Defense against UAV's

In article ,
says...
Mark Borgerson mborgerson.at.comcast.net wrote:

:In article ,
says...
: wrote:
:
: :
: :Fred J. McCall wrote:
: : wrote:
: :
: : : Hint #3: A fighter with a 20mm Vulcan will flat mess up a "small,
: : : slow UAV" and actually has a radar on board so that he can see it and
: : : some actual training on how to do an air intercept, neither of which a
: : : helicopter has.
: : :
: : :Always assuming that the radar is capable of getting a lock on the UAV.
: :
: : No such assumption is necessary. It's not like in the movies.
: :
: :What makes you so certain that gunnery radar WILL lock on to a stealthy
: :UAV?
:
: What makes you think that fighter aircraft use gunnery radar?
:
: :The UAVs are designed, after all, to avoid being picked up by
: :radar. For defence planning purposes the assumption has to be that
: :radar will not probably work against them, unless and until it is
: roved to be capable of doing so. To take any other attitude would be
: :foolish complacency.
:
: Which means nothing, since a fighter attacking with a gun uses
: EYEBALLS to get the target and they're way up close.
:
: : :If not, his chance of scoring a hit is remote - the speed differential
: : :is so huge that he could do no more than 'spray and pray'.
: :
: : Hint #1: What do you think the landing speed of a jet fighter is?
: :
: : Hint #2: Guns work off the pilot's eyeballs.
: :
: :And exactly how will the pilot aim his guns, if the radar gunsight
: :won't lock on and the sights he's got are no better than WW2 standards?
:
: He'll aim them the same way he aims them against anything else. Times
: have changed since WW2 and no 'radar gunsight' is required.
:
: :Hint #1: in WW2 the Luftwaffe found that only between 2% and 5% of the
: :shots they fired hit the target - and they were shooting at B-17s! Now
: :scale down the target size to a UAV with a wingspan of a couple of
: :metres, and work out how much ammo would have to be fired to nail one.
:
: About 5 rounds.
:
:Hmmm, coming up behind a UAV with a 6-foot wingspan, the cross-sectional
:area of the target might be only 1 or 2 square feet. How close does
:the fighter pilot have to be to hit a 2 square foot target with 5
:rounds?

He doesn't have to hit it with 5 rounds. He has to hit it with 1
round out of 5.

This source: http://www.simhq.com/_air/air_028a.html

Says that 80% of round will fall inside a 5-foot diameter circle
at 1000 feet. That's pretty good for a high-speed cannon in
an aircraft mount.

Now let's look at the math: out of 5 rounds fired, 4 will be inside
a 5-foot diameter circle. That's 4 rounds in an area of 78.5 square
feet, or about one round for each 19 square feet. I think that
means that there is a significant probability that all five rounds
will miss a 2-square foot target at 1000 feet range. At
much closer ranges, there will be a higher projectile density,
but tracking the target may become more difficult---particularly
if the small UAV is turning with a radius that the fighter cannot
match.

In any case, I doubt that only 5 round will be fired---more likely
something on the order of 50 to 60 rounds. That makes a kill
much more likely.


I also think that a high-speed pass with a miss distance of 50 to 75
feet would probably generate enough turbulence to disturb the
flight control system and probably overstress the airframe. Most
of the UAVs I've come across have fairly high aspect ratio wings
and cost concerns probably exclude titanium main wing spars! ;-)

This is probably not that difficult from hundreds of yards away. The
HUD shows him what the bullet path is going to be. Initially they'll
probably get FAR too close until they realize how small the targets
are.


That's true. And if you get too close, you will run into parallax
problems between the sight and the gun, if the gun is boresighted
for 1000 feet.

50 round at 500 feet ought to do the trick if the UAV is
flying in a straight line.


Mark Borgerson