To assure mission success of the Solar Probe Plus (SPP) spacecraft, defined by achieving its final mission orbit with a perihelion distance of less than 10 solar radii, it is necessary to define the dust hypervelocity impact (HVI) protection levels provided by its Multi-Layer Insulation (MLI)/thermal blankets with a reliability that is on par with that available for metallic Whipple shields. Recently, we presented an experimentally validated approach being developed at the Johns Hopkins University Applied Physics Laboratory (JHU/APL) for designing and analyzing MLI to meet this challenge. This paper extends the results to Whipple shield configurations consisting of an MLI bumper, 0-1" standoff, and an Aluminum honeycomb rear wall. With 0" MLI-honeycomb standoff, 0.05 g/cm 2 MLI layered in a manner similar to that found in actual blankets and an Aluminum honeycomb consisting of 8 mil-thk. facesheets, 0.125"-dia. cells and 1%"-thk. core is adopted for 2D and 3D analyses. Bonding of the core to the facesheets was included in the modeling to account for channeling of the debris cloud within the core. The passage of the dust through the center of the core's symmetry axis is considered to be the most conservative dust-H/C interaction as the other scenarios - normal dust entry closer to a core wall or oblique dust entry - are expected to be less damaging overall owing to interactions with the core material and disruption of channeling. For this reason, dust impact along a core symmetry axis is evaluated. The failure criterion chosen is complete perforation of the rear facesheet and extending to the entire cell area. The average critical particle diameter is indicated to be in the 300-900 μm range. It is noteworthy that the pass-fail transition is not sharp and is indicated to occur over a ±100 μm particle size range for the 0" standoff configuration considered. For comparison purposes, the average critical particle diameter is indicated to be in the 140-750 μm range for the bare honeycomb (no MLI). With 1" MLI-honeycomb standoff, direct modeling of the passage of the vapor/debris cloud through the honeycomb was found to be computationally prohibitive. Test data shows that a honeycomb offers better HVI shielding than an equivalent monolithic wall with the same areal density. So for this set of analyses, the honeycomb was (conservatively) represented as a monolithic 16 mil-thk. wall, obtained by combining the two facesheets and neglecting the core. The average critical particle diameter is indicated to be in the 425-1300 μm range for this configuration. The size range over which the pass-fail transition occur is ±200 μm at 7 km/s but only ±25 μm at 150 km/s. In addition to presenting these new ballistic limit equations (BLEs) for honeycomb structure shielded by MLI in the 7-150 km/s range, an empirical method for predicting the critical particle size at 7 km/s is provided, developed from data obtained for honeycomb configurations used in the New Horizons, Rosetta, METOP and ATV spacecraft. Insights gained from sensitivity analyses using a 12 mil-thk. facesheet and elimination of the core are also discussed.
The size of relatively large dynamic conchoidal fractures, i.e., surface spalls, immediately adjacent to and around interplanetary dust (IDP) hypervelocity impact (HVI) craters or pits in glass substrates is relevant to spacecraft solar cell and science instrument lens performance metrics, as well as glass pane design and safety in manned missions. This paper presents an analysis of the diameter of surface spalls in glass for the Solar Probe Plus (SPP) spacecraft, whose solar arrays and instruments must survive a 7-year mission involving significant dust interaction. Previously published data and regressions for surface spalling obtained from ground-HVI-tested and space-returned glass samples and solar cells are collated for this purpose. Analysis of the collective dataset reveals an unexpected and design-relevant finding: spall diameter, D S , obtained with dust-scale particles (diameter, d P <; 55 μm) and solar cells scales differently with impact velocity as compared with diameters obtained with "macroparticles" (d P = 400-3,500 μm) and glass monoliths. The average D S /d P obtained with dust-scale particles and glass in a layered substrate is approximately 1/5th of that obtained with macroparticles and a glass monolith. It is also found that a Ballistic Limit Equation (BLE) developed for glass HVI cratering at relatively low velocities (<; 10 km/s) can be modified for spalling and used successfully for bounding design calculations at the higher velocities considered.
The Solar Probe Plus (SPP) spacecraft is expected to encounter unprecedented levels of interplanetary dust particle (IDP) exposure during its approximately 7-year journey. To assure mission success it is necessary to define the dust hypervelocity impact (HVI) protection levels provided by its Multi-Layer Insulation (MLI)/thermal blankets with a reliability that is on par with that available for metallic Whipple shields. Development of a new ballistic limit equation (BLE) in the 7-150 km/s HVI range for representative 2-wall Whipple shields in which spacecraft MLI is the bumper material impacted by fused silica dust, was necessitated and is presented. A baseline SPP configuration was adopted for analysis: 0.0176 cm-thk. Kapton bumper (monolithic and layered), 2.54 cm standoff and 0.0762 cm-thk. Ti-6Al-4V rear wall. With a solid Kapton bumper, the critical particle diameter for incipient spall, which is chosen to be the failure criterion for SPP, is found to be in the ~650-1100 μm range, with the largest and the smallest sizes corresponding to 30 km/s and 150 km/s HVI, respectively. When the bumper is layered in a manner similar to that found in actual blankets (140 μm spacing), the critical particle diameter is indicated to be in the ~450-600 μm range. The existing BLE with an equivalently thick Aluminum bumper is found to be in reasonable agreement with the computed results in the 30-150 km/s range but non-conservative by a factor of ~2x at 7 km/s. A limited analysis has also been performed to assess the effect of spacing between the Kapton layers - 140 μm versus 320 μm - in a blanket on critical particle size in the 30-150 km/s HVI range. Little change in the critical particle size is found, suggesting that the response of the blanket layers to high-velocity IDP may be similar to that of multi-shock shields.
Interplanetary dust particles and meteoroids mostly originate from comets and asteroids. Understanding their distribution in the Solar system, their dynamical behavior and their properties, sheds light on the current state and the dynamical behavior of the Solar system. Dust particles can endanger Earth-orbiting satellites and deep-space probes, and a good understanding of the spatial density and velocity distribution of dust and meteoroids in the Solar system is important for designing proper spacecraft shielding. The study of interplanetary dust and meteoroids provides clues to the formation of the Solar system. Particles having formed 4.5 billion years ago can survive planetary accretion and those that survived until now did not evolve significantly since then. Meteoroids and interplanetary dust can be observed by measuring the intensity and polarization of the zodiacal light, by observing meteors entering the Earth’s atmosphere, by collecting them in the upper atmosphere, polar ices and snow, and by detecting them with in-situ detectors on space probes.
Meteorites have long been considered as reflections of the compositional diversity of main belt asteroids and consequently they have been used to decipher their origin, formation, and evolution. However, while some meteorites are known to sample the surfaces of metallic, rocky and hydrated asteroids (about one-third of the mass of the belt), the low-density icy asteroids (C-, P-, and D-types), representing the rest of the main belt, appear to be unsampled in our meteorite collections. Here we provide conclusive evidence that the surface compositions of these icy bodies are compatible with those of the most common extraterrestrial materials (by mass), namely anhydrous interplanetary dust particles (IDPs). Given that these particles are quite different from known meteorites, it follows that the composition of the asteroid belt consists largely of more friable material not well represented by the cohesive meteorites in our collections. In the light of our current understanding of the early dynamical evolution of the solar system, meteorites likely sample bodies formed in the inner region of the solar system (0.5-4AU) whereas chondritic porous IDPs sample bodies that formed in the outer region (>5 AU).
Cometary material and pristine interplanetary dust particles (IDPs) best resemble the unaltered components from which our solar system was built because they have remained largely unaltered in a cold undisturbed environment since accretion in the outer protoplanetary disk. IDPs might supply more primitive assemblages for laboratory analysis than Stardust samples from comet 81P/Wild 2 but their individual provenances are typically unknown. We speculate that some IDPs collected by NASA in April 2003 may be associated with comet 26P/Grigg–Skjellerup because their particularly pristine character coincides with the collection period that was predicted to show an enhanced flux of particles from this Jupiter-family comet. Some IDPs from this collection contain the most primitive assembly of interstellar matter found to date including an unusually high abundance of presolar grains and very isotopically anomalous and disordered organic matter as well as fine-grained carbonates and an amphibole associated with a GEMS-like object (glass with embedded metals and sulfides) that potentially imply formation in a nebular rather than planetary environment. The two most primitive IDPs may contain assemblages of molecular cloud material at the percent level which is supported by the presence of four rare O-depleted presolar silicate grains possibly of supernova(e) origin within one ~ 70 μm -sized IDP and the close association of a Group 1 Mg-rich olivine from a low-mass red giant star with a carbonaceous nano-globule of potentially interstellar origin. Our study together with observations of comet 9P/Tempel 1 during the Deep Impact experiment and 81P/Wild 2 dust analyses reveal some compositional variations and many similarities among three Jupiter-family comets. Specifically carbonates and primitive organic matter or amorphous carbon were widespread in the comet-forming regions of the outer protoplanetary disk and not all comets contain as much inner solar system material as has been inferred for comet 81P/Wild 2. The bulk and hotspot hydrogen and nitrogen isotopic anomalies as well as the carbon Raman characteristics of the organic matter in IDPs and the most primitive meteorites are remarkably similar. This implies that the same mixture of molecular cloud material had been transported inward into the meteorite-forming regions of the solar system.
This study investigates the origin of interplanetary dust particles (IDPs) through the optical properties, albedo and spectral gradient, of zodiacal light. The optical properties were compared with those of potential parent bodies in the solar system, which include D-type (as analogs of cometary nuclei), C-type, S-type, X-type, and B-type asteroids. We applied Bayesian inference to the mixture model composed of the distribution of these sources, and found that >90% of the IDPs originate from comets (or their spectral analogs, D-type asteroids). Although some classes of asteroids (C-type, X-type, and B-type) may make a moderate contribution, ordinary chondrite-like particles from S-type asteroids occupy a negligible fraction of the interplanetary dust cloud complex. The overall optical properties of the zodiacal light were similar to those of chondritic porous IDPs, supporting the dominance of cometary particles in the zodiacal cloud.
We present an improved model for interplanetary dust grain fluxes in the outer Solar System constrained by in situ dust density observations. A dynamical dust grain tracing code is used to establish relative dust grain densities and three-dimensional velocity distributions in the outer Solar System for four main sources of dust grains: Jupiter-family comets, Halley-type comets, Oort-Cloud comets, and Edgeworth-Kuiper Belt objects. Model densities are constrained by in situ dust measurements by the Student Dust Counter, the 10 meteoroid detector, and the Dust Detection System (DDS). The model predicts that Jupiter-family comet grains dominate the interplanetary dust grain mass flux inside approximately 10 AU, Oort-Cloud cometary grains may dominate between 10 and 25 AU, and Edgeworth-Kuiper Belt grains are dominant outside 25 AU. The model also predicts that while the total interplanetary mass flux at Jupiter roughly matches that inferred by the analysis of the DDS measurements, mass fluxes to Saturn, Uranus, and Neptune are at least one order-of-magnitude lower than that predicted by extrapolations of dust grain flux models from 1 AU. Finally, we compare the model predictions of interplanetary dust oxygen influx to the giant planet atmospheres with various observational and photochemical constraints and generally find good agreement, with the exception of Jupiter, which suggests the possibility of additional chemical pathways for exogenous oxygen in Jupiter’s atmosphere.
The Stardust mission returned the first sample of a known outer solar system body, comet 81P/Wild 2, to Earth. The sample was expected to resemble chondritic porous interplanetary dust particles because many, and possibly all, such particles are derived from comets. Here, we report that the most abundant and most recognizable silicate materials in chondritic porous interplanetary dust particles appear to be absent from the returned sample, indicating that indigenous outer nebula material is probably rare in 81P/Wild 2. Instead, the sample resembles chondritic meteorites from the asteroid belt, composed mostly of inner solar nebula materials. This surprising finding emphasizes the petrogenetic continuum between comets and asteroids and elevates the astrophysical importance of stratospheric chondritic porous interplanetary dust particles as a precious source of the most cosmically primitive astromaterials.