Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “point contacts”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
NASA NTRS2015

Email-Based Informed Consent: Innovative Method for Reaching Large Numbers of Subjects for Data Mining Research

Since the 2010 NASA authorization to make the Life Sciences Data Archive (LSDA) and Lifetime Surveillance of Astronaut Health (LSAH) data archives more accessible by the research and operational communities, demand for data has greatly increased. Correspondingly, both the number and scope of requests have increased, from 142 requests fulfilled in 2011 to 224 in 2014, and with some datasets comprising up to 1 million data points. To meet the demand, the LSAH and LSDA Repositories project was launched, which allows active and retired astronauts to authorize full, partial, or no access to their data for research without individual, study-specific informed consent. A one-on-one personal informed consent briefing is required to fully communicate the implications of the several tiers of consent. Due to the need for personal contact to conduct Repositories consent meetings, the rate of consenting has not kept up with demand for individualized, possibly attributable data. As a result, other methods had to be implemented to allow the release of large datasets, such as release of only de-identified data. However the compilation of large, de-identified data sets places a significant resource burden on LSAH and LSDA and may result in diminished scientific usefulness of the dataset. As a result, LSAH and LSDA worked with the JSC Institutional Review Board Chair, Astronaut Office physicians, and NASA Office of General Counsel personnel to develop a "Remote Consenting" process for retrospective data mining studies. This is particularly useful since the majority of the astronaut cohort is retired from the agency and living outside the Houston area. Originally planned as a method to send informed consent briefing slides and consent forms only by mail, Remote Consenting has evolved into a means to accept crewmember decisions on individual studies via their method of choice: email or paper copy by mail. To date, 100 emails have been sent to request participation in eight HRP-funded studies. The development of the Remote Consent process, the laws allowing transmission of consent via electronic means, total metrics to date, and remaining challenges (e.g., response issues, use of International Partner data, biospecimens/genetic data) for the research use of LSAH/LSDA data will be described.

Lee, Lesley R.↗
NASA NTRS1980

Global observations of the composition and dynamics of the ionosphere of Venus - Implications for the solar wind interaction

The in-situ measurements of the global composition and Venus ionosphere dynamics recorded by the Bennett ion mass spectrometer on the Pioneer Venus orbiter during Dec. 1978-Aug. 1979 are presented. The observations of three plasma regimes show the bowshock-ionosheath region, the thermal ionosphere, and a superthermal flowing ion layer contacting the ionosphere at the ionopause and extending outward to different heights above the planet. An abundant ionosphere dominated by O(+) above 200 km and by O2(+) down to the typical periapsis altitudes of 160 km occur during quiet periods; less disturbed data shows strong day to night changes in the distributions of ions including O(+), O2(+), CO2(+), and N(+). The ionopause is located near the subpolar point at 250-400 km; under disturbed nighttime conditions it may have randomly spaced concentration gradients in the dusk region.

Taylor, H. A., Jr.↗
NASA NTRS1990

Performance results of Grumman prototype Space Station Space Erectable Radiator System ground test articles

The paper addresses individual-radiator performance results of the prototype Space Erectable Radiator System (SERS) in both ambient and thermal vacuum environments. The radiator design utilizing a two-phase fluid loop is outlined, along with SERS design requirements, radiator panel hardware, and whiffletree clamp hardware providing a dry-contact interface of the SERS panel with the heat exchanger of the thermal bus. It is observed that throughout integrated thermal-bus tests, SERS panels managed the load demands whether interfacing with twin condensers, in parallel-flow configuration, or with shear-flow condensers, in a cross-flow configuration. It is found that the insulation losses in the integrated and stand-alone test points are approximately 2 to 6 pct. The motorized whiffletree clamp is seen as performing satisfactorily during remote operations as well as maintaining 28,800-lb force throughout the test duration without requiring further adjustments.

Gisondo, Francine↗
NASA NTRS1993

Preliminary system design of a Three Arm Capture Mechanism (TACM) flight demonstration article

The overall objective of the Three Arm Capture Mechanism (TACM) is to serve as a demonstration of capability for capture of objects in space. These objects could be satellites, expended boosters, pieces of debris, etc.; anything of significant size. With this capability we can significantly diminish the danger of major collisions of debris with valuable space assets and with each other, which would otherwise produce many smaller, high velocity pieces of debris which also become concerns. The captured objects would be jettisoned into the atmosphere, relocated in 'parking' orbits, or recovered for disposition or refurbishment. The dollar value of satellites launched into space continues to grow along with the cost of insurance; having a capture capability takes a positive step towards diminishing this added cost. The effort covered is a planning step towards a flight demonstration of the satellite capture capability. Based on the requirement to capture a communication class satellite, its associated booster, or both, a preliminary system definition of a retrieval kit is defined. The objective of the flight demonstration is to demonstrate the techniques proposed to perform the mission and to obtain data on technical issues requiring an in situ space environment. The former especially includes issues such as automated image recognition techniques and control strategies that enable an unmanned vehicle to rendezvous and capture a satellite, contact dynamics between the two bodies, and the flight segment level of automation required to support the mission. A development plan for the operational retrieval capability includes analysis work, computer and ground test simulations, and finally a flight demonstration. A concept to perform a selected mission capturing a precessing communications satellite is described. Further development efforts using analytical tools and laboratory facilities are required prior to reaching the point at which a full commitment to the flight demonstration design can be made.

Schaefer, Otto↗
NASA NTRS1994

Quick connect fastener

A quick connect fastener and method of use is presented wherein the quick connect fastener is suitable for replacing available bolts and screws, the quick connect fastener being capable of installation by simply pushing a threaded portion of the connector into a member receptacle hole, the inventive apparatus being comprised of an externally threaded fastener having a threaded portion slidably mounted upon a stud or bolt shaft, wherein the externally threaded fastener portion is expandable by a preloaded spring member. The fastener, upon contact with the member receptacle hole, has the capacity of presenting cylindrical threads of a reduced diameter for insertion purposes and once inserted into the receiving threads of the receptacle member hole, are expandable for engagement of the receptacle hole threads forming a quick connect of the fastener and the member to be fastened, the quick connect fastener can be further secured by rotation after insertion, even to the point of locking engagement, the quick connect fastener being disengagable only by reverse rotation of the mated thread engagement.

Weddendorf, Bruce↗
NASA NTRS1992

Image Tiling for Profiling Large Objects

Three dimensional surface measurements of large objects arc required in a variety of industrial processes. The nature of these measurements is changing as optical instruments arc beginning to replace conventional contact probes scanned over the objects. A common characteristic of the optical surface profilers is the trade off between measurement accuracy and field of view. In order to measure a large object with high accuracy, multiple views arc required. An accurate transformation between the different views is needed to bring about their registration. In this paper, we demonstrate how the transformation parameters can be obtained precisely by choosing control points which lie in the overlapping regions of the images. A good starting point for the transformation parameters is obtained by having a knowledge of the scanner position. The selection of the control points arc independent of the object geometry. By successively recording multiple views and obtaining transformation with respect to a single coordinate system, a complete physical model of an object can be obtained. Since all data arc in the same coordinate system, it can thus be used for building automatic models for free form surfaces.

Venkataraman, Ajit↗
NASA NTRS2003

Architecture and System Engineering Development Study of Space-Based Satellite Networks for NASA Missions

Traditional NASA missions, both near Earth and deep space, have been stovepipe in nature and point-to-point in architecture. Recently, NASA and others have conceptualized missions that required space-based networking. The notion of networks in space is a drastic shift in thinking and requires entirely new architectures, radio systems (antennas, modems, and media access), and possibly even new protocols. A full system engineering approach for some key mission architectures will occur that considers issues such as the science being performed, stationkeeping, antenna size, contact time, data rates, radio-link power requirements, media access techniques, and appropriate networking and transport protocols. This report highlights preliminary architecture concepts and key technologies that will be investigated.

Ivancic, William D.↗
NASA NTRS2016

Proximity Link Design and Performance Options for a Mars Areostationary Relay Satellite

Current and near-term Mars relay telecommunications services are provided by a set of NASA and ESA Mars science orbiters equipped with UHF relay communication payloads employing operationally simple low-gain antennas. These have been extremely successful in supporting a series of landed Mars mission, greatly increasing data return relative to direct-to-Earth lander links. Yet their relay services are fundamentally constrained by the short contact times available from the selected science orbits. Future Mars areostationary orbiters, flying in circular, equatorial, 1- sol orbits, offer the potential for continuous coverage of Mars landers and rovers, radically changing the relay support paradigm. Achieving high rates on the longer slant ranges to areostationary altitude will require steered, high-gain links. Both RF and optical options exist for achieving data rates in excess of 100 Mb/s. Several point designs offer a measure of potential user burden, in terms of mass, volume, power, and pointing requirements for user relay payloads, as a function of desired proximity link performance.

telecommunications↗
NASA NTRS2016

Proximity Link Design and Performance Options for a Mars Areostationary Relay Satellite

Current and near-term Mars relay telecommunications services are provided by a set of NASA and ESA Mars science orbiters equipped with UHF relay communication payloads employing operationally simple low gain antennas. These have been extremely successful in supporting a series of landed Mars mission, greatly increasing data return relative to direct-to-Earth lander links. Yet their relay services are fundamentally constrained by the short contact times available from the selected science orbits. Future Mars areostationary orbiters, flying in circular, equatorial, 1- sol orbits, offer the potential for continuous coverage of Mars landers and rovers, radically changing the relay support paradigm. Achieving high rates on the longer slant ranges to areostationary altitude will require steered, high-gain links. Both RF and optical options exist for achieving data rates in excess of 100 Mb/s. Several point designs offer a measure of potential user burden, in terms of mass, volume, power, and pointing requirements for user relay payloads, as a function of desired proximity link performance.

telecommunications↗
NASA NTRS1989

Tele-autonomous control involving contacts: The applications of a high precision laser line range sensor

The object localization algorithm based on line-segment matching is presented. The method is very simple and computationally fast. In most cases, closed-form formulas are used to derive the solution. The method is also quite flexible, because only few surfaces (one or two) need to be accessed (sensed) to gather necessary range data. For example, if the line-segments are extracted from boundaries of a planar surface, only parameters of one surface and two of its boundaries need to be extracted, as compared with traditional point-surface matching or line-surface matching algorithms which need to access at least three surfaces in order to locate a planar object. Therefore, this method is especially suitable for applications when an object is surrounded by many other work pieces and most of the object is very difficult, is not impossible, to be measured; or when not all parts of the object can be reached. The theoretical ground on how to use line range sensor to located an object was laid. Much work has to be done in order to be really useful.

Volz, R. A.↗
NASA NTRS1992

A comparison between theoretical prediction and experimental measurement of the dynamic behavior of spur gears

A comparison was made between computer model predictions of gear dynamics behavior and experimental results. The experimental data were derived from the NASA gear noise rig, which was used to record dynamic tooth loads and vibration. The experimental results were compared with predictions from the DSTO Aeronautical Research Laboratory's gear dynamics code for a matrix of 28 load speed points. At high torque the peak dynamic load predictions agree with the experimental results with an average error of 5 percent in the speed range 800 to 6000 rpm. Tooth separation (or bounce), which was observed in the experimental data for light torque, high speed conditions, was simulated by the computer model. The model was also successful in simulating the degree of load sharing between gear teeth in the multiple tooth contact region.

Rebbechi, Brian↗
NASA NTRS2005

Physics-based Simulation of Human Posture Using 3D Whole Body Scanning Technology for Astronaut Space Suit Evaluation

Over the past few years high precision three-dimensional (3D) full body laser scanners have been developed to be used as a powerful anthropometry tool for quantification of the morphology of the human body. The full body scanner can quickly extract body characteristics in non-contact fashion. It is required for the Anthropometry and Biomechanics Facility (ABF) to have capabilities for kinematics simulation of a digital human at various postures whereas the laser scanner only allows capturing a single static posture at each time. During this summer fellowship period a theoretical study has been conducted to estimate an arbitrary posture with a series of example postures through finite element (FE) approximation and found that four-point isoparametric FE approximation would result in reasonable maximum position errors less than 5%. Subsequent pilot scan experiments demonstrated that a bead marker with a nominal size of 6 mm could be used as a marker for digitizing 3-D coordinates of anatomical landmarks for further kinematic analysis. Two sessions of human subject testing were conducted for reconstruction of an arbitrary postures from a set of example postures for each joint motion for the forearm/hand complex and the whole upper extremity.

Kim, Kyu-Jung↗
NASA NTRS2002

Dynamical Studies of the Middle Atmosphere Using High Resolution Doppler Imager Observations

This report summarizes the activities of NASA grant NAG5-11068, "Dynamicai Studies of the Middle Atmosphere Using High Resolution Doppler Imager Observations." The High Resolution Doppler Imager (HRDI) on the Upper Atmosphere Research Satellite (UARS) has been providing direct measurements of the Earth's horizontal wind field in the stratosphere, mesosphere and lower thermosphere. Mesospheric temperatures, ozone, and O((sup 1) D) densities, and stratospheric aerosol extinctions coefficients, are also retrieved. The goal of HRDI is to measure the vector winds in the stratosphere (10-40 km), mesosphere, and lower thermosphere (approximately 50-120 km) during the day, and the lower thermosphere at night (approximately 95 km) to an accuracy of 5 m/s. The horizontal wind vector is measured by observing the Doppler shift of rotational lines of molecular oxygen along two lines of sight. In addition to winds, temperatures and volume emission rates are determined in the mesosphere and lower thermosphere, from which ozone and O((sup 1) D) concentrations can be derived, and aerosol scattering coefficients are determined in the stratosphere. UARS was launched on September 12, 1991, into a 585-km circular orbit inclined 57 degrees to the equator HRDI was activated September 28, 1991 and following a period of checkout and adjustment of the instrument parameters, scientific observations began November 2, 199 1. HRDI operated nearly continuously from launch until April 1995. At that time the UARS solar array drive failed, forcing the instruments to time-share the available power. From July 1995 to July 1996 HRDI operated approximately 50% of the time. At that point, one of the three spacecraft batteries failed and from then until September 1998 the duty cycle was less than 20% per month, At that time it was determined that HRDI could operate during each daytime pass, which increased the daytime duty cycle to close to l00%, while nighttime operations were limited to about a week per month. In the fall of 1999, the second tape recorder failed requiring a real time contact with a TRDSS satellite to retrieve that data. This resulted in about 60% data collection efficiency. Finally, in the summer of 2000, the second star sensor failed requiring the spacecraft attitude to be controlled by a three axis magnetometer and sun sensor. This resulted in a loss of attitude knowledge but operations continue with the anticipation of correcting the attitude. A new method for determining the tide and mean structure from satellite data in conjunction with a new tidal model has been devised. For brevity, it shall be referred to as the TMAT or Tide-Mean Assimilation Technique. Most previous methods of tidal analysis are based on various ways of slicing the data set.

Skinner, Wilbert↗
NASA NTRS2006

Fast Erase Method and Apparatus For Digital Media

A non-contact fast erase method for erasing information stored on a magnetic or optical media. The magnetic media element includes a magnetic surface affixed to a toroidal conductor and stores information in a magnetic polarization pattern. The fast erase method includes applying an alternating current to a planar inductive element positioned near the toroidal conductor, inducing an alternating current in the toroidal conductor, and heating the magnetic surface to a temperature that exceeds the Curie-point so that information stored on the magnetic media element is permanently erased. The optical disc element stores information in a plurality of locations being defined by pits and lands in a toroidal conductive layer. The fast erase method includes similarly inducing a plurality of currents in the optical media element conductive layer and melting a predetermined portion of the conductive layer so that the information stored on the optical medium is destroyed.

Oakely, Ernest C.↗
NASA NTRS1978

The practical impact of elastohydrodynamic lubrication

Elastohydrodynamic lubrication has had its most significant impact on, among all the types of concentrated contact mechanisms, rolling element bearings. EHL technology, through its inclusion in computer codes, now provides us with more effective methods for optimizing bearing design and for predicting bearing life, power loss, temperature and dynamic behavior. Bearing life prediction has advanced to a much more sophisticated level as compared to the calculation of fatigue life based on Lundberg-Palmgren theory. Application of elastohydrodynamics to gearing has, more or less, been limited to the calculation of pitch point film thicknesses. Techniques for calculating film thicknesses over the entire range of tooth meshes for arbitrarily shaped gear teeth (noninvolute, spur, helical, etc.) need to be developed. Elastomer seals with both unidirectional and reciprocating motion offer a fruitful application for the elastohydrodynamics of low modulus materials.

Anderson, W. J.↗
NASA NTRS1980

Fire extinguishing apparatus having a slidable mass for a penetrator nozzle

A fire extinguishing apparatus for delivering an extinguishing agent through a tarrier surrounding a structure into its interior includes an elongated tubular nozzle body which has a pointed penetrating head carried on one end of the tubular body. A source of extinguishing agent coupled to the opposite end of the tubular body is fed through and passes through passages adjacent the head for delivering the extinguishing agent to the interior of the structure. A slidable mass is carried on the tubular body on a remote end of the tubular body from the penetrating head. By manipulating the slidable mass and bringing such in contact with an abutment the force imparted to the tubular body causes the head to penetrate the structure.

Gray, N. C.↗
NASA NTRS2012

JWST Near-Infrared Detector Degradation: Finding the Problem, Fixing the Problem, and Moving Forward

The James Webb Space Telescope (JWST) is the successor to the Hubble Space Telescope. JWST will be an infrared optimized telescope, with an approximately 6.5 m diameter primary mirror, that is located at the Sun-Earth L2 Lagrange point. Three of JWST's four science instruments use Teledyne HgCdTe HAWAII-2RG (H2RG) near infrared detector arrays. During 2010, the JWST Project noticed that a few of its 5 micron cutoff H2RG detectors were degrading during room temperature storage, and NASA chartered a "Detector Degradation Failure Review Board" (DD-FRB) to investigate. The DD-FRB determined that the root cause was a design flaw that allowed indium to interdiffuse with the gold contacts and migrate into the HgCdTe detector layer. Fortunately, Teledyne already had an improved design that eliminated this degradation mechanism. During early 2012, the improved H2RG design was qualified for flight and JWST began making additional H2RGs. In this article we present the two public DD-FRB "Executiye Summaries" that: (1) determined the root cause of the detector degradation and (2) defined tests to determine whether the existing detectors are qualified for flight. We supplement these with a brief introduction to H2RG detector arrays, and a discussion of how the JWST Project is using cryogenic storage to retard the degradation rate of the existing flight spare H2RGs.

Rauscher, Bernard J.↗
NASA NTRS1982

The stability of the axially symmetric pendent drop

The axially symmetric pendent drop as it occurs in three different physical settings is analyzed: Problem A with constant pressure and a fixed circular opening (the siphon); Problem B with constant volume and a fixed circular opening (the medicine dropper); and Problem C with prescribed volume and a constant angle of contact with a horizontal plate. As examples, the results are verified. For Problem B it is shown that if the opening is small enough to support a stable pendent drop with a bulge, then as the exposed volume is increased, stable pendent drops with both a neck and a bulge will be formed. For Problem C it is shown that with increasing volume the profile curves for the family of stable pendent drops will develop an inflection point before instability arises.

Wente, H. C.↗