Impact Flash Research Articles

Hypervelocity impact induced light flash experiments on single and dual layer Kapton targets to develop a time of flight space dust and debris detector

The impact flash from hypervelocity impact on thin (12.5 µm) Kapton film was observed. The projectile sizes ranged from 0.1 to 1 mm, with speeds from 2 to 5 km s−1 and penetrated the Kapton intact, leaving holes the same size as the projectile (to within measurement errors). The flash intensity (normalised to impactor mass) scaled with impact speed to the power 5.5. However, the data also suggest that at constant speed the intensity scales with the area of the hole in the Kapton and not the projectile mass (i.e. with some property of the target and not as a function of the projectile energy or momentum). Using two layers of Kapton, it was possible to construct a Time of Flight (TOF) system, which used the time of the onset of the flash in each layer to produce flight speeds accurate to within typically 1%. When compared to the projectile speed pre-impact, there was no indication of projectile deceleration during passage through the Kapton film. In addition, when PVDF acoustic sensors were placed on the Kapton film, they exhibited an electromagnetic “pick-up” signal from the impact of projectile on the Kapton, confirming suspicions of signal interference from past work with acoustic sensors. The ability of the light flash to provide accurate impact timing signals suggests the TOF system would be suitable for use as a cosmic dust or debris impact detector in space (e.g. Low Earth Orbit).

Energy distribution characteristic of impact flash of metallic target impacted by hypersonic projectile

The impact flash as a physical phenomenon of hypervelocity impact has been widely studied for decades, but these ballistic impact researches related to impact flash of low-mass particles were mostly concerned with hypervelocity impact at a speed beyond 4 km/s. In comparison to the substantial literature on light emission from hypervelocity impact events, our knowledge of light signatures from hypersonic impact is relatively limited presently, especially for those occur in air and associated with explosively accelerated fragments, which typically have maximum velocities in the range of 1∼2 km/s. This study attentively investigates the impact flash generated by hypersonic projectile impacting metallic targets from the perspective of energy distribution. Firstly, series of hypersonic impact tests were conducted using the two-stage light gas gun, and the wavelength-resolved flash signals and optical data in the band of 200∼1000 nm under different impact conditions were simultaneously measured, where the target plate made of 6061 aluminum, pure aluminum and 45 steel were impacted by projectiles made of the same material over a velocity range of 1∼2 km/s, and the ambient pressure (AP) varied from 100 Pa to 105 Pa. The flash signal composed of components of low frequency with high amplitude and high frequency with low amplitude was split. The cumulative integration of flash intensity over the wavelength range was calculated to derive its energy distribution. Besides, the probability distribution characteristic of flash intensity was obtained through computing its probability density function. The influences of impact velocity, ambient pressure and target parameter on energy distribution of impact flash were discussed. The above research findings may promote deeper understanding of the energy release and transition of hypersonic impact process.

Extending lunar impact flash observations into the daytime with short-wave infrared

ABSTRACT Lunar impact flash (LIF) observations typically occur in R, I, or unfiltered light, and are only possible during night, targeting the night side of a 10–60 per cent illumination Moon, while >10° above the observers horizon. This severely limits the potential to observe, and therefore the number of lower occurrence, high energy impacts observed is reduced. By shifting from the typically used wavelengths to the J-band short-wave infrared, the greater spectral radiance for the most common temperature (2750 K) of LIFs and darker skies at these wavelengths enables LIF monitoring to occur during the daytime, and at greater lunar illumination phases than currently possible. Using a 40.0 cm f/4.5 Newtonian reflector with a Ninox 640SU camera and a J-band filter, we observed several stars and lunar nightside at various times to assess the theoretical limits of the system. We then performed LIF observations during both day and night to maximize the chances of observing a confirmed LIF to verify the methods. We detected 61 > 5σ events, from which 33 candidate LIF events could not be discounted as false positives. One event was confirmed by multiframe detection, and by independent observers observing in visible light. While this LIF was observed during the night, the observed signal can be used to calculate the equivalent signal-to-noise ratio for a similar daytime event. The threshold for daylight LIF detection was found to be between Jmag = +3.4 ± 0.18 and Jmag = +5.6 ± 0.18 (equivalent to Vmag = +4.5 and Vmag = +6.7, respectively, at 2750 K). This represents an increase in opportunity to observe LIFs by almost 500 per cent.

First contact: Fine structure of the impact flash and ejecta during hypervelocity impact.

Hypervelocity impacts are a significant threat in low-earth orbit and in hypersonic flight applications. The earliest observable phenomena and mechanisms activated under these extreme conditions are typically obscured by a very bright flash, called the impact flash, that contains the signatures of the critical mechanisms, the impacting materials, and the impact environment. However, these signatures have been very difficult to observe because of the small length and time scales involved coupled with the high intensities associated with the flash. Here we perform experiments investigating the structure and characteristics of the impact flash generated by 3 km s spherical projectile impacts on structural metals using temporally co-registered high-resolution diagnostics. Reciprocal impact configurations, in which the projectile and target material are swapped, are used to demonstrate the coupling of early-stage mechanisms in the flash and later-stage ejection mechanisms responsible for the development of the impact crater.

Modelling the optical energy profile of the 2021 October Jupiter impact flash

ABSTRACT We have conducted numerical simulations to reproduce the observed optical energy profile of the 2021 October 15 (ut) impact flash on Jupiter, which was the largest and the most well-observed flash event detected by ground-based movie observations. The observed long-duration (∼5.5 s) optical emission can be reproduced by an impact of an object with an exceptionally small angle of entry relative to the horizontal. The apparent lack of the impact debris feature despite the large impact object was possibly due to the shallower angle of entry (≤12°), which resulted in the lower ablation per unit volume at altitudes higher than $50 \, {\rm km}$, and the volume densities of the ablated materials were too low to allow the debris particulates to coagulate. The absence of temporal methane absorption change in the observed flash spectrum is consistent with the best-fitting results. The model better fits the observed optical energy profile for weaker material (cometary and stony) cases than for metallic ones. Based on the simulation results, prospects for future observations of impact flashes are discussed.

Score Based Garbage Collection Algorithm for Flash Based Storage System

A solid-state drive’s garbage collection technique considerably influences the drive’s writing performance and life duration. The garbage collection technique chooses the block to be erased so that the block can be reused. Several techniques, such as hot data identification, enhance the efficiency of garbage collection and impact flash memory access speed and lifespan. This paper proposes a garbage collection algorithm, SGC (Score-based Garbage Collection) which tries to identify data on the basis of threshold into hot and cold blocks then the process is followed by choosing victim block with the help of score for garbage collection. The SGC approach minimises SSD wear frequency and garbage collection overhead, extending SSD life and data reliability. A novel hot and cold identification system helps to reduces program/erasure cycles while increasing identification accuracy, basedon threshold data are clustered into hot and cold. The experimental findings illustrate that the SGC outperforms the existing approach under various benchmarks by reducing the frequency of block wear leveling. The simulation result shows how SGC performs well and lowers the costs, such as the number of copy and erase operation done, wear on the block, and energy consumption.Improvement percentage for wear leveling is calculated for input traces exchange, financial 1 and financial 2. For exchange trace our policy outperforms CB,CAT,GR and CATA by 19.04%,15.0%,37.03% and 10.5% respectively.

Present-day model of lunar meteoroids and their impact flashes for LUMIO mission

The Lunar Meteoroid Impacts Observer (LUMIO) is a CubeSat mission to observe, quantify, and characterize the meteoroid impacts by detecting their flashes on the lunar farside. It complements lunar nearside observations performed by ground-based observatories to yield global information synthesis on the lunar meteoroid environment. Predicting LUMIO’s scientific outcome involves devising a methodology to model the meteoroid environment. We propose a method where numerous known meteoroid streams, as well as sporadic collisions with the lunar surface, are modeled. Impacts are generated with a stochastic approach based on experimental observations of fireballs, impact flashes, and meteors. A catalog collecting data of both meteoroid streams and sporadic background is made available to the community. Sample scenarios are reproduced to show the capabilities of our method. A synthesis of the statistical analysis performed on the collision dynamics is presented. Results show that a typical scenario counts almost 2 million impacts with impact kinetic energy larger than 10−7 kton TNT Equivalent, out of which approximately 200.000 fall in the energy range of interest for the LUMIO mission. For that subset, the equivalent black body temperature is estimated to range in 1510-2290K, the average impact flash duration is expected to be approximately 15ms, and the average plume area is predicted to be roughly 70m2.

Detection of an Extremely Large Impact Flash on Jupiter by High-cadence Multiwavelength Observations

We report the detection of an optical impact flash on Jupiter on 2021 October 15 by a dedicated telescope, Planetary ObservatioN Camera for Optical Transient Surveys, for the first time. Our temporally resolved three-band observations of the flash allowed investigations of its optical energy without the need for approximations on the impact brightness temperature. The kinetic energy of the impactor was equivalent to approximately two megatons of TNT, an order of magnitude greater than that of previously detected flashes on Jupiter and comparable with the Tunguska impact on Earth in 1908. This detection indicates that Tunguska-like impact events on Jupiter occur approximately once per year, two to three orders of magnitude more frequently than terrestrial impacts. The observed flash displayed a single-temperature blackbody spectrum with an effective temperature of approximately 8300 K without clear temporal variation, possibly representing common radiative features of terrestrial Tunguska-class superbolides.

Analysis of the First Optical Detection of a Meteoroidal Impact on the Lunar Surface Recorded from Brazil

Two lunar flashes are reported and fully analyzed, with one of them fulfilling every criterion preconized in the literature for the characterization of an impact, including confirmation by two simultaneous observations. It happened at 07:13:46 UT on 14 December 2017, at the selenographic coordinates of 9.79° (±0.06°)N and 45.42 (±0.07°)E. The peak magnitudes in the R and V bands vary from 6.3 to 7.9 and from 7.4 to 9.0, respectively, depending on the observatory, as the cameras’ exposure times were considerably different. The impactor mass is estimated to be between 1.6 and 2.0 kg, with a diameter of 10 to 11 cm, having produced a crater of 8.4 to 8.9 m in diameter. Results for the second flash are also presented and discussed, although the confirmation of an impact was not possible due to a pause in the recordings at one of the sites. The observations took place as part of an inaugural observing campaign in Brazil for lunar impact flash (LIF) detection conceived by the Brazilian Meteor Observation Network (BRAMON) and were carried out by two teams located in different states in the Northeast Region of Brazil, about 353 km apart from each other, at a time when the Moon was crossing the densest part of the Geminid meteoroid stream in 2017. The observing setups included 0.13 m and 0.2 m telescopes, both equipped with sensitive cameras. The Maceió setup probably delivered the finest definition ever reported in the literature for lunar impact monitoring, resulting in high-accuracy positioning. This will certainly aid in finding the associated crater from orbiter images, which will substantiate another work, aimed at performing a comparative analysis between the results from our photometry and the data retrieved by the LRO images. These observations were also very likely the first and the only one so far made by a normal framerate camera and a long-exposure camera simultaneously. The associated benefits are commented on. The source of the impactors is also discussed. In view of the successful results of this experience, national observing campaigns of this kind will be given continuation.

PyNAPLE: Lunar Surface Impact Crater Detection

ABSTRACT In the last 20 yr, over 600 impact flashes have been documented on the lunar surface. This wealth of data presents a unique opportunity to study the meteoroid flux of the Earth–Moon environment, and in recent years the physical properties of the impactors. However, other than through serendipitous events, there has not been yet a systematic search and discovery of the craters associated to these events. Such a meteoroid-crater link would allow us to get insight into the crater formation via these live observations of collisions. Here, we present the pynaple (python NAC Automated Pair Lunar Evaluator) software pipeline for locating newly formed craters using the location and epoch of an observed impact flash. We present the first results from pynaple, having been implemented on the 2017-09-27 impact flash. A rudimentary analysis on the impact flash and linked impact crater is also performed, finding that the crater’s ejecta pattern indicates an impact angle between 10–30°, and although the rim-to-rim diameter of the crater is not resolvable in current LRO NAC images, using crater scaling laws we predict this diameter to be 24.1–55.3 m, and using ejecta scaling predict a diameter of 27.3–37.7 m. We discuss how pynaple will enable large scale analyses of sub-kilometer scale cratering rates and refinement of both scaling laws, and the luminous efficiency.

Hypervelocity impact of anorthosite: Excavation, spallation and crater reconstruction

We report the results of eleven unconfined hypervelocity experiments, each involving the impact of a 316 stainless steel projectile (3.175 mm diameter sphere) with an anorthosite rock target. Impact velocities ranged from 1.75 to ∼6.7 km/s. The experiments were performed using a two-stage light gas gun. Three successive impact stages are distinguished: (1) initial contact, with shock wave and, at impact velocities >4 km/s, impact flash generation (<0.1 ms duration); (2) crater excavation (<0.4 ms duration), which is correlated with an initial ejecta event, where the ejecta velocity is supersonic and proportional to impact energy; and (3) spallation (>0.4 ms duration), which is associated with a later, second ejecta event, where the ejecta velocity is subsonic and unrelated to impact energy. Anorthosite mass loss, via cratering and spalling, is proportional to impact energy. Resulting crater shapes in the anorthosite were assessed via 3-D laser scanning. They show an overall increase in crater depth with velocity. Three mathematical fits were evaluated to define crater shape: parabolic, hyperbolic and power law. Each of the fitted equations was then used to predict the shape of the transient crater. Out of nine samples that retained viable crater shapes, the hyperbolic fit performed best in seven cases, and power law best in two. Monte Carlo simulation was deployed to reconstruct pre-spall crater volume. Total material loss versus calculated crater volume shows increasing divergence above ∼5.5 km/s, which is attributed to the growing role of spall in removing target material at increasing velocity. Shock calculations based on known densities, zero-pressure bulk sound velocities and particle velocity coefficients for target and projectile allow the determination of shock wave velocity, particle velocity and pressure relations, as well as penetration velocity; the latter indicating underdriven excavation conditions. The calculated maximum contact shock pressures attained for the eleven shots range from 24 GPa (1.75 km/s) to 149 GPa (6.69 km/s). For the impact velocities experienced and following crater reconstruction (to pre-spall state) the results indicate that (1) crater shape and depth/diameter ratios are velocity independent, and (2) consideration be given to the hyperbolic form for craters generated by hypervelocity impact.

Assessing the Present-Day Impact Flux to the Lunar Surface Via Impact Flash Monitoring and Its Implications for Sustained Lunar Exploration

Whitepaper #200 submitted to the Planetary Science and Astrobiology Decadal Survey 2023-2032. Topics: planetary defense; Mercury and/or the Moon; solar system formation, dynamics processes, and chronology

Inversion of spectral information obtained during hypersonic impact

A large number of space activities are generating a high amount of undesirable space debris, which causes inevitable damage to spacecraft and satellites. Moreover, the damage assessment of ultrahigh-speed debris is a challenging task that requires both theoretical and ground-level experimental simulations. One should note that the location and damage degree can be preliminarily determined by measuring the impact flash spectrum, which provides basic data for damage assessment. Herein, the radiation spectrum of an ultrahigh-speed collision between plastic projectile and aluminum target is measured by using spectroscopic technology. The surface temperature of the colliding material, electron temperature, and electron density in the plasma are simultaneously retrieved by using a single-frame spectrum. The single-frame spectrum is separated into a continuous spectrum and a line spectrum by using continuous thermal radiation spectrum inversion material interface temperature and line spectrum inversion electron temperature and electron density in the plasma.

Hypervelocity impact flash expansion geometry under various spacecraft surface electrical conditions

A more congested space environment due to increasing space activities introduces new threats to spacecraft operators. Among these threats include hypervelocity impacts from microparticles (<1 µg) in the form of meteoroids and space debris. These microparticles travel at speeds between 11.2 and 72.8 km/s with respect to the Earth and can impact spacecraft forming a small (∼1 µm) and dense (∼1026 m−3) plasma. This plasma can generate a strong optical emission (impact flash) and a radio frequency (RF) emission. These emissions can lead to spacecraft electrical anomalies when the impacted spacecraft surface (target) carries high electrical potential due to various space weather effects.To understand the microparticle hypervelocity impact plasma and its associated threat to spacecraft electronics, we studied the hypervelocity impact flash expansion geometry under various spacecraft surface electrical conditions. Three high-speed broadband photomultiplier tubes (PMT) are used to capture the temporal evolution of the impact flash and the temporal evolution of the angular distribution of the impact flash expansion geometry in a 3 MV electrostatic dust accelerator during a ground-based experiment. Results indicate that the impact surface electrical condition has a statistically significant influence on the impact flash geometry, and a strong similarity between the impact plasma and flash expansion geometry. Thus, this paper provides new experimental support for the impact flash origin from and connection with the impact plasma, and serves as the first impact flash expansion geometry characterization under various impact surface electrical conditions in a collisionless environment (<10−5 Torr).

Impact flash evolution of CO2 ice, water ice, and frozen Martian and lunar regolith simulant targets

AbstractThe wavelength dependence and temporal evolution of the hypervelocity impact self‐luminous plume (or “flash”) from CO2 ice, water ice, and frozen Martian and lunar regolith simulant targets have been investigated using the Kent two‐stage light‐gas gun. An array of 10 band‐pass filtered photodiodes and a digital camera monitored changes in the impact flash intensity during the different phases of the emitting ejecta. Early‐time emission spectra were also recorded to examine short‐lived chemical species within the ejecta. Analyses of the impact flash from the varied frozen targets show considerable differences in temporal behavior, with a strong wavelength dependence observed within monitored near‐UV to near‐IR spectral regions. Emission spectra showed molecular bands across the full spectral range observed, primarily due to AlO from the projectile, and with little or no contribution from vaporized metal oxides originating from frozen regolith simulant targets. Additional features within the impact flash decay profiles and emission spectra indicate an inhomogeneity in the impact ejecta composition. A strong correlation between the density of water ice‐containing targets and the impact flash rate of decay was shown for profiles uninfluenced by significant atomic/molecular emission, although the applicability to other target materials is currently unknown. Changes in impact speed resulted in considerable differences in the temporal evolution of the impact flash, with additional variations observed between recorded spectral regions. A strong correlation between the impact speed and the emission decay rate was also shown for CO2 ice targets. These results may have important implications for future analyses of impact flashes both on the lunar/Martian surface and on other frozen bodies within the solar system.

An experimental study of the impact flash: The relationship between luminous efficiency and vacuum level

When a meteoroid impacts on the Moon, a brief flash phenomenon—called a “lunar impact flash”—can be observed by ground-based telescopes. The statistics of these events can efficiently determine the meteoroid size-frequency distribution in cis-lunar space. The luminous efficiency—that is, the ratio of luminous energy emitted to the impactor’s kinetic energy—is the most important parameter for precise meteoroid-size estimation. Thus, it is necessary to understand the impact-flash mechanism and determine the luminous efficiency under various conditions. We have, therefore, performed hypervelocity-impact experiments at JAXA, and measured the relation between luminous efficiency and ambient pressure at various vacuum levels. Based on a high-speed spectroscopy, we find that the flash consists of blackbody radiation from hot ejecta and blackbody radiation from a vapor cloud together with emission lines and molecular bands. Spectrum analysis reveals that the initial luminous efficiency within the first few μs does depend on the vacuum level, whereas the luminous efficiency over several ms does not depend on the vacuum level.

Mission to Earth–Moon Lagrange Point by a 6U CubeSat: EQUULEUS

EQUULEUS (EQUilibriUm Lunar-Earth point 6U Spacecraft) will be the world's smallest spacecraft to explore the Earth-Moon Lagrange point. It is being jointly developed by JAXA (Japan Aerospace Exploration Agency) and the University of Tokyo, and will be launched by NASA's Space Launch System Exploration Mission-1. The spacecraft will fly to a libration orbit around the Earth-Moon L2 point (EML2) and will demonstrate low-energy trajectory-control techniques within the Sun-Earth-Moon region for the first time by a nano-class spacecraft. EQUULEUS also carries three scientific observation missions: imaging of Earth's plasmasphere by extreme ultraviolet wavelength, lunar impact flash observation on the far side of the moon, and micrometeoroid flux measurements in the cis-lunar region. While all these missions have their own scientific objectives, they will also contribute to future human activity and/or infrastructure development in the cis-lunar region. Most parts of the spacecraft system use commercial off-the-shelf components, or are designed based on the experiences of various past space missions, with the exception of the newly developed water resistojet propulsion system. EQUULEUS uses X-band frequency for deep space telecommunication. Japanese deep space antennas (64-m and 34-m) will be nominally used for spacecraft operation, and support from the deep space network of JPL (Jet Propulsion Laboratory) is also being planned, especially for the initial phase of operation. The spacecraft will fly to EML2 in less than one year, and will remain there for scientific observations until shortly before the depletion of the onboard propellant, when the spacecraft will leave the orbit for space-debris compliance.

Fragmentation modelling of the 2019 August impact on Jupiter

Abstract On 2019 August 7, an impact flash lasting ∼1 s was observed on Jupiter. The video of this event was analysed to obtain the light curve, and determine the energy release and initial mass. We find that the impactor released a total energy of 96–151 kilotons of TNT, corresponding to an initial mass between 190 and 260 metric tonnes with a diameter between 4 and 10 m. We developed a fragmentation model to simulate the atmospheric breakup of the object and reproduce the light curve. We model three different materials: cometary, stony, and metallic at speeds of 60, 65, and 70 km s−1, respectively, to determine the material make-up of the impacting object. The slower cases are best fitted by a strong, metallic object while the faster cases require a weaker material.

Hypersonic impact flash characteristics of a long-rod projectile collision with a thin plate target

Impact flash occurs when objects collide at supersonic speeds and can be used for real-time damage assessment when weapons rely on kinetic energy to destroy targets. However, the mechanism of impact flash remains unclear. A series of impact flash experiments of flat-head long-rod projectiles impacting thin target plates were performed with a two-stage light gas gun. The impact flash spectra for 6061 aluminum at 1.3–3.2 km/s collision speeds were recorded with a high-speed camera, a photoelectric sensor, and a time-resolved spectrometer. The intensity of the impact flash exhibited a pulse characteristic with time. The intensity (I) increased with impact velocity (V0) according to I∝V0n , where n = 4.41 for V0 > 2 km/s. However, for V0 < 2 km/s, n = 2.21, and the intense flash duration is an order of magnitude less than that of higher V0. When V0 > 2 km/s, a continuous spectrum (thermal radiation background) was observed and increased in intensity with V0. However, for V0 < 2 km/s, only atomic line spectra were detected. There was no aluminum spectral lines for V0 < 2 km/s, which indicated that it had not been vaporized. The initial intense flash was emission from excited and ionized ambient gases near the impact surface, and had little relationship with shock temperature rise, indicating a new mechanism of impact flash.

Short-duration precipitation extremes over Canada in a warmer climate

Short-duration precipitation extremes are widely used in the design of engineering infrastructure systems and they also lead to high impact flash flood events and landslides. Better understanding of these events in a changing climate is therefore critical. This study assesses characteristics of short-duration precipitation extremes of 1-, 3-, 6- and 12-h durations in terms of the precipitation-temperature (P–T) relationship in current and future climates for ten Canadian climatic regions using the limited area version of the global environment multiscale (GEM) model. The GEM simulations, driven by ERA-Interim reanalysis and two coupled global climate models (CanESM2 and MPI-ESM), reproduce the general observed regional P–T relationship characteristics in current climate (1981–2010), such as sub-CC (Clausius–Clapeyron) and CC scalings for the coastal and northern, and inland regions, respectively, albeit with some underestimation. Analysis of the transient climate change simulations suggests important shifts and/or extensions of the P–T curve to higher temperature bins in future climate (2071–2100) for RCP4.5 and 8.5 scenarios, particularly for 1-h duration. Analysis of the spatial patterns of dew point depression (temperature minus dew point temperature) and convective available potential energy (CAPE) corresponding to short-duration precipitation extremes for different temperature bins show their changing relative importance from low to high temperature bins. For the low-temperature bins, short-duration precipitation extremes are largely due to high relative humidity, while for high-temperature bins, strong convection due to atmospheric instability brought by surface warming is largely responsible. The analysis thus addresses some of the key knowledge gaps related to the behavior of P–T relationship and associated mechanisms for the Canadian regions.