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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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NASA NTRS1935

Infrared radiation from explosions in a spark-ignition engine

This report presents the results of an investigation to determine the variations in intensity and spectral distribution of the radiant energy emitted by the flames during normal and knocking explosions in an engine. Radiation extending into the infrared was transmitted by a window of fluorite, placed either near the spark plug or over the detonation zone at opposite ends of the combustion chamber. Concave, surface-silvered mirrors focused the beam, first at the slit of a stroboscope which opened for about 2 degrees of crank angle at any desired point in the engine cycle, and then upon the target of a sensitive thermocouple for measuring radiation intensity. Spectral distribution of the radiant energy was determined by placing over the window, one at a time, a series of five filters selected with a view to identifying, as far as possible without the use of a spectrograph, the characteristic emissions of water vapor, carbon dioxide, and incandescent carbon.

Marvin, Charles F , Jr↗
NASA NTRS1993

Explosive volcanism and the compositions of the cores of differentiated asteroids

Eleven iron meteorite groups showing correlations between Ni and siderophile trace elements that are predictable by distribution coefficients between liquid and solid metal of fractionally crystallizing metal magmas, are interpreted to be fragments of the fractionally crystallized cores of 11 differentiated asteroids. Many of these groups crystallized from S-depleted magmas which we propose resulted from removal of the first partial melt (a Fe,Ni-FeS cotectic) by explosive pyroclastic volcanism. It is shown that these dense, negatively buoyant melts can be driven to asteroidal surfaces by the combination of an excess pressure in the melt and the presence of buoyant bubbles of gas which decrease the bulk density of the melt. It is also shown that in typical asteroidal materials, veins will form which grow into dikes and serve as pathways for migration of melt and gas to asteroidal surfaces. Since cotectic Fe,Ni-FeS melt consists of about 85 wt. percent FeS and 15 wt. percent Fe,Ni, removal of small volumes of eutectic melts results in major loss of S but only minor loss of Fe,Ni, thus leaving sufficient Fe,Ni to form sizeable asteroidal cores.

Keil, Klaus↗
NASA NTRS1994

Cubanes: Super explosives and potential pharmaceutical intermediates

The cubane molecule, in which eight carbon atoms are locked in a cubic framework, shows great potential for both military and pharmaceutical applications. Octanitrocubane, with a predicted density of 2.1 g/cc and strain energy of more than 165 kcal/mol, is considered to be the 'super-explosive', while cubane derivatives submitted to the National Institutes of Health for preliminary biological activity screening have displayed promising anti-cancer and anti-HIV activity.

Bashir-Hashemi, A.↗
NASA NTRS1994

Explosion of comet Shoemaker-Levy 9 on entry into the Jovian atmosphere

We use the astrophysical hydrocode ZEUS to compute high-resolution models of the disruption and deceleration of cometary fragments striking Jupiter. We find that simple analytic and semianalytic models work well for kilometer-size impactors. We show that previous numerical models that placed the explosion much deeper in the atmosphere failed to fully resolve important gasdynamical instabilities. These instabilities tear the comet apart, greatly increase its effective cross section, and bring it to an abrupt halt. A 1 km diameter fragment loses over 90% of its kinetic energy within a single scale height at an atmospheric pressure of order 10 bars. For all practical purposes, it explodes.

Mac Low, Mordecai-Mark↗
NASA NTRS1995

Formation of a very thin current sheet in the near-earth magnetotail and the explosive growth phase of substorms

A magnetofricional method is used to construct two-dimensional MHD equilibria of the Earth's magnetosphere for a given distribution of entropy functions(S = pV(exp gamma), where p is the plasma pressure and V is the tube volume per unit magnetic flux. It is found that a very thin current sheet with B (sub zeta) is less than 0.5 nu T and thickness less than 1000 km can be formed in the near-earth magnetotail (x is approximately -8 to -20R(sub e) during the growth phase of substorm. The tail current sheets are found to become thinner as the entropy or the entropy gradient increases. It is suggested that the new entropy anti-diffusion instability associated with plasma transport across field lines leads to magnetic field dipolarization and accelerates the formation of thin current sheet, which may explain the observed explosive growth phase of substorms.

Lee, L. C.↗
NASA NTRS1996

Oven Evaporates Isopropyl Alcohol Without Risk Of Explosion

Ordinary convection oven with capacity of 1 ft.(sup3) modified for use in drying objects washed in isopropyl alcohol. Nitrogen-purge equipment and safety interlocks added to prevent explosive ignition of flammable solvent evaporating from object to be dried.

Morgan, Gene E.↗
NASA NTRS1996

Comparison of Separation Shock for Explosive and Nonexplosive Release Actuators on a Small Spacecraft Panel

Functional shock, safety, overall system costs, and emergence of new technologies, have raised concerns regarding continued use of pyrotechnics on spacecraft. NASA Headquarters-Office of Chief Engineer requested Langley Research Center (LaRC) study pyrotechnic alternatives using non-explosive actuators (NEA's), and LARC participated with Lockheed Martin Missile and Space Co. (LMMSC)-Sunnyvale, CA in objectively evaluating applicability of some NEA mechanisms to reduce small spacecraft and booster separation event shock. Comparative tests were conducted on a structural simulator using five different separation nut mechanisms, consisting of three pyrotechnics from OEA-Aerospace and Hi-Shear Technology and two NEA's from G&H Technology and Lockheed Martin Astronautics (LMA)-Denver, CO. Multiple actuations were performed with preloads up to 7000 pounds, 7000 being the comparison standard. All devices except LMA's NEA rotary flywheel-nut concept were available units with no added provisions to attenuate shock. Accelerometer measurements were recorded, reviewed, processed into Shock Response Spectra (SRS), and comparisons performed. For the standard preload, pyrotechnics produced the most severe and the G&H NEA the least severe functional shock levels. Comparing all results, the LMA concept produced the lowest levels, with preload limited to approximately 4200 pounds. Testing this concept over a range of 3000 to 4200 pounds indicated no effect of preload on shock response levels. This report presents data from these tests and the comparative results.

Lucy, M. H.↗
NASA NTRS1994

Explosion Calculations of SN1087

Explosion calculations of SNT1987A generate pictures of Rayleigh-Taylor fingers of radioactive Ni-56 which are boosted to velocities of several thousand km/s. From the KAO observations of the mid-IR iron lines, a picture of the iron in the ejecta emerges which is consistent with the "frothy iron fingers" having expanded to fill about 50% of the metal-rich volume of the ejecta. The ratio of the nickel line intensities yields a high ionization fraction of greater than or equal to 0.9 in the volume associated with the iron-group elements at day 415, before dust condenses in the ejecta. From the KAO observations of the dust's thermal emission, it is deduced that when the grains condense their infrared radiation is trapped, their apparent opacity is gray, and they have a surface area filling factor of about 50%. The dust emission from SN1987A is featureless: no 9.7 micrometer silicate feature, nor PAH features, nor dust emission features of any kind are seen at any time. The total dust opacity increases with time even though the surface area filling factor and the dust/gas ratio remain constant. This suggests that the dust forms along coherent structures which can maintain their radial line-of-sight opacities, i.e., along fat fingers. The coincidence of the filling factor of the dust and the filling factor of the iron strongly suggests that the dust condenses within the iron, and therefore the dust is iron-rich. It only takes approximately 4 x 10(exp -4) solar mass of dust for the ejecta to be optically thick out to approximately 100 micrometers; a lower limit of 4 x 10(exp -4) solar mass of condensed grains exists in the metal-rich volume, but much more dust could be present. The episode of dust formation started at about 530 days and proceeded rapidly, so that by 600 days 45% of the bolometric luminosity was being emitted in the IR; by 775 days, 86% of the bolometric luminosity was being reradiated by the dust. Measurements of the bolometric luminosity of SN1987A from 1000 - 1800 days are based on 10 micrometers and 20 micrometers photometry and rely on the suppositions that the IR emission is a greybody (proven to be true by the KAO observations at 615 and 775 days) and that the dust temperature drops to and remains at 150 K. The late time bolometric luminosity is stronger than that expected from the radioactive decay of Co-56, Co-57, Ti-44, and Na-22 and the possibility of an embedded compact object will be discussed.

Wooden, Diane H.↗
NASA NTRS1942

Thermal Theory of Combustion and Explosion: Theory of Normal Flame Propagation - 3

The technical memorandum covers experimental data on flame propagation, the velocity of flame propagation, analysis of the old theoretical views of flame propagation, confirmation of the theory for simple reactions (theory of combustion of explosive substances and in particular nitroglycol), and check of the theory by example of a chain oxidizing reaction (theory of flame propagation in carbon monoxide, air and carbon monoxide - oxygen mixtures).

Semenov, N. N.↗
NASA NTRS1942

Thermal Theory of Combustion and Explosion

This paper discusses the thermal theory of combustion and explosion, and conditions of ignition: transformation accompanied by heat liberation, transformation rate and temperature dependence.

Semenov, N. N.↗
NASA NTRS2003

Evidence for Gradual External Reconnection Before Explosive Eruption of a Solar Filament

We observe a slowly-evolving quiet region solar eruption of 1999 April 18, using EUV images from the EUV Imaging Telescope (EIT) on the Solar and Heliospheric Observatory (SOHO), and soft X-ray images from the Soft X-ray Telescope (SXT) on Yohkoh. Using difference images, where an early image is subtracted from later images, we examine dimmings and brightenings in the region for evidence of the eruption mechanism. A filament rose slowly at about 1 kilometer per second for six hours before being rapidly ejected at about 16 kilometers per second, leaving flare brightenings and post-flare loops in its wake. Magnetograms from the Michelson Doppler Imager (MDI) on SOHO show that the eruption occurred in a large quadrupo1ar magnetic region, with the filament located on the neutral line of the quadrupole's central inner lobe, between the inner two of the four polarity domains. In step with the slow rise, subtle EIT dimmings commence and gradually increase over the two polarity domains on one side of the filament, i.e. in some of the loops of one of the two side lobes of the quadrupole. Concurrently, soft X-ray brightenings gradually increase in both side lobes. Both of these effects suggest heating in the side-lobe magnetic arcades, which gradually increase over several hours before the fast eruption. Also during the slow pre-eruption phase, SXT dimmings gradually increase in the feet and legs of the central lobe, indicating expansion of the central-lobe magnetic arcade enveloping the filament. During the rapid ejection, these dimmings rapidly grow in darkness and in area, especially in the ends of the sigmoid field that erupts with the filament, and flare brightenings begin underneath the fast-moving but still low-altitude filament. We consider two models for explaining the eruption: "breakout," which says that reconnection occurs high above the filament prior to eruption, and tether cutting, which says that the eruption is unleashed by reconnection beneath the filament. The pre-eruption evolution is consistent with gradual breakout that led to (and perhaps caused) the fast eruption. Tether-cutting reconnection below the filament begins early in the rapid ejection, but our data are not complete enough to determine whether this reconnection began early enough to be the cause of the fast-phase onset. Thus, our observations are consistent with gradual breakout reconnection causing the long slow rise of the filament, but allow the cause of the sudden onset of the explosive fast phase to be either a jump in the breakout reconnection rate or the onset of runaway tether-cutting reconnection, or both.

Sterling, Alphonse C.↗
NASA NTRS2004

Evidence for Gradual External Reconnection Before Explosive Eruption of a Solar Filament

We observe a slowly evolving quiet-region solar eruption of 1999 April 18, using extreme-ultraviolet (EUV) images from the EUV Imaging Telescope (EIT) on the Solar and Heliospheric Observatory (SOHO) and soft X-ray images from the Soft X-ray Telescope (SXT) on Yohkoh. Using difference images, in which an early image is subtracted from later images, we examine dimmings and brightenings in the region for evidence of the eruption mechanism. A filament rose slowly at about 1 km/s for 6 hours before being rapidly ejected at about 16 km/s leaving flare brightenings and postflare loops in its wake. Magnetograms from the Michelson Doppler Imager (MDI) on SOHO show that the eruption occurred in a large quadrupolar magnetic region with the filament located on the neutral line of the quadrupole s central inner lobe between the inner two of the four polarity domains. In step with the slow rise, subtle EIT dimmings commence and gradually increase over the two polarity domains on one side of the filament, i.e., in some of the loops of one of the two sidelobes of the quadrupole. Concurrently, soft X-ray brightenings gradually increase in both sidelobes. Both of these effects suggest heating in the sidelobe magnetic arcades. which gradually increase over several hours before the fast eruption. Also, during the slow pre- eruption phase, SXT dimmings gradually increase in the feet and legs of the central lobe, indicating expansion of the central-lobe magnetic arcade enveloping the filament. During the rapid ejection. these dimmings rapidly grow in darkness and in area, especially in the ends of the sigmoid field that erupts with the filament. and flare brightenings begin underneath the fast-moving but still low-altitude filament. We consider two models for explaining the eruption: "breakout. which says that reconnection occurs high above the filament prior to eruption, and tether cutting, which says that the eruption is unleashed by reconnection beneath the filament. The pre-eruption evolution is consistent with gradual breakout that led to (and perhaps caused) the fast eruption. Tether-cutting reconnection below the filament begins early in the rapid ejection. but our data are not complete enough to determine whether this reconnection began early enough to be the cause of the fast-phase onset. Thus, our observations are consistent with gradual breakout reconnection causing the long slow rise of the filament, but allow the cause of the sudden onset of the explosive fast phase to be either a jump in the breakout reconnection rate or the onset of runaway tether-cutting reconnection. or both.

Sterling, Alphonse C.↗
NASA NTRS2004

Main-Sequence CMEs as Magnetic Explosions: Compatibility with Observed Kinematics

We examine the kinematics of 26 CMEs of the morphological main sequence of CMEs, those having the classic three-part bubble structure of (1) a bright front eveloping (2) a dark cavity within which rides (3) a bright blob/filamentary feature. Each CME is observed in Yohkoh/SXT images to originate from near the limb (> or equal to 0.7 R(sub Sun) from disk center). The basic data (from the SOHO LASCO CME Catalog) for the kinematics of each CME are the sequence of LASCO images of the CME, the time of each image, the measured radial distance of the front edge of the CME in each image, and the measured angular extent of the CME. About half of our CMEs (12) occur with a flare, and the rest (14) occur without a flare. While the average linear-fit speed of the flare CMEs (1000 km/s) is twice that of the non-flare CMEs (510 km/s), the flare CMEs and the non-flare CMEs are similar in that some have nearly flat velocity-height (radial extent) profiles (little acceleration), some have noticeably falling velocity profiles (noticeable deceleration), and the rest have velocity profiles that rise considerably through the outer corona (blatant acceleration). This suggests that in addition to sharing similar morphology, main-sequence CMEs all have basically the same driving mechanism. The observed radial progression of each of our 26 CMEs is fit by a simple model magnetic plasmoid that is in pressure balance with the radial magnetic field in the outer corona and that propels itself outward by magnetic expansion, doing no net work on its surroundings. On average over the 26 CMEs, this model fits the observations as well as the assumption of constant acceleration. This is compatible with main-sequence CMEs being magnetically driven, basically magnetic explosions, with the velocity profile in the outer corona being largely dictated by the initial Alfien speed in the CME (when the front is at approx. 3 (sub Sun), analogous to the mass of a main-sequence star dictating the luminosity.

Moore, Ron↗
NASA NTRS2005

Going to the Bottom of the Explosion that Formed Cas A

The purpose of this INTEGRAL AO 1 proposal was to observe the gamma-ray lines at 1157 keV, as well as 68 keV and 78 keV of the (44)Ti decay chain from the youngest known galactic supernova remnant Cas A. The radioactive decay of (44)Ti in Cas A was first detected by COMPTEL in the 1157 keV line and later confirmed in the lower energy lines using BeppoSAX data. Despite the second confirming measurement, the flux value still has a considerable error, due to a low signal over background ratio and the poor definition of the continuum background in the range of 70 - 100 keV above the line energies. In addition to improving this flux measurement, INTEGRAL has the unique capability, in principle, to measure the line width of the emission. This type of measurement can further constrain supernova explosion models. Unfortunately, the INTEGRAL instrumental background, especially in the SPI spectrometer, turned out to be significantly higher than estimated at the time of proposal submission before launch. This, and to a smaller extent the reduced effective exposure time of about 1.5 Ms compared to requested 2.5 Ms, has precluded us from reaching the sensitivity necessary for this measurement. Studies of the background variability with the goal of improving background modeling are ongoing, and additional 2.5 Ms observing time has just been approved for the next observing cycle.

Oberlack, Uwe↗
NASA NTRS2006

The Mysterious Origins of Solar Flares: New observations are beginning to reveal what triggers these hughes explosions of the sun's atmosphere

Solar flares can release the energy equivalent of billions of atomic bombs in the span of just a few minutes. These explosions give off a burst of x-rays and charged particles, some of which may later hit Earth, endangering satellites and causing power outages. The sun's tumultuous magnetic fields provide the fuel of flares. The sudden release of energy in a flare results from a process called reconnection, whereby oppositely directed magnetic field lines come together and partially annihilate each other. Although theoretical studies of magnetic reconnection on the sun have been carried out for decades, only recently have space probes uncovered observational evidence for this phenomenon. The telltale signs include pointed magnetic loops located below the spot where magnetic reconnection is taking place.

Holman, Gordon D.↗