From: hibbert@netcom.com, Fri Jul 21 2000
>Amara.Graps@mpi-hd.mpg.de said:
>> Some of you earth spacecraft/rocket people might be interested in the
>> following paper, avail in HTML at:
>> http://galileo.mpi-hd.mpg.de/~graps/earth
>Amara,
>I don't read high-level (pun acknowledged, but not intended) physics
>very well.
I remade the Web site anyway, since it was "too flat" before, and now
it's layered better.
>Can you say whether this work has implications for our continuing
>ability to put up satellites and to leave Earth orbit?
Yes.
---------------------
See the number of abstracts at the recent (past) COSPAR meeting on this
topic.
http://134.76.234.216/DetailsScientificProgram/b0.1-pedas1..oral.htm
B0.1/PEDAS1 Space Debris
Operations in Earth orbit have generated both large and small
particulates which remain in orbit for extended periods and cause a
flux which exceeds the interplanetary meteoroid flux. The meeting will
address techniques to measure the space debris and near-Earth
meteoroid population, the results of data taken from the ground and in
space to measure the environment, the results of analyses of
spacecraft returned from space, methods and results of modeling and
supporting ground tests to predict the environment over short and long
time intervals, and atmospheric reentry of orbiting objects including
the fragmentation process. The meeting will also discuss hypervelocity
impacts, the effects of impacting debris on spacecraft structures and
instrumentation, and detrimental effects of space debris on space
activities and research, e.g. astronomy. The meeting will examine new
developments which may influence the debris environment such as
satellite constellations. Measures will be addressed to reduce the
growth of the debris population and keep the hazard to operational
spacecraft within tolerable limits.
------------------------
March 19-21 2001 there is a conference: Third European Conference on Space
Debris in ESOC, Damstadt, Germany. Contact W. Flury (wflury@soc.esa.de)
for information.
------------------------
>Is the situation with microparticles going to get continually worse
>over some time frame?
Yes.
Since 1957, more than 4000 space launches have occurred. About 8500
objects, larger than 10cm are being tracked in Earth orbit, only
about 700 of those are spacecraft. About 100 000 to 150 000 objects,
larger than 1cm, are not being tracked.
Objects 1cm and larger can destroy a spacecraft. Those particles, can
easily have relative velocities of tens of km/sec, which act like a
bullet hitting the spacecraft.
[For example, About the small particles that worry spacecraft
operators: the Cassini mission designers are planning now the Saturn
ring-plane crossing sequences, about 5 years from now, and yes indeed,
they are worried about the big dust particles >1cm, that they might
encounter. Of course us dust people want to sample the dust, but we
like the "smaller" dust, and we certainly don't want the spacecraft
damaged!]
>Are the negative potentials in themselves harmful to vehicles either in or
>transiting through the magnetosphere?
Yes. Portions of spacecraft have been observed to charge to many
kVolts (negative) during Earth substorms and those spacecraft surfaces
can suffer discharges. However, spacecraft surfaces are *supposed* to
be (designed) nonconducting, but sometimes they are not. The ones that
are not could experience difficulties.
I've heard stories of objects from Earth orbit being brought back to
Earth for examination (for example, solar panels from HST), and the
objects stored charges for months (process: "internal charging"),
resulting in a strong electrical discharge when someone/something
tried to handle the object.
A good old reference:
_Photon and Particle interactions with Surfaces in Space_
R.J.L. Grard, editor, Reidel, 1973.
>Any chance of harnessing this kind
>of effect to clean out some of the debris?
Interesting idea. Don't know.
>Chris
Amara
--*************************************************************** Amara Graps | Max-Planck-Institut fuer Kernphysik Interplanetary Dust Group | Saupfercheckweg 1 +49-6221-516-543 | 69117 Heidelberg, GERMANY Amara.Graps@mpi-hd.mpg.de * http://galileo.mpi-hd.mpg.de/~graps *************************************************************** "Never fight an inanimate object." - P. J. O'Rourke
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