>> Assuming the collision or whatever generated many pieces 
>> with their own
>> vectors in all different directions, does that mean that 
>> the amount of
>> space junk is increased, and possibility of other 
>> collisions are
>> possible (likely), and some of those vectors create 
>> meteor like
>> displays? :) ~) (maybe faces interchanged or ??)


I started to write a reply, but here are two comments from 
another list that cover it better than I would have

The first is from Henry Spencer who is an internationally 
respected authority on everything.
The second is from Dave Hall whose job is, er , we probably 
don't know what his job REALLY is ... (but his wife builds 
large missiles), and he says he doesn't know anyway. Not 
that he'd tell us if he did, of course.


        Russell

____________

> ...The optimal trajectory would be one that impacts while 
> travelling on
> the retrograde of the target's orbit, providing maximum 
> relative
> velocity...

The actual optimum may well be the trajectory that involves 
the *minimum*
relative velocity, because there is plenty of kinetic energy 
there to
destroy the target even so, and a lower closing rate makes 
the guidance
system's job easier.  More generally, what's "optimum" in 
practice is
almost certainly mostly a guidance issue rather than an 
energy issue, and
so the dominant factor is what sort of encounter geometry 
the guidance
system does best.  Anyone who knows the answer, can't tell 
us. :-)

> ...Another good method would be hitting it from below 
> perpendicular
> to the velocity vector, but that would scatter some debris 
> higher.

Not actually very important.

For one thing, any debris scattered upward will come back 
down half an
orbit later, and will then drop *below* the original 
altitude, so it will
actually burn up sooner.  The only case where debris might 
end up in a
longer-lived orbit is if it's kicked *forward*, adding 
orbital energy.
That's not very likely.

For another thing, for such a low-altitude intercept, the 
rather lower
sectional density of most of the debris will shorten its 
life considerably
even if it's in the same orbit or better, so the direction 
in which debris
is kicked probably doesn't matter very much.

Finally, no matter which direction the interceptor is 
launched in, it's
very much suborbital, so at impact, it will be moving *much* 
more slowly
than the satellite.  So the satellite's velocity dominates 
the encounter
regardless of the interceptor trajectory:  to a first 
approximation, the
interceptor positions itself in the satellite's path, and 
the satellite
slams into it.  Think roadblock, not sniper.

> The one shown on TV seems to indicate that it followed a 
> trajectory that
> ended up chasing the satellite. Unless the missile was 
> travelling at
> higher than orbital velocity I can't see this one working.

You're assuming that the interceptor's guidance system is 
looking
*forward*, so it must close from behind.  But outside the 
atmosphere,
that's not required.

If my suggestion above is correct, and the optimum 
trajectory is the one
that provides the lowest encounter velocity, then you do 
indeed launch
into a trajectory that ends up with the interceptor moving 
parallel to the
satellite, but rather more slowly, *ahead* of the satellite. 
Once clear
of the atmosphere, the interceptor turns 180deg so it's 
looking rearward,
because the satellite is moving much faster and will be 
coming up on the
interceptor from *behind*.

                                                           Henry 
Spencer
                                                       henry@zoo.utoronto.ca
                                                       (henry@spsystems.net)


_______________________________________________

Dave says:


To "chase" the satellite would imply that the SM-3 is 
capable of orbit.  I don't think there's anybody who 
believes that to be the case.  So... If that's what the 
stated trajectory is, it can only mean one thing: The real 
trajectory is classified.  Don't bother asking.

David Findlay wrote:
Well, kind of.  As Philip noted, that was an Air Force 
mission.  Not
widely known is that the target was a working U.S. Navy 
observatory:
the U.S. Air Force shot down a U.S. Navy satellite.  (That 
had to
feel good.)  (But boy were the owners bent out of shape! 
They
weren't told in advance.)  This week was the Navy's day in 
the sun.

I have some issues with the trajectory shown on TV for the 
SM-3 Missile that
struck USA-193. The optimal trajectory would be one that 
impacts while
travelling on the retrograde of the target's orbit, 
providing maximum
relative velocity. It does however present the greatest 
difficulty in terms
of accuracy. Another good method would be hitting it from 
below perpendicular
to the velocity vector, but that would scatter some debris 
higher. The one
shown on TV seems to indicate that it followed a trajectory 
that ended up
chasing the satellite. Unless the missile was travelling at 
higher than
orbital velocity I can't see this one working. What was the 
trajectory?
Thanks,

David
_______________________________________________




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