Debris Mass Research Articles

Enlargement of depressions on comet 81P/Wild 2: Constraints based on 30-year cometary activity in the inner Solar System

The Stardust flyby mission to Jupiter-family comet (JFC) 81P/Wild 2 (hereafter, 81P) captured its dense quasicircular depressions. The formation mechanism behind these depressions remains a subject of debate. We aim to study how cometary activity contributed to the formation and enlargement of these depressions by analyzing Stardust flyby images and ground-based observation data. We calculated the time-dependent water production rate of 81P inside the snow line ($<$3 au) and compared it with the observational data. In addition, we estimated the fallback debris mass using an observation-based model, where a dust ejection from 81P was considered to reproduce ground-based observations of the dust tail. We compared the total excavated volume of water and dust with the total depression volume derived, using the 81P shape model. We find that the total excavated volume after 81P was injected into the inner Solar System accounts for up to only 30 % of the depression volume. This suggests that a large portion ($>$70 %) of the depressions had already existed before the comet was injected into the current orbit. In addition, we estimated the dust-to-ice mass ratio for 81P to be 2--14. We suggest that most depressions observed for 81P were formed in their source regions.

Fracture and fractal characteristics of high-temperature granite under confined space water jet impact

In the application of jet assisted deep drilling technology, the fracture mode and rock fragment characteristics of high-temperature rock in the confined space of jet drilling are not yet clear. We analyzed the fragmentation and debris distribution of high-temperature granite under confined space jet action using 3D reconstruction technology and statistical fractal theory to examine their fragmentation patterns and fractal characteristics. The results show that high-temperature rocks exhibit obvious thermal fracturing characteristics under the impact of confined water jet, and as the rock temperature increases, vertical compression shear cracks connect with radial tensile cracks. The maximum damage area is located near the bottom of the confined hole, and the distribution of cracks is more complex. As the degree of jet confinement decreases, the rock cracking form changes from radial tensile cracking to vertical compression shear cracking. As the rock temperature increases and the confined space size decreases, the total mass and large debris mass percentages of rock debris increase. The particle size distribution of rock debris follows an Rosin-Rammler (R-R) distribution and has obvious fractal characteristics. The fracture and fragmentation of high-temperature rocks under confined water jet impact are mainly caused by the combination of jet impact stress waves and thermal stress. The temperature difference of rocks affects the heat transfer between jet and rock, and the confined space size directly affects the heat transfer efficiency between jet and rock, which is manifested in different numbers of fracture cracks, internal damage area, and rock debris size distribution. These findings can provide a theoretical and parameter optimization basis for jet-assisted deep reservoir drilling applications.

Therapeutic Misadventure in a Case of Isolated Mastoid Cholesteatoma.

Cholesteatoma is a mass of keratin debris in the middle ear cavity or mastoid. Congenital cholesteatomas may remain asymptomatic for many years and present during adulthood or may even be an incidental finding. We hereby describe a case of 41-year male with an isolated mastoid congenital cholesteatoma with sigmoid plate erosion and posterior cranial dura exposure extending into digastric muscle. Tympanomastoid exploration with sigmoid sinus resurfacing with hydroxyapatite granules was done. However, the case got complicated by extrusion of granules which was then successfully managed. This case report throws light on diagnosis and surgical management of isolated mastoid cholesteatoma. From this misadventure, we learnt that a successful mastoid cavity obliteration (using hydroxyapatite granules) in a canal wall up mastoidectomy can be achieved by providing hermetic seal.

CubeSats for space debris removal from LEO: Prototype design of a robotic arm-based deorbiter CubeSat

Space debris has become a growing problem, and various studies indicate that the population of space objects has reached a critical density in low Earth orbits (LEO). Therefore, removing debris from the LEO is key to stabilizing the growth of space objects and making some of the orbits reusable for future launches. Deorbiting larger debris objects using miniaturized satellites, CubeSats is both economically viable and requires relatively less time for design & deployment. In this paper, we present a system-level study of orbital debris removal from LEO using CubeSats, detailing various existing debris tracking, rendezvous, capture, and deorbit mechanisms. A deep learning-based object detection algorithm has been utilized to improve the accuracy of detecting and localizing debris. We also present a discussion on the CubeSat-compatible capture & deorbit mechanisms identified from our study and an upper bound on the debris mass that can be deorbited from a given LEO orbit using CubeSats. We aim to demonstrate a case study for the orbital decay analysis of a CubeSat deorbiting the XSat, a microsatellite launched by Singapore. We detail the design of a 27U CubeSat deorbiter prototype equipped with a pair of robotic arms to capture the XSat. This analysis considers active deorbiting using Hall-effect thrusters, for which the required delta-V & propellant mass have also been computed.

Experimental and numerical research on the debris bed formation in severe accidents of nuclear reactors

The formation and coolability of the debris bed play a crucial role in the core meltdown process in nuclear reactors. Previous studies mainly focused on experiments involving interactions between small masses of molten material and water, with emphasis on the steam explosion process, lacking analytical data on debris beds and fragments. Therefore, the formation of the debris bed is studied by visual experiments, along with the relevant models are established and applied in this study. In the experiments, a large mass of zirconium dioxide is heated to a molten state in the crucible and then released into a water tank through the release device. The water tank is equipped with four glass windows and high-speed cameras to capture snapshots.Firstly, experiments on the formation of hundred-kilogram-scale debris beds were conducted using the prototype material, zirconium dioxide. The molten material temperature was 3000 K, the molten material mass ranged from 50 to 100 kg, the jet diameter varied from 10 to 20 mm, the water pool depth ranged from 0.55 to 1 m, and the water subcooling varied from 10 to 80 K. Visualized images of the debris bed formation were obtained, and an experimental database of debris bed formation was established, primarily including key parameters such as debris morphology, debris size, debris bed accumulation form, and debris bed porosity. The results indicate that the rise in the mass of molten material and the decrease in water subcooling increase the proportion of large-sized fragments. The experiments did not form a “cake” debris bed but instead achieved loose debris beds due to the small jet diameter. With an increase in the jet diameter and a decrease in water subcooling, the porosity of the debris bed will also increase. Subsequently, computational analysis codes were developed for the processes of jet break-up, debris bed accumulation, and formation, and finally, the deviation of the predicted accumulation morphology was less than 20 %. The results reveal that the influence of the jet diameter and mass of the molten debris on the deposition characteristics of the debris bed is very pronounced. Experimental research and code development hold significant reference value for the formulation of preventive and mitigative measures for severe accidents in nuclear power plants.

KELIMPAHAN MAKRO DEBRIS DI EKOSISTEM MANGROVE MUARA TUKAD MATI, BALI

Macro debris refers to waste materials ranging in size from 2.5 cm to 1 m, commonly found both on the water's surface and on the seabed. The accumulation of such large debris in coastal and marine environments can lead to various consequences, including disturbances to ecosystem stability and threats to the survival of organisms. Additionally, it diminishes the aesthetic quality of the environment. Among the ecosystems most susceptible to becoming repositories for this waste is the mangrove ecosystem. This study aims to quantify the amount, types, and abundance of macro debris scattered in the Tukad Mati Estuary Mangrove Area, Badung Regency, Bali. The research methodology involved several steps, starting with the selection of research stations. Transects measuring 5 x 5 meters were established. Within these designated areas, samples of macro debris were collected and categorized according to their composition, including materials such as plastic, fabric, glass, metal, and rubber. The results revealed that the total mass of macro debris collected in the Tukad Mati Estuary area amounted to 42,630 grams. The types of macro debris found in the Tukad Mati Estuary mangrove ecosystem consist of plastic, fabric, glass, metal, and rubber. Based on their quantity, the composition of macro debris is dominated by plastic at 87.02%, followed by fabric at 4.24%, rubber at 4.17%, glass at 2.67%, and metal being the least at 1.89%. Based on their weight, the composition of macro debris is highest for plastic at 32.33%, followed by rubber at 27.29%, fabric at 20.23%, glass at 14.36%, and metal being the lowest at 5.78%. The abundance of macro debris in the Tukad Mati Estuary mangrove ecosystem ranges from 0.85 items/m² to 10.68 items/m². Keywords: Marine Debris; Pollution; Tukad Mati Estuary; Mangrove

Experimental Investigation on the Influence of Water on Rockburst in Rock-like Material with Voids and Multiple Fractures.

To investigate the influence of water content on the rockburst phenomena in tunnels with horizontal joints, experiments were conducted on simulated rock specimens exhibiting five distinct levels of water absorption. Real-time monitoring of the entire blasting process was facilitated through a high-speed camera system, while the microscopic structure of the rockburst debris was analyzed using scanning electron microscopy (SEM) and a particle size analyzer. The experimental findings revealed that under varying degrees of water absorption, the specimens experienced three stages: debris ejection; rockburst; and debris spalling. As water content increased gradually, the intensity of rockburst in the specimens was mitigated. This was substantiated by a decline in peak stress intensity, a decrease in elastic modulus, delayed manifestation of pre-peak stress drop, enhanced amplitude, diminished elastic potential energy, and augmented dissipation energy, resulting in an expanded angle of rockburst debris ejection. With increasing water content, the bond strength between micro-particles was attenuated, resulting in the disintegration of the bonding material. Deformation failure was defined by the expansion of minuscule pores, gradual propagation of micro-cracks, augmentation of fluffy fine particles, exacerbation of structural surface damage akin to a honeycomb structure, diminishment of particle diameter, and a notable increase in quantity. Furthermore, the augmentation of secondary cracks and shear cracks, coupled with the enlargement of spalling areas, signified the escalation of deformation failure. Simultaneously, the total mass of rockburst debris gradually diminished, accompanied by a corresponding decrease in the proportion of micro and fine particles within the debris.

Method for monitoring and forecasting landslide phenomenon based on machine learning

A landslide involves the downward movement of a mass of rock, debris, earth, or soil. Landslides happen when gravitational forces and other types of shear stresses on a slope surpass the shear strength of the materials. Additionally, landslides can be triggered by processes that weaken the shear strength of the slope's material. Shear strength primarily depends on two factors such as frictional strength, which is the resistance to movement between the interacting particles of the slope material, and cohesive strength, which is the bonding between those particles. A landslide is a terrible natural disaster that causes much damage to both human life and the economy. It often occurs in steep mountainous areas or hilly regions, ranging in scale from medium to large. It progresses slowly (20–50 mm/year), but when it occurs, it can move at a speed of 3 m/s. Therefore, early detection or prevention of this disaster is an essential and significant task. This paper developed a method to collect and analyze data, with the purpose of determining the possibility of landslide occurrences to reduce its potential losses.•The proposed method is convenient for users to grasp information of landslide phenomenon.•A machine learning model is applied to forecast landslide phenomenon.•Internet of things (IoT) system is utilized to manage and send a warning text to individual email address and mobile devices.

Three-Dimensional Hepatocyte Spheroids: Model for Assessing Chemotherapy in Hepatocellular Carcinoma.

Three-dimensional cellular models provide a more comprehensive representation of in vivo cell properties, encompassing physiological characteristics and drug susceptibility. Primary hepatocytes were seeded in ultra-low attachment plates to form spheroids, with or without tumoral cells. Spheroid structure, cell proliferation, and apoptosis were analyzed using histological staining techniques. In addition, extracellular vesicles were isolated from conditioned media by differential ultracentrifugation. Spheroids were exposed to cytotoxic drugs, and both spheroid growth and cell death were measured by microscopic imaging and flow cytometry with vital staining, respectively. Concerning spheroid structure, an active outer layer forms a boundary with the media, while the inner core comprises a mass of cell debris. Hepatocyte-formed spheroids release vesicles into the extracellular media, and a decrease in the concentration of vesicles in the culture media can be observed over time. When co-cultured with tumoral cells, a distinct distribution pattern emerges over the primary hepatocytes, resulting in different spheroid conformations. Tumoral cell growth was compromised upon antitumoral drug challenges. Treatment of mixed spheroids with different cytotoxic drugs enables the characterization of drug effects on both hepatocytes and tumoral cells, determining drug specificity effects on these cell types.

Patterns of deadwood amount and deadwood diversity along a natural forest recovery gradient from agriculture to old-growth lowland tropical forests

AbstractDeadwood is a key component of nutrient cycling in natural tropical forests, serving as a globally important carbon storage and habitat for a high number of species. The conversion of tropical forests to agriculture modifies deadwood pools, but we know little about deadwood dynamics in forests recovering from human disturbance. Here we quantified the volume and diversity of coarse woody debris (CWD, ≥ 7 cm diameter) and the mass of fine woody debris (FWD, < 7 cm) along a chronosequence of natural forest recovery in the lowlands of the Ecuadorian Chocó region. We sampled forest plots ranging from 1–37 years of recovery post-cessation of agricultural use as either cacao plantation or cattle pasture, as well as actively managed cacao plantations and cattle pastures, and old-growth forests. In contrast to our expectation, we found no significant increase in deadwood volume with recovery time. The diversity in size, decay stage and type of CWD increased along the recovery gradient, with no effect of previous land use type. The mass of FWD increased overall across the recovery gradient, but these results were driven by a steep increase in former pastures, with no change observed in former cacao plantations. We suggest that the range of sizes and decomposition stages of deadwood found in these two major tropical agricultural systems could provide suitable resources for saproxylic organisms and an overlooked carbon storage outside old-growth forests. Our estimates of deadwood in agricultural systems and recovering forests can help improve global assessments of carbon storage and release in the tropics.

Abstract 3066: Pro-Atherogenic Macrophages Induce The Upregulation Of MLKL And Cell Death In Vascular Smooth Muscle Cells During Atherogenic Stimulation

Background: A hallmark of advanced, rupture-prone atherosclerotic plaques is the presence of a necrotic core - a dense mass of pro-inflammatory and cellular debris. Traditionally, it has been thought that most of the foam cells within this core are derived from macrophages. However, recent advances in single cell technologies have revealed that vascular smooth muscle cells have the capacity to transdifferentiate into "macrophage-like foam cells", accounting for almost half of the cell content in advanced plaques. Our lab and others have discovered that a primary cause of the necrotic core is necroptotic cell death, where the mixed lineage kinase domain like pseudokinase MLKL is a key executioner of this process. While the contribution of necroptotic macrophage-derived foam cells to atherosclerotic lesion growth and instability has been fairly well-studied, the role of necroptotic vascular smooth muscle cell-derived foam cells in this process remains unclear. Hypothesis: MLKL regulates cell death differently in macrophages and vascular smooth muscle cells when challenged with pro-atherogenic stimuli. Methods and Results: Bone marrow-derived macrophages (BMDMs) and aortic vascular smooth muscle cells (VSMCs) were isolated from wildtype mice and treated with pro-atherogenic stimuli in the presence or absence of apoptotic and necroptotic inhibitors, zVAD and Necrostatin-1 (Nec1). BMDMs underwent cell death in response to treatment with oxLDL or LPS plus zVAD within 24 hours (as measured by LDH release and SYTOX assays) while VSMCs survive up to 72 hours. However, when VSMCs are treated with BMDM conditioned media in addition to pro-atherogenic stimuli, VSMCs begin to show higher relative rates of cell death compared to controls. Confocal microscopy and Western blots revealed that VSMCs treated with cell death ligands in conjunction with BMDM conditioned media showed an increase in relative expression of total and pMLKL- a hallmark of necroptosis, compared to VSMCs without conditioned media. Conclusions: Overall, this work suggests VSMCs are inherently resistant to necroptosis unless treated with conditioned media from BMDMs, which may suggest that macrophages have the capacity to prime necroptosis in VSMCs, likely via secreted factors.

Forming Mercury from Excited Initial Conditions

Mercury is notoriously difficult to form in Solar System simulations, due to its small mass and iron-rich composition. Smooth particle hydrodynamics simulations of collisions have found that a Mercury-like body could be formed by one or multiple giant impacts, but due to the chaotic nature of collisions, it is difficult to create a scenario where such impacts will take place. Recent work has found more success forming Mercury analogues by adding additional embryos near Mercury’s orbit. In this work, we aim to form Mercury by simulating the formation of the Solar System in the presence of the giant planets Jupiter and Saturn. We test out the effect of an inner disk of embryos added on to the commonly used narrow annulus of initial material. We form Mercury analogues with core-mass fractions (CMFs) > 0.4 in ∼10% of our simulations, and twice that number of Mercury analogues form during the formation process but are unstable and do not last to the end of the simulations. Mercury analogues form at similar rates for both disks with and without an inner component, and most of our Mercury analogues have lower CMFs than that of Mercury, ∼0.7, due to significant accretion of debris material. We suggest that a more in-depth understanding of the fraction of debris mass that is lost to collisional grinding is necessary to understand Mercury’s formation, or some additional mechanism is required to stop this debris from accreting.

The formation of transiting circumplanetary debris discs from the disruption of satellite systems during planet–planet scattering

Abstract Several stars show deep transits consistent with discs of roughly 1 R⊙ seen at moderate inclinations, likely surrounding planets on eccentric orbits. We show that this configuration arises naturally as a result of planet–planet scattering when the planets possess satellite systems. Planet–planet scattering explains the orbital eccentricities of the discs’ host bodies, while the close encounters during scattering lead to the exchange of satellites between planets and/or their destabilisation. This leads to collisions between satellites and their tidal disruption close to the planet. Both of these events lead to large quantities of debris being produced, which in time will settle into a disc such as those observed. The mass of debris required is comparable to a Ceres-sized satellite. Through N-body simulations of planets with clones of the Galilean satellite system undergoing scattering, we show that 90 % of planets undergoing scattering will possess debris from satellite destruction. Extrapolating to smaller numbers of satellites suggests that tens of percent of such planets should still possess circumplanetary debris discs. The debris trails arising from these events are often tilted at tens of degrees to the planetary orbit, consistent with the inclinations of the observed discs. Disruption of satellite systems during scattering thus simultaneously explains the existence of debris, the tilt of the discs, and the eccentricity of the planets they orbit.

Mapping Landslide Vulnerability using Machine Learning Approach along the Taba Penanjung-Kepahiang Road, Bengkulu Province

Landslides occur when masses of rock, debris or soil move due to various factors and processes that cause land movement. The Taba Penanjung-Kepahiang route is one of the areas in Bengkulu Province that is highly prone to landslides. This causeway is the only fastest land route connecting the Bengkulu-Kepahiang area. In recent years, the road area has often been cut off due to landslides and fallen trees, which have caused road access to be cut off and obstructed and claimed lives. This study uses a Machine Learning (ML) and GIS approach with Variable Frequency Ratio using 16 independent factors obtained from the spatial database and DEM, which correlate with landslide events. This research aims to gain an in-depth understanding of the factors that cause landslides. In addition, the research focus is the development of a Disaster Mitigation Model to design and implement effective strategies to reduce the risk and impact of landslide disasters through in-depth analysis The dependent factor is the location of the landslide from the historical landslide area for the last five years, with a distribution of 70/30%. Furthermore, frequency ratio is used to analyze the correlation between conditioning factors and historical landslides. Then, the independent and dependent factors were normalized to create a landslide susceptibility map. Frequency Ratio (FR) indicates the likelihood of an event occurring, with drainage density (FR= 0.69), shear wave velocity (Vs30) (FR= 0.66), slope (FR= 0.60), and rainfall (FR= 0.55). The output of the processed data is in the table below.

Experimental study on the failure characteristic and mechanism of granite time-delayed rockburst under true triaxial condition

A series of tests for time-delayed rockburst of granite under true triaxial condition was designed and carried out. By using the true triaxial rockburst test system, an acoustic emission (AE) system, a high-speed camera system, and a digital image motion analysis software, the time-delayed rockburst development process was monitored and studied. Four stages were found in the failure of granite time-delayed rockburst, i.e. grains ejection, slab breaks and ejects, first fragments ejection and second fragments ejection. There is a “V” shear crack generated in the time-delayed rockburst sample, and several tensile cracks in the lower part of the rock sample cross through the “V” shear crack. The longer the duration (the time elapsed between the moments the AE hits rises rapidly and the rockburst occurs), the smaller the depth of the rockburst pit. The time-delayed rockburst debris are mainly composed of blocks and fragments. The longer the duration, the smaller the total debris mass, the percentage of ejected debris and the ejection kinetic energy. The fractal dimension of the debris is positively correlated with the duration. The longer the duration, the higher the degree of fragmentation. The cracks generated are tensile-shear composite cracks. In the loading stage, it is dominated by shear cracks. However, in the time-lag stage, it is dominated by tensile cracks. With the increase of the duration, the proportion of tensile cracks increased and the proportion of shear cracks decreased. The research results will have a certain reference value for the warning and risk mitigation of time-delayed rockbursts.

Risk Index for the Optimal Ranking of Active Debris Removal Targets

The first step of any active debris removal (ADR) mission is the selection of the target. The optimal choice is to find the most dangerous debris that can be removed considering the chaser spacecraft requirements and mission constraints. After creating a catalog of the current space population in low Earth orbit (LEO), the MIT Monte Carlo Orbital Capacity Assessment Tool (MOCAT-MC) is used to simulate and predict the future space environment and the interaction among the space population. A novel performance index to quantify the criticality of each debris and the risk that it presents to the space environment is proposed. The new risk index considers the proximity of the debris to highly populated regions, its persistence in orbit, its likelihood to collide, and the estimated number and mass of debris that it can generate. The risk index is then optimized to work either with the full space population or a subset of it, where the ranking of risk among debris is highlighted. Multiple risk analyses are proposed in the test cases, where the ranked list of optimal targets is provided.

Mobility and erosion of granular flows travelling on an erodible substrate: Insights from the small-scale flume experiments

Rock avalanches are extremely rapid, flow-like movements of dry debris mass with extreme destructive potential. Among the dynamical aspects of rock avalanches still inadequately understood, the flow along an erodible substrate stands out as a particularly significant one. We carried out a series of flume experiments to investigate the mobility and the erosion of granular flows on an erodible substrate. It was found that granular flows with a large total mass could evolve into a stable multi-layer flow when suffering the enhanced basal resistance (e.g., loose and dry erodible substrate). Without the variation of the properties of erodible material, the increase of total mass (from 5 kg to 15 kg) as well as the reduction of grain size (from 4 to 8 mm to 1–2 mm) has a positive influence on the mobility of the granular flows (max. 12% and max. 3.4% growths in runout distance, respectively), emphasizing the important roles of both the event magnitude and the internal friction. Total mass and the grain size have prominent influences also on the erosion effect of granular flow. An increase in flow mass causes an enhancement of the eroded depth and of the expansion in both backward and forward directions, while grain size enhanced only forward expansion in addition to the eroded depth. Altogether, the experiments indicate that an erodible substrate may have dramatic effects on the dynamics of an experimental granular flow. When applied to the field, they point to the importance of the nature of the basal material onto which a natural landslide collapses.

On the relative importance of shocks and self-gravity in modifying tidal disruption event debris streams

ABSTRACT In a tidal disruption event (TDE), a star is destroyed by the gravitational field of a supermassive black hole (SMBH) to produce a stream of debris, some of which accretes onto the SMBH and creates a luminous flare. The distribution of mass along the stream has a direct impact on the accretion rate, and thus modelling the time-dependent evolution of this distribution provides insight into the relevant physical processes that drive the observable properties of TDEs. Analytic models that only account for the ballistic evolution of the debris do not capture salient and time-dependent features of the mass distribution, suggesting that fluid dynamical effects significantly modify the debris dynamics. Previous investigations have claimed that shocks are primarily responsible for these modifications, but here we show – with high-resolution hydrodynamical simulations – that self-gravity is the dominant physical mechanism responsible for the anomalous (i.e. not predicted by ballistic models) debris stream features and its time dependence. These high-resolution simulations also show that there is a specific length-scale on which self-gravity modifies the debris mass distribution, and as such there is enhanced power in specific Fourier modes. Our results have implications for the stability of the debris stream under the influence of self-gravity, particularly at late times and the corresponding observational signatures of TDEs.

Low-cost debris deorbiting plus planetary protection

Space debris can be deorbited by a coating of volatile material that evaporates in sunlight. Consider a roque CubeSat that gets splashed with black gel while on the night side of its orbit. As it emerges into the rays of the Sun, kinetic evaporation provides a retro force relative to the orbital velocity, causing speed to diminish. At midpoint of orbital dayside, the net force is downward, towards the Earth’s atmosphere, where drag increases. If sufficient gel remains unevaporated during the transition back to nightside, there could be acceleration, but the dose of gel is limited to avoid this. Gel balls can be delivered from a standoff distance such that orbital matching need not be perfect, saving time and fuel for the debris-hunter. Larger chunks of debris can be shot with multiple gel balls designed that rupture and wet the surface, similar to a paint marking capsule (“paintball”), to provide more retroforce. For very large objects, such as earth orbit-crossing asteroids, judicious application of volatile material can provide a net force away from the Sun, altering the trajectory sufficiently to avoid impact. This work considers the velocity distribution in a liquid assuming the Maxwell-Boltzmann equation, the vapor pressure using the Clausius-Clapeyron equation, and the evaporative flux using the explicit Schrage equation to model vapor kinetics from the Knudsen layer under direct solar irradiation. A concept of operations for a notional debris-hunter satellite design allows an estimate of debris mass that can be deorbited in a given period of time. From this, and an estimate of launch mass, the number and mass of space junk that can be removed from a higher low-earth orbit (LEO) can be calculated. These expenses are sufficiently smaller than the consequence of a Kessler syndrome to compel spacefaring nations to implement this proactive approach without delay.

Hybrid-Compliant System for Soft Capture of Uncooperative Space Debris

Active debris removal (ADR) is positioned by space agencies as an in-orbit task of great importance for stabilizing the exponential growth of space debris. Most of the already developed capturing systems are designed for large specific cooperative satellites, which leads to expensive one-to-one solutions. This paper proposed a versatile hybrid-compliant mechanism to target a vast range of small uncooperative space debris in low Earth orbit (LEO), enabling a profitable one-to-many solution. The system is custom-built to fit into a CubeSat. It incorporates active (with linear actuators and impedance controller) and passive (with revolute joints) compliance to dissipate the impact energy, ensure sufficient contact time, and successfully help capture a broader range of space debris. A simulation study was conducted to evaluate and validate the necessity of integrating hybrid compliance into the ADR system. This study found the relationships among the debris mass, the system’s stiffness, and the contact time and provided the required data for tuning the impedance controller (IC) gains. This study also demonstrated the importance of hybrid compliance to guarantee the safe and reliable capture of a broader range of space debris.