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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS2017

Apparatus for Controlling Low Power Voltages in Space Based Processing Systems

A low power voltage control circuit for use in space missions includes a switching device coupled between an input voltage and an output voltage. The switching device includes a control input coupled to an enable signal, wherein the control input is configured to selectively turn the output voltage on or off based at least in part on the enable signal. A current monitoring circuit is coupled to the output voltage and configured to produce a trip signal, wherein the trip signal is active when a load current flowing through the switching device is determined to exceed a predetermined threshold and is inactive otherwise. The power voltage control circuit is constructed of space qualified components.

Petrick, David J.↗
NASA NTRS1973

Parametric investigation of enclosed keeper discharge characteristics

Volt-ampere discharge characteristics of an enclosed keeper hollow cathode discharge were measured as a function of the mercury flow rate and external circuit impedance. Discharge currents were varied from 0 to 1 ampere and voltages were 7 to 39 volts. Batteries and a vacuum tube control circuit were used to obtain characteristics curves that were independent of power supply impedance. Variation of the neutral flow results in changes in the discharge which interact with the impedance of the external circuit, and under some conditions, give rise to multiple operating points.

Sheheen, T. W.↗
NASA NTRS2018

Modeling and Control Design for a Turboelectric Single Aisle Aircraft Propulsion System

A nonlinear dynamic model with full flight envelope controller is developed for the propulsion system of a partially turboelectric single-aisle aircraft. The propulsion system model consists of two turbofan engines with a large percentage of power extraction, feeding an electric tail fan for boundary layer ingestion. The dynamic model is compared against an existing steady state design model. An electrical system model using a simple power flow approach is integrated into existing modeling tools used for dynamic simulation of the turbomachinery of the vehicle. In addition to the simple power flow model of the electrical system, a more detailed model is used for comparison at a key vehicle transient flight condition. The controller is a gain scheduled proportional-integral type that is examined throughout the flight envelope for performance metrics such as rise time and operability margins. Potential improvements in efficiency for the vehicle are explored by adjusting the power split between the energy used for thrust by the turbofans and that extracted to supply power to the tail fan. Finally, an operability study of the vehicle is conducted using a 900 nautical mile mission profile for a nominal vehicle configuration, a deteriorated propulsion system at the end of its operating life, and an optimized power schedule with improved efficiency.

Turboelectric↗
NASA NTRS2009

Development Status of the Carbon Dioxide and Moisture Removal Amine Swing-Bed System (CAMRAS)

Under a cooperative agreement with NASA, Hamilton Sundstrand has successfully designed, fabricated, tested and delivered three, state-of-the-art, solid amine prototype systems capable of continuous CO2 and humidity removal from a closed, habitable atmosphere. Two prototype systems (CAMRAS #1 and #2) incorporated a linear spool valve design for process flow control through the sorbent beds, with the third system (CAMRAS #3) employing a rotary valve assembly that improves system fluid interfaces and regeneration capabilities. The operational performance of CAMRAS #1 and #2 has been validated in a relevant environment, through both simulated human metabolic loads in a closed chamber and through human subject testing in a closed environment. Performance testing at Hamilton Sundstrand on CAMRAS #3, which incorporates a new valve and modified canister design, showed similar CO2 and humidity removal performance as CAMRAS #1 and #2, demonstrating that the system form can be modified within certain bounds with little to no effect in system function or performance. Demonstration of solid amine based CO2 and humidity control is an important milestone in developing this technology for human spaceflight. The systems have low power requirements; with power for air flow and periodic valve actuation and indication the sole requirements. Each system occupies the same space as roughly four shuttle non-regenerative LiOH canisters, but have essentially indefinite CO2 removal endurance provided a regeneration pathway is available. Using the solid amine based systems to control cabin humidity also eliminates the latent heat burden on cabin thermal control systems and the need for gas/liquid phase separation in a low gravity environment, resulting in additional simplification of vehicle environmental control and life support system process requirements.

Papale, William↗
NASA NTRS2014

Novel Active Combustion Control Valve

This project presents an innovative solution for active combustion control. Relative to the state of the art, this concept provides frequency modulation (greater than 1,000 Hz) in combination with high-amplitude modulation (in excess of 30 percent flow) and can be adapted to a large range of fuel injector sizes. Existing valves often have low flow modulation strength. To achieve higher flow modulation requires excessively large valves or too much electrical power to be practical. This active combustion control valve (ACCV) has high-frequency and -amplitude modulation, consumes low electrical power, is closely coupled with the fuel injector for modulation strength, and is practical in size and weight. By mitigating combustion instabilities at higher frequencies than have been previously achieved (approximately 1,000 Hz), this new technology enables gas turbines to run at operating points that produce lower emissions and higher performance.

Caspermeyer, Matt↗
NASA NTRS1992

Subsonic flight test evaluation of a performance seeking control algorithm on an F-15 airplane

The subsonic flight test evaluation phase of the NASA F-15 (powered by F 100 engines) performance seeking control program was completed for single-engine operation at part- and military-power settings. The subsonic performance seeking control algorithm optimizes the quasi-steady-state performance of the propulsion system for three modes of operation. The minimum fuel flow mode minimizes fuel consumption. The minimum thrust mode maximizes thrust at military power. Decreases in thrust-specific fuel consumption of 1 to 2 percent were measured in the minimum fuel flow mode; these fuel savings are significant, especially for supersonic cruise aircraft. Decreases of up to approximately 100 degree R in fan turbine inlet temperature were measured in the minimum temperature mode. Temperature reductions of this magnitude would more than double turbine life if inlet temperature was the only life factor. Measured thrust increases of up to approximately 15 percent in the maximum thrust mode cause substantial increases in aircraft acceleration. The system dynamics of the closed-loop algorithm operation were good. The subsonic flight phase has validated the performance seeking control technology, which can significantly benefit the next generation of fighter and transport aircraft.

Gilyard, Glenn B.↗
NASA NTRS1992

Method and apparatus for minimizing multiple degree of freedom vibration transmission between two regions of a structure

Arrays of actuators are affixed to structural elements to impede the transmission of vibrational energy. A single pair is used to provide control of bending and extensional waves and two pairs are used to control torsional motion. The arrays are applied to a wide variety of structural elements such as a beam structure that is part of a larger framework that may or may not support a rigid or non-rigid skin. Electrical excitation is applied to the actuators that generate forces on the structure. These electrical inputs may be adjusted in their amplitude and phase by a controller in communication with appropriate vibrational wave sensors to impede the flow of vibrational power in all of the above mentioned wave forms beyond the actuator location. Additional sensor elements can be used to monitor the performance and adjust the electrical inputs to maximize the attenuation of vibrational energy.

Silcox, Richard J.↗
NASA NTRS2014

Development and Experimental Evaluation of Passive Fuel Cell Thermal Control

To provide uniform cooling for a fuel cell stack, a cooling plate concept was evaluated. This concept utilized thin cooling plates to extract heat from the interior of a fuel cell stack and move this heat to a cooling manifold where it can be transferred to an external cooling fluid. The advantages of this cooling approach include a reduced number of ancillary components and the ability to directly utilize an external cooling fluid loop for cooling the fuel cell stack. A number of different types of cooling plates and manifolds were developed. The cooling plates consisted of two main types; a plate based on thermopyrolytic graphite (TPG) and a planar (or flat plate) heat pipe. The plates, along with solid metal control samples, were tested for both thermal and electrical conductivity. To transfer heat from the cooling plates to the cooling fluid, a number of manifold designs utilizing various materials were devised, constructed, and tested. A key aspect of the manifold was that it had to be electrically nonconductive so it would not short out the fuel cell stack during operation. Different manifold and cooling plate configurations were tested in a vacuum chamber to minimize convective heat losses. Cooling plates were placed in the grooves within the manifolds and heated with surface-mounted electric pad heaters. The plate temperature and its thermal distribution were recorded for all tested combinations of manifold cooling flow rates and heater power loads. This testing simulated the performance of the cooling plates and manifold within an operational fuel cell stack. Different types of control valves and control schemes were tested and evaluated based on their ability to maintain a constant temperature of the cooling plates. The control valves regulated the cooling fluid flow through the manifold, thereby controlling the heat flow to the cooling fluid. Through this work, a cooling plate and manifold system was developed that could maintain the cooling plates within a minimal temperature band with negligible thermal gradients over power profiles that would be experienced within an operating fuel cell stack.

Fuel Cells↗
NASA NTRS2004

Investigation of Injector Slot Geometry on Curved-Diffuser Aerodynamic Performance

The Compressor Branch vision is to be recognized as world-class leaders in research for fluid mechanics of compressors. Its mission is to conduct research and develop technology to advance the state of the art of compressors and transfer new technology to U.S. industries. Maintain partnerships with U.S. industries, universities, and other government organizations. Maintain a balance between customers focused and long range research. Flow control comprises enabling technologies to meet compression system performance requirements driven by emissions and fuel reduction goals (e.g., in UEET), missions (e.g., access-to-space), aerodynamically aggressive vehicle configurations (e.g., UAV and future blended wing body configurations with highly distorted inlets), and cost goals (e.g., in VAATE). The compression system requirements include increased efficiency, power-to-weight, and adaptability (i.e., robustness in terms of wide operability, distortion tolerance, and engine system health and reliability). The compressor flow control task comprises efforts to develop, demonstrate, and transfer adaptive flow control technology to industry to increase aerodynamic loading at current blade row loss levels, to enable adaptive1 y wide operability, and to develop plant models for adaptive compression systems. In this context, flow control is the controlled modification of a flow field by a deliberate means beyond the natural (uncontrolled) shaping of the solid surfaces that define the principal flow path. The objective of the compressor flow control task is to develop and apply techniques that control circulation, aerodynamic blockage, and entropy production in order to enhance the performance and operability of compression systems for advanced aero-propulsion applications. This summer I would be working with a curved-diffuser because it simulates what happens with flow in the stator blades in the compressor. With this experiment I will be doing some data analysis and parametric study of the injector slot geometries to get the best aerodynamic performance of it. This includes some data reduction, redesign and fast prototyping of the injector nozzle.

Silva, Odlanier↗
NASA NTRS1989

Noise generated by a flight weight, air flow control valve in a vertical takeoff and landing aircraft thrust vectoring system

Tests were conducted in the NASA Lewis Research Center's Powered Lift Facility to experimentally evaluate the noise generated by a flight weight, 12 in. butterfly valve installed in a proposed vertical takeoff and landing thrust vectoring system. Fluctuating pressure measurements were made in the circular duct upstream and downstream of the valve. This data report presents the results of these tests. The maximum overall sound pressure level is generated in the duct downstream of the valve and reached a value of 180 dB at a valve pressure ratio of 2.8. At the higher valve pressure ratios the spectra downstream of the valve is broad banded with its maximum at 1000 Hz.

Huff, Ronald G.↗
NASA NTRS2005

Drive Motor Improved for 8- by 6-Foot Supersonic Wind Tunnel/9- by 15-Foot Low-Speed Wind Tunnel Complex

An operational change made recently in the drive motor system for the 8- by 6-Foot Supersonic Wind Tunnel (8x6 SWT)/9- by 15-Foot Low-Speed Wind Tunnel (9x15 LSWT) complex resulted in dramatic power savings and expanded operating range. The 8x6 SWT/9x15 LSWT complex offers a unique combination of wind tunnel conditions for both high- and low-speed testing. Prior to the work discussed in this article, the 8- by 6-ft test section offered airflows ranging from Mach 0.36 to 2.0. Subsonic testing was done in the 9-ft high, 15-ft wide test area in the return leg of the facility. The air speed in this test section can range from 0 to 175 mph (Mach 0.23). In the past, we varied the air speed by using a combination of the compressor speed and the position of the tunnel flow-control doors. When very slow speeds were required in the 9x15 LSWT, these large tunnel flow control doors might be very nearly full open, bleeding off large quantities of air, even with the drive system operating at its previous minimum speed of about 510 rpm. Power drawn during this mode of operation varied between 15 and 18 MW/hr, but clearly much of this power was not being used to provide air that would be used for testing in the test section. The air exiting these large doors represented wasted power. Early this year, the facility's tunnel drive system was run on one motor instead of three to see if lower drive speeds could be achieved that would, in turn, result in large power savings because unnecessary air would not be blown out of the flow-control doors unnecessarily. In addition, if the drive could be run slower, then slower speeds would also be possible in the 8x6 SWT test section as an added benefit. Results of the first tests performed early last year showed that in fact the drive, when operating on only one motor, actually reached a steady-state speed of only 337 rpm and drew an amazingly small 6 MW/hr of electrical power. During daytime operation of the drive, this meant that it would be possible to save as much as 10 MW/hr, or nearly $600 per hour of operation, for many of the 9x15 LSWT's testing regimes. An added benefit of this power-saving venture was that since the 8x6 SWT and 9x15 LSWT are indeed on a common loop, if the compressor is slowed down to benefit the 9x15 LSWT, then the air moving through the 8x6 SWT is also moving slower than ever before. In fact, testing has proven that the 8x6 SWT can now achieve Mach 0.25, whereas its previous lower limit was Mach 0.36. This added benefit has attracted additional customers

Source record↗
NASA NTRS2010

The Evolution of Utilizing Manual Throttling to Avoid Excessively Low LH2 NPSP at the SSME Inlet

In the late 1970s, years before the Space Shuttle flew its maiden voyage, it was understood low liquid hydrogen (LH2) Net Positive Suction Pressure (NPSP) at the inlet to the Space Shuttle Main Engine (SSME) could have adverse effects on engine operation. A number of failures within both the External Tank (ET) and the Orbiter Main Propulsion System (MPS) could result in a low LH2 NPSP condition, which at extremely low levels can result in cavitation of SSME turbomachinery. Operational workarounds were developed to take advantage of the onboard crew s ability to manually throttle down the SSMEs (via the Pilot s Speedbrake/Throttle Controller), which alleviated the low LH2 NPSP condition. Manually throttling the SSME to a lower power level resulted in an increase in NPSP, mainly due to the reduction in frictional flow losses while at the lower throttle setting. Early in the Space Shuttle Program s history, the relevant Flight Rule for the Booster flight controller in Mission Control did not distinguish between ET and Orbiter MPS failures and the same crew action was taken for both. However, after a review of all Booster operational techniques following the Challenger disaster in the late 1980s, it was determined manually throttling the SSME to a lower power was only effective for Orbiter MPS failures and the Flight Rule was updated to reflect this change. The Flight Rule and associated crew actions initially called for a single throttle step to minimum power level when a low threshold for NPSP was met. As engineers refined their understanding of the NPSP requirements for the SSME (through a robust testing program), the operational techniques evolved to take advantage of the additional capabilities. This paper will examine the evolution of the Flight rule and associated procedure and how increases in knowledge about the SSME and the Space Shuttle vehicle as a whole have helped shape their development. What once was a single throttle step when NPSP decreased to a certain low threshold has now become three throttle steps, each occurring at a lower NPSP threshold. Additionally the procedure, which for early Space Shuttle missions required a Return-to-Launch-Site abort, now results in a nominal Main Engine Cut Off and no loss of mission objectives.

Henfling, Rick↗
NASA NTRS2011

The Evolution of Utilizing Manual Throttles to Avoid Excessively Low LH2 NPSP at the SSME Inlet

In the late 1970s, years before the Space Shuttle flew its maiden voyage, it was understood low liquid hydrogen (LH2) Net Positive Suction Pressure (NPSP) at the inlet to the Space Shuttle Main Engine (SSME) could have adverse effects on engine operation. A number of failures within both the External Tank (ET) and the Orbiter Main Propulsion System (MPS) could result in a low LH2 NPSP condition, which at extremely low levels can result in cavitation of SSME turbomachinery. Operational workarounds were developed to take advantage of the onboard crew s ability to manually throttle down the SSMEs (via the Pilot s Speedbrake/Throttle Controller), which alleviated the low LH2 NPSP condition. Manually throttling the SSME to a lower power level resulted in an increase in NPSP, mainly due to the reduction in frictional flow losses while at the lower throttle setting. Early in the Space Shuttle Program s history, the relevant Flight Rule for the Booster flight controllers in Mission Control did not distinguish between ET and Orbiter MPS failures and the same crew action was taken for both. However, after a review of all Booster operational techniques following the Challenger disaster in the late 1980s, it was determined manually throttling the SSME to a lower power was only effective for Orbiter MPS failures and the Flight Rule was updated to reflect this change. The Flight Rule and associated crew actions initially called for a single throttle step to minimum power level when a low threshold for NPSP was met. As engineers refined their understanding of the NPSP requirements for the SSME (through a robust testing program), the operational techniques evolved to take advantage of the additional capabilities. This paper will examine the evolution of the Flight rule and associated procedure and how increases in knowledge about the SSME and the Space Shuttle vehicle as a whole have helped shape their development. What once was a single throttle step when NPSP decreased to a certain threshold has now become three throttle steps, each occurring at a lower NPSP threshold. Additionally the procedure, which for early Space Shuttle missions required a Return-to-Launch-Site abort, now results in a nominal Main Engine Cut Off and no loss of mission objectives.

Henfling, Rick↗
NASA NTRS2003

Magnetogasdynamic Power Extraction and Flow Conditioning for a Gas Turbine

An extension of the Russian AJAX concept to a turbojet is being explored. This magnetohydrodynamic (MHD) energy bypass engine cycle incorporating conventional gas turbine technology has MHD flow conditioning at the inlet to electromagnetically extract part of the inlet air kinetic energy. The electrical power generated can be used for various on-board vehicle requirements including plasma flow control around the vehicle or it may be used for augmenting the expanding flow in the high speed nozzle by MHD forces to generate more thrust. In order to achieve this interaction, the air needs to be ionized by an external means even up to fairly high flight speeds, and the leading candidates may be classified as electrical discharge devices. The present kinetic modeling calculations suggest that the use of electron beams with characteristics close to the commercially available e-beam systems (electron energy approx. 60 keV, beam current approx. 0.2 mA/sq cm) to sustain ionization in intermediate pressure, low-temperature (P = 0.1 atm, T = 300 K) supersonic air flows allows considerable reduction of the flow kinetic energy (up to 10 to 20 percent in M = 3 flows). The calculations also suggest that this can be achieved at a reasonable electron beam efficiency (eta approx. 5), even if the e-beam window losses are taken into account. At these conditions, the exit NO and O atom concentrations due to e-beam initiated chemical reactions do not exceed 30 ppm. Increasing the beam current up to approx. 2 mA/sq cm, which corresponds to a maximum electrical conductivity of sigma(sub max) approx. 0.8 mho/m at the loading parameter of K = 0.5, would result in a much greater reduction of the flow kinetic energy (up to 30 to 40 percent). The MHD channel efficiency at these conditions would be greatly reduced (to eta approx. 1) due to increased electron recombination losses in the channel. At these conditions, partial energy conversion from kinetic energy to heat would result in a significant total pressure loss (P(sub 0)/P(sub 0i) approx. 0.3). The total pressure loss can be reduced operating at the loading parameter closer to unity, at the expense of the reduced electrical power output. Raising the beam current would also result in the increase of the exit O atom concentrations (up to 600 ppm) and NO (up to 150 ppm).

Adamovich, Igor V.↗
NASA NTRS2011

Assessment of the Use of Nanofluids in Spacecraft Active Thermal Control Systems

The addition of metallic nanoparticles to a base heat transfer fluid can dramatically increase its thermal conductivity. These nanofluids have been shown to have advantages in some heat transport systems. Their enhanced properties can allow lower system volumetric flow rates and can reduce the required pumping power. Nanofluids have been suggested for use as working fluids for spacecraft Active Thermal Control Systems (ATCSs). However, there are no studies showing the end-to-end effect of nanofluids on the design and performance of spacecraft ATCSs. In the present work, a parametric study is performed to assess the use of nanofluids in a spacecraft ATCSs. The design parameters of the current Orion capsule and the tabulated thermophysical properties of nanofluids are used to assess the possible benefits of nanofluids and how their incorporation affects the overall design of a spacecraft ATCS. The study shows that the unique system and component-level design parameters of spacecraft ATCSs render them best suited for pure working fluids. The addition of nanoparticles to typical spacecraft thermal control working fluids actually results in an increase in the system mass and required pumping power.

Ungar, Eugene K.↗
NASA NTRS1983

Measuring Power Flow in Electric Vehicles

Instrument accommodates fast rise and fall times of waveforms characteristic of modern, efficient power controllers. Power meter multiplies analog signals proportional to voltage and current, and converts resulting signal to frequency. Two mechanical counters provided: one for charging, one for discharging.

Griffin, Daniel C., Jr↗
NASA NTRS1994

YAV-8B reaction control system bleed and control power usage in hover and transition

Using a calibrated Rolls-Royce Pegasus engine and existing aircraft instrumentation and pressure taps, total and individual nozzle reaction control system (RCS) bleed flow rates have been measured on a YAV-8B Harrier during typical short takeoff, transition, hover, and vertical landing maneuvers. RCS thrust forces were calculated from RCS nozzle total pressure measurements, and control power was determined from the moments produced by these thrusts and the aircraft's moments of inertia. These data document the characteristics of the YAV-8B RCS with its basic stability augmentation system (SAS) engaged. Advanced control system designs for the YAV-8B can be compared to the original SAS based on the total bleed use and the percentage of available bleed used. In addition, the peak and mean values of the bleed and control power data can be used for sizing the reaction controls for a future short takeoff and vertical landing (STOVL) aircraft.

Borchers, Paul F.↗