Orbital Debris A Technical Assessment (1995) / Chapter Skim
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5 TOOLS FOR DAMAGE ASSESSMENT AND PREDICTION
5 TOOLS FOR DAMAGE ASSESSMENT AND PREDICTION
Pages 101-118
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From page 101... ...
GROUND-BASED HYPERVELOCI~ TESTING Experimental laboratory testing can simulate and/or verify three major types of orbital debris-related phenomena: (1) the effects of orbital debris impacts on spacecraft component performance, reliability, lifetime, and survivability; (2)
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From page 102... ...
As with component testing, it is economically infeasible to test all possible shield configurations against all possible impact conditions, so a mixture of experimental testing, analytic methods, and numerical methods is used. Because the debris threat is not well enough known to "optimize" debris shielding against any particular type of impactor, shield designers develop shields to protect spacecraft against a wide range of impactor sizes, shapes, and velocities without greatly increasing the spacecraft's mass.
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From page 103... ...
Figure 5-1 also points out size arid velocity regimes of debris impacts that could potentially be shielded against but that cannot be achieved with current hypervelocity impact capabilities. As seen in Figure 5-1, the capability exists to perform impact tests win even fairly large masses at velocities typical of collisions in highaltitude orbits.
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From page 104... ...
However, the applicability of these data to orbital debris issues has not been studied, and in any case, the data may be considered too sensitive for wide release. For studies of debris impacts at higher velocities, the standard laboratory tool is the two-stage light gas gun.
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From page 105... ...
Light gas guns cannot launch impactors to the velocities typical of LEO debris impacts (10-15 km/s) , but several ultrahigh-speed launchers have been developed that extend the impact velocity range for debris impact studies.
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From page 106... ...
This unusual shape complicates analysis of the data because analytical models for the damage caused by objects of this shape have not yet been developed. NASA is using a light gas gun to launch hollow cylinders at velocities of up to 8 km/s in order to learn more about the damage caused by this type of projectile.
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From page 107... ...
Russian investigators have developed a more radical method to simulate target conditions produced by ultrahigh-velocity particles; rather than launching an impactor, they have used electron beams and laser deposition to simulate the kinetic energy of high-velocity particles (Anisimov et al., 1985~. Researchers in the United States, Germany, and Israel have also done extensive work on simulating impacts using ion beams and lasers (Gilath et al., 1992; Krueger, 1993)
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From page 108... ...
Although information about the capabilities of laboratory facilities able to study debris impacts can usually be obtained from a variety of sources, such as published journals, company brochures, and word of mouth, there is no systematic process for obtaining this information. Detailed information regarding the capabilities of a specific laboratory is usually acquired through individual visits by researchers.
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From page 109... ...
, and the Ravid and Bonder model (Ravid and Bonder, 1983; O'Donoghue et al., 1989~. There are, however, currently no standardized risk assessment models to determine the probability of component degradation or failure due to orbital debris impacts.
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From page 110... ...
Numerical simulations also can be used to predict the damage to spacecraft from debris impacts or to determine the characteristics of the fragmentation debris released in spacecraft or rocket body breakups. Some such computer codes, usually referred to as "hydrocodes," can model the spacecraft and impact in three dimensions, though many calculations are performed in two dimensions, particularly when the code is being used for "phenomena scoping" and "parameter sensitivity" calculations (i.e., to determine the degree to which changes in material properties would change the size or shape of the impact damage)
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From page 111... ...
Figure 5-3 illustrates how the size of the rupture on the backwall of a Whipple bumper shield can vary greatly with impactor shape. Because of these shape effects, shields designed based on experience with spherical impactors may not be as effective as predicted in protecting spacecraft from actual orbital debris impacts.
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From page 112... ...
The inability to launch large impactors at typical LEO collision velocities not only causes the same type of problems described above but also limits the accuracy of breakup models. Currently, masses capable of breaking up even the smallest spacecraft can be launched only to low
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From page 114... ...
Finding 2: Facilities in a number of nations are capable of carrying out hypervelocity impact tests for debris research but information about and access to these facilities is often difficult to obtain, there is no coordinated interfacility approach to either impact research or new facility development, and the results of experiments are not widely available. The general inaccessibility of facility capabilities and of the impact data generated at these facilities has resulted in considerable duplication of effort, slowing the development of good models of debris impact damage.
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From page 115... ...
International Journal of Impact .
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From page 116... ...
1993. Simulation of orbital debris impacts on bumper shields.
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From page 117... ...
International Journal of Impact Engineering 14:719-728.
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