Heat-seaking missiles

[doltish]

A friend of mine joked the other day (rather tastelessly, so I apologize for its crudeness) that Santa should be careful when flying over the West Bank because he might get hit with a surface-to-air missile. My sarcastic response was that terrorists only have heat seeking missiles, and the reindeer most likely don't give off enough heat to attract a missile.

I'll preface this by saying that I know nothing of missiles, physics, or much of anything that is commonly discussed on this forum. But what I do know is that if I ever wonder about anything of this nature I can more than likely find the answer here.

This joke got me thinking - heat seeking missiles obviously (or maybe not so obviously) look for the strongest source of heat around and then head for it. And so my question: why don't heat seeking missiles simply head for the sun? If a flare is strong enough to distract a missile from the engine of an aircraft, certainly a massive ball of flame can throw it off too. Is there perhaps some kind of "tare" option whereby the missile can ignore the ready sources of heat around its environment?

[Saluki]

Well, when the massive ball of flame is 92 million miles away, it is a little out of the missile's range. The flares, on the other hand, are close enough to the desired target to confuse the missle.

[Evan]

The sun is a problem for heat seeking missiles as it can blind the sensors. A standard defensive tactic against early sidewinders was to fly into the sun if you had someone on your tail. In recent years much improved target detection has been developed. Multispectral sensors are used in infrared, visible and ultraviolet to distinguish the target from clutter.

The most recent generation of the stingers use an imaging array that identifies the target by shape and can be programmed to strike the cockpit area of the target.

[TravisM]

And radar to lock on the last few hundred yards...

[skrap1r0n]

yeah they used to be able to fool them my heading into the sun

[Inferno]

Is it true where in the movies the good guy simply moves past the bad guy, and hence the nearest object to the missile giving off heat is now the bad guy's plane?

Similar to this, where a sub fires a torpedo only to find there is no enemy and the torpedo turns around and heads back to attack the sub?

[Wally]

Just a WAG here, but I don't think a sub's torpedo would do a 180 on its own. It'd have to be "guided" into a return course by some other target, just like in the climax of Hunt for Red October. Otherwise, it would probably just continue in a straight line until it lost propulsion.

As for heat seeking missiles, I don't know if they go for the closest target, or the hottest (or perhaps a combo of the 2).

[Evan]

Is it true where in the movies the good guy simply moves past the bad guy, and hence the nearest object to the missile giving off heat is now the bad guy's plane?

I'm not understanding. If plane A is being followed by B and B fires a sidewinder then A is in trouble. I don't know the spec for the sidewinder but I do know the lastest Stinger can manouver at around 9 gees which is enough to follow any fighter in the inventory. There is one aircraft that is able to pull off a sudden manouver that allows B to overshoot A. It is the Harrier. The move is called "VIFFing" which stand for "Vectoring In Forward Flight". Using the moveable engine nozzles the Harrier can decelerate from Mach 1 to standstill in 30 seconds causing a following enemy to overshoot. This is a very risky move as it leaves the Harrier a sitting duck to any other enemy in the area. Some of the new aircraft with thrust vectoring are also able to pull off a similar move.

This may or may not help to avoid an already launched missile. Once locked on to a target a seeker missile will continue for that target unless it loses sight of it. It won't aquire another target. Target aquisition is performed before the missile is launched. This is the case for nearly all missiles. The use of chaff or flares doesn't cause a seeker to change target lock, it makes it lose lock.

[Nergal]

Similar to this, where a sub fires a torpedo only to find there is no enemy and the torpedo turns around and heads back to attack the sub?

This falls under the category, "Possible, but unlikely to the point of being nearly impossible."

[Extravoice]

I believe that torpedos have safety interlocks to prevent them from locking onto their launching submarine. In fact, one theory regarding the sinking of the USS Scorpion involves the captain turning the boat 180 degrees to disarm a torpedo that had accidently gone active onboard.

According to PBS Nova Program

Had Scorpion turned around, and if so, why? The Navy has a possible explanation, but keeps it secret for 25 years. Finally, in 1993, the Navy releases its findings. The most likely scenario, the Navy believes, begins when stray electrical current activates an on-board torpedo. The captain orders an immediate 180 degree turn, which he expects will trigger a safety mechanism and disarm the torpedo. Then the crew ejects the torpedo. But it doesn't disarm. The torpedo begins to search for a target.

[joema]

Although generally not depicted in movies, modern torpedoes are usually wire-guided. A fine guidance wire unspools from the rear. The launching sub communicates with the torpedo over that, actively steering it. Despite this they have very long range -- over 35 miles for the Mark 48 ADCAP.

Although the torpedo has its own sonar, the submarine's sonar is much more capable. Hence it makes sense to wire guide the torpedo as long as possible. Wire-guided torpedoes are also more resistant to countermeasures.

Obviously a wire-guided torpedo guided won't turn back on the launching sub -- it's being guided.

They can cut the wires and let the torpedo use its own sonar to seek the target. This is usually deferred as long as possible.

As mentioned there are also safety interlocks that prevent the torpedo from turning back to the launching sub. E.g, if guidance wires are cut, it's inhibited from turning sharply close to the launching sub. As it gets further away, its guidance computer allows it to turn more sharply.

[vonmazur]

Back when I was a "transadult", I did two tours in Vietnam as an Army Aviator. Once Nguyen fired a Soviet shoulder launched heat seeker at my Helicopter, I turned the tail pipe away from the missile, it lost lock and headed off towards the sky. I do not know if it locked onto the sun, but it did not follow me. The Huey used so much torque that the heat energy coming out of the exaust was not all that much, about 9 to 12 lbs of thrust, I think the Soviets set the missile to seek jet fighters and their higher infra red output. We feared the .51 Soviet quad mount more than the ineffective missiles, guided and unguided both!!

Dale in Ala

[russ_watters]

Is it true where in the movies the good guy simply moves past the bad guy, and hence the nearest object to the missile giving off heat is now the bad guy's plane?

Similar to this, where a sub fires a torpedo only to find there is no enemy and the torpedo turns around and heads back to attack the sub?

Both questions are really a matter of range: a plane can't ever get into a position where his missile can circle back around on him before it runs out of fuel. Ever see the movie "Behind Enemy Lines" where the missile follows the guy's jet for miles, slowly closing in? Reality is nothing like that. Missiles go more than 1,000 mph faster than a maneuvering jet and a 10 mile flight lasting 30 seconds would be a really long time.

For a sub, it is theoretically possible, but unlikely (for the Mk48 anyway...) for reasons already stated. There are potential problems though: some torpedos like the Mk50 (smaller, not sub launched, not wire-guided) will get dropped from a plane, helo, or ship, and sprial down, looking for any available target. Many mines are just modified versions of torpedos that float around and listen for an approaching ship/sub, then wake up and go after it.

Russian torpedos (Hunt for Red October...), I don't know about...

[Evan]

Russian torpedos are an entirely different animal. Rocket powered with a top underwater speed of possibly 450 mph (not a typo) and possible range of 100+km. No countermeasures exist.

http://www.deepangel.com/html/the_squall.html

[Wally]

Russian torpedos are an entirely different animal. Rocket powered with a top underwater speed of possibly 450 mph (not a typo) and possible range of 100+km. No countermeasures exist.

http://www.deepangel.com/html/the_squall.html

hell, at that speed, who'd have time for countermeasures! :-?

[joema]

The tradeoff is at that speed, it's thought they aren't wire guided, and the acoustic noise is too great for sonar self guidance. While fast, it's an "aim and shoot" weapon.

There's speculation newer versions can sprint then slow down, use sonar while going slow, then speed back up again.

[tofu]

Russian torpedos are an entirely different animal. Rocket powered with a top underwater speed of possibly 450 mph (not a typo) and possible range of 100+km. No countermeasures exist.

I haven't heard that soviet torps go quite that fast, but I know that most of soviet naval strategy was based around taking out US aircraft carriers. They had to do that in order to hunt merchant shipping in the atlantic. So, I'd guess that such a torpeado like that was an anti carrier weapon. Is that correct?

You know, between the subs, surface ships like the kirov, and waves of backfire bombers, there would have been quite a battle if a shooting war had ever broken out!