Jettisoned space junk -- how big?

At ISS altitude, small things tend to decay quite quickly relative to
the station, even if they are dense. Intuition might make you think
that the ISS (being essentially aluminum cans and big "wings") wold
have a lower ballistic number than say, a steel bolt, but the
cube/square relation of mass to surface area means that it is usually
the other way around.

Ah, got it.

I guess I should have seen that my mental shortcut of thinking of
"density" was too much of a shortcut, and you have done a good job of
explaining why.

On Sat, 17 Jun 2006 15:09:36 -0700, hop wrote:

Also, the potential re-contact velocity of anything thrown off of ISS
is roughly the same as the velocity it was thrown at.

Err... not exactly.

They still have the potential to cause damage, but not nearly as much
as something on a different orbit that happens to cross the ISS path.

Except when minor orbital pertubations arrange
exactly that... impact velocity estimates for the
ball ISS, given some time has passed to allow
for asymmetry, masscons, precession etc to tweak
the orbits, get up into the kilometers/sec range.

It's not the zero-sum game of a physics textbook.

Real LEO has other factors affecting it than just
a hypothetical perfectly symmetrical Earth.

--
Chuck Stewart
"Anime-style catgirls: Threat? Menace? Or just studying algebra?"

On Sun, 18 Jun 2006 02:41:46 -0700, hop wrote:

Chuck Stewart wrote:

Except when minor orbital pertubations arrange
exactly that... impact velocity estimates for the
ball ISS, given some time has passed to allow
for asymmetry, masscons, precession etc to tweak
the orbits, get up into the kilometers/sec range.

A good point, but at ISS altitude, most things too small to be tracked
aren't going to hang around long enough for that to happen. A regular
golf ball, for example, would decay far out of reach of ISS in a matter
of days. A depleted uranium golf ball

(Airplane! mode/)

"We're familiar with it."

(/Airplane! mode)

(or more realistically, a good size solid steel bolt) would be a
different story.

Even something that decays at roughly the same rate as the station will
be left behind on the next reboost, so the time for perturbations to
accumulate is limited. Not to say that it is impossible, just that it
isn't a realistic possibility for a lot of items.

Variable, of course, and some of the higher
velocity estimates do seem to be curve-fitting
for worst-case damage... but that's what should
be done in this case, right?

But the main point, which thousands of forum and
blog pundits seem to have missed and keep on
missing with a vengeance, is that it's perfectly
*feasible* for the ball to return at some later
date and impact ISS with a relative velocity
orders of magnitude greater than the one the
cosmonaut imparted to it.

--
Chuck Stewart
"Anime-style catgirls: Threat? Menace? Or just studying algebra?"

There was a minor fuss a while ago when it was reported that the
Pentagon had wargamed aggressive responses to the European Galileo
project - including trying to blow up the launch vehicles during ascent
and destroying the satellites once they were in orbit. And I thought
they were our friends...

Regardless of whether these reports were in any way accurate, if
somebody did try to blow up a GPS-style satellite in MEO, under what
circumstances would the resulting debris cloud damage the others in the
constellation and could it affect others in a similar constellation at
a similar but different altitude? Galileo isn't that far away from
Navstar, after all, and I wonder about chain reactions.

(And what would happen in GEO?)

Rupert

In GEO its a BIG place. Sadly a expert reports the debris will diffuse
thru the area, cauising more collisions.

If a country like N korea ever wanted to screw lots of other countries
they could make popular orbits unusable.

Even minor debris can ruin delicate things like solar panels

"Rupert Goodwins" wrote in message
ups.com...
There was a minor fuss a while ago when it was reported that the
Pentagon had wargamed aggressive responses to the European Galileo
project - including trying to blow up the launch vehicles during ascent
and destroying the satellites once they were in orbit. And I thought
they were our friends...

If we're willing to do that to our friends, then our enemies should be much
more concerned...

Good point, but I do believe it has already reentered.

not to confuse it with Skylab itself...

Matthew Ota

Rusty wrote:
Jim Oberg wrote:
To put the fuss over the hazards of the golk ball
stunt in proportion, what are the largest cases of
jettison of materials from space stations -- Skylab,
Salyuts, mir, ISS, any of them -- to compare it to?

There was one Progress that separated without
adequate deorbit propellant, and what happened to the
Kvant-1 service module?

More specifically, I'm interested in EVA manual
jettsions -- trashbags, spacesuits, unneeded external
structureal elements and packing material, etc. How
big have they gotten to be?


The Saturn V second stage (S-II), that launched Skylab, also went into
orbit.
Can't get much bigger than that.

Rusty

In article . com,
Matthew Ota wrote:
The Saturn V second stage (S-II), that launched Skylab, also went into
orbit...

Good point, but I do believe it has already reentered.

Long ago -- it came down well before Skylab.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |

Matthew Ota wrote:

Good point, but I do believe it has already reentered.

not to confuse it with Skylab itself...




Yes, it decayed fairly quickly due to its size and low mass.
The Skylab S-IVB boosters were intentionally decayed over the Pacific; I
assume hat this was also done to the S-II stage.

Pat

In article ,
Pat Flannery wrote:
...The Skylab S-IVB boosters were intentionally decayed over the Pacific; I
assume hat this was also done to the S-II stage.

No, the S-II was allowed to decay naturally.

They would have *liked* to deorbit it. They studied how to do it, and
concluded that the same technique used on the S-IVBs would work:
propellant dumping through the engines. But to do that on the S-II, you
had to add an attitude-control system, and make various other little
additions (e.g., bigger battery packs) to keep it "alive" long enough to
reach a good deorbit opportunity. The S-IVB already had all this stuff,
because of Apollo requirements for it to hold still long enough (with
plenty of margin for trouble) to extract a Lunar Module or whatever, but
the S-II didn't. None of it was terribly hard, but Skylab was on a
shoestring budget by this time, and they just couldn't quite afford it.

So the S-II got to take its chances. If memory serves, it came down in
a remote area of Africa.
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spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |