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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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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

A fully coupled variable properties thermohydraulic model for a cryogenic hydrostatic journal bearing

The goal set forth here is to continue the work started by Braun et al. (1984-1985) and present an integrated analysis of the behavior of the two row, 20 staggered pockets, hydrostatic cryogenic bearing used by the turbopumps of the Space Shuttle main engine. The variable properties Reynolds equation is fully coupled with the two-dimensional fluid film energy equation. The three-dimensional equations of the shaft and bushing model the boundary conditions of the fluid film energy equation. The effects of shaft eccentricity, angular velocity, and inertia pressure drops at pocket edge are incorporated in the model. Their effects on the bearing fluid properties, load carrying capacity, mass flow, pressure, velocity, and temperature form the ultimate object of this paper.

Braun, M. J.↗
NASA NTRS2006

Gas Seal Pad With Herringbone-Grooved Rotor-Stiffness and Load Capacity

The principle of herringbone-grooved journal bearings has been applied to the case of a seal disc running under a finger seal pad. The inward pumping action of herringbone grooves on the disc generates load capacity and stiffness to maintain a fluid film and prevent contact of the pad and disc. This mechanism does not depend on a converging film under the pad, such as analyzed in previous works. Analysis shows that significant stiffness and load capacity can be supplied by herringbone grooves. In order for the grooves to be effective, the seal pressure drop must be taken outside of the grooved portion of the rotor, but this may be acceptable in order to gain freedom from maintaining a precise film convergence.

Flemming, David P.↗
NASA NTRS1985

A simple, first step to the optimization of regenerator geometry

This paper presents a simplified set of equations for calculating and optimizing regenerator geometries. A number of competing parameters must be accounted for in the design of a regenerator. To obtain high values of effectiveness, there is need for a large surface area for heat transfer and high heat capacity. The void volume should be small to maintain the pressure ratio in the entire system. Moreover, the pressure drop should be small compared to the absolute pressure. With the assumptions made here, the calculations can be done with a hand calculator. The equations show that the optimum regenerator length, hydraulic radius, and porosity are independent of mass flow rate and the gas cross sectional area is proportional to the mass flow rate. It is shown that using gas gaps between parallel plates produces a significantly better regenerator than is possible with packed spheres or screens, particularly at temperatures below approximately 50%.

Radebaugh, R.↗
NASA NTRS1992

Cardiovascular orthostatic function of Space Shuttle astronauts during and after return from orbit

Routine entry, landing, and seat egress after Space Shuttle flights is observed to be associated with drops in blood pressure and increases in heart rate that indicate that the cardiovascular system is performing at its maximum capacity in a large fraction (30 percent) of the study population. It is not apparent that adequate cardiovascular reserve capacity remains to accommodate unaided emergency egress after either current or extended space flights.

Charles, John B.↗
NASA NTRS1994

Radiometric resolution enhancement by lossy compression as compared to truncation followed by lossless compression

Recent advances in imaging technology make it possible to obtain imagery data of the Earth at high spatial, spectral and radiometric resolutions from Earth orbiting satellites. The rate at which the data is collected from these satellites can far exceed the channel capacity of the data downlink. Reducing the data rate to within the channel capacity can often require painful trade-offs in which certain scientific returns are sacrificed for the sake of others. In this paper we model the radiometric version of this form of lossy compression by dropping a specified number of least significant bits from each data pixel and compressing the remaining bits using an appropriate lossless compression technique. We call this approach 'truncation followed by lossless compression' or TLLC. We compare the TLLC approach with applying a lossy compression technique to the data for reducing the data rate to the channel capacity, and demonstrate that each of three different lossy compression techniques (JPEG/DCT, VQ and Model-Based VQ) give a better effective radiometric resolution than TLLC for a given channel rate.

Tilton, James C.↗
NASA NTRS1989

An improved high power hybrid capillary pumped loop

In order to improve performance testing, NASA's High-Power Spacecraft Thermal Management system has been modified through (1) an augmentation of heat-dissipation capacity of the condenser sink for steady-state high power operation, (2) the addition of more pressure transducers for pressure-drop monitoring in various system components, (3) the installation of pressure-contact thermocouples on the evaporators to measure heating surface temperature, (4) the provision of a coolant loop to one of the evaporator plates, (5) the placing of a transient fluid flow-monitoring load cell in the reservoir, and (6) the reorientation of the reservoir to reduce compressed vapor effects. The system is now capable of 10 hours of continuous capillary mode operation at an input power level of 20 kW.

Ku, Jentung↗
NASA NTRS1987

Real time charge efficiency monitoring for nickel electrodes in NICD and NIH2 cells

The charge efficiency of nickel-cadmium and nickel-hydrogen battery cells is critical in spacecraft applications for determining the amount of time required for a battery to reach a full state of charge. As the nickel-cadmium or nickel-hydrogen batteries approach about 90 percent state of charge, the charge efficiency begins to drop towards zero, making estimation of the total amount of stored charge uncertain. Charge efficiency estimates are typically based on prior history of available capacity following standardized conditions for charge and discharge. These methods work well as long as performance does not change significantly. A relatively simple method for determining charge efficiencies during real time operation for these battery cells would be a tremendous advantage. Such a method was explored and appears to be quite well suited for application to nickel-cadmium and nickel-hydrogen battery cells. The charge efficiency is monitored in real time, using only voltage measurements as inputs. With further evaluation such a method may provide a means to better manage charge control of batteries, particularly in systems where a high degree of autonomy or system intelligence is required.

Zimmerman, A. H.↗
NASA NTRS2002

Performance and Safety Tests on Samsung 18650 Li-ion Cells: Two Cell Designs

In order to meet the applications for space shuttle in future, two types of Samsung cells, with capacity 1800 mAh and 2000 mAh, have been investigated. The studies focused on: (1) Performance tests: completed 250 cycles at various combinations of charge/discharge C rates and discharge capacity measurements at various temperatures; and (2) Safety tests: overcharge and overdischarge, heat abuse, short circuit, internal and external short, and vibration, vacuum, and drop tests

Deng, Yi↗
NASA NTRS1960

An Analysis of Nuclear-Rocket Nozzle Cooling

A nuclear-rocket regenerative-cooling analysis was conducted over a range of reactor power of 46 to 1600 megawatts and is summarized herein. Although the propellant (hydrogen) is characterized by a large heat-sink capacity, an analysis of the local heat-flux capability of the coolant at the nozzle throat indicated that, for conventional values of system pressure drop, the cooling capability was inadequate to maintain a selected wall temperature of 1440 R. Several techniques for improving the cooling capability were discussed, for example, high pressure drop, high wall temperature, refractory wall coatings, thin highly conductive walls, and film cooling. In any specific design a combination of methods will probably be utilized to achieve successful cooling.

Robbins, William H.↗
NASA NTRS1990

Rate-based congestion control in networks with smart links, revision

The author uses a network simulator to explore rate-based congestion control in networks with smart links that can feed back information to tell senders to adjust their transmission rates. This method differs in a very important way from congestion control in which a congested network component just drops packets - the most commonly used method. It is clearly advantageous for the links in the network to communicate with the end users about the network capacity, rather than the users unilaterally picking a transmission rate. The components in the middle of the network, not the end users, have information about the capacity and traffic in the network. The author experiments with three different algorithms for calculating the control rate to feed back to the users. All of the algorithms exhibit problems in the form of large queues when simulated with a configuration modeling the dynamics of a packet-voice system. However, the problems are not with the algorithms themselves, but with the fact that feedback takes time. If the network steady-state utilization is low enough that it can absorb transients in the traffic through it, then the large queues disappear. If the users are modified to start sending slowly, to allow the network to adapt to a new flow without causing congestion, a greater portion of the network's bandwidth can be used.

Heybey, Andrew Tyrrell↗
NASA NTRSDate not supplied

Particle Loading Tests on HEPA Flat Sheet Media at Sub-Ambient Pressures Using a Lunar Dust Simulant

When humans return to the moon under the NASA Artemis program, their activities on the lunar surface will inevitably lead to the intrusion of some level of lunar dust into the lander cabin. Therein the crew would be exposed to the potential hazards of lunar dust and the possibility of subsequent transfer into orbiting segments after docking. The spacecraft’s cabin filtration system will need to be effective at removing the airborne lunar dust to properly purify the breathable cabin air and minimize the spreading of the dust throughout the vehicle and orbital segments through the mission duration. The fine nature of the lunar dust will require high efficiency filtration, such as HEPA. A series of tests were performed in a specially designed recirculating sealed flow loop, for testing filter media and filter elements at the NASA Glenn Research Center. The flow loop was used to assess the performance and capacity of flat sheet filter media at representative cabin pressures using JSC-1AF lunar dust simulant and at high rates of particle loading. The pressure drop across the filter media was measured as a function of accumulated particle mass load at ambient pressure and at two sub-ambient pressures, 0.0703MPa and 0.0565MPa, and at a media velocity that was scaled relative to its pleated configuration. The challenge particle flows were generated by a custom designed particle generator that introduces dispersed particles of the lunar simulant at high concentrations. An optical particle counting instrument provided filter efficiency measurements within the sealed environment. The pressure drop was found to increase linearly with the amount of dust load on the media, for all test conditions, while the starting pressure drop was found to be lower at the lowest sub-ambient pressure case. High filter efficiency was maintained after high particle loads on the media.

Sub-ambient↗
NASA NTRSDate not supplied

An Analysis of COVID-19’s Impact on U.S. Aviation

To better understand the effects of COVID-19 and prepare for crises in the future, the changes in the aviation industry during the pandemic were analyzed. Data was gathered on airlines’ economic status, passenger travel, air cargo, avionics manufacturing, and the environment. It was found that passenger air travel was severely depressed, dropping 96% in April 2020 compared to April 2019. Air cargo and manufacturing also felt the effects of the decrease in air traffic. In comparison to the previous year, air cargo capacity in July 2020 was down 28%, and manufacturing companies, such as Boeing, have seen more than a 10% decrease in revenue. Many companies have adapted to the pandemic with new protocols and procedures, such as social distancing guidelines and using passenger planes as cargo planes. Based on these actions taken guidelines were created for future crises. The objective is to facilitate a faster recovery and a more prepared airspace system. Lastly, health guidelines and areas of research that are relevant after a global pandemic are outlined.

Trishala Madhu Jain↗
NASA NTRS2020

An Analysis of COVID-19’s Impact on U.S. Aviation

To better understand the effects of COVID-19 and prepare for crises in the future, the changes in the aviation industry during the pandemic were analyzed. Data was gathered on airlines’ economic status, passenger travel, air cargo, avionics manufacturing, and the environment. It was found that passenger air travel was severely depressed, dropping 96% in April 2020 compared to April 2019 [1]. Air cargo and manufacturing also felt the effects of the decrease in air traffic. In comparison to the previous year, air cargo capacity in July 2020 was down 28% [2], and manufacturing companies, such as Boeing, have seen more than a 10% decrease in revenue [3]. Many companies have adapted to the pandemic with new protocols and procedures, such as social distancing guidelines and using passenger planes as cargo planes. Based on these actions taken guidelines were created for future crises. The objective is to facilitate a faster recovery and a more prepared airspace system. Lastly, health guidelines and areas of research that are relevant after a global pandemic are outlined.

Trishala Jain↗
NASA NTRS2020

Impact of COVID-19 on Aviation in America

To better understand the effects of COVID-19 and prepare for crises in the future, the changes in the aviation industry during the pandemic were analyzed. Data was gathered on airlines’ economic status, passenger travel, air cargo, avionics manufacturing, and the environment. It was found that passenger air travel was severely depressed, dropping 96% in April 2020 compared to April 2019 [1]. Air cargo and manufacturing also felt the effects of the decrease in air traffic. In comparison to the previous year, air cargo capacity in July 2020 was down 28% [2], and manufacturing companies, such as Boeing, have seen more than a 10% decrease in revenue [3]. Many companies have adapted to the pandemic with new protocols and procedures, such as social distancing guidelines and using passenger planes as cargo planes. Based on these actions taken guidelines were created for future crises. The objective is to facilitate a faster recovery and a more prepared airspace system. Lastly, health guidelines and areas of research that are relevant after a global pandemic are outlined.

Trishala Jain↗
NASA NTRS1987

Two-watt, 4-Kelvin closed cycle refrigerator performance

A 2-watt, 4-K helium refrigerator using the Gifford-McMahon/Joule Thomson cycle is described. The unit features a removable displacer cylinder and high-efficiency, low-pressure drop heat exchangers. These improvements result in a 100 percent increase in cooling power over the existing Deep Space Network system. The effects of the heat exchanger efficiency and Gifford-McMahon expander performance on refrigerator capacity are also discussed.

Britcliffe, M.↗
NASA NTRS1985

Measurement of High Temperature Thermophysical Properties

Technique development and the application of electromagnetic levitation to thermophysical property measurement, including determining heats of fusion, heat capacities, and enthalpy increment functions for extremely refractory materials are discussed. Tungsten properties and the development of an apparatus employing electromagnetic levitation and electron beam heating capable of melting levitating tungsten high temperature heat content measurements by drop calorimetry are emphasized. The development of a prototype microcomputer data acquisition system suitable for controlling the ground based system, with consequent improvement in system handling, which can serve as a model for the system needed for flight experiments is described, which include the development of techniques for imaging pyrometry at temperatures above 3500 K, a semiautomatic calorimeter system capable of handling liquid tungsten, and development of a two color imaging pyrometer system.

Bonnell, D. W.↗
NASA NTRSDate not supplied

Particle Loading Tests on HEPA Flat Sheet Media at Sub-Ambient Pressures Using a Lunar Dust Simulant

When humans return to the moon under the NASA Artemis program, their activities on the lunar surface will inevitably lead to the intrusion of some level of lunar dust into the lander cabin. Therein the crew would be exposed to the potential hazards of lunar dust and the possibility of subsequent transfer into orbiting segments after docking. The spacecraft’s cabin filtration system will need to be effective at removing the airborne lunar dust to properly purify the breathable cabin air and minimize the spreading of the dust throughout the vehicle and orbital segments through the mission duration. The fine nature of the lunar dust will require high efficiency filtration, such as HEPA. A series of tests were performed in a specially designed recirculating sealed flow loop, for testing filter media and filter elements at the NASA Glenn Research Center. The flow loop was used to assess the performance and capacity of flat sheet filter media at representative cabin pressures using JSC-1AF lunar he filter media was measured as a function of accumulated particle mdust simulant and at high rates of particle loading. The pressure drop across tass load at ambient pressure and at two sub-ambient pressures, 0.0703MPa and 0.0565MPa, and at a media velocity that was scaled relative to its pleated configuration. The challenge particle flows were generated by a custom designed particle generator that introduces dispersed particles of the lunar simulant at high concentrations. An optical particle counting instrument provided filter efficiency measurements within the sealed environment. The pressure drop was found to increase linearly with the amount of dust load on the media, for all test conditions, while the starting pressure drop was found to be lower at the lowest sub-ambient pressure case. High filter efficiency was maintained after high particle loads on the media

Sub-ambient↗