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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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Case study of UAS ignition of prescribed fire in a mixedwood on the William B. Bankhead National Forest, Alabama

Abstract Background For at least four decades, practitioners have recognized advantages of aerial versus ground ignition for maximizing the effectiveness of prescribed fires. For example, larger areas can be ignited in less time, or ignition energy may be variously targeted over an area in accordance with the uneven distribution of fuels. The maturation of wireless communication, geopositioning systems, and unmanned aerial systems (UAS) has enhanced those advantages, and UAS approaches also provide further advantages relative to helicopter ignitions, such as reduced risk to human safety, lower operating costs, and higher operational flexibility. In a long running study at the Bankhead National Forest in northcentral Alabama, prescribed fire has been used for nearly 20 years. Most of the burns have been hand-ignited via drip torches, while some have been aerially ignited via helicopter. In March 2022, for the first time, a UAS was used to ignite prescribed fires across a landscape that included a long-term research stand. This field note relates comparisons of both fire behavior and fuel consumption metrics for the UAS-ignited burn versus previous burns on the same stand, and versus burns of other research stands in the same year. Results The UAS-ignited prescribed fire experienced burn effects similar to those from ground-ignited prescribed fires on the same stand in previous years, as well as those from ground-ignited prescribed fires on other stands in the same year. Conclusion This post hoc analysis suggests that UAS ignition approaches may be sufficient for achieving prescribed burn goals, thereby enabling practitioners to realize the advantages offered by that ignition mode.

Environmental Sciences & Ecology↗
NASA NTRS2017

Survey of Constellation-Era LOX/Methane Development Activities and Future Development Needs

NASA formed the Constellation Program in 2005 to achieve the objectives of maintaining American presence in low-Earth orbit, returning to the moon for purposes of establishing an outpost, and laying the foundation to explore Mars and beyond in the first half of the 21st century. The Exploration Technology Development Program (ETDP) was formulated to address the technology needs to address Constellation architecture decisions. The Propellants and Cryogenic Advanced Development (PCAD) project was tasked with risk mitigation of specific propulsion related technologies to support ETDP. Propulsion systems were identified as critical technologies owing to the high gear-ratio of lunar Mars landers Cryogenic propellants offer performance advantage over storables (NTOMMH) Mass savings translate to greater payload capacity In-situ production of propellant an attractive feature; methane and oxygen identified as possible Martian in-situ propellants New technologies were required to meet more difficult missions High performance LOX/LH2 deep throttle descent engines High performance LOX/LCH4 ascent main and reaction control system (RCS) engines The PCAD project sought to provide those technologies through Reliable ignition pulse RCS Fast start High efficiency engines Stable deep throttling.

Propulsion system components↗
NASA NTRS2026

Proactive Wildfire Management: A Remote Sensing and Multimodal CNN-MLP Architecture for Ignition Risk Forecasting

As the frequency and intensity of wildfires increase, with fire seasons now starting earlier and ending later than they have over the past decades, current monitoring systems, such as lookout towers and satellites, are hindered by cloud cover, low-resolution imagery, and static data gaps that fail to track vegetation moisture levels fast enough to catch rapid pre-ignition changes. This report proposes a Machine Learning-enabled Wildfire Ignition Prediction framework that combines satellite monitoring with dynamic and high-resolution remote sensing from Unmanned Aerial Vehicle (UAV) swarms. The method would use multispectral and thermal data from the Landsat program to create a baseline for vegetation health, calculating a two-band Enhanced Vegetation Index (EVI2) and the moisture content of the vegetation. These inputs will later be fused with microscale UAV weather data, including thermal hotspots found through thick canopies, hyperspectral chemical signatures of pre-visual combustion, and local weather streams. The multispectral satellite, multispectral Light Detection and Ranging (LiDAR), and thermal data would then be processed through a Convolutional Neural Network (CNN), alongside a Multilayer Perceptron (MLP) for the micro-weather telemetry. The outputs of these networks would be fused into a single feature representation and passed through a final prediction network to generate real-time ignition risk scores and hotspot alerts. Model performance would be assessed using standard classification metrics, including a Receiver Operating Characteristic - Area Under the Curve (ROC AUC) and F1 score. This system would allow first responders to identify high-risk zones and intervene before ignition occurs, improving emergency response time compared to current approaches.

machine learning↗
NASA NTRS1994

Laser Initiated Ordnance (LIO) activities in NASA

Laser initiated ordnance appears to offer the advantages of greater reliability, enhanced safety, lighter, less costly products, and improvements in spacecraft system designs which can lead to higher operational efficiency. But the lack of flight demonstrations has prevented the application of this new technology into new programs. Hence, a three-phase technology program was initiated by NASA to provide flight proof of their technical and programmatic feasibility: flight demonstration aboard an unmanned commercial vehicle (Pegasus), use as a Space Shuttle payload, and the most demanding of applications, namely, solid rocket motor vehicle ignition and flight termination. The programs investigate, via flight demonstrations the use of fully solid state laser diode systems to reduce potential hazards imposed by stray electrical signals. Inadvertent ignition has proven to cause serious problems. While the current electromechanical have been made safe, the result has been complex systems. Now is the time to take advantage of this new technology to further enhance safety and reliability of spacecraft systems. Two of the three phases are underway; an announcement of opportunity for the third, a sounding rocket flight demonstration, was made at the workshop.

Schulze, Norman R.↗
NASA NTRSDate not supplied

Fire Safety Implications of Preliminary Results from Saffire IV and V Experiments on Large Scale Spacecraft Fires

The spread and growth of flames over large solid fuel samples and their effect on the pressurized spacecraft were studied inside the Cygnus spacecraft while in orbit after departing the International Space Station. These experiments were developed by NASA’s Advanced Exploration Systems Division in the Human Exploration and Operations Mission Directorate. The ignited materials consisted of poly-methyl methacrylate (PMMA), cotton fabric and a cotton/fiberglass fabric blend. The samples were all 40 cm wide and with various lengths ranging from 18 cm for the PMMA samples to 50 cm for the fabrics. The overall results from these tests and their impact on the spacecraft are presented with emphasis on the fire safety implications of the results. The experiments included, a post-fire cleanup system, vehicle internal volume measurements, and transport of acid gases (HCl and HF). Measurements included video images, flame spread rate, flame temperatures and radiant heat output; energy release through oxygen calorimetry; distributed measurements of CO2 concentration and temperature at six locations in the spacecraft; CO2, CO, O2, HF and HCl concentrations; vehicle pressurized volume; and aerosol concentrations. Details of the flame growth and spread are discussed in other papers as are details of the post-fire cleanup system performance. The fire events had a measurable impact on the vehicle pressure, temperature, and carbon dioxide concentration. However, despite having heat release rates up to 10 kW, the average vehicle conditions did not rise to unacceptable levels. The combined results of the experiments provide significant new understanding of the impact of sample and flow duct height on flame spread and growth in addition to an improved perspective of the impact of a fire event on a spacecraft.

micorgravity↗
NASA NTRSDate not supplied

Fire Safety Implications of Preliminary Results from Saffire IV and V Experiments on Large Scale Spacecraft Fires

The spread and growth of flames over large solid fuel samples and their effect on the pressurized spacecraft were studied inside the Cygnus spacecraft while in orbit after departing the International Space Station. These experiments were developed by NASA’s Advanced Exploration Systems Division in the Human Exploration and Operations Mission Directorate. The ignited materials consisted of poly-methyl methacrylate (PMMA), cotton fabric and a cotton/fiberglass fabric blend. The samples were all 40 cm wide and with various lengths ranging from 18 cm for the PMMA samples to 50 cm for the fabrics. The overall results from these tests and their impact on the spacecraft are presented with emphasis on the fire safety implications of the results. The experiments included, a post-fire cleanup system, vehicle internal volume measurements, and transport of acid gases (HCl and HF). Measurements included video images, flame spread rate, flame temperatures and radiant heat output; energy release through oxygen calorimetry; distributed measurements of CO2 concentration and temperature at six locations in the spacecraft; CO2, CO, O2, HF and HCl concentrations; vehicle pressurized volume; and aerosol concentrations. Details of the flame growth and spread are discussed in other papers as are details of the post-fire cleanup system performance. The fire events had a measurable impact on the vehicle pressure, temperature, and carbon dioxide concentration. However, despite having heat release rates up to 10 kW, the average vehicle conditions did not rise to unacceptable levels. The combined results of the experiments provide significant new understanding of the impact of sample and flow duct height on flame spread and growth in addition to an improved perspective of the impact of a fire event on a spacecraft.

microgravity fire safety↗
NASA NTRS1986

Testing metals and alloys for use in oxygen systems

When oxygen is present in high concentrations or large quantities, as in oxygen-based life-support systems, the likelihood of combustion and the probable intensity of a conflagration increase, together with the severity of the damage caused. Even stainless steel will burn vigorously when ignited in a 1000-psi oxygen environment. The hazards involved in the use of oxygen increase with system operation at the elevated temperatures typical of propulsion systems. Fires in oxygen systems are generally catastrophic, causing a threat to life in manned vehicles. When mechanical components of a mechanism generate friction heat in the presence of oxygen, many commonly used metal alloys ignite and burn. Attention is presently given to frictional heating, particle impact, and flame propagation tests conducted in oxygen environments.

Stoltzfus, Joel M.↗
NASA NTRS2000

Some Notes on Sparks and Ignition of Fuels

This report compliments a concurrent analysis of the electromagnetic field threat to the fuel system of a transport aircraft. The accompanying effort assessed currents, voltages and power levels that may be induced upon fuel tank wiring from radio transmitters (inside and outside the aircraft). In addition to this, it was also essential to determine how much voltage, current, or power is required to create a fuel-vapor ignition hazard. The widely accepted minimum guideline for aircraft fuel-vapor ignition is the application of a 0.2 millijoule energy level. However, when considering radio frequency (RF) sources, this guideline is seriously inadequate. This report endeavors to bridge the gap between a traditional understanding of electrical breakdown, heating and combustion; and supplement the knowledge with available information regarding aircraft fuel-vapor ignition by RF sources

Fisher, Franklin A.↗
DOE OSTI2024

Skeletal reaction models for methane combustion

A local-sensitivity-analysis technique is employed to generate new skeletal reaction models for methane combustion from the foundational fuel chemistry model (FFCM-1). Here, the sensitivities of the thermo-chemical variables with respect to the reaction rates are computed via the forced-optimally time dependent (f-OTD) methodology. In this methodology, the large sensitivity matrix containing all local sensitivities is modeled as a product of two low-rank time-dependent matrices. The evolution equations of these matrices are derived from the governing equations of the system. The modeled sensitivities are computed for the auto-ignition of methane at atmospheric and high pressures with different sets of initial temperatures, and equivalence ratios. These sensitivities are then analyzed to rank the most important (sensitive) species. A series of skeletal models with different number of species and levels of accuracy in reproducing the FFCM-1 results are suggested. The performances of the generated models are compared against FFCM-1 in predicting the ignition delay, the laminar flame speed, and the flame extinction. The results of this comparative assessment suggest the skeletal models with 24 and more species generate the FFCM-1 results with an excellent accuracy.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1973

Thermokinetics and combustion phenomena in nonflowing gaseous systems - An invited review.

The current status of our understanding of combustion phenomena observed in nonflowing premixed gaseous systems is reviewed. The phenomena include slow oxidation, explosion, multiple ignition, oscillatory oxidation, as well as photolytic phenomena. Detailed experimental data on each of these phenomena are given, and analytical methods of analyzing them are outlined. The correlation between theory and experiment is studied for several special cases.

Berlad, A. L.↗
NASA NTRS1986

Investigation of beamed-energy ERH thruster performance

The objective of this study was to determine the performance of an External Radiation Heated (ERH) thruster. In this thruster, high intensity laser energy is focused to ignite either a Laser Supported Combustion (LSC) wave or a Laser Supported Detonation (LSD) wave. Thrust is generated as the LSC or LSD wave propagates over the thruster's surface, or in the proposed thruster configuration, the vehicle afterbody. Thrust models for the LSC and LSD waves were developed and simulated on a computer. Performance parameters investigated include the effect of laser intensity, flight Mach number, and altitude on mean-thrust and coupling coefficient of the ERH thruster. Results from these models suggest that the ERH thruster using LSC/LSD wave ignition could provide propulsion performance considerably greater than any propulsion system currently available.

Myrabo, Leik N.↗
NASA NTRS1988

Detailed mechanism of toluene oxidation and comparison with benzene

A detailed mechanism for the oxidation of toluene in both argon and nitrogen dilutents is presented. The mechanism was used to compute experimentally ignition delay times for shock-heated toluene-oxygen-argon mixtures with resonably good success over a wide range of initial temperatures and pressures. Attempts to compute experimentally measured concentration profiles for toluene oxidation in a turbulent reactor were partially successful. An extensive sensitivity analysis was performed to determine the reactions which control the ignition process and the rates of formation and destruction of various species. The most important step was found to be the reaction of toluene with molecular oxygen, followed by the reactions of hydroperoxyl and atomic oxygen with benzyl radicals. These findings contrast with the benzene oxidation, where the benzene-molecular oxygen reaction is quite unimportant and the reaction of phenyl with molecular oxygen dominates. In the toluene mechanism the corresponding reaction of benzyl radicals with oxygen is unimportant. Two reactions which are important in the oxidation of benzene also influence the oxidation of toluene for several conditions. These are the oxidations of phenyl and cyclopentadienyl radicals by molecular oxygen. The mechanism presented successfully computes the decrease of toluene concentration with time in the nitrogen diluted turbulent reactor. This fact, in addition to the good prediction of ignition delay times, shows that this mechanism can be used for modeling the ignition and combustion process in practical, well-mixed combustion systems.

Bittker, David A.↗
NASA NTRS1989

Hybrid propulsion technology program: Phase 1, volume 1

A number of booster propulsion system concepts are being considered for the next generation of manned and unmanned space launch vehicles. The one propulsion system concept that has potential for reducing costs with increased safety, reliability, and performance is hybrid propulsion (HP). A HP system may be thought of as a liquid propulsion system with solid fuel or a solid propulsion system with a liquid oxidizer. The liquid propulsion features that are most attractive are the higher specific impulse, clean exhaust, separated propellants, and oxidizer loading just prior to launch. The most attractive solid propulsion features includes low life cycle costs, no rotating machinery, compact size, and a robust case. In addition, a HP system has a robust LO2 tank; provides thrust control for ignition, to alleviate flight loads, and for thrust termination; and uses an inert grain that is not sensitive to anomalies such as cracks, voids, and separations. The object is to develop the technology to enable the application of HP to manned and unmanned space launch vehicles. This program will identify the necessary technology, acquire that technology, and demonstrate that technology. This volume is the executive summary.

Schuler, A. L.↗
NASA NTRS2006

A non-PRE double-peaked burst with oscillations: burning front propagation and stalling

Non-photospheric-radius-expansion (non-PRE) double-peaked bursts may be explained in terms of spreading (and temporary stalling) of thermonuclear flames from a rotational pole on the neutron star surface, as we argued in a previous study. Here we analyze Rossi X-ray Timing Explorer (RXTE) Proportional Counter Array (PCA) data of such a burst from the low mass X-ray binary (LMXB) system 4U 1636-536, and show that our model (with ignition at high latitudes) can qualitatively explain the observed burst profile, and spectral evolution. Moreover, the evolution of the source radius inferred from the data shows a strong signature of temporary stalling of the burning front, which is an essential ingredient of our model. This implies that an understanding of thermonuclear flame spreading on neutron stars can be achieved by a simultaneous study of the evolution of intensity and spectrum of these bursts. We also report the discovery of millisecond period brightness oscillations from this burst, which is the first such observation from a non-PRE double-peaked burst. Our model can explain the corresponding oscillation amplitude during the first (weaker) peak, and the absence of oscillations during the second peak. We discuss how observations of oscillations during non-PRE double-peaked bursts provide an additional t 001 for understanding thermonuclear flame spreading successfully.

Bhattacharyya, Sudip↗
NASA NTRSDate not supplied

Test Capabilities of the NASA Langley Direct Connect Supersonic Combustion Test Facility with Historical Perspective

In 1969, a combustion-heated direct-connect test facility was assembled at the NASA Langley Research Center to conduct basic research in ramjet and scramjet propulsion systems. The facility was initially used in assessing the mixing, ignition, flame holding, and combustion characteristics of various ramjet and scramjet combustors. Over the years, the facility was updated and modified to conduct increasingly longer and more complicated tests. Today, the facility is known as the Direct Connect Supersonic Combustion Test Facility and is part of the NASA Langley Scramjet Test Complex. More recently, the facility has been used by external customers to test fuel-cooled and uncooled, flight-like test articles. Tests have been conducted at ramjet flight conditions for up to 15 minutes of continuous operation. Even though the facility is nearly 50 years old, it remains a viable and useful tool in the support of various U.S. hypersonic programs.

direct connect test facility↗
NASA NTRS2014

Morpheus Vertical Test Bed Flight Testing

NASA's Morpheus Project has developed and tested a prototype planetary lander capable of vertical takeoff and landing, that is designed to serve as a testbed for advanced spacecraft technologies. The lander vehicle, propelled by a LOX/Methane engine and sized to carry a 500kg payload to the lunar surface, provides a platform for bringing technologies from the laboratory into an integrated flight system at relatively low cost. Morpheus onboard software is autonomous from ignition all the way through landing, and is designed to be capable of executing a variety of flight trajectories, with onboard fault checks and automatic contingency responses. The Morpheus 1.5A vehicle performed 26 integrated vehicle test flights including hot-fire tests, tethered tests, and two attempted freeflights between April 2011 and August 2012. The final flight of Morpheus 1.5A resulted in a loss of the vehicle. In September 2012, development began on the Morpheus 1.5B vehicle, which subsequently followed a similar test campaign culminating in free-flights at a simulated planetary landscape built at Kennedy Space Center's Shuttle Landing Facility. This paper describes the integrated test campaign, including successes and setbacks, and how the system design for handling faults and failures evolved over the course of the project.

Hart, Jeremy↗
DOE OSTI2025

Direct Experimental Proof of the Principal Role of Reduced High-Mode Hydrodynamic Mix in Recent Ignition Success on NIF

This Letter details the role of reduced hydrodynamic mix in achieving the first fusion plasma to satisfy the Lawson criterion for ignition. Using novel 3D measurements of the temperature and density of the burning deuterium-tritium plasma across a series of experiments, we demonstrate that hydrodynamic mixing from small-scale capsule defects was a key degradation mechanism inhibiting ignition. A series of five layered deuterium-tritium experiments using 1.9 MJ of laser energy demonstrates a 2 × reduction of the thermonuclear yield when a lower quality capsule, typical of preignition experiments, is used. Radiation hydrodynamic calculations consistent with the observed mix profile show that the mixed fuel’s reduced compression and increased radiative loss explain the yield reduction. Furthermore, a hydroscaling argument suggests that a ∼ 3 MJ laser would be needed to reach ignition with such a capsule, well beyond the current capabilities of high energy laser systems. As such, this Letter gives critical insight into the physics of mix in self-heated fusion plasmas and establishes a foundation to evaluate capsule quality needs of future inertial fusion designs that aim at ignition and high gain.

High-energy-density plasmas↗