Defense against UAV's

wrote:

rb wrote:

Highly unlikely that it went undetected for 25 mins.
More likely it's Iranian sabre rattling again.


Regardless of the accuracy of this particular account, it is true that
UAVs pose a new problem for navies and armies, especially in the
smaller versions. Defensive systems are generally designed to detect
and destroy much bigger and more obvious targets, and even if they
manage to spot a small UAV, what would be used to shoot it down?

This is the subject of much debate at the moment. Ordinary homing
missiles may not be able to lock-on to a stealthy little UAV (and even
if they could, there's not much logic in using a very expensive missile
to shoot down a very cheap plane). A radar-directed gun system like
Phalanx might also not lock-on to such a target. The best bet at the
moment IMO would be a 35mm gun firing the Oerlikon AHEAD 'shrapnel'
type airburst ammo, using electro-optical guidance.

Block 1B CIWS has an infrared and optical tracker that would do nicely
against any UAV within it's range...the question is finding the UAV in
the first place. An Infrared search system with the ability to designate
to a B1B Phalanx would work quite well I think...

....Ken

Ken Chaddock wrote:


Block 1B CIWS has an infrared and optical tracker that would do nicely
against any UAV within it's range...the question is finding the UAV in
the first place. An Infrared search system with the ability to designate
to a B1B Phalanx would work quite well I think...

But a prop-driven UAV with a small engine and some attention to exhaust
masking would not be an easy IR target.

If all you want to do is locate and identify a ship, and beam an
illuminating laser at it to guide the incoming ordnance, then the UAV
can be very small and very hard to detect.

Tony Williams
Military gun and ammunition website: http://www.quarry.nildram.co.uk

wrote:
Ken Chaddock wrote:


Block 1B CIWS has an infrared and optical tracker that would do nicely
against any UAV within it's range...the question is finding the UAV in
the first place. An Infrared search system with the ability to designate
to a B1B Phalanx would work quite well I think...


But a prop-driven UAV with a small engine and some attention to exhaust
masking would not be an easy IR target.

If all you want to do is locate and identify a ship, and beam an
illuminating laser at it to guide the incoming ordnance, then the UAV
can be very small and very hard to detect.

Tony Williams
Military gun and ammunition website: http://www.quarry.nildram.co.uk

Have you ever seen the radar return from a prop ? Looks like a bloody
747...a prop-job wouldn't be a particular problem and contrary to
popular misconception, most modern IR trackers don't rely on a hugh heat
gradient but rather on the difference in emissivity between the target
and the background, IOW it's tracking the delta, not the absolute IR
output of the target...

....Ken

In article %AMfg.1638$I61.24@clgrps13,
says...
wrote:
Ken Chaddock wrote:


Block 1B CIWS has an infrared and optical tracker that would do nicely
against any UAV within it's range...the question is finding the UAV in
the first place. An Infrared search system with the ability to designate
to a B1B Phalanx would work quite well I think...


But a prop-driven UAV with a small engine and some attention to exhaust
masking would not be an easy IR target.

If all you want to do is locate and identify a ship, and beam an
illuminating laser at it to guide the incoming ordnance, then the UAV
can be very small and very hard to detect.

Tony Williams
Military gun and ammunition website: http://www.quarry.nildram.co.uk

Have you ever seen the radar return from a prop ? Looks like a bloody
747...a prop-job wouldn't be a particular problem and contrary to
popular misconception, most modern IR trackers don't rely on a hugh heat
gradient but rather on the difference in emissivity between the target
and the background, IOW it's tracking the delta, not the absolute IR
output of the target...

So what IS the radar return from a wooden or fiberglass propellor like?

The UAVs that I've seen and the powered paragliders don't have metal
propellors. I suspect the reason is economics, rather than stealth,
though.



Mark Borgerson

Mark Borgerson wrote:
In article %AMfg.1638$I61.24@clgrps13,
says...

wrote:

Ken Chaddock wrote:



Block 1B CIWS has an infrared and optical tracker that would do nicely
against any UAV within it's range...the question is finding the UAV in
the first place. An Infrared search system with the ability to designate
to a B1B Phalanx would work quite well I think...


But a prop-driven UAV with a small engine and some attention to exhaust
masking would not be an easy IR target.

If all you want to do is locate and identify a ship, and beam an
illuminating laser at it to guide the incoming ordnance, then the UAV
can be very small and very hard to detect.

Tony Williams
Military gun and ammunition website: http://www.quarry.nildram.co.uk

Have you ever seen the radar return from a prop ? Looks like a bloody
747...a prop-job wouldn't be a particular problem and contrary to
popular misconception, most modern IR trackers don't rely on a hugh heat
gradient but rather on the difference in emissivity between the target
and the background, IOW it's tracking the delta, not the absolute IR
output of the target...


So what IS the radar return from a wooden or fiberglass propellor like?

Not as strong as from metal but still there and the main feature of the
return is the doppler...which is unique and quite distinctive since it
varies from hub (near zero doppler) to quite high since the prop tip is
almost certainly supersonic. Remember Mark, you do get a radar return
from wood and fiberglass

Fundamentals of Stealth Design

The following article was written by Alan Brown, who retired as Director
of Engineering at Lockheed Corporate Headquarters in 1991. He is
generally regarded as one of the 'founding fathers' of stealth, or low
observable technology. He served for several years as director of low
observables technology at Lockheed Aeronautical Systems Co. in Marietta,
Ga. From 1978 to 1982, he was the program manager and chief engineer for
the F-117 stealth fighter and had been active in stealth programs since
1975. This article first appeared in 1992. Design for low observability,
and specifically for low radar cross section (RCS), began almost as soon
as radar was invented. The predominantly wooden deHavilland Mosquito was
one of the first aircraft to be designed with this capability in mind.
Against World War II radar systems, that approach was fairly successful,
but it would not be appropriate today. First, wood and, by extension,
composite materials, are not transparent to radar, although they may be
less reflective than metal; and second, the degree to which they are
transparent merely amplifies the components that are normally hidden by
the outer skin. These include engines, fuel, avionics packages,
electrical and hydraulic circuits, and people.

The UAVs that I've seen and the powered paragliders don't have metal
propellors. I suspect the reason is economics, rather than stealth,
though.

I'm absolutely positive...

....Ken

Ken Chaddock wrote:
Mark Borgerson wrote:

snip

The UAVs that I've seen and the powered paragliders don't have metal
propellors. I suspect the reason is economics, rather than stealth,
though.


I'm absolutely positive...

...Ken

I think weight vs. strength is a factor, too.

John Mullen

In article Ad6gg.5190$771.1108@edtnps89,
(Ken Chaddock) wrote:

The predominantly wooden deHavilland Mosquito was
one of the first aircraft to be designed with this capability
in mind. Against World War II radar systems, that approach was
fairly successful, but it would not be appropriate today.


I think stealth came way down the list when the Mosquito was
designed, especially as radar was so secret those days. Design of
the Mosquito started in 1938 when German Radar was unknown. It
was more likely wood was adopted because De Haviland had far more
experience with that material than metal. IIRC the DH4 had a
monocoque fuselage.

Ken Young

wrote in message
...
In article Ad6gg.5190$771.1108@edtnps89,
(Ken Chaddock) wrote:

The predominantly wooden deHavilland Mosquito was
one of the first aircraft to be designed with this capability
in mind. Against World War II radar systems, that approach was
fairly successful, but it would not be appropriate today.


I think stealth came way down the list when the Mosquito was
designed, especially as radar was so secret those days. Design of
the Mosquito started in 1938 when German Radar was unknown. It
was more likely wood was adopted because De Haviland had far more
experience with that material than metal. IIRC the DH4 had a
monocoque fuselage.

My grandfather was the engineer in the RAE's timber mechanics
laboratory in Bucks in the 30s and early 40s. AIUI, the idea of low
observability just wasn't a factor considered when he did the tests on
de Havilland's plywood aircraft construction to prove the concept for
combat aircraft. What was important was durability and structural
integrity after aerobatic stress or battle damage. If you look up the
research in the archives you'll find much of it associated with C.J.
Chaplin, M.Sc.
--
Andrew Chaplin
SIT MIHI GLADIUS SICUT SANCTO MARTINO
(If you're going to e-mail me, you'll have to get "yourfinger." out.)

wrote in message
...
In article Ad6gg.5190$771.1108@edtnps89,
(Ken Chaddock) wrote:

The predominantly wooden deHavilland Mosquito was
one of the first aircraft to be designed with this capability
in mind. Against World War II radar systems, that approach was
fairly successful, but it would not be appropriate today.


I think stealth came way down the list when the Mosquito was
designed, especially as radar was so secret those days. Design of
the Mosquito started in 1938 when German Radar was unknown. It
was more likely wood was adopted because De Haviland had far more
experience with that material than metal. IIRC the DH4 had a
monocoque fuselage.

Ken Young

Plus there was a surfeit of woodworkers, joiners and cabinet makers unable
to practise their normal trade due to the war economy. The complement of
metal-bashers were committed to aircraft and vehicle manufacture, and the
'new' science of laminated materials utilising resins was becoming
available. All these factors culminated in the 'Ministry of Aircraft
Production(?)' authorising the production of the wooden-hulled aircraft and
allocating the necessary engines and hydraulic componentry to DH.

The book 'The New Science of Strong Materials - or Why You Don't Fall
Through the Floor' is recommended for the background to the development of
the Mosquito airframe.

--

Brian

wrote:
In article Ad6gg.5190$771.1108@edtnps89,
(Ken Chaddock) wrote:

The predominantly wooden deHavilland Mosquito was
one of the first aircraft to be designed with this capability
in mind. Against World War II radar systems, that approach was
fairly successful, but it would not be appropriate today.

I think stealth came way down the list when the Mosquito was
designed, especially as radar was so secret those days. Design of
the Mosquito started in 1938 when German Radar was unknown. It
was more likely wood was adopted because De Haviland had far more
experience with that material than metal. IIRC the DH4 had a
monocoque fuselage.

I didn't write the article that I quoted and I tend to agree with you
that low observability was not even on the agenda. The point is that
even the Mosquito which was constructed almost entirely of wood, while
certainly giving less of a radar return than say, a Boston or Wellington
or even P38, STILL gave a significant radar return to the low efficiency
radar of the day...so wood isn't the answer for UAVs...

....Ken