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- Newsgroups: sci.military
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- From: Adrian Hurt <adrian@cee.heriot-watt.ac.uk>
- Subject: Re: Anti-aircraft
- Message-ID: <C1F750.L4F@law7.DaytonOH.NCR.COM>
- Sender: military@law7.DaytonOH.NCR.COM (Sci.Military Login)
- Organization: Dept of Computing & Electrical Engineering, Heriot-Watt
- References: <C124wI.7op@law7.DaytonOH.NCR.COM> <C143J8.2wt@law7.DaytonOH.NCR.COM>
- Date: Mon, 25 Jan 1993 17:26:59 GMT
- Approved: military@law7.daytonoh.ncr.com
- Lines: 76
-
-
- From Adrian Hurt <adrian@cee.heriot-watt.ac.uk>
-
- In article <C143J8.2wt@law7.DaytonOH.NCR.COM> creps@silver.ucs.indiana.edu (Stephen A. Creps) writes:
- >In article <C124wI.7op@law7.DaytonOH.NCR.COM> "John M. Wu" <johnwu@netcom.com> writes:
- >>1) When anti-aircraft shells go up, they have to eventually come
- >>back down. With a gun shooting 90 deg., the bullet will go up to
- >>around 9000 ft. and then start coming down up to terminal
- >>velocity (300 fps?).
-
- "Coming _down up_ to ..." wonderful phrasing! :-) (Yes, I do know the
- meaning that was intended, but I had to chuckle.)
-
- >> Do anti-aircraft weapons like those in Iraq cause large
- >>ground damage and numerous casualties due to what eventually
- >>happens to fired shells (eg. the Baghdad hotel damage)?
-
- If the shells don't have time fuses to make them explode while in the air,
- probably. If they do have such fuses, the shell splinters will still come
- down on the city, but at lower terminal velocity and minus the explosive
- warhead.
-
- >>Wouldn't not firing anything cause less damage to Baghdad?
-
- Yes, but not just for the above reason. What I heard on TV was that the U.S.
- admitted it was a cruise missile which hit the hotel, after the missile had
- been hit and knocked out of control by AAA. Not firing means that all the
- missiles go where they are intended; firing AAA means that most of the missiles
- go where they are intended, and a few go somewhere else. Of course, if that
- "somewhere else" happens to be a civilian building, then Iraq gets some free
- anti-U.S. propaganda (well, not free, there's the cost of the shells and the
- cost of the building, neither of which bother Iraq much).
-
- > Hmm, this is kind of an old topic here, but I might be able to add
- >something that I don't remember seeing here before. Terminal velocity
- >does in fact come into play when shooting into the air, and it is in
- >fact a way that much of a projectile's energy can be lost. I would
- >assume that the angle at which the most energy is lost is 90 degrees.
- >
- > However, while terminal velocity affects the Y-vector (vertical) of
- >an object's velocity, it should not affect its X-vector (horizontal).
-
- Time for me to get a lesson in physics by posting what I think, and seeing
- someone else correct me. (Without flames, please. :-)
-
- Terminal velocity is reached when the force of gravity is cancelled out by
- the force of air resistance, which means that the Y-vector is not being
- reduced by air resistance any more. The X-vector doesn't have the help of
- gravity, and will continue to be reduced until it reaches zero, either by
- air resistance or by collision with something harder. It is air resistance
- which takes away the projectile's kinetic energy - terminal velocity is when
- the projectile stops losing kinetic energy, at least from that part of its
- kinetic energy given by its vertical velocity.
-
- > Therefore, is it valid to assume that this kind of damage is not
- >caused so much by the projectile _coming down_, but by it _continuing
- >in the same horizontal direction_, where terminal velocity does not
- >come into play?
-
- Therefore, damage will be caused by whatever energy is left in the projectile
- when it hits something. That may be chemical energy, i.e. an unexploded
- warhead, or it may be kinetic energy due to remaining horizontal velocity,
- or it may be kinetic energy due to vertical terminal velocity. (Those are
- not exclusive "or"s - combinations are allowed.) Given that the projectile
- in this case is AAA, which was probably fired at a high angle, most of that
- kinetic energy will be from the vertical velocity. If it exploded while in
- the air, the projectiles which hit the ground will be the shell's splinters,
- whose high drag will result in a low vertical terminal velocity and very little
- remaining horizontal velocity.
-
- --
- "Keyboard? How quaint!" - M. Scott
-
- Adrian Hurt | JANET: adrian@uk.ac.hw.cee
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