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Question on Radar versus Sonar

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Gil View Drop Down
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    Posted: 18 Feb 2016 at 11:46pm
I've never been the sharpest tool in any shed, but I have a question that has perplexed me for several years.  I asked it a few years ago on possibly this board, and nobody responded.

Initially the question came from reading the book "The Skunk Works", written by Ben Rich who succeeded Kelly Johnson at the division of Lockheed called the Skunk Works, and responsible for some unique aircraft.  Ben Rich ran it until around 1975, and before that he was Kelly Johnson's right hand man, and responsible keep him from being so cantankerous to Lockheed's customers.  The book covers the time period from the U-2 spy plane , through the F-104 and SR-71, to the beginnings of the F-118 stealth fighter.  I found it a tremendous read, and Lockheed and Kelly Johnson IMO are American heroes.

I find planes and submarines fascinating, and after I left the Navy I was able to go to school on the GI Bill and become a buyer of aircraft, missile, and satellite parts for four major aerospace companies over thirty years.  Missiles and spacecraft are boring to me, but aircraft are not.  Pilots would complain about the shape or position of gauges.  We got a call from the Air Force while I was at Northrop that an F-5 was firing its weapons while maintenance was being performed on it.  I bough the armament switch,which was installed in the landing gear, and it was designed to go on safety when the plane was on it.  I got to follow my part all the way to Palmdale where we witnessed a South American country have it painted and flown home - the purpose was to find out where we introduced the force to disable the switch - it was determined Honeywell's switch had a design flaw.

In the book Ben Rich describes the initiation of the F-118 into combat during the Gulf War.  The chosen pilots to fly the stealth fighters were to put it mildly uneasy.  The planes were unproven in combat, and although flown at night were slow and defenseless if the stealth technology didn't work.

According to Ben Rich the pilots were somewhat relieved when they found dead bats around their planes - evidently during the night the bats had killed themselves crashing into the planes.  That sounds a little fishy to my smell factor, and I wonder if Mr. Rich fabricated this story.

Since bats have sonar, not radar how does this make sense?  Are radar and sonar that similar that the shapes and coating of the planes have the same effect for sonar as radar.  Anyway the F-118's performed as diagrammed and we did not take any losses at the time.  Since that time I believe one was shot down by a special radar set up.  Can somebody weigh in on this and clarify sonar versus radar for me.

Anyway "The Skunk Works" wasa very fascinating book for me.  Growing up my favorite fighter was the F-104 Starfighter, another Lockheed and Kelly Johnson design.  Interesting thing about the U-2 being shot fown.  Kelly Johnson was pissed that Francis Gary Powers didn't take his cyanide tablet, and although Soviet radar improved and started detecting the U-2's, the missile that downed it wasn't really close, but the U-2's were so fragile that the explosion knocked it out of control.  Also Kelly Johnson was old school, and his philosophy was great planes have to also look good.  Kelly retired as the F-118 was being introduced, and he never embraced it.  If it wasn't for computers it would be unflieable.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote oldsubs Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2016 at 5:38am
Sounds like a bit of urban legend.  However, a bat's sonar is very high frequency and very short range.  It is possible that there is something about the plane's skin that deadens the return echo so the bat misjudges the distance and hits the plane.  Just a guess.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom McNulty Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2016 at 6:41am
Radar waves and sonar waves are both energy pulses. The difference is in their strength. The energy is made up of matter so when it strikes an object some of that energy will be bounced back in the general direction of which it was originated. Some will be absorbed in the form of heat and some will be dissipated due to angular surfaces. Theoretically, and with new technology, it's possible to analyze the small part that is returned in the direction of the source.
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Gil View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gil Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2016 at 10:29am
I guess what I'm trying to get at is if it were possible to make a submarine in the same  shape and material as an F-118 it wouldn't necessarily be able to eliminate or reduce sonar detection would it?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SaltiDawg Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2016 at 12:38pm
Gil,
The aircraft shape would not be effective at reducing Target Strength.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dr. Stan Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2016 at 3:50pm
Originally posted by Tom McNulty Tom McNulty wrote:

Radar waves and sonar waves are both energy pulses. The difference is in their strength. The energy is made up of matter so when it strikes an object some of that energy will be bounced back in the general direction of which it was originated. Some will be absorbed in the form of heat and some will be dissipated due to angular surfaces. Theoretically, and with new technology, it's possible to analyze the small part that is returned in the direction of the source.


While it is true that radar and sonar are both emitted energy, they differ qualitatively in their basic characteristics.  Radar is radiated pulse of electromagnetic energy of extremely high frequency which travels at approximately the speed of light, 186,000 miles per second, in a vacuum.  Sonar is mechanical energy radiated as a pressure pulse traveling at approximately the speed of sound, 768 mph, depending on the nature of the  propagating medium (temp., density, salinity, etc.). 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote SubVet49 Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 2016 at 6:20pm
Very different radar and sonar.  Sonar being mechanical energy in an acoustic wave actually reflects off varying materials, depending on the speed of sound in the material.  Keep in mind that the acoustic wave that hits a submerged submarine does not reflect or bounce off the steel hull, but the air inside.  Sound travels at approximately 4800 feet per second in water and approximately 1100 feet per second in air.  Thus, the air in a submerged submarine acts as a reflector, thus the return signal. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Runner485 Quote  Post ReplyReply Direct Link To This Post Posted: 20 Feb 2016 at 6:50am
Originally posted by SubVet49 SubVet49 wrote:

Very different radar and sonar.  Sonar being mechanical energy in an acoustic wave actually reflects off varying materials, depending on the speed of sound in the material.  Keep in mind that the acoustic wave that hits a submerged submarine does not reflect or bounce off the steel hull, but the air inside.  Sound travels at approximately 4800 feet per second in water and approximately 1100 feet per second in air.  Thus, the air in a submerged submarine acts as a reflector, thus the return signal. 


With zero knowledge of how this stuff works, if it is the air inside the boat, then why the special coating on the boats of today, which, as I have been told prevents the return bounce (in most cases) back to the source. Confused
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Post Options Post Options   Thanks (0) Thanks(0)   Quote atozdbf Quote  Post ReplyReply Direct Link To This Post Posted: 20 Feb 2016 at 7:16am
I dunno. Maybe its because the coating absorbs the energy rather than the steel hull resonating with it and letting it vibrate the air inside. But then again . . .

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Post Options Post Options   Thanks (0) Thanks(0)   Quote GaryKC Quote  Post ReplyReply Direct Link To This Post Posted: 20 Feb 2016 at 8:05am
I doubt the air inside a boat or any coating outside a boat matter much cause you'd haffta be a dern fool to use yer active sonar, pinging away in a big ol ocean, lookin fer a itty bitty little boat with a bunch of big ol nasty weapons, silently lookin fer a place to point em.
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