I have a question about "spalling", as in "space junk is a huge problem
because it is in orbit; and it self amplifies due to a process called
spalling." I agree "Very little natural
debris will be in orbit... " but if one piece of orbiting material hits
another, in order for both to stay in orbit don't they have to have very
"tight" trajectories in both directions and speed coming out of the
collision to stay in orbit? I would think after the collision, assume no
new pieces just to make this simple, both would likely be in orbits which
would take them into the atmosphere within an orbit, and so they would soon
be gone. Thus collisions between orbiting debris should help clean out the
debris. Multiple pieces coming out could well leave a few much smaller
pieces in orbit, but the most of the mass would drop out of orbit from
aerobraking after a single collision. I know there was a video broadcast (I
believe on FOX) on this, but I think this like "beaming people" on star
trek, not taken seriously by scientist. Sincerely, Jay Huebner at
jhuebn@...
> I have a question about "spalling", as in "space
> junk is a huge problem
> because it is in orbit; and it self amplifies due to
> a process called
> spalling." I agree "Very little natural
> debris will be in orbit... " but if one piece of
> orbiting material hits
> another, in order for both to stay in orbit don't
> they have to have very
> "tight" trajectories in both directions and speed
> coming out of the
> collision to stay in orbit? I would think after the
> collision, assume no
> new pieces just to make this simple, both would
> likely be in orbits which
> would take them into the atmosphere within an orbit,
> and so they would soon
> be gone. Thus collisions between orbiting debris
> should help clean out the
> debris. Multiple pieces coming out could well leave
> a few much smaller
> pieces in orbit, but the most of the mass would drop
> out of orbit from
> aerobraking after a single collision. I know there
> was a video broadcast (I
> believe on FOX) on this, but I think this like
> "beaming people" on star
> trek, not taken seriously by scientist. Sincerely,
> Jay Huebner at
> jhuebn@...
>
beachcop51503
> I have a question about "spalling", as in "space junk is a huge problem
> because it is in orbit; and it self amplifies due to a process called
> spalling." I agree "Very little natural
> debris will be in orbit... " but if one piece of orbiting material hits
> another, in order for both to stay in orbit don't they have to have very
> "tight" trajectories in both directions and speed coming out of the
> collision to stay in orbit?
generates a particle that is travelling at only slightly different
velocity than the orbiting body, then the resulting particle will
still be in orbit, in fact almost the same orbit, and the orbits
intersect in two places for a sufficiently small perturbation.
> I would think after the collision, assume no
> new pieces just to make this simple, both would likely be in orbits which
> would take them into the atmosphere within an orbit, and so they would soon
> be gone. Thus collisions between orbiting debris should help clean out the
> debris.
That certainly happens.
But the problem isn't between orbiting debris, it's between
orbiting debris and spacecraft.
Each collision causes a spray of new particles to be produced,
atleast some of which are likely to still be in fairly stable
orbit- the amount of orbiting debris goes up after a collision
(its an exponential process, but at the moment enough material is
decaying from orbit that the runaway point is still a way off.)
> but I think this like "beaming people" on star
> trek, not taken seriously by scientist.
I believe you may be mistaken on this topic. My understanding is
that this is indeed a potentially serious issue. Indeed the Space
Shuttle has suffered damaged windows from this, although in that
case the window did not fail, thankfully- it was a very tiny fleck
of paint.
A friend of mine works as a space weapons researcher and for what
little he would say, they have to take this very seriously indeed-
exploding weapons or satellites in space could have devastating
effects for hundreds of years.
I may indeed "... be mistaken on this topic." But one paint fleck
chipping a shuttle window (not windows) does not seem too serious to me, as
I know that the Long Duration Exposure Facility had a micro-meteor (or is
it meteoroid?) impact. I am certainly not sure these two are all of the
impacts there have been, but if they are, then the score is one "industrial"
impact to one "natural" impact. So what does your friend say about impacts
with the natural background, the meteoroids? That is an important
bench-mark, below which we could never get, even if there were no
satellites.
And I still don't see how two orbiting objects can collide and have much
mass remain in orbit. "Exploding" does not change that. Exploding a
weapon, say a hand-grenade, from which all metal fragments fly out from the
center of mass should take those (to hedge a little, maybe I should say
nearly all) fragments out of orbit. The word exploding sounds dangerous and
destructive, but that is from our terrestrial reference. It might be the
best way to get satellites which can not be brought down in one piece out of
orbit. I doubt that intuition is very useful here, and that some serious
work is required to settle this question. But maybe all we have to do is
collect data on what happens and we will see.
Sincerely, Jay Huebner at jhuebn@...
Now that I think about this some more, maybe I should say that I am
assuming low orbits like the shuttles (can only) orbit in. For high orbits
I concede the numbers could be different. But when the shuttle is to
deorbit, it slows down by about 200 miles per hour, and down it goes with
aerobraking.
Sincerely,
Jay Huebner at jhuebn@...
Before I launch into this, let me say that I'm not an orbital mechanics
expert. Here is my rudimentary analysis.
that we have an object in circular orbit 235 miles above the Earth (say,
ISS Alpha), and a second object impacts the first. The natural thing to
ask is at what angle relative to the tangent the second object impacts the
first.
Suppose first that the second object impacts the first in the same
direction as the velocity vector of the first. In that case, most of the
fragments produced by the collision can be expected to have greater
orbital energy than that of the first object, and would hence end up in
orbits with greater semi-major axes than 235 miles. Fragments ejected
directly along the velocity vector would go into elliptical orbits with
perigee equal to 235 miles and apogee greater than 235 miles.
Of course, the opposite could happen and the second object could impact
the first 180 degrees opposite of the velocity vector of the first. In
that case, fragments ejected along the velocity vector of the impacting
object would go into elliptical orbits with apogee equal to 235 miles.
Whether or not the perigee of those orbits brings the fragments down into
the upper reaches of the atmosphere, thus experiencing the aerobraking you
envision, depends entirely on how energetic the collision was in terms of
delta-v.
Yet another possibility is that the second object impacts the first normal
to the velocity vector of the first. In this case, fragments ejected
along the velocity vector of the impacting object would go into elliptical
orbits with semi-major axes equal to 235 miles.
What say you to this analysis?
Ron
"Huebner, Jay" jhuebn@...
11/15/01 05:23 PM
I may indeed "... be mistaken on this topic." But one paint fleck
chipping a shuttle window (not windows) does not seem too serious to me,
as
I know that the Long Duration Exposure Facility had a micro-meteor (or is
it meteoroid?) impact. I am certainly not sure these two are all of the
impacts there have been, but if they are, then the score is one
"industrial"
impact to one "natural" impact. So what does your friend say about
impacts
with the natural background, the meteoroids? That is an important
bench-mark, below which we could never get, even if there were no
satellites.
And I still don't see how two orbiting objects can collide and have
much
mass remain in orbit. "Exploding" does not change that. Exploding a
weapon, say a hand-grenade, from which all metal fragments fly out from
the
center of mass should take those (to hedge a little, maybe I should say
nearly all) fragments out of orbit. The word exploding sounds dangerous
and
destructive, but that is from our terrestrial reference. It might be the
best way to get satellites which can not be brought down in one piece out
of
orbit. I doubt that intuition is very useful here, and that some serious
work is required to settle this question. But maybe all we have to do is
collect data on what happens and we will see.
Sincerely, Jay Huebner at jhuebn@...
> I may indeed "... be mistaken on this topic." But one paint fleck
> chipping a shuttle window (not windows) does not seem too serious to me,
> as
> I know that the Long Duration Exposure Facility had a micro-meteor (or is
> it meteoroid?) impact.
Sure.
> I am certainly not sure these two are all of the
> impacts there have been, but if they are, then the score is one "industrial"
> impact to one "natural" impact.
We probably don't know exactly. Some satellites go away and are
never heard from again. We don't know what happened to them.
> So what does your friend say about impacts
> with the natural background, the meteoroids? That is an important
> bench-mark, below which we could never get, even if there were no
> satellites.
Sure, sure. That's not the issue. The issue is that the more stuff
gets put into orbit, the more things there are to hit, and the more
fragments get produced. The more fragments get produced, the more
things get hit...
> And I still don't see how two orbiting objects can collide and have much
> mass remain in orbit. "Exploding" does not change that. Exploding a
> weapon, say a hand-grenade, from which all metal fragments fly out from the
> center of mass should take those (to hedge a little, maybe I should say
> nearly all) fragments out of orbit. The word exploding sounds dangerous and
> destructive, but that is from our terrestrial reference.
No. Exploding is very dangerous- the most dangerous of all. Look
let's say we have an object in circular orbit at 7.6km/s, and it
explodes after impact with a millimeter sized asteroid- for
arguments sake assume that it explodes in all directions. There's
going to be a lot of little bits, many of them bigger than a
millimeter. Let's also assume that it explodes at 300m/s (about the
speed of sound).
Some bits are going to be thrown backwards along the orbit- they
are probably going to reenter. some of them will be thrown mostly
forwards along the orbit. They will now be in an elliptical orbit
that has its lowest point in LEO, and somewhat higher at its
highest point- but they are still in orbit; it's going to be luck
each time they come around as to whether they impact something else.
Once in orbit they are acted on by the sun, moon and the earth (the
earth isn't a perfect sphere) and the orbit can end up as a polar
orbit or even going east-west or at a significant angle to other
objects in orbit. Any impact is going to be measured in multiple
km/s; occasionally it will be >10 km/s. At those kind of speeds
satellites tend to vapourise.
> It might be the
> best way to get satellites which can not be brought down in one piece out of
> orbit. I doubt that intuition is very useful here, and that some serious
> work is required to settle this question. But maybe all we have to do is
> collect data on what happens and we will see.
No. Don't go there. Space junk is a nightmare- it's the space
equivalent of the hole in the ozone layer. We are some way below
the self sustaining point right now- but as more things live in LEO
and MEO orbit it's going to get worse.
Space Junk is not junk science. Inspite of the name. ;-)
More on this?
> ... one paint fleck chipping a shuttle window ..." vs. "... It broke
the window." See, http://www.wstf.nasa.gov/Hazard/Hyper/debris.htm , where
the word "pit" was used, and
http://science.ksc.nasa.gov/shuttle/missions/sts-73/news/sts-73-mcc-16.txt
where the word "ding" was used. I don't think we should panic at this
point.
I agree we "... don't know exactly. Some satellites go away and are
never heard from again...", and about "... the more things there are to
hit, and the more fragments get produced. The more fragments get produced,
the more things get hit..." I understand exponentials, they work both ways,
as in exponential growth and decay. But what about "> ... the natural
background, the meteoroids? " As an aside, this weekend is the annual
Leonid meteor shower. See
http://www.space.com/scienceastronomy/leonids_update_011115.html.
I also have not studied the math of collisions and orbits. And I agree
that an object in a Highly Eccentric Earth Orbit (HEEO) could catch an
object in a Low (and circular) Earth Orbit (LEO) from "behind" at perigee
and scatter debris forward. Pieces which go straight ahead will also end up
in less eccentric HEEO. But pieces which angle down from LEO will reenter.
Less obvious is that objects which angle up will also. To see this, extend
their trajectories back past the collision site. Those extensions which
pass into the atmosphere indicate that the associated objects will reenter
on the other side of Earth. So both types will be taken out of orbit, which
is not all of the material, I agree. The lower the orbit the higher the
percentage of material that will be lost from orbit this way. A significant
question is how the materials scatter from such collisions.
But, most collisions will be "head-on" not "rear-end", probably by a huge
margin, I would suggest by a ratio of (V1 + V2)/(V1 - V2), where these V's
are the satellite speeds. And in "front-end" collisions the debris will
share linear momentum and I believe most pieces will end up in the
atmosphere in less than a couple of hours.
This is how I respond. Sincerely, Jay Huebner
Well, I respond you should read some of the web sites out there
on this subject. Check out:
Apparently MIR was impacted by several fragments, and I know there
were a few near misses of objects large enough to destroy it
completely, and it is estimated that the ISS stands a 20% chance of
being depressurised per decade.
Also, the Space Shuttle has had to move to avoid several pieces of
junk...
That's NASA. ESA is also worried about the issue (check the links
from that site.)
In response to " Check out:
http://www.theatlantic.com/issues/98jul/junk.htm ", I read this site and I
would give it a C+. It promotes studying this problem which is good but
also self serving. It has some nonsense, such as "As long as an object is
above the last traces of Earth's atmosphere, it will stay in orbit for
thousands or even millions of years." The Earth orbits in a solar wind,
which blows out to the outer planets, so there is no "last traces" of the
atmosphere. These guys should study exponentials. There are factual
errors. Like the MIR collision was with a resupply ship that was trying to
dock, hardly a collision with space debris. I acknowledge the collision
with a French satellite, which now that I think about it was with another
French made object.
My main criticism of this site, is that there is no mention of the
natural debris, which from the site I gave in a previous response,
apparently drops ~ 110 tons of debris per day into the atmosphere. Why
don't we get a comparison between the impact (pun) of the industrial and
natural materials? Any honest discussion of this topic must include that.
I think this will be my last comments on this topic as I think we have
given it a good airing. I agree that blowing up orbiting satellites to get
rid of them is a bad idea, but I suspect natural debris is more to worry
about than unknown space junk, though I agree with tracking the large and
trackable objects and trying to keep significant assets, such as the
Shuttle, out of their paths.
Sincerely, Jay Huebner
To Jay Huebner:
happen when a fragmentation event occurred. There's a relevant article
on space.com today (c.f.,
http://www.space.com/missionlaunches/junk_iss_020107.html) which states
that,
"
Cosmos 2367 had been the latest of the Cosmos 699 series of
three-metric-ton spacecraft that started space operations in 1974.
For unknown reasons, the spacecraft broke up on November 21. In an orbit
just 19 miles (30 kilometers) above the ISS, the Russian craft busted up
into over 300 large and small pieces. Most fragments were concentrated in
a 124-mile (200 kilometer) to 310-mile (500 kilometer) altitude, while
other bits were tossed into orbits that reached 1000 kilometer altitude.
Approximately 40 percent of the debris were immediately thrown into orbits
that crossed the orbit of ISS.
"
Ron
rmenich@...
11/15/01 05:35 PM
Before I launch into this, let me say that I'm not an orbital mechanics
expert. Here is my rudimentary analysis.
I'd guess what would happen would depend on a number of factors. Suppose
that we have an object in circular orbit 235 miles above the Earth (say,
ISS Alpha), and a second object impacts the first. The natural thing to
ask is at what angle relative to the tangent the second object impacts the
first.
Suppose first that the second object impacts the first in the same
direction as the velocity vector of the first. In that case, most of the
fragments produced by the collision can be expected to have greater
orbital energy than that of the first object, and would hence end up in
orbits with greater semi-major axes than 235 miles. Fragments ejected
directly along the velocity vector would go into elliptical orbits with
perigee equal to 235 miles and apogee greater than 235 miles.
Of course, the opposite could happen and the second object could impact
the first 180 degrees opposite of the velocity vector of the first. In
that case, fragments ejected along the velocity vector of the impacting
object would go into elliptical orbits with apogee equal to 235 miles.
Whether or not the perigee of those orbits brings the fragments down into
the upper reaches of the atmosphere, thus experiencing the aerobraking you
envision, depends entirely on how energetic the collision was in terms of
delta-v.
Yet another possibility is that the second object impacts the first normal
to the velocity vector of the first. In this case, fragments ejected
along the velocity vector of the impacting object would go into elliptical
orbits with semi-major axes equal to 235 miles.
What say you to this analysis?
Ron
"Huebner, Jay" jhuebn@...
11/15/01 05:23 PM
I may indeed "... be mistaken on this topic." But one paint fleck
chipping a shuttle window (not windows) does not seem too serious to me,
as
I know that the Long Duration Exposure Facility had a micro-meteor (or is
it meteoroid?) impact. I am certainly not sure these two are all of the
impacts there have been, but if they are, then the score is one
"industrial"
impact to one "natural" impact. So what does your friend say about
impacts
with the natural background, the meteoroids? That is an important
bench-mark, below which we could never get, even if there were no
satellites.
And I still don't see how two orbiting objects can collide and have
much
mass remain in orbit. "Exploding" does not change that. Exploding a
weapon, say a hand-grenade, from which all metal fragments fly out from
the
center of mass should take those (to hedge a little, maybe I should say
nearly all) fragments out of orbit. The word exploding sounds dangerous
and
destructive, but that is from our terrestrial reference. It might be the
best way to get satellites which can not be brought down in one piece out
of
orbit. I doubt that intuition is very useful here, and that some serious
work is required to settle this question. But maybe all we have to do is
collect data on what happens and we will see.
Sincerely, Jay Huebner at jhuebn@...