct modes present in the ducted fan. The system is a radial rake emersed into the duct that continuously rotates about the duct centerline. For the two stator configurations, data were acquired at several different fan speeds which included nominal, approach, cutback, and takeoff conditions. Analysis of the mode power level results at the fan fundamentals showed the improved designed set resulted in lower rotor-stator and rotor-strut interaction acoustic levels for the interaction modes. Varying the angle between the stators and struts was shown to be a viable method to achieve a minimum in rotor-strut interaction mode power level. Multiple-pure-tones generated by the Quiet High Speed Fan II in the inlet were also measured.

Turbofan, Duct Modes↗
NASA NTRSDate not supplied

Quiet High Speed Fan II (22-inch) Duct Mode Characteristics as Measured by the Rotating Rake Mode Measurement System while Operated in the NASA Glenn 9x15 Low Speed Wind Tunnel

Wind Tunnel at a tunnel Mach number of 0.10. This was an entry to investigate the effect of “stator clocking” on noise. The fan consisted of a moderately aft swept rotor and an aft swept set of stator vanes. The fan stage consisted of 22 rotor blades, 50 stator vanes, and 10 downstream support struts. A set of stator vanes designed for lower noise was tested as well as a baseline stator vane set. The stator assembly could be rotated several degrees to adjust the clocking angle between the stator vane pack and the strut assembly. All configurations were with a hard wall duct (no acoustic treatment). The NASA Glenn Research Center’s Rotating Rake Mode Measurement System was utilized to obtain a complete map of the acoustic duct modes present in the ducted fan. The system is a radial rake emersed into the duct that continuously rotates about the duct centerline. For the two stator configurations, data were acquired at several different fan speeds which included nominal, approach, cutback, and takeoff conditions. Analysis of the mode power level results at the fan fundamentals showed the improved designed set resulted in lower rotor-stator and rotor-strut interaction acoustic levels for the interaction modes. Varying the angle between the stators and struts was shown to be a viable method to achieve a minimum in rotor-strut interaction mode power level. Multiple-pure-tones generated by the Quiet High Speed Fan II in the inlet were also measured.

Turbofan, Duct Modes↗
NASA NTRSDate not supplied

Source Diagnostic Fan II (22-Inch) Duct Mode Characteristics as Measured by the Rotating Rake Mode Measurement System while Operated in the NASA Glenn 9x15 Low Speed Wind Tunnel

A 22-inch scale model of the Honeywell Quiet High Speed Fan II was tested in the NASA Glenn 9- by 15-foot Low Speed Wind Tunnel at a tunnel Mach number of 0.10. This was an entry to investigate the effect of “stator clocking” on noise. The fan consisted of a moderately aft swept rotor, and an aft swept set of stator vanes. The fan stage consisted of 22 rotor blades, 50 stator vanes, and 10 downstream support struts. A set of stator vanes designed for lower noise was tested as well as a baseline stator vane set. The stator assembly could be rotated several degrees to adjust the clocking angle between the stator vane pack and the strut assembly. All configurations were with a hard wall duct (no acoustic treatment). The NASA Glenn Research Center’s Rotating Rake Mode Measurement System was utilized to obtain a complete map of the acoustic duct modes present in the ducted fan. The system is a radial rake emersed into the duct that continuously rotates about the duct centerline. For the two stator configurations, data were acquired at several different fan speeds which included nominal, approach, cutback, and takeoff conditions. Analysis of the mode power level results at the fan fundamentals showed the improved designed set resulted in lower rotor-stator and rotor-strut interaction acoustic levels for the interaction modes. Varying the angle between the stators and struts was shown to be a viable method to achieve a minimum in rotor-strut interaction mode power level. Multiple-pure-tones generated by the Quiet High Speed Fan II in the inlet were also measured.

Fan Noise↗
NASA NTRS2004

The Morrison Bearingless Switched Reluctance Motor

Switched reluctance motors typically consist of pairs of poles protruding outward from a central rotor, surrounded by pairs of coils protruding inward from a stator. The pairs of coils, positioned a short distance from opposing sides of the rotor, are connected in series. A current runs through the coils, generating a magnetic flux between the coils. This attracts the protruding poles on the rotor, and just as the poles on the rotor approach the coils, the current to the coils is inverted, repelling the rotor s poles as they pass the coils. This current switching, back and forth, provides a continuous rotational torque to the rotor. reliability, durability, low cost, and operation in adverse environments such as high temperatures, extreme temperature variations, and high rotational speeds. However, because rotors are often manufactured with minute flaws due to imperfections in the machining process, traditional switched reluctance motors often suffer from substantial amounts of vibration. In addition, the current in the coils imparts a strong radial magnetic force on the rotor; the continuous alternating of the direction of this force also causes vibration. As a result, switched reluctance motors require bearings that, run at high speeds, can require lubrication apparatus and are subject to problems with heat and wear. My mentor s recent invention, the "Bearingless" Switched Reluctance Motor, actually uses magnetic bearings instead of traditional physical bearings. Sensors are used to continuously determine the position of the rotor. A computer reads the position sensor input, performs calculations, and outputs a current to a set of extra coils (in addition to the coils rotating the rotor). This current provides a magnetic force that counters and damps the vibration. The sense-calculate-update loop iterates more than thirty thousand times per second. For now, our goal is to have the rotor rotate at about 6000 rprn, and at that speed, the magnetic bearing is adjusting the rotor s position more than 300 times per rotation. and vibration-suppression capacity for the switched reluctance motor. Traditional switched reluctance motors possess many positive traits, including It is hoped that this new invention will increase load-carrying capacity, stiffness, and vibration-suppression capacity for the switched reluctance motor.

Wong, David S.↗
NASA NTRS2009

The Soil Moisture Active/Passive (SMAP) Mission Radar: A Novel Conically Scanning SAR

The Soil Moisture Active/Passive (SMAP) mission is a NASA mission identified by the NRC "decadal survey" to measure both soil moisture and freeze/thaw state from space. The mission will use both active radar and passive radiometer instruments at L-Band. In order to achieve a wide swath at sufficiently high resolution for both active and passive chan-nels, an instrument architecture that uses a large rotating reflector is employed. The active radar will further utilize SAR processing in order to obtain the sub-footprint resolution necessary for the geophysical retrievals. The SMAP radar has a unique geometry where the antenna footprint is continuously rotated about nadir in a conical fashion, as opposed to the more common side-looking SAR design. In additional to the unconventional scan geometry, the SMAP radar must address the effects of Faraday rotation and radio frequency interference (RFI), both consequences of the L-Band frequency of operation.

L-band↗
NASA NTRS2003

Space Station Power Generation in Support of the Beta Gimbal Anomaly Resolution

The International Space Station (ISS) is the largest and most complex spacecraft ever assembled and operated in orbit. The first U.S. photovoltaic (PV) module, containing two solar arrays, was launched, installed, and activated in early December 2000. After the first week of continuously rotating the U.S. solar arrays, engineering personnel in the ISS Mission Evaluation Room (MER) observed higher than expected electrical currents on the drive motor in one of the Beta Gimbal Assemblies (BGA), the mechanism used to maneuver a U.S. solar array. The magnitude of the motor currents continued to increase over time on both BGA's, creating concerns about the ability of the gimbals to continue pointing the solar arrays towards the sun, a function critical for continued assembly of the ISS. A number of engineering disciplines convened in May 2001 to address this on-orbit hardware anomaly. This paper reviews the ISS electrical power system (EPS) analyses performed to develop viable operational workarounds that would minimize BGA use while maintaining sufficient solar array power to continue assembly of the ISS. Additionally, EPS analyses performed in support of on-orbit BGA troubleshooting exercises is reviewed. EPS capability analyses were performed using SPACE, a computer code developed by NASA Glenn Research Center (GRC) for the ISS program office.

Delleur, Ann M.↗