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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 109 records · Page 6
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NASA NTRS2014

MMOD Protection and Degradation Effects for Thermal Control Systems

Micrometeoroid and orbital debris (MMOD) environment overview Hypervelocity impact effects & MMOD shielding MMOD risk assessment process Requirements & protection techniques - ISS - Shuttle - Orion/Commercial Crew Vehicles MMOD effects on spacecraft systems & improving MMOD protection - Radiators Coatings - Thermal protection system (TPS) for atmospheric entry vehicles Coatings - Windows - Solar arrays - Solar array masts - EVA Handrails - Thermal Blankets Orbital Debris provided by JSC & is the predominate threat in low Earth orbit - ORDEM 3.0 is latest model (released December 2013) - http://orbitaldebris.jsc.nasa.gov/ - Man-made objects in orbit about Earth impacting up to 16 km/s average 9-10 km/s for ISS orbit - High-density debris (steel) is major issue Meteoroid model provided by MSFC - MEM-R2 is latest release - http://www.nasa.gov/offices/meo/home/index.html - Natural particles in orbit about sun Mg-silicates, Ni-Fe, others - Meteoroid environment (MEM): 11-72 km/s Average 22-23 km/s.

Christiansen, Eric↗
NASA NTRS2017

Kinetic Damage from Meteorites

A Near Earth object impacting into Earth's atmosphere may produce damaging effects at the surface due to airblast, thermal pulse, or kinetic impact in the form of meteorites. At large sizes (greater than many tens of meters), the damage is amplified by the hypersonic impact of these large projectiles moving with cosmic velocity, leaving explosively produced craters. However, much more common is simple "kinetic" damage caused by the impact of smaller meteorites moving at terminal speeds. As of this date a handful of instances are definitively known of people or structures being directly hit and/or damaged by the kinetic impact of meteorites. Meteorites known to have struck humans include the Sylacauga, Alabama fall (1954) and the Mbale meteorite fall (1992). Much more common is kinetic meteorite damage to cars, buildings, and even a post box (Claxton, Georgia - 1984). Historical accounts indicate that direct kinetic damage by meteorites may be more common than recent accounts suggest (Yau et al., 1994). In this talk we will examine the contemporary meteorite flux and estimate the frequency of kinetic damage to various structures, as well as how the meteorite flux might affect the rate of human casualties. This will update an earlier study by Halliday et al (1985), adding variations expected in meteorite flux with latitude (Le Feuvre and Wieczorek, 2008) and validating these model predictions of speed and entry angle with observations from the NASA and SOMN fireball networks. In particular, we explore the physical characteristics of bright meteors which may be used as a diagnostic for estimating which fireballs produce meteorites and hence how early warning of such kinetic damage may be estimated in advance through observations and modeling.

Cooke, William↗
NASA NTRS2017

Kinetic Damage from Meteorites

A Near Earth object impacting into Earth's atmosphere may produce damaging effects at the surface due to airblast, thermal pulse, or kinetic impact in the form of meteorites. At large sizes (>many tens of meters), the damage is amplified by the hypersonic impact of these large projectiles moving with cosmic velocity, leaving explosively produced craters. However, much more common is simple "kinetic" damage caused by the impact of smaller meteorites moving at terminal speeds. As of this date a handful of instances are definitively known of people or structures being directly hit and/or damaged by the kinetic impact of meteorites. Meteorites known to have struck humans include the Sylacauga, Alabama fall (1954) and the Mbale meteorite fall (1992). Much more common is kinetic meteorite damage to cars, buildings, and even a post box (Claxton, Georgia - 1984). Historical accounts indicate that direct kinetic damage by meteorites may be more common than recent accounts suggest (Yau et al., 1994). In this talk we will examine the contemporary meteorite flux and estimate the frequency of kinetic damage to various structures, as well as how the meteorite flux might affect the rate of human casualties. This will update an earlier study by Halliday et al (1985), adding variations expected in meteorite flux with latitude (Le Feuvre and Wieczorek, 2008) and validating these model predictions of speed and entry angle with observations from the NASA and SOMN fireball networks. In particular, we explore the physical characteristics of bright meteors which may be used as a diagnostic for estimating which fireballs produce meteorites and hence how early warning of such kinetic damage may be estimated in advance through observations and modelling.

Cooke, William↗
NASA NTRS1979

Origin of differentiated meteorites

The larger asteroids with low inclination in the inner portion of the asteroid belt are evaluated as sources of differentiated meteorites (irons, stony irons and achondrites). It is found that the calculated earth impact rate is in agreement with the observed flux of these bodies. The frequent occurrence of elapsed times before impact of 0-1000 m.y. is in agreement with the observed typical exposure ages of iron meteorites, and the observed occurrence of some very young (less than 100 m.y.) exposure ages. The absence of many greater than 1000 m.y. iron meteorite exposure ages and greater than 50 m.y. achondrite exposure ages must be attributed to collisional destruction as the calculations predict a significant number of these older ages. Chemical and isotopic data on these bodies suggest a relationship to the earth and moon, and it may be that they represent residual material from earth's accretional zone.

Wetherill, G. W.↗
NASA NTRS2006

Earth after the Moon-forming Impact

The Hadean Earth is widely and enduringly pictured as a world of exuberant volcanism, exploding meteors, huge craters, infernal heat, and billowing sulfurous steams; i.e., a world of fire and brimstone punctuated with blows to the head. In the background the Moon looms gigantic in the sky. The popular image has given it a name that celebrates our mythic roots. A hot early Earth is an inevitable consequence of accretion. The Moon-forming impact ensured that Earth as we know it emerged from a fog of silicate vapor. The impact separated the volatiles from the silicates. It took approx. 100 years to condense and rain out the bulk of the vaporized silicates, although relatively volatile elements may have remained present in the atmosphere throughout the magma ocena stage. The magma ocean lasted approx. 2 Myr, its lifetime prolonged by tidal heating and thermal blanketing by a thick CO2-rich steam atmosphere. Water oceans condensed quickly after the mantle solidified, but for some 10-100 Myr the surface would have stayed warm (approx. 500 K) until the CO2 was removed into the mantle. Thereafter the faint young Sun suggests that a lifeless Earth would always have been evolving toward a bitterly cold ice world, but the cooling trend was fiequently interrupted by volcanic or impact induced thaws. A cartoon history of water, temperature, and carbon dioxide in the aftermath of the moon-formining-impact is shown. How long it stays hot depends on how long it takes to scrub the C02 out of the atmosphere.

Zahnle, K. J.↗
NASA NTRS1984

The asteroidal source region of ordinary chondrites

The final, Earth-impacting orbits of ordinary chondritic meteorites have a very special distribution. By use of visual radiant and time of fall data, as well as photographic fireball orbits (1) it is inferred that chondrite perihelia are concentrated near 1 A.U., eccentricities are usually rather high (approximately 0.5), and inclinations are low (approximately 10 deg). Velocity selection resulting from atmospheric ablation plays a significant role in determining this orbital distribution, but by no means suffices to explain it. The observed distribution is a fragile one, and can easily be destroyed by Earth and Venus perturbations. This places severe constraints on the location of the original source bodies, of which these meteorites are fragments. New calculations were made of the expected distribution of final orbits from a range of initial sources, taking into consideration close encounter planetary perturbations, secular resonance, destruction by collision in space, and atmospheric ablation.

Wetherill, G. W.↗
NASA NTRS1992

A Southern Hemisphere radar meteor orbit survey

A meteor radar system has been operated on a routine basis near Christchurch, New Zealand, to determine the orbits of Earth-impacting interplanetary dust and meteoroids. The system sensitivity is +13 visual magnitude, corresponding to approximately 100 micron sized meteoroids. With an orbital precision of 2 degrees in angular elements and 10 percent in orbital energy (1/a), the operation yields an average of 1500 orbits daily with a total to date in excess of 10(exp 5). The use of pc's and automated data reduction permit the large orbital data sets we collect to be routinely reduced. Some illustrative examples are presented of the signal formats/processing and the results of data reduction, giving the individual orbital elements and hence the overall distributions. Current studies include the distribution of dust in the inner solar system; the influx of meteoroids associated with near-Earth asteroids; and the orbital structure existing in comet-produced streams.

Baggaley, W. Jack↗
NASA NTRS1989

Global environmental effects of impact-generated aerosols: Results from a general circulation model

Interception of sunlight by the high altitude worldwide dust cloud generated by impact of a large asteroid or comet would lead to substantial land surface cooling, according to the three-dimensional atmospheric general circulation model (GCM). This result is qualitatively similar to conclusions drawn from an earlier study that employed a one-dimensional atmospheric model, but in the GCM simulation the heat capacity of the oceans, not included in the one-dimensional model, substantially mitigates land surface cooling. On the other hand, the low heat capacity of the GCM's land surface allows temperatures to drop more rapidly in the initial stages of cooling than in the one-dimensional model study. GCM-simulated climatic changes in the scenario of asteroid/comet winter are more severe than in nuclear winter because the assumed aerosol amount is large enough to intercept all sunlight falling on earth. Impacts of smaller objects could also lead to dramatic, though of course less severe, climatic changes, according to the GCM. An asteroid or comet impact would not lead to anything approaching complete global freezing, but quite reasonable to assume that impacts would dramatically alter the climate in at least a patchy sense.

Covey, Curt↗
NASA NTRS2004

Lunar and Planetary Science XXXV: Undergraduate Education and Research Programs, Facilities, and Information Access

The titles in this section include: 1) GRIDVIEW: Recent Improvements in Research and Education Software for Exploring Mars Topography; 2) Software and Hardware Upgrades for the University of North Dakota Asteroid and Comet Internet Telescope (ACIT); 3) Web-based Program for Calculating Effects of an Earth Impact; 4) On-Line Education, Web- and Virtual-Classes in an Urban University: A Preliminary Overview; 5) Modelling Planetary Material's Structures: From Quasicrystalline Microstructure to Crystallographic Materials by Use of Mathematica; 6) How We Used NASA Lunar Set in Planetary and Material Science Studies: Textural and Cooling Sequences in Sections of Lava Column from a Thin and a Thick Lava-Flow, from the Moon and Mars with Terrestrial Analogue and Chondrule Textural Comparisons; 7) Classroom Teaching of Space Technology and Simulations by the Husar Rover Model; 8) New Experiments (In Meteorology, Aerosols, Soil Moisture and Ice) on the New Hunveyor Educational Planetary Landers of Universities and Colleges in Hungary; 9) Teaching Planetary GIS by Constructing Its Model for the Test Terrain of the Hunveyor and Husar; 10) Undergraduate Students: An Untapped Resource for Planetary Researchers; 11) Analog Sites in Field Work of Petrology: Rock Assembly Delivered to a Plain by Floods on Earth and Mars; 12) RELAB (Reflectance Experiment Laboratory): A NASA Multiuser Spectroscopy Facility; 13) Full Text Searching and Customization in the NASA ADS Abstract Service.

Source record↗
NASA NTRS1989

Global environmental effects of impact-generated aerosols: Results from a general circulation model, revision 1

Interception of sunlight by the high altitude worldwide dust cloud generated by impact of a large asteroid or comet would lead to substantial land surface cooling, according to our three-dimensional atmospheric general circulation model (GCM). This result is qualitatively similar to conclusions drawn from an earlier study that employed a one-dimensional atmospheric model, but in the GCM simulation the heat capacity of the oceans substantially mitigates land surface cooling, an effect that one-dimensional models cannot quantify. On the other hand, the low heat capacity of the GCM's land surface allows temperatures to drop more rapidly in the initial stage of cooling than in the one-dimensional model study. These two differences between three-dimensional and one-dimensional model simulations were noted previously in studies of nuclear winter; GCM-simulated climatic changes in the Alvarez-inspired scenario of asteroid/comet winter, however, are more severe than in nuclear winter because the assumed aerosol amount is large enough to intercept all sunlight falling on earth. Impacts of smaller objects could also lead to dramatic, though less severe, climatic changes, according to our GCM. Our conclusion is that it is difficult to imagine an asteroid or comet impact leading to anything approaching complete global freezing, but quite reasonable to assume that impacts at the Alvarez level, or even smaller, dramatically alter the climate in at least a patchy sense.

Covey, Curt↗
NASA NTRS1985

Terrestrial record of the solar system's oscillation about the galactic plane

A new study is presented of the observational evidence pertaining to the theory which attributes the episodic component of the earth's impact cratering record over the past 600 Myr to gravitational encounters between the solar system and interstellar clouds that cause comets to fall into the solar system and impact the earth. Contrary to a claim by Thaddeus and Chanan (1985), the vertical scale height of the clouds seems to be sufficently small and the sun's vertical trajectory sufficiently large for the modulating effect of the sun's galactovertical motion to be detectable in the terrestrial record of impact cratering with at least a 50 percent a priori probability.

Stothers, R. B.↗
NASA NTRS2015

Los Alamos RAGE Simulations of the HAIV Mission Concept

The mitigation of potentially hazardous objects (PHOs) can be accomplished by a variety of methods including kinetic impactors, gravity tractors and several nuclear explosion options. Depending on the available lead time prior to Earth impact, non- nuclear options can be very effective at altering a PHOs orbit. However if the warning time is short nuclear options are generally deemed most effective at mitigating the hazard. The NIAC mission concept for a nuclear mission has been presented at several meetings, including the last PDC (2013).We use the adaptive mesh hydrocode RAGE to perform detailed simulations of this Hypervelocity Asteroid Intercept Vehicle (HAIV) mission concept. We use the RAGE code to simulate the crater formation by the kinetic impactor as well as the explosion and energy coupling from the follower nuclear explosive device (NED) timed to detonate below the original surface to enhance the energy coupling. The RAGE code has been well validated for a wide variety of applications. A parametric study will be shown of the energy and momentum transfer to the target 100 m diameter object: 1) the HAIV mission as planned; 2) a surface explosion and 3) a subsurface (contained) explosion; both 2) and 3) use the same source energy as 1).Preliminary RAGE simulations show that the kinetic impactor will carve out a surface crater on the object and the subsequent NED explosion at the bottom of the crater transfers energy and momentum to the target effectively moving it off its Earth crossing orbit. Figure 1 shows the initial (simplified) RAGE 2D setup geometry for this study. Figure 2 shows the crater created by the kinetic impactor and Figure 3 shows the time sequence of the energy transfer to the target by the NED.

Asteroid Mitigation↗
NASA NTRS2015

Enhanced Gravity Tractor Technique for Planetary Defense

Given sufficient warning time, Earth-impacting asteroids and comets can be deflected with a variety of different "slow push/pull" techniques. The gravity tractor is one technique that uses the gravitational attraction of a rendezvous spacecraft to the impactor and a low-thrust, high-efficiency propulsion system to provide a gradual velocity change and alter its trajectory. An innovation to this technique, known as the Enhanced Gravity Tractor (EGT), uses mass collected in-situ to augment the mass of the spacecraft, thereby greatly increasing the gravitational force between the objects. The collected material can be a single boulder, multiple boulders, regolith or a combination of different sources. The collected mass would likely range from tens to hundreds of metric tons depending on the size of the impactor and warning time available. Depending on the propulsion system's capability and the mass collected, the EGT approach can reduce the deflection times by a factor of 10 to 50 or more, thus reducing the deflection times of several decades to years or less and overcoming the main criticism of the traditional gravity tractor approach. Additionally, multiple spacecraft can orbit the target in formation to provide the necessary velocity change and further reduce the time needed by the EGT technique to divert hazardous asteroids and comets. The robotic segment of NASA's Asteroid Redirect Mission (ARM) will collect a multi-ton boulder from the surface of a large Near-Earth Asteroid (NEA) and will provide the first ever demonstration of the EGT technique and validate one method of collecting in-situ mass on an asteroid of hazardous size.

Mazanek, Daniel D.↗
NASA NTRS1980

Skylab orbital lifetime prediction and decay analysis

A record (from preflight planning to earth impact) of skylab's orbital lifetime predictions, its actual decay and analysis are presented. Skylab provided a unique opportunity to develop, confirm and check out procedures and computer programs used for predicting lifetime and reentry. It provided verification of aerodynamic environment which was predicted for several aerodynamic configurations. It also provided data on the density model's reaction to rapidly changing solar flux over relatively short time periods. The effects of solar flux (and the uncertainty in the solar flux predictions) on orbital lifetime are discussed.

Dreher, P. E.↗
NASA NTRS1988

Irradiation records in meteorites

The approximately 4.6 billion-year history of a meteorite will encompass at least one episode of exposure to such energetic particles as cosmic rays; measurements of such exposure allow determination of how long a meteorite existed as a meter-sized body prior to earth impact. Meteorite exposure to energetic particles before their ejection from a parent body entails that the meteorite reside in the upper several m of that parent regolith. At the periods closest to the 4.6 billion year horizon, early solar system conditions may have been characterized by much gas and dust; irradiation records from this period may prove invaluable in reconstructing its characteristics.

Caffee, M. W.↗
NASA NTRS2006

Creating a NASA-Wide Museum Alliance

NASA's Museum Alliance is a nationwide network of informal educators at museums, science centers, and planetariums that present NASA information to their local audiences. Begun in 2002 as the Mars Museum Visualization Alliance with advisors from a dozen museums, the network has grown to over 300 people from 200 organizations, including a dozen or so international partners. The network has become a community of practice among these informal educators who work with students, educators, and the general public on a daily basis, presenting information and fielding questions about space exploration. Communications are primarily through an active listserve, regular telecons, and a pass word protected website. Professional development is delivered via telecons and downloadable presentations. Current content offerings include Mars exploration, Cassini, Stardust, Genesis, Deep Impact, Earth observations, STEREO, and missions to explore beyond our solar system.

planetary sciences↗