Student 01: Good summary on an event that I think is universally looked at as a “bad idea.” I will avoid
expressing my full sentiments on the subject other than to say that when the US of A demonstrates
similar technology, it does it in a fast degrading orbit, on a faster target, from a boat. Case Closed.
Student 02: Excellent! This highlights the number one problem with studying the space environment:
It’s hard to figure out what the heck happened to satellites due to the extraordinary cost of recovering
the things yet when you do recover, the wealth of information is equally extraordinary. I run into this
question and problem with my undergrad class often. Students want to know why there are so many
unanswered questions. It’s hard for them to grasp that we can know a lot from a little, but that does
not allow us to know all.
Student 03: Not my original intent for the assignment but one that still sheds light on a previously
unconsidered question in the space environment. I dig it. This may not apply to operators as much as
astrobiologists, but it still applies. Very cool indeed.
Student 04: The point made in the article about orientation is an extremely important one. The shuttle
flew upside down and backwards in most orbits to protect the windows from just such damage. I don’t
know much about the ISS orientation, but I can imagine that similar consideration was put into where
the windows are in the different modules.
Student 05: Very good. This is definitely the kind of thing we will miss with the Shuttle’s retirement.
Student 06: I had not considered the prevalence of secondary impacts as much. Good find and nice
verification of the natural environment.
Student 07: The only student to use the LDEF mission as the paper, interesting. It was an excellent
mission and one that has shed considerable light on the darkness of the space environment. Good find
and good write-up.
My articles:
(Cour-Palais 1987)
(Johnson, Krisko et al. 2001)
(Kitazawa, Fujiwara et al. 1999)
(Love, Brownlee et al. 1995)
(Mandeville 1993)
Cour-Palais, B. G. (1987). "Hypervelocity impact in metals, glass and composites." International Journal
of Impact Engineering 5(1–4): 221-237.
This paper is a review of hypervelocity impact research carried out during the intense activity
period leading up to the Apollo lunar missions. It is intended as a historical note on the research
into hypervelocity impact phenomena in metallic, glass, and composite materials and the
spacecraft applications of that research. The specific areas covered include cratering and
spallation in thick, semi-infinite targets, perforation and hole formation in thin, single-thickness
targets, spaced dual sheet armor, impact radiation, and impact ionization. Optimum and
nonoptimum dual sheet combinations are treated in some detail because of the current interest
in hypervelocity impact protection for the Space Station. On the other hand, the treatment of
hypervelocity impacts on composites, phenolic resins and thermosetting epoxy systems
reinforced with graphite or other high strength fibers, is limited because work in this area has
just begun.
Johnson, N. L., et al. (2001). "NASA's new breakup model of evolve 4.0." Advances in Space Research
28(9): 1377-1384.
Analyses of the fragmentation (due to explosions and collisions) of spacecraft and rocket bodies
in low Earth orbit (LEO) have been performed this year at NASA/JSC. The overall goals of this
study have been to achieve a better understanding of the results of fragmentations on the
orbital debris environment and then to implement this understanding into the breakup model of
EVOLVE 4.0. The previous breakup model implemented in EVOLVE 3.0 and other long-term
orbital debris environment models was known to be inadequate in two major areas. First, it
treated all fragmentational debris as spheres of a density which varied as a function of fragment
diameter, where diameter was directly related to mass. Second, it underestimated the
generation of fragments smaller than 10-cm in the majority of explosions. Without reliable data
from both ground tests and on-orbit breakups, these inadequacies were unavoidable. Recent
years, however, have brought additional data and related analyses: results of three ground
tests, better on-orbit size and mass estimation techniques, more regular orbital tracking and
reporting, additional radar resources dedicated to the observation of small objects, and simply a
longer time period with which to observe the debris and their decay. Together these studies and
data are applied to the reanalysis of the breakup model. In this paper we compare the new
breakup model to the old breakup model in detail, including the size distributions for explosions
and collisions, the area-to-mass and impact velocity assignments and distributions, and the
delta-velocity distributions. These comparisons demonstrate a significantly better understanding
of the fragmentation process as compared to previous versions of EVOLVE.
Kitazawa, Y., et al. (1999). "Hypervelocity impact experiments on aerogel dust collector." Journal of
Geophysical Research: Planets 104(E9): 22035-22052.
Laboratory hypervelocity impact experiments were conducted to verify the performance of
aerogel dust collectors used for gathering meteoroids and space debris in the near-Earth
environment and to derive the relationships of various parameters characterizing the projectile
with morphology of tracks left by the penetrating projectile in the aerogel collector pad. Silica
aerogel collectors of 0.03 g/cm3 density were impacted at velocities ranging from 1 to 14 km/s
with projectiles of aluminum oxide, olivine, or soda-lime glass, with diameters ranging from 10
to 400 μm. At impact velocities below 6 km/s the projectiles were captured without
fragmentation by the aerogel collector and, in many instances, without complete ablation even
at 12 km/s. The shapes and dimensions of the penetration tracks left in the aerogel collector
were correlated with the impact parameters, and the results permitted derivation of a series of
equations relating the track dimensions to incoming projectile size, impact energy, and other
projectile parameters. A simplified model, similar to meteor-entry phenomena, was used to
predict the trends in experimental penetration track lengths and the diameters of captured
projectiles.
Love, S. G., et al. (1995). "Morphology of meteoroid and debris impact craters formed in soft metal
targets on the LDEF satellite." International Journal of Impact Engineering 16(3): 405-418.
We have measured the depths, average diameters and circularity indices of over 600
micrometeoroid and space debris impact craters formed in surfaces exposed to space aboard
the Long Duration Exposure Facility satellite. The target surfaces had a variety of orientations
and physical properties. The average depth-diameter ratio of craters formed in aluminum
targets by nearly normal impacts is between 0.56 and 0.60, higher than the canonical and widely
accepted value of 0.50 which corresponds to a hemispherical shape. The depth-diameter ratio
does not change significantly with target Brinell hardness values between 40 and 90, or with
average impact velocity above 5 km s−1. The depth-diameter ratio is found to vary as roughly
the one-tenth power of target density. Less than 10% of the craters examined had major-tominor axis ratios higher than 1.5, consistent with the production of shallow, elongated craters
exclusively by grazing impacts. The variation in depth-diameter ratio for circular craters most
likely results from variation in projectile shapes.
Mandeville, J. C. (1993). "Orbital debris and meteoroids: Results from retrieved spacecraft surfaces."
Advances in Space Research 13(8): 123-127.
Near-Earth space contains natural and man-made particles, whose size distribution ranges from
submicron sized particles to cm sized objects. This environment causes a grave threat to space
missions, mainly for future manned or long duration missions. Several experiments devoted to
the study of this environment have been recently retrieved from space. Among them several
were located on the NASA Long Duration Exposure Facility (LDEF) and on the Russian MIR Space
Station. Evaluation of hypervelocity impact features gives valuable information on size
distribution of small dust particles present in low Earth orbit. Chemical identification of
projectile remnants is possible in many instances, thus allowing a discrimination between
extraterrestrial particles and man-made orbital debris. A preliminary comparison of flight data
with current modeling of meteoroids and space debris shows a fair agreement. However impact
of particles identified as space debris on the trailing side of LDEF, not predicted by the models,
could be the result of space debris in highly excentric orbits, probably associated with GTO
objects.