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Results for “Fuel Fragmentation”

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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

Imaging Fluorescent Combustion Species in Gas Turbine Flame Tubes: On Complexities in Real Systems

Planar laser-induced fluorescence (PLIF) is used to visualize the flame structure via OH, NO, and fuel imaging in kerosene- burning gas turbine combustor flame tubes. When compared to simple gaseous hydrocarbon flames and hydrogen flames, flame tube testing complexities include spectral interferences from large fuel fragments, unknown turbulence interactions, high pressure operation, and the concomitant need for windows and remote operation. Complications of these and other factors as they apply to image analysis are considered. Because both OH and gas turbine engine fuels (commercial and military) can be excited and detected using OH transition lines, a narrowband and a broadband detection scheme are compared and the benefits and drawbacks of each method are examined.

Hicks, Y. R.↗
NASA NTRS2017

NASA's Ground-Based Observing Campaigns of Rocket Bodies with the UKIRT and NASA ES-MCAT Telescopes

Rocket bodies comprise a class of human-made space debris that are at the same time essential for launching every spacecraft from the Earth, but are also a significant source of debris both as intact objects, as well as fragmented debris. Unspent fuel has been long theorized as a potential cause of catastrophic rocket body break-ups. Given typical orbital speeds range from approximately 2-3 kilometers per second at Geosynchronous Orbit (GEO) and up to 15 kilometers per second in low Earth orbit (LEO), collisions with uncatalogued and undetected debris can also cause catastrophic breakups. Understanding break-ups is a necessary step in preventing them, and one key step in that process is to correlate and characterize daughter fragments with their parent bodies. Two very different methods include (1) conducting photometric surveys to correlate an object's motion and orbital elements to the parent body, and (2) characterizing what materials comprise the target to determine whether those materials are consistent with the parent body or like objects. With this in mind, photometric data were taken shortly after the breakup of one rocket body for short-term orbital studies, and a suite of spectral data were taken of rocket bodies that are fully intact to compare with debris, for characterization studies. Targets included Titan Transtage, Briz-M, and Ariane rocket bodies and debris. Spectra of each sub-class of rocket body were very similar within their rocket body type, but differed distinctly from one type to the next, supporting the effectiveness of this approach.

Lederer, Susan M.↗
NASA NTRS1982

Holographic studies of the vapor explosion of vaporizing water-in-fuel emulsion droplets

Holographic studies were performed which examined the fragmentation process during vapor explosion of a water-in-fuel (hexadecane/water) emulsion droplet. Holograms were taken at 700 to 1000 microseconds after the vapor explosion. Photographs of the reconstructed holograms reveal a wide range of fragment droplet sizes created during the explosion process. Fragment droplet diameters range from below 10 microns to over 100 microns. It is estimated that between ten thousand and a million fragment droplets can result from this extremely violent vapor explosion process. This enhanced atomization is thus expected to have a pronounced effect on vaporization processes which are present during combustion of emulsified fuels.

Sheffield, S. A.↗
NASA NTRS1978

Gaseous fuel reactors for power systems

The Los Alamos Scientific Laboratory is participating in a NASA-sponsored program to demonstrate the feasibility of a gaseous uranium fueled reactor. The work is aimed at acquiring experimental and theoretical information for the design of a prototype plasma core reactor which will test heat removal by optical radiation. The basic goal of this work is for space applications, however, other NASA-sponsored work suggests several attractive applications to help meet earth-bound energy needs. Such potential benefits are: small critical mass, on-site fuel processing, high fuel burnup, low fission fragment inventory in reactor core, high temperature for process heat, optical radiation for photochemistry and space power transmission, and high temperature for advanced propulsion systems.

Helmick, H. H.↗
NASA NTRS1993

Probabilistic simulation of fragment dynamics and their surface impacts in the SSME turbopump

Numerical simulations are used to model the dynamics of solid fragments in the high pressure fuel turbopump of the space shuttle main engine (SSME HPFTP). The simulations are conducted in a probabilistic structure in order to simulate the variance in the geometrical configuration, material properties and initial conditions of the solid fragments. The results of the particle dynamics simulations are presented in the form of the probability of surface impacts, and probability distributions of the impacting velocity and impingement angle.

Hamed, A.↗
NASA NTRS1991

Radioactive satellites - Intact reentry and breakup by debris impact

There is a substantial mass of radioactive material in nuclear reactors or radioisotope thermal generators (RTGs) in orbit about the earth. This paper examines the reentry of intact nuclear fuel cores and RTGs and the fragmentation and subsequent radioactive debris cloud deposition and evolution resulting from the impact of orbital debris upon an orbiting reactor, fuel core, or RTG. To assess the intact reentry, decay rates and a predicted decay date using historical and projected orbital decay data, are estimated. The current NASA debris environment model is utilized to estimate impact rates and debris cloud evolution of a fragmentation event. Results of these analyses are compared and concepts are tendered which would tend to minimize the radiological debris hazard to personnel and structures both on the earth's surface and in low earth orbit.

Anz-Meador, P. D.↗
NASA NTRS1991

Probabilistic simulation of fragment dynamics and their surface impacts in the SSME turbopump

Numerical simulations are used to model the dynamics of solid fragments in the high-pressure fuel turbopump of the Space Shuttle Main Engine (SSME HPFTP). The simulations are conducted in a probabilistic structure in order to simulate the variance in the geometrical configuration, material properties and initial conditions of the solid fragments. The results of the particle dynamics simulations are presented in the form of the probability of surface impacts, and probability distributions of the impacting velocity and impingement angle.

Hamed, A.↗
NASA NTRS1992

Optimization of armored spherical tanks for storage on the lunar surface

A redundancy strategy for reducing micrometeroid armoring mass is investigated, with application to cryogenic reactant storage for a regenerative fuel cell (RFC) on the lunar surface. In that micrometeoroid environment, the cryogenic fuel must be protected from loss due to tank puncture. The tankage must have a sufficiently high probability of survival over the length of the mission so that the probability of system failure due to tank puncture is low compared to the other mission risk factors. Assuming that a single meteoroid penetration can cause a storage tank to lose its contents, two means are available to raise the probability of surviving micrometeoroid attack to the desired level. One can armor the tanks to a thickness sufficient to reduce probability of penetration of any tank to the desired level or add extra capacity in the form of spare tanks that results in survival of a given number out of the ensemble at the desired level. A combination of these strategies (armoring and redundancy) is investigated. The objective is to find the optimum combination which yields the lowest shielding mass per cubic meter of surviving fuel out of the original ensemble. The investigation found that, for the volumes of fuel associated with multikilowatt class cryo storage RFC's, and the armoring methodology and meteoroid models used, storage should be fragmented into small individual tanks. Larger installations (more fuel) pay less of a shielding penalty than small installations. For the same survival probability over the same time period, larger volumes will require less armoring mass per unit volume protected.

Bents, D. J.↗
NASA NTRS1991

On the effect of grain burnback on STS-SRM fragment velocity

Concerns raised during the Ulysses Final Safety Analysis Review (FSAR) process called the solid rocket motor (SRM) fragment velocity prediction model into question. The specific area of concern was that there was a section of the SRM casing which was exposed to SRM chamber pressure as the grain (fuel) was consumed. These questions centered on the velocity of fragments which originated from the field joint region given that failure occurred between 37 and 72 seconds mission elapsed time (MET). Two dimensional coupled Eulerian-Lagrangian calculations were performed to assess the hot gas flow field which resulted from SRM casing fragmentation. The fragment to gas interface-pressure time-history obtained from these analyses was reduced to a boundary condition algorithm which was applied to an explicit-time-integration, finite element, three dimensional shell model of the SRM casing and unburned fuel. The results of these calculations showed that the velocity of fragments originating in the field joint was adequately described by the range of velocities given in the Shuttle Data Book (1988). Based on these results, no further analyses were required, and approval was obtained from the Launch Abort Subpanel of the Interagency Nuclear Safety Review Panel to use the SRM fragment velocity environments presented in the Ulysses FSAR (1990).

Eck, Marshall B.↗
NASA NTRS1989

Albedo estimates for debris

The albedo of upper-stage breakup debris is proposed as an accurate discriminator among the various possible causes of breakup, which encompass residual fuel explosions and hypervelocity particle impacts. The fragments from an impact are covered with a thin layer of soot deposited from the destruction of polymeric circuit boards, while pressure vessel explosion fragments can be expected to remain soot-free. Albedo also facilitates the interpretation of small-debris optical telescope measurements.

Potter, A. E.↗
NASA NTRS1977

Gaseous fuel reactor systems for aerospace applications

Research on the gaseous fuel nuclear rocket concept continues under the programs of the U.S. National Aeronautics and Space Administration (NASA) Office for Aeronautics and Space Technology and now includes work related to power applications in space and on earth. In a cavity reactor test series, initial experiments confirmed the low critical mass determined from reactor physics calculations. Recent work with flowing UF6 fuel indicates stable operation at increased power levels. Preliminary design and experimental verification of test hardware for high-temperature experiments have been accomplished. Research on energy extraction from fissioning gases has resulted in lasers energized by fission fragments. Combined experimental results and studies indicate that gaseous-fuel reactor systems have significant potential for providing nuclear fission power in space and on earth.

Thom, K.↗
NASA NTRS1989

NOx formation from the combustion of monodisperse n-heptane sprays doped with fuel-nitrogen additives

A series of experiments with simulated synthetic fuels were conducted in order to investigate the effect of droplet size on the conversion of fuel-nitrogen to NOx. Pyridine and pyrrole were added to n-heptane as nitrogen-containing additives and burned as monodisperse fuel droplets under various operating conditions in a spray combustion facility. The experimental results indicate that under stoichiometric and fuel-rich conditions, reducing the droplet size increases the efficiency of fuel-N conversion to NOx. This observation is associated with improved oxidation of the pyrolysis fragments of the additive by better oxygen penetration through the droplet flame zone. The dominant reactions by which fuel-N is transformed to NOx were also considered analytically by a premixed laminar flame code. The calculations are compared to the small droplet size results.

Sarv, Hamid↗
NASA NTRS2001

Design and Fabrication of a Hele-Shaw Apparatus for Observing Instabilities of Diffusion Flames

Examinations of flame fronts spreading over solid fuels in an opposed flow of oxidizer have shown that the flame front fragments into smaller (cellular) flames. These 'flamelets' will oscillate, recombine, or extinguish, indicating that they are in the near extinction limit regime (i.e., to one side of the quenching branch of the flammability map). Onset of unstable cellular flamelet formation for flame spread over thin fuels occurs when a heat-sink substrate is placed a small distance from the underside of the fuel. This heat-sink substrate (or backing) displaces the quenching branch of the flammability map in a direction that causes the instabilities to occur at higher air velocities. Similar near-limit behavior has been observed in other works using different fuels, thus suggesting that these dynamic mechanisms are fuel-independent and therefore fundamental attributes of flames in this near-limit flame spread regime. The objective of this project is to determine the contributions of the hydrodynamic and thermodiffusive mechanisms to the observed formation of flame instabilities. From this, a model of diffusion flame instabilities shall be generated. Previously, experiments were conducted in NASA drop towers, thereby limiting observation time to O(1-5 sec). The NASA tests exhibited flamelet survival for the entire drop time, suggesting that flamelets (i.e., small cellular flames) might exist, if permitted, for longer time periods. By necessity, experiments were limited to thermally thin cellulose fuels (approximately 0.001 in thick): instabilities could form by virtue of faster spread rates over thin fuels. Unstable behavior was unlikely in the short drop time for thicker fuels. In the International Space Station (ISS), microgravity time is unlimited, so both thin and thick fuels can be tested.

Wichman, I. S.↗
NASA NTRS1999

Meteorites and the Evolution of Our Solar System

The study of meteorites has long been of intense interest ever since these objects were discovered to be of extraterrestrial origin. Meteorite research contributes to unraveling the mysteries in understanding the formation and evolution processes of our solar system. Meteorites, of which there are a variety of widely diverse types of chemical and mineralogical compositions, are the most ancient of solar system objects that can be studied in the laboratory. They preserve a unique historical record of the astronomical and astrophysical events of our solar system. This record is being discerned by a host of ever evolving analytical laboratory methods. Recent discoveries of what are believed to be Martian meteorites, lunar meteorites, a meteorite containing indigenous water, and the recovery from the Cretaceous layer of a small meteorite fragment thought to be from the dinosaur-killing asteroid have fueled additional excitement for studying meteorites.

Nava, David F.↗
NASA NTRS2009

The ESA/NASA Multi-Aircraft ATV-1 Re-Entry Campaign: Analysis of Airborne Intensified Video Observations from the NASA/JSC Experiment

In September 2008, a joint ESA/NASA multi-instrument airborne observing campaign was conducted over the Southern Pacific ocean. The objective was the acquisition of data to support detailed atmospheric re-entry analysis for the first flight of the European Automated Transfer Vehicle (ATV)-1. Skilled observers were deployed aboard two aircraft which were flown at 12.8 km altitude within visible range of the ATV-1 re-entry zone. The observers operated a suite of instruments with low-light-level detection sensitivity including still cameras, high speed and 30 fps video cameras, and spectrographs. The collected data has provided valuable information regarding the dynamic time evolution of the ATV-1 re-entry fragmentation. Specifically, the data has satisfied the primary mission objective of recording the explosion of ATV-1's primary fuel tank and thereby validating predictions regarding the tanks demise and the altitude of its occurrence. Furthermore, the data contains the brightness and trajectories of several hundred ATV-1 fragments. It is the analysis of these properties, as recorded by the particular instrument set sponsored by NASA/Johnson Space Center, which we present here.

Barker, Ed↗
NASA NTRS1978

Experimental and analytical study of nitric oxide formation during combustion of propane in a jet-stirred combustor

A jet-stirred combustor, constructed of castable zirconia and with an Inconel injector, was used to study nitric oxide formation in propane-air combustion with residence times in the range from 3.2 to 3.3 msec and equivalence ratios varying from 0.7 to 1.4. Measurements were made of combustor operating temperature and of nitric oxide concentration. Maximum nitric oxide concentrations of the order of 55 ppm were found in the range of equivalence ratio from 1.0 to 1.1. A finite-rate chemical kinetic mechanism for propane combustion and nitric oxide formation was assembled by coupling an existing propane oxidation mechanism with the Zeldovich reactions and reactions of molecular nitrogen with hydrocarbon fragments. Analytical studies using this mechanism in a computer simulation of the experimental conditions revealed that the hydrocarbon-fragment-nitrogen reactions play a significant role in nitric oxide formation during fuel-rich combustion.

Wakelyn, N. T.↗
NASA NTRS1989

Explosive fragmentation of orbiting propellant tanks

An examination is made of the in-orbit explosive characteristics of the Delta second stage and Ariane third stage, with a view to the vehicle breakups of the Ariane SPOT third-stage fuel tank in November, 1986, and of two Delta second stage tanks. Attention is given to the possible role of residual propellants in these breakups. After reviewing orbital data and comparing predicted fragment velocities with observed fragment velocities in debris patterns, a comparison has been made of total debris energy with total calculated explosion energy. Both physical and chemical explosions are deemed possible.

Benz, F. J.↗
NASA NTRS1986

Aircraft accident report: NASA 712, Convair 990, N712NA, March Air Force Base, California, July 17, 1985, facts and analysis

On July 17, l985, at 1810 P.d.t., NASA 712, a Convair 990 aircraft, was destroyed by fire at March Air Force Base, California. The fire started during the rollout after the pilot rejected the takeoff on runway 32. The rejected takeoff was initiated during the takeoff roll because of blown tires on the right landing gear. During the rollout, fragments of either the blown tires or the wheel/brake assemblies penetrated a right-wing fuel tank forward of the right main landing gear. Leaking fuel ignited while the aircraft was rolling, and fire engulfed the right wing and the fuselage after the aircraft was stopped on the runway. The 4-man flightcrew and the 15 scientists and technicians seated in the cabin evacuated the aircraft without serious injury. The fire was not extinguished by crash/rescue efforts and the aircraft was destroyed.

Batthauer, Byron E.↗