Orbital Debris A Technical Assessment (1995) / Chapter Skim
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4 HAZARDS TO SPACE OPERATIONS FROM DEBRIS
4 HAZARDS TO SPACE OPERATIONS FROM DEBRIS
Pages 79-100
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From page 79... ...
The nature of the operations is a factor because the same piece of debris that could cause serious damage to one type of spacecraft might do little harm to a spacecraft with a different configuration or orbital attitude. The first step in determining the hazard to a spacecraft from orbital debris is to estimate the debris flux for the spacecraft's orbital region.
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From page 80... ...
Low Earth Orbit Although Figure 4-1 oversimplifies the nature of the LEO debris population, it provides a starting point for estimating the debris impact probability for spacecraft in LEO by showing how the flux of debris varies with debris size. The main oversimplification is the grouping of data 10 - ' ' ' '""I ' ' ' ""'1 ' ' ' ""'1 ' ' ' ""'I ' ' ' ''"'I ' ' ' ""'1 ' ' ' ""'1 ' ' ' ""'I ' ' ' "A ~ <)
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From page 81... ...
The uncertainty of debris population estimates is, however, reflected by the error bars in the figure. Figure 4-1 predicts the average number of collisions with different sizes of debris that a spacecraft in a "typical" low Earth orbit will experience in a 10-year orbital lifetime.
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From page 82... ...
Since data on the altitude variation of the small debris population do not exist and model predictions vary significantly depending on the sources of these smaller particles, it is unclear whether the chance of being struck by small debris also exhibits such a large variation with altitude. Collision probability also varies with orbital inclination, although to a much lesser extent than it varies with altitude.
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From page 83... ...
Figure 4-4 shows the "average" variation In collision probability with inclination for all altitudes below 1,000 km based on the cataloged population. Because the orbital inclination distribution varies slightly with both time and altitude, this variation in collision probability with ir~clination will also change as a function of time and altitude.
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From page 84... ...
As shown in Figure 3-3, the average spatial density of cataloged objects in even the relatively densely populated semisynchronous and geosynchronous orbits is about 100 times lower than the average spatial density of cataloged objects in LEO. In less densely populated high Earth orbits, the spatial density of cataloged objects is often 1,000 times lower
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From page 85... ...
For GEO spacecraft, the chance of collision with cataloged objects decreases sharply with the distance from the geostationary orbit. Figure 4-6 shows how the cataloged space object flux (and thus the probability of collision with a cataloged object)
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From page 86... ...
Space objects in highly elliptical orbits experience different collision probabilities in different parts of their orbit. Objects in Molniya-type orbits experience a very low ctebr~s flux through most of their orbit but can spend a small portion of their orbit traveling at high velocities through the relatively intense LEO debris flux.
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From page 87... ...
FIGURE 4-? Estimated orbital debris environment in GEO resulting from satellite breakups.
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From page 88... ...
While not perfect, analyses of typical collision velocities and impact angles are based on the known debris population, so they have less uncertainty than many of the other elements factored into debris hazard predictions. Collision velocities vary with orbital altitude and inclination (see Box 4-2~.
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From page 89... ...
20 FIGURE 4-9 Calculated collision velocity distribution versus inclination for cataloged objects in LEO (averaged over all LEO altitudes)
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From page 90... ...
If the calculations incorporate the population of objects detected by the Haystack radar in addition to the cataloged population, the plotted variation of collision velocity with altitude looks similar to Figure 4-9, but with slightly lower average collision velocities at all inclinations. In a 51.6-degree-inclination orbit, for example, the predicted average collision velocity with cataloged objects is 10.8 km/s, but the predicted average collision velocity with objects detected by Haystack is 9.2 km/s.
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From page 91... ...
Debris in highly elliptical orbits may impact the sides and rear of a spacecraft more frequently than debris in circular orbits; such impacts were detected on the rear surfaces of LDEF. Breakups Due to Debris Impact ~` A' ~ ~ ~ `~,h-energy collisions may not just incapacitate a spacecraft, but actually fragment it into many small pieces.
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From page 92... ...
Breakup models also predict the number and mass of fragments produced in a catastrophic collision. The mass distribution Is also related to the ratio of the impacting object's kinetic energy to the mass of the target space object; as this ratio increases, the number of large fragments produced also increases.
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From page 93... ...
In GEO, typical collision velocities are much lower they are comparable to speeds involved in a midair aircraft collision so only the largest medium-sized GEO particles are probably capable of causing serious damage. Hypervelocity impact can cause various modes of damage to spacecraft, including craters, spallations, perforations, and petaled holes and cracks, depending on impact conditions and the configuration of the impacted spacecraft; this damage may result in different failure modes depending on the nature of the spacecraft and the location of the impact.
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From page 95... ...
the coolant loop is not designed to allow shutdown of perforated radiator coolant pipes, a loss of coolant could occur. Surface Degradation Caused by the Impact of Debris Even if the impacts of smaller debris do not cause structural or component damage, the craters, spallations, and perforations they produce in impacted materials can degrade spacecraft surfaces.
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From page 96... ...
Small debris impacts may also create localized plasmas, which can cause discharges and failures in some components such as electronics or solar arrays. In addition, impact damage may combine with other space environmental effects (such as those caused by atomic oxygen and ultraviolet light)
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From page 97... ...
Small debris impacts into telescope tubes or optical baffles can also degrade optical components by releasing large amounts of particulates (which can temporarily confuse or blind optical sensors) or contaminants (which can affect the scattering of an optical sensor)
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From page 98... ...
At higher altitudes, where collision velocities are slower, a much larger impactor would be needed to cause catastrophic breakup. Finding 3: Impacting space objects not large enough to break up a spacecraft can still cause significant damage through a variety of mechanisms, v
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From page 99... ...
NASA Conference Publication 10120, Third LDEF Post-Retrieval Symposium Abstracts. Hampton, Virginia: NASA Langley Research Center.
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From page 100... ...
1989. Orbital Debris Environment for Spacecraft Designed to Operate in Low Earth Orbit.
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