SEARCH · Engineering Papers

Results for “ground loop”

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.

SourceResearch connectionFrom yearThrough year

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

At least 559 records · Page 31

All sources NASA NTRS DOE OSTI

DOE OSTI2017

Thermal Response Testing Takes a Step Forward

Oak Ridge National Labs has independently confirmed the accuracy of a new breakthrough Advanced Thermal Response Test (TRT) method that it claims “uses less than half of the test time, allows for a fluctuating or interruptible heat flux, performs quality validation of a GHEX installation, and yields new insights into ground thermal conductivity that warrant further research.” The new Advanced TRT approach will reduce costs and, for the first time, also determine the actual thermal conductivity of grout as it is installed. As everyone in the ground source heat pump (GSHP) industry knows, assuring the quality of the grout job of a ground heat exchanger (GHEX) is an especially vexing problem. Unless one is standing at the borehole head the entire time grouting is underway, they basically have no idea how good or bad the grouting job is or even if the loop pipe itself is installed correctly. This problem has been further brought to light with formal third party grout reports confirming that grout had been poured from the surface and that many loops were shorter than the specified depth in several projects

58 GEOSCIENCES↗

NASA NTRS1988

Pointing a ground antenna at a spinning spacecraft using Conscan-simulation results

The results are presented for an investigation of ground antenna pointing errors which are caused by fluctuations of the receiver AGC signal due to thermal noise and a spinning spacecraft. Transient responses and steady-state errors and losses are estimated using models of the digital Conscan (conical scan) loop, the FFT, and antenna characteristics. Simulation results are given for the on-going Voyager mission and for the upcoming Galileo mission, which includes a spinning spacecraft. The simulation predicts a 1 sigma pointing error of 0.5 to 2.0 mdeg for Voyager, assuming an AGC loop SNR of 35 to 30 dB with a scan period varying from 128 to 32 sec, respectively. This prediction is in agreement with the DSS 14 antenna Conscan performance of 1.7 mdeg for 32 sec scans as reported in earlier studies. The simulation of Galileo predicts 1 mdeg error with a 128 sec scan and 4 mdeg with a 32 sec scan under similar AGC conditions.

Mileant, A.↗

NASA NTRS1989

Pointing a ground antenna at a spinning spacecraft using conical scan - Simulation results

Mileant, Alexander↗

NASA NTRS2016

SEXTANT X-Ray Pulsar Navigation Demonstration: Flight System and Test Results

The Station Explorer for X-ray Timing and Navigation Technology (SEXTANT) is a technology demonstration enhancement to the Neutron-star Interior Composition Explorer (NICER) mission. NICER is a NASA Explorer Mission of Opportunity that will be hosted on the International Space Station (ISS). SEXTANT will, for the first time, demonstrate real-time, on-board X-ray Pulsar Navigation (XNAV), a significant milestone in the quest to establish a GPS-like navigation capability available throughout our Solar System and beyond. This paper gives an overview of the SEXTANT system architecture and describes progress prior to environmental testing of the NICER flight instrument. It provides descriptions and development status of the SEXTANT flight software and ground system, as well as detailed description and results from the flight software functional and performance testing within the highfidelity Goddard Space Flight Center (GSFC) X-ray Navigation Laboratory Testbed (GXLT) software and hardware simulation environment. Hardware-in-the-loop simulation results are presented, using the engineering model of the NICER timing electronics and the GXLT pulsar simulator-the GXLT precisely controls NASA GSFC's unique Modulated X-ray Source to produce X-rays that make the NICER detector electronics appear as if they were aboard the ISS viewing a sequence of millisecond pulsars.

SEXTANT↗

DOE OSTI2014

Baryon magnetic moments in large-N{sub c} chiral perturbation theory: Effects of the decuplet-octet mass difference and flavor symmetry breaking

The magnetic and transition magnetic moments of the ground-state baryons are computed in heavy baryon chiral perturbation theory in the large-N{sub c} limit, where N{sub c} is the number of colors. SU(3) symmetry breaking is systematically studied twofold: On the one hand, one-loop nonanalytic corrections of orders m{sub q}{sup 1/2} and m{sub q} ln m{sub q} are included, with contributions of baryon intermediate states from both flavor octet and flavor decuplet multiplets, assuming degeneracy between baryon states within a given flavor multiplet but nondegeneracy between baryons of different multiplets. On the other hand, perturbative SU(3) symmetry breaking is also analyzed by including all relevant leading-order operators that explicitly break SU(3) at linear order. The resultant expressions are compared with the available experimental data and with other determinations in the context of conventional heavy baryon chiral perturbation theory for three flavors of light quarks and at the physical value N{sub c}=3. The agreement reached is quite impressive.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

NASA NTRS1999

Flight Testing of a Cryogenic Capillary Pumped Loop

Future space-based cryogenic systems will require enhanced integration flexibility, lower weight reduced parasitic penalties, better vibration isolation, and a variety of other improvements to meet performance goals. Additionally, there is an increasing need to locate cooling sources remotely from cooled components. In the past flexible conductive links were used and worked well in most cases. However, as the transport lengths increase, conductive couplings become heavier and less effective, and must be replaced by higher performance systems. One available option, which can meet many of these future requirements, is the cryogenic capillary pumped loop (CCPL). The development of the CCPL technology started in 1992, following the success of the room temperature CPLS. The extrapolation of CCPL technology to cryogenic temperatures offers many performance benefits, which are not currently within the reach of traditional heat pipes or conductive links. Specific advantages of the CCPL technology pertaining to cryocooler integration include: (1) greater capillary pumping pressure for improved ground testability; (2) improved mechanical isolation; (3) faster diode shutdown and lower reverse heat leaks; (4) tighter control of detector temperature; (5) variable or fixed conductance operation; and (6) ease of integration due to their flexibility. The applications of CCPL technology are numerous. Military and commercial applications include surveillance satellites, earth observing satellites, deep space observation systems, medical devices, and many other cryogenic systems. Over the past few years, several breadboard and prototype CCPLs have been built and ground tested. A prototype CCPL has demonstrated successful operation between 80K and 110K with heat loads between O.5W and 12W using nitrogen as the working fluid, and 35K and 40K with head loads of 0.25W to 3.5W using neon. In order to verify CCPL performance in a microgravity environment, a flight unit, CCPL-5, was tested onboard the Space Shuttle STS-95 in October of 1998 as part of the CRYOTSU Flight Experiment. This flight was the first in-space demonstration of the CCPL. The CCPL-5 utilized nitrogen as the working fluid and operated between 75K and 110K. Flight results indicated excellent performance of the CCPL-5 under zero-G environment The CCPL could start from a supercritical condition in all tests, and the loop operating temperature could be tightly controlled regardless of changes in the heat load and/or the sink temperature. In addition, the loop demonstrated successful operation with a heat load of 0.5W as well as with parasitic heat loads alone. There were no noticeable differences between zero-G and one-G operation.

Ku, Jentung↗

NASA NTRS2015

Human Research Program Advanced Exercise Concepts (AEC) Overview

Exercise countermeasures provide benefits that are crucial for successful human spaceflight, to mitigate the spaceflight physiological deconditioning which occurs during exposure to microgravity. The NASA Human Research Program (HRP) within the Human Exploration and Operations Mission Directorate (HEOMD) is managing next generation Advanced Exercise Concepts (AEC) requirements development and candidate technology maturation to Technology Readiness Level (TRL) 7 (ground prototyping and flight demonstration) for all exploration mission profiles from Multi Purpose Crew Vehicle (MPCV) Exploration Missions (up to 21 day duration) to Mars Transit (up to 1000 day duration) missions. These validated and optimized exercise countermeasures systems will be provided to the ISS Program and MPCV Program for subsequent flight development and operations. The International Space Station (ISS) currently has three major pieces of operational exercise countermeasures hardware: the Advanced Resistive Exercise Device (ARED), the second-generation (T2) treadmill, and the cycle ergometer with vibration isolation system (CEVIS). This suite of exercise countermeasures hardware serves as a benchmark and is a vast improvement over previous generations of countermeasures hardware, providing both aerobic and resistive exercise for the crew. However, vehicle and resource constraints for future exploration missions beyond low Earth orbit will require that the exercise countermeasures hardware mass, volume, and power be minimized, while preserving the current ISS capabilities or even enhancing these exercise capabilities directed at mission specific physiological functional performance and medical standards requirements. Further, mission-specific considerations such as preservation of sensorimotor function, autonomous and adaptable operation, integration with medical data systems, rehabilitation, and in-flight monitoring and feedback are being developed for integration with the exercise countermeasures systems. Numerous technologies have been considered and evaluated against HRP-approved functional device requirements for these extreme mission profiles, and include wearable sensors, exoskeletons, flywheel, pneumatic, and closed-loop microprocessor controlled motor driven systems. Each technology has unique advantages and disadvantages. The Advanced Exercise Concepts project oversees development of candidate next generation exercise countermeasures hardware, performs trade studies of current and state of the art exercise technologies, manages and supports candidate systems physiological evaluations with human test subjects on the ground, in flight analogs and flight. The near term goal is evaluation of candidate systems in flight, culminating in an integrated candidate next generation exercise countermeasures suite on the ISS which coalesces research findings from HRP disciplines in the areas of exercise performance for muscle, bone, cardiovascular, sensorimotor, behavioral health, and nutrition for optimal benefit to the crew.

Countermeasures↗

DOE OSTI2023

The connection between nonzero density and spontaneous symmetry breaking for interacting scalars

We consider U(1)-symmetric scalar quantum field theories at zero temperature. At nonzero charge densities, the ground state of these systems is usually assumed to be a superfluid phase, in which the global symmetry is spontaneously broken along with Lorentz boosts and time translations. We show that, in d > 2 spacetime dimensions, this expectation is always realized at one loop for arbitrary non-derivative interactions, confirming that the physically distinct phenomena of nonzero charge density and spontaneous symmetry breaking occur simultaneously in these systems. We quantify this result by deriving universal scaling relations for the symmetry breaking scale as a function of the charge density, at low and high density. Moreover, we show that the critical value of μ above which a nonzero density develops coincides with the pole mass in the unbroken, Poincaré invariant vacuum of the theory. The same conclusions hold non-perturbatively for an O(N) theory with quartic interactions in d = 3 and 4, at leading order in the 1/N expansion. We derive these results by computing analytically the zero-temperature, finite-μ one-loop effective potential, paying special attention to subtle points related to the iε terms. We check our results against the one-loop low-energy effective action for the superfluid phonons in λΦ 4 theory in d = 4 previously derived by Joyce and ourselves, which we further generalize to arbitrary potential interactions and arbitrary dimensions. As a byproduct, we find analytically the one-loop scaling dimension of the lightest charge-n operator for the λΦ 6 conformal superfluid in d = 3, at leading order in 1/n, reproducing a numerical result of Badel et al. For a λΦ 4 superfluid in d = 4, we also reproduce the Lee-Huang-Yang relation and compute relativistic corrections to it. Finally, we discuss possible extensions of our results beyond perturbation theory.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

NASA NTRS1980

An automatic locating system for cloud-to-ground lightning

Automatic locating systems which respond to cloud to ground lightning and which discriminate against cloud discharges and background noise are described. Subsystems of the locating system, which include the direction finder and the position analyzer, are discussed. The direction finder senses the electromagnetic fields radiated by lightning on two orthogonal magnetic loop antennas and on a flat plate electric antenna. The position analyzer is a preprogrammed microcomputer system which automatically computes, maps, and records lightning locations in real time using data inputs from the direction finder. The use of the locating systems for wildfire management and fire weather forecasting is discussed.

Krider, E. P.↗

NASA NTRS1961

An Investigation of the Effects of the Time Lag Due to Long Transmission Distances upon Remote Control: Tracking Experiments - Phase 1

A series of pursuit tracking tasks were performed incorporating a transport lag in the control loop. The target was a mixture of four sine waves, the fastest having a frequency of 16 cycles per minute at full speed. An attempt was made to design the experiments so that they would provide data applicable to remote control of a ground vehicle over long transmission distances. Three programs were run. In each the time lag was placed between the control and the display. In the first program a velocity control was used and the operator was told that his knob controlled a vehicle, the problem represented a road 9 and he was to drive his vehicle along the road 9 using the delayed vehicle position as feedback for whatever means he desired. The objective was not to match the display traces. In the second program a velocity control was used, and the operator was told that the problem trace represented a road and the delayed trace represented a vehicle and he was to keep them together. The objective was to match display traces. The third program was identical with the first, except that an acceleration control was used rather than a velocity control. Target speeds used were full speed, 1/2 speed, 1/4 speed, 1/8 speed, and 1/16 speed. Time lags were 1/4 second, l/2 second, 1 second, 1-1/2 second, 2 second, 3 second, and 6 seconds. The experimental results are presented in the last section of this report.

Adams, James L.↗

NASA NTRS2008

Human Rating Requirements for NASA's Constellation Program

NASA s Constellation Program (CxP) will conduct a series of human space expeditions of increasing scope, starting with missions supporting the International Space Station and expanding to encompass the Moon and Mars. Although human-rating is an integral part of all CxP activities throughout their life cycle, NASA Procedural Requirements document NPR 8705.2B, Human-Rating Requirements (HRR) for Space Flight Systems, defines the additional processes, procedures, and requirements necessary to produce human-rated space systems that protect the safety of crew members and passengers on these NASA missions. In order to be in compliance with 8705.2B the CxP must show appropriate implementation or progression toward the HRR, or justification for an exception. Compliance includes an explanation of how the CxP intends to meet the HRR, analyses to be performed to determine implementation; and a matrix to trace the HRR to CxP requirements. The HRR requires the CxP to establish a human system integration team (HSIT), consisting of astronauts, mission operations personnel, training personnel, ground processing personnel, human factors personnel, and human engineering experts, with clearly defined authority, responsibility, and accountability to lead the human-system integration. For example, per the HRR the HSIT is involved in the evaluation of crew workload, human-in-the-loop usability evaluations, determining associated criteria, and in assessment of how these activities influenced system design. In essence, the HSIT is invaluable in CxP s ability to meet the three fundamental tenets of human rating: the process of designing, evaluating, and assuring that the total system can safely conduct the required human missions; the incorporation of design features and capabilities that accommodate human interaction with the system to enhance overall safety and mission success; and the incorporation of design features and capabilities to enable safe recovery of the crew from hazardous situations.

Berdich, Debbie↗

NASA NTRS2016

SEXTANT X-Ray Pulsar Navigation Demonstration: Flight System and Test Results

The Station Explorer for X-ray Timing and Navigation Technology (SEXTANT) is a technology demonstration enhancement to the Neutron-star Interior Composition Explorer (NICER) mission. NICER is a NASA Explorer Mission of Opportunity that will be hosted on the International Space Station (ISS). SEXTANT will, for the first time, demonstrate real-time, on-board X-ray Pulsar Navigation (XNAV), a significant milestone in the quest to establish a GPS-like navigation capability available throughout our Solar System and beyond. This paper gives an overview of the SEXTANT system architecture and describes progress prior to environmental testing of the NICER flight instrument. It provides descriptions and development status of the SEXTANT flight software and ground system, as well as detailed description and results from the flight software functional and performance testing within the high-fidelity Goddard Space Flight Center (GSFC) X-ray Navigation Laboratory Testbed (GXLT) software and hardware simulation environment. Hardware-in-the-loop simulation results are presented, using the engineering model of the NICER timing electronics and the GXLT pulsar simulator-the GXLT precisely controls NASA GSFC's unique Modulated X-ray Source to produce X-rays that make the NICER detector electronics appear as if they were aboard the ISS viewing a sequence of millisecond pulsars

Pulsar↗

NASA NTRS1978

NASA Pioneer: Venus reverse playback telemetry program TR 78-2

During the entry of the Pioneer Venus Atmospheric Probes into the Venus atmosphere, there were several events (RF blackout and data rate changes) which caused the ground receiving equipment to lose lock on the signal. This caused periods of data loss immediately following each one of these disturbing events which lasted until all the ground receiving units (receiver, subcarrier demodulator, symbol synchronizer, and sequential decoder) acquired lock once more. A scheme to recover these data by off-line data processing was implemented. This scheme consisted of receiving the S band signals from the probes with an open loop reciever (requiring no lock up on the signal) in parallel with the closed loop receivers of the real time receiving equipment, down converting the signals to baseband, and recording them on an analog recorder. The off-line processing consisted of playing the analog recording in the reverse direction (starting with the end of the tape) up, converting the signal to S-band, feeding the signal into the "real time" receiving system and recording on digital tape, the soft decisions from the symbol synchronizer.

Modestino, J. W.↗

NASA NTRS1986

X-29A technology demonstrator flight test program overview

An overview of the X-29A functional flight program and concept evaluation program is presented, including some of the unique and different preparations for the first flight. Included are a discussion of the many organizational responsibilities and a description of the program management structure for the test team. Also discussed are preflight ground, flight functional envelope expansion, and flight research test objectives and qualitive results to date for both a limited-envelope flight control system and an expanded-envelope system. The aircraft, including the instrumentation system and measurements, is described. In addition, a discussion is included regarding the use of major support facilities, such as ground and flight simulators, the NASA Western Aeronautical Test Range and mission control center, and the Grumman automated telemetry station. An overview of the associated real-time and postflight batch data processing software approaches is presented. The use of hardware-in-the-loop simulation for independent verification and validation and mission planning and practice is discussed. Also included is a description of the flight-readiness review, the airworthiness and flight safety review, work scheduling, technical briefings, and preflight and postflight crew briefings. The configuration control process used on the X-29A program is described, and its relationship to both simulation and aircraft operations is discussed. An X-29A schedule overview is presented with an outline of a proposed follow-on program.

Sefic, W. J.↗

NASA NTRS1989

An algorithm for the solution of dynamic linear programs

The algorithm's objective is to efficiently solve Dynamic Linear Programs (DLP) by taking advantage of their special staircase structure. This algorithm constitutes a stepping stone to an improved algorithm for solving Dynamic Quadratic Programs, which, in turn, would make the nonlinear programming method of Successive Quadratic Programs more practical for solving trajectory optimization problems. The ultimate goal is to being trajectory optimization solution speeds into the realm of real-time control. The algorithm exploits the staircase nature of the large constraint matrix of the equality-constrained DLPs encountered when solving inequality-constrained DLPs by an active set approach. A numerically-stable, staircase QL factorization of the staircase constraint matrix is carried out starting from its last rows and columns. The resulting recursion is like the time-varying Riccati equation from multi-stage LQR theory. The resulting factorization increases the efficiency of all of the typical LP solution operations over that of a dense matrix LP code. At the same time numerical stability is ensured. The algorithm also takes advantage of dynamic programming ideas about the cost-to-go by relaxing active pseudo constraints in a backwards sweeping process. This further decreases the cost per update of the LP rank-1 updating procedure, although it may result in more changes of the active set that if pseudo constraints were relaxed in a non-stagewise fashion. The usual stability of closed-loop Linear/Quadratic optimally-controlled systems, if it carries over to strictly linear cost functions, implies that the saving due to reduced factor update effort may outweigh the cost of an increased number of updates. An aerospace example is presented in which a ground-to-ground rocket's distance is maximized. This example demonstrates the applicability of this class of algorithms to aerospace guidance. It also sheds light on the efficacy of the proposed pseudo constraint relaxation scheme.

Psiaki, Mark L.↗

NASA NTRS2011

A Human-in-the-Loop Evaluation of Multi-Sector Planning in Mixed Equipage Airspace (MSP III)

A human-in-the-loop (HITL) simulation was conducted in May 2010 to determine the feasibility and value 01 conducting multi-sector planning (MSP) operations in a mixed equipage environment. Aircraft were categorized as equipped or unequipped based on the presence or absence of an air-ground data communications (Data Comm) capability for receiving auto-loadable clearances and transfer of communication messages from the air navigation service provider (ANSP). The purpose of the study was to determine the feasibility and possible benefits of introducing multi-sector planning in a mixed equipage context, or whether Data Comm equipage was required for MSP operations. Each test scenario presented one of three different equipage levels to the controllers (10%, 50% or 90% equipped aircraft), so that the operational impact of different equipage levels could be observed. Operational feasibility assessment addressed two related questions: (1) are MSP operations feasible for unequipped aircraft, and (2) are they feasible in a mixed equipage context. Similarly, two categories of potential benefits were explored: (1) system performance improvements (e.g., throughput, workload) associated with MSP at different equipage levels, and (2) the possibility of providing differential service for equipage through MSP operations. Tool requirements (for both planning and controller stations), as well as planning and coordination procedures - within facility (traffic management unit/operational area) and within sector (R-Side/D-Side) - were two other topics addressed in the study. Overall, results suggested that MSP operations were feasible in a mixed equipage environment and that the tools were effective with both equipped and unequipped aircraft. Using the MSP tools, traffic management coordinators were able to manage controller task load, effectively balancing throughput with complexity and controller task load at each of the three equipage levels tested.

Smith, Nancy↗

NASA NTRS2023

Ventilation Heat Exchanger / Flow Meter for xPLSS

The flow meter / heat exchanger (FMHX) in the ventilation loop of the exploration EMU cools the ventilation gas and measures the ventilation flow rate. The heat exchanger transfers heat from the ventilation gas to the thermal control loop via a miniature shell-and-tube heat exchanger. The flow meters calculate the flow rate of gas through the ventilation loop based on the pressure drop across the heat exchanger core. Creare has delivered four design validation test (DVT) heat exchangers and five DVT flow meters to NASA JSC to support development of the exploration portable life support system (xPLSS). This paper describes the design and performance of the DVT units.The heat exchangers are designed to cool the ventilation gas to a specified temperature with low pressure losses under the most challenging operating conditions. The measured performance of the DVT heat exchangers agrees well with design models and meets all performance requirements. The flow meters use a MEMS thermal flow sensor to produce a signal that is proportional to a small bypass flow around the heat exchanger core. They are designed to achieve high measurement accuracy across the full range of xPLSS operating conditions. We calibrated the flow meters in a special-purpose flow facility that simulates operation in the xPLSS ventilation loop. Calibration testing shows that DVT flow meters produce digital output for vent loop mass flow that meets NASA’s accuracy requirements across the range of xPLSS operating conditions. This paper reviews the design of the heat exchangers and flow meters and presents data from the final flow meter calibration testing, heat exchanger performance validation, and initial ground testing in NASA’s xPLSS.

spacesuit↗

NASA NTRS2023

Ventilation Heat Exchanger / Flow Meter for xPLSS

spacesuit↗