169,754 research outputs found
Impact fragments from honeycomb sandwich panels
No full textSandwich panels are currently employed in space structure thanks to their light weight, good mechanical resistance, and enhanced capability to protect internal component from space debris. In case of impacts, sandwich panels may fragment differently from simple plates in terms of number and shape of generated debris. The effect of this different behaviour on satellites break-ups is currently under scrutiny, as existing fragmentation models are mostly based on data on aluminium plates. In this context, the University of Padova performed a set of impact experiments on different materials employed in the space sector. In particular, the test campaign focused on honeycomb sandwich panels with aluminium and carbon-fibre reinforced panels (CFRPs) skins. For all tests the generated fragments were collected, weighed, and sifted in size classes; their shape and size were acquired through image acquisition. In this paper the main results of the test campaign are presented, in terms of fragments characteristic length distributions and shape fragments distributions. Results show that at the same impact conditions the number of fragments generated by panels with CFRP skins is larger than the ones generated by panels with aluminium skin; with respect to the shape, it was noted that a large fraction of the fragments generated by panels with CFRP skins showed needle-like shapes
Analysis of fragments larger than 2 mm generated by a picosatellite fragmentation experiment
No full textSatellite breakup models rely on laboratory tests and in-space collision observations; current models can match fragments distributions generated by traditional satellites but may need to be improved for small spacecraft and modern satellites employing new configurations and materials. In the last years, ground tests have been employed to assess the influence of dimensions, materials and internal configurations on fragments distributions and to define the limits of the current models. In this context, an impact test was performed at the impact facility of the University of Padova to characterize the fragmentation of a picosatellite mock-up; more than 7000 fragments were collected, classified and analysed with automatic image recognition algorithms. It was observed that the experimental characteristic length distribution is line with the prediction of the NASA SBM even for the smallest size classes, while the fragments shape distribution is strongly affected by the materials employed in the picosatellite manufacturing.
The subset of the collected fragments larger than 2 mm was recently subjected to a more detailed analysis: each fragment was individually weighed, and its three main dimensions were measured. In this paper, resulting fragments distributions are compared with literature data and the NASA Standard Breakup Model; in particular, an analytic relation between fragments characteristic length and size is found. In addition, results show that characteristic length and area-to-mass distributions are affected by the target materials and are clearly influenced by the size resolution of the analysed fragments
Simulations of satellites mock-up fragmentation
No full textHigh energy in-space collisions may lead to the catastrophic fragmentation of entire spacecraft. Current empirical models employed to predict spacecraft breakup are based on ground experiments and observation of debris cloud generated by collision events. Due to the continuous growth of the number of resident objects orbiting the Earth and the risk they pose to operational satellites, in the last years the interest in collecting new test data on spacecraft collisions has increased, as well as the request to improve current breakup models and develop new ones. In this context the University of Padova performed a set of impact simulations, with a custom fragmentation algorithm, on satellites mock-ups consisting of cubic, cylindrical, and parallelepiped shapes with internal boxes representing on-board components. The considered scenarios include several targets and impactors masses and sizes and different impact geometries (in terms of velocity, impact angle and location). Simulations results consist in the generated fragments characteristic length cumulative distributions. It was observed that all distributions show different sections that can be attributed to different damage modes: the smaller fragments are generated by the spacecraft components fragmentation, the intermediate ones by the detached internal boxes, and the largest ones consisting in intact pieces of the spacecraft separated from the main structure. The limits, extent and slope of these sections depend on the impact conditions, the satellite structure and the impact point; a piecewise analytical model is derived for the simulation data, showing a good accordance with the fragments distribution trends
Fragments analysis of an hypervelocity impact experiment on a solar array
No full textA large fraction of spacecraft external surfaces or appendages often consists of solar arrays, which can be subjected to space debris impacts as in the case of the Sentinel 1 A event of August 2016. Therefore, it is of interest to understand how solar arrays respond to hypervelocity impacts and to investigate the generated fragments population. In this context, the University of Padova performed an impact experiment on a solar array consisting in a composite sandwich panel, coated with a Kapton layer, and provided with solar cells: a nylon cylinder of 0.039 g collided with the solar panel at a velocity of 4.86 km/s with an impact angle of 45 deg, detaching a solar cell and damaging the panel structure. More than 4500 fragments larger than 0.2 mm were collected and classified after the impact.In this paper the impact experiment is described and the fragments analysis is presented in terms of size and shape distributions; a comparison with a test on a composite sandwich panel shows that the distributions are strongly affected by material and manufacturing choices, in particular regarding the fragments generated by delamination
Experimental fragments distributions for thin aluminium plates subjected to hypervelocity impacts
No full textNumerical simulation research on Fragmentation effect of hypervelocity impact of ellipsoid shaped projectile normally onto a thin plate
No full textProjectile shape has a crucial influence on the fragmentation of projectile and target subjected to hypervelocity impact. However, most of analytic and empirical models for predicting fragmentation in hypervelocity impact were derived based on spherical projectile. This paper presents a work performed for characterizing fragmentation of aluminum thin plates due to normal incoming aluminum ellipsoid shaped projectile by utilizing smoothed particle hydrodynamics (SPH) methodology. In simulations, the masses of ellipsoid shaped projectiles were fixed as the same, while the aspect ratio was varying from 0.05 to 5, the impact velocity was limited in the range of 3km/s to 7km/s, and the impact attitude was limited in the normal case which the rotational axis of ellipsoid being perpendicular with the target surface. In the postprocess of simulations, critical fragmentation characteristics including the velocity of the leading edge and the expanding velocity of the fragments cloud, perforation hole size, mass and velocity of primary fragment were analysed, with varying impact condition parameters. Furthermore, empirical equations of some fragmentation characteristics were proposed, and the parameters included in the equations were fit with simulation data
Glancing Impact on a Picosatellte Mock-up: Test Results
No full textIn the study of hypervelocity collisions between space debris and satellite components, the literature mainly focuses on central impact, with less data available on glancing impact scenarios. In these situations, only a fraction of the colliding objects is directly involved in the event; with respect to central impacts, they can cause only partial fragmentation and generate debris clouds with different characteristics in terms of objects mass and size distributions. Reconstructing in-space glancing impacts from observations after the event is really challenging, as a precise assessment of the collision geometry is extremely complex and, as further consequence, modelling the fragmentation after glancing impacts cannot be supported by observation data. In this context, a glancing impact experiment was performed at the Hypervelocity Impact Facility of the University of Padova. In the test, a nylon projectile was launched at 2.6 km/s onto a cubic picosatellite mock-up; the impact angle between the target and the impacted face was 45 deg, while the impact point was at the middle of a face edge. High-speed video of the experiment showed that most of the largest debris were produced by structural links failure, while the generation of smaller fragments was observed only in the area directly involved in the collision. In this paper, the impact test is described, as well as the main characteristics of the generated fragments; in addition, fragments cumulative distributions are compared with the ones generated by a central impact on an equivalent target-projectile configuration
NUMBER, SIZE AND SPEED DISTRIBUTION OF PARTICLES EJECTED FROM SPACECRAFT SURFACES DURING HYPERVELOCITY IMPACT
No full textFragments Distribution Prediction for ENVISAT Catastrophic Fragmentation
No full textENVISAT is currently one of the largest debris in Low Earth Orbit and it resides in a highly populated orbital zone with higher impact risk. A collision with other satellites or rocket stages could generate and scatter fragments into altitudes occupied by many operational spacecraft, and in the worst case could restrict the access to polar orbits at about 800 km altitude. In this context, there is a need to evaluate the contamination of the orbital regions possibly involved by the spread of debris originated after a possible ENVISAT fragmentation.
In this paper the results of a campaign of hypervelocity impacts simulations with ENVISAT as target body are presented. A set of potential configurations for the collision have been simulated, varying the impacting body (small-class 100 kg satellite, defunct rocket stage) as well as the impact position (glancing impact on ENVISAT radiator, collision on the central body); for each impact configuration, fragments distributions are reported and the severity of different collision scenarios is discussed. Then, newly generated fragments are propagated to identify and assess local variations of the space debris spatial density. This is achieved by overlaying ENVISAT fragments population to ESA Meteoroid and Space Debris Terrestrial Environment Reference (MASTER) population and studying their evolution with a continuum model
Simulation and validation of a fragmentation model for carbon fibre reinforced polymers subjected to hypervelocity collision
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