Submariners: What's a "firing point solution"?

Factual Questions
1

“The Hunt for Red October” was on tonight, and it reminded me of a question I’ve always had: Just what the heck is a “firing point solution”? Why does one need to ‘load it into the computers’? I think I remember hearing this in a couple of documentaries, so it sounds plausible, but I just don’t understand the mechanics behind submarine weapons.

See, fighter aircraft either have a radar lock on a target to track and hit enemy aircraft, or the missiles themselves have a tracking system. I was under the impression that the Mk 48 torpedoes had it’s own active sonar tracking system, essentially making it “fire and forget”.

Am I missing something?

Tripler
I just pave runways and put up buildings. I do like to know my fiction is relatively accurate, though.

2

IANA Submariner, but…

My understanding of it is that the ship is moving in X direction at some speed and the target is moving in Y direction at some other speed, so you need to calculate your own speed, its speed, the torpedo speed, and all sorts of other stuff to figure out where to aim the torpedo. If the torpedo is modern enough to be smart, you then download this data into the torpedo’s computer and send it on its merry way.

Here’s a couple of good links that explain it better than I can:

3

I’m used to it being called a firing solution, but I think it’s the same thing. Before you launch a weapon, you need to know your own ship’s position, heading, and speed, plus the position, heading and speed of the target. This may be simple for a surface ship that is tracking its target on radar. For a submarine, it can be much more difficult. Passive sonar may give you a bearing to the target, but it doesn’t tell you range or the target’s speed. Assuming the target is moving in a straight line and at a constant speed, the submarine can develop a firing solution by making course/speed changes and noting the rate-of-change in the bearing to the target. With the help of a computer, a firing solution can be developed that matches the information from the passive sonar. A sonar operator can help by identifying the class of the target (garbage scow, fast destroyer, slow diesel-electric submarine) and making an estimate of the target’s speed by listening for engine/propellor noise. The simple solution is to use active sonar to get a quick and accurate fix on the target. The problem is that this tells every bad guy in the area that there is a submarine and where to find it.

4

Well, I thank you mks57, but given your explanation, what makes it so different from the ‘firing solution’ of aircraft? An enemy “bandit” is moving a helluva lot quicker than an enemy sub, and is also a heck of a lot smaller of a cross section than a large submarine. Yet, as a few friends have informed me (and this may be where I listen to fighter jocks, but haven’t heard tales from those in the silent service), that a fighter can lock and launch inside of less than a minute.

I’m starting to think I might be:

A) Unduly under the impressions of Hollywood and/or polite disinformation
B) Not completely understanding the “pace of speed” in an underwater fight.

Tripler
If’n you tell me either or, I’ll take that as an answer.

5

If you google “patriot” or “missile” with “firing solution” you’ll find the term is used for missiles too. I guess Hollywood just uses it strictly for submarines.

6

A fighter pilot can see his enemy and can visually determine bearing and range. He still needs to get sensor (IR or radar) lock before launching a missile. A missile also travels much faster than an aircraft.

When it’s sub vs. sub, many things are different. Passive sonar is affected by water temperature and salinity, which can bend or reflect sound waves. That’s why the thermocline is so important. A sub on the other side of the thermocline may be invisible to passive sonar. With modern submarines, it’s a battle of stealth. If you can detect the enemy without him detecting you, you have a major advantage. Torpedoes are relatively slow. If detected early, the targeted sub can often outrun the torpedo. For the attacking sub, the ideal situation is to launch a torpedo in wire guided mode and low speed, steer the torpedo into the baffles (stern area) of the target, where the target’s passive sonar is least effective, and switch the torpedo to high speed and active sonar guidance only when it is close to the target. It’s also a good idea to have the torpedo approach the target at a different bearing than that of the attacking sub. That makes it less likely that the target can get lucky by firing a torpedo down the bearing of the incoming torpedo. It can take a long time to develop a firing solution for a target that is far away and relatively quiet. Both subs are moving at relatively slow speeds and it takes time to get a good estimate of range. It’s more like a chess game than a 30-second dog fight. It would be simple to charge in at full speed, active sonar pinging away, firing torpedoes. But the Navy and the crew would prefer that the attack submarine survived the battle to fight another day.

7

Ex-bubble head here, mks57 is dead on target. The HFRO was one of the most detailed and factual books/movie on sub warfare and caused quite a stir among the sub community when it came out because some of the stuff was still considered classified info. A section tracking party can spend many hours tracking a target, only to have to completely scrap the solution because the target changed course, depth, or speed. The protocol is when at battle stations and a firing point solution has been derived, the CO or XO will announce firing point procedures, in essence preparing for launch.

8

NOW I understand (especially through that part of the pilot actually seeing his “bandit”). I had completely forgotten about the conditions of the environment (salinity, temperature, etc.) dictating tactics of the fight.

Much obliged mks57. I kinda figured it was a bit more detailed than flicking a master arm switch, and pulling the trigger.

Tripler
And BF, I’m glad to hear HFRO is pretty well regarded as far as factuality goes.

9

Wow, I just wanted to pop in to give a thanks for the detailed replies. I finished reading HFRO a few weeks ago and this thread really throws some light on the novel. Thanks for the information.

10

Just one more thing to help visualize this in your head, you have to think in 3D. When most people think of guns, it’s a rifle or a tank aimed at each other, not floating above or below.

11

I think the passive nature of a sub acquiring a target needs to be emphasized here. Technically the sub can get an active target acquisition using a ping but that is nearly always a very bad idea as it gives away that the sub is there and points enemies to it. A sub can also get a visual acquisition using the periscope but that also comes with some risk of exposing the sub. Best option, if they have the time, is to work out a firing solution based on bearing changes as described by mks57.

Modern torpedoes do have active acquisition modes but you do not want them to be using that straight out of the tube as again it alerts everything in the area to your and the torpedo’s presence allowing them to try to evade and (perhaps) counter attack the sub. Remember it can take minutes for a torpedo to reach its target but once close the torpedo may go into active acquisition to finish its end run. At that point the sub has moved and it would be pretty obvious to everyone the torpedo is there anyway so no loss with the torp tipping its hand at that point (I think modern torpedoes may even be programmed to take a roundabout rather than direct route to a target so the enemy cannot pinpoint the area the sub is in as easily).

I think it was in HFRO but in some sub movie (Crimson Tide?) you may have heard them order a “snap shot” of a torpedo. I understood this to mean the sub does not have a refined firing solution but in a pinch pops off a torp or two in the general direction of the target and hope the torp can acquire it on its own.

12

Correct. A snapshot can be used at any time. The Fire Controlmen of the Watch maintains firing solutions on all contacts that sonar is tracking. When the Officer of the Deck announces snapshot and ID’s the target, the FT and the torpedo room dial in the firing solution and setup the torpedo for minimum safety distances and maximum acquisition distances. When the torpedo is launched the boat cuts the guidance wire, closes tube doors and goes to a flank bell 180 degrees away from the target and the torpedo.

13

[Sea Story]I had just qualified as OOD (Officer of the Deck) back in the early 90s on a 688-I Los Angeles-class attack sub. On my second watch, unbeknownst to me, the CO/XO decided to run a drill on my watch section.

The XO and the Sonar division chief entered the sonar shack and told the folks in there that they were going to run a drill on the control room watch section. They also tipped off the torpedomen.

False targets could be entered into the sonar system’s computer for drills. That’s exactly what they did. They then waited to see if the OOD (me) would notice the new contact.

I was paying close attention to everything, being so newly qualified, and noticed the contact on the control room sonar repeater within a minute or two after it popped on the screen. I immediately questioned sonar (via intercom) about the contact. They replied that they had just noticed it as well, and were about to report it to me. They added they were working on classification.

Contacts at sea are pretty common, but both for safety and for practice, the fire controlman started working up a solution.

Then things got interesting.

Sonar reported over the intercom that the contact was a probable submerged contact. That got my attention in a hurry. The most dangerous thing for a sub is another sub. If it was a friendly sub, we would have known about it in advance from SUBLANT. That made this contact presumably non-friendly.

I immediately called the CO (Commanding Officer) to inform him of the contact.

Before the words had even left my mouth. Sonar came in excitedly over the intercom, “Torpedo in the water, bearing 095!!”

In the back of my head, I remember thinking, “This is probably a drill,” but I pushed the thought out of my head.

I immediately grabbed the 1MC (announcement system for the whole ship), and shouted, “Snap Shot, Tube 1, Bearing 095!” My Captain’s Standing Orders did not permit me to actually shoot a live warshot until the CO reached the control room, but that announcement would bring him in a hurry.

My next order was to accelerate to flank speed for a torpedo evasion, but I held off because I wanted to be sure my shot got off before we put on too much speed.

At that moment, the CO rushed into control. I quickly informed him of the situation and requested permission to shoot. (Again, unbeknownst to me, a drill monitor was in the torpedo room to ensure we did not inadvertently launch a $1.2 million ADCAP torpedo for a drill.)

At that point, the CO stood down the drill.

All in all, it was a pretty exciting second watch.[/Sea Story]

By the way, the reason you fire a snap shot for a torpedo coming at you is primarily to give the other sub something to think about beyond wire-guiding their torpedo at you.

14

Nothing like increasing the pucker factor by running this drill at 0300 in the morning… :stuck_out_tongue:

Which was designed specifically for the Alfa class boats that were chasing the Dallas and the RO at the end. Alfa’s could achieve 50 plus knots. Their major downside was they could be heard 500 miles away.

15

Cool story. Sounds like you performed well under pressure. Not being a military person myself, when something like that happens, do you get a pat on the back, or an attaboy, or a beer, or what?

16

How likely is it a torp would have been launched by accident? Especially if the torpedo room was in on it? Granted no harm being extra careful with a dangerous and expensive weapon but can a torpedo even be launched on a moment’s notice? I seem to recall that torpedoes needed to be “spun up” (or something) which I took to mean getting a gyroscope going which took some time. Add to that are torpedoes even carried loaded in the tubes? IANASubmariner of course…just curious. Perhaps too many WWII movies (I seem to remember from some sub simulation that some WWII era torpedoes had to have their batteries warmed prior to use…all-in-all a pain-in-the-arse to use them).

17

According to MrWhatsIt: “US submariners in the early days of WWII (specifically Mush Morton, but surely others too) found that the failure rate of warshots went up significantly with even brief exposure to salt water :smack:. OTOH, IIRC, it was not uncommon to embark on war patrols with tubes loaded but not to flood them until firing time, because that let them carry an extra 6 to 12 fish (we recently toured the USS Clamagore, SS-343, commissioned in 1945, and it only had room for one or two reloads per tube).”

18

This has already been answered ably by others, but I hope it’s OK to add just one more perspective.

Acquiring a firing solution means solving for the target’s position and velocity, a 6 degree-of-freedom problem. From passive sonar, you only get bearing information (2 d.o.f.), and this can be misleading due to variable refraction in the water due to salinity gradients and pressure. So, it’s a matter of introducing spatial and temporal diversity to your measurements, meaning you track the target for awhile as the sub motors around in such a way that you can best triangulate the target and solve either by inference or measurement for the probable water conditions between you and the target (a sub keeps a close track on changing conditions with depth for this reason, and to use favorable layers in avoiding detection). And you may not know directly if the target has changed heading during tracking, although speed changes are easier to detect from the propeller signature.

Lots of d.o.f.'s here, which is why it’s not as simple as the aircraft firing solution; in that case, radar can come up with bearing and range, as well as closing/receding velocity from the Doppler on the returned signal.

19

Taking the liberty to respond, a) not likely, b) not likely at all, c) Yes. On patrol all the tubes are loaded and the torpedoes wired up. Flooding the tube and opening the outer doors takes about 30 seconds. By that time the FT has fed the firing solution to the fish and she’s ready to go. After launch the torpedo calibrates gyro’s, etc., within the first 1000 feet.

American torpedoes at the start of WWII were notoriously bad, IIRC, some estimates put the early failure rate at 50%. That was one of the reasons for best practice solutions like firing a spread (2-4) torpedoes at one target to ensure at least one hit. There was also speculation that a number of American boats went down by their own fish, with gyro failures, etc, causing the fish to 180 on them.

20

The Germans also had similar problems with their torpedoes, leading Admiral Raeder to court martial the responsible officers. Something that many American sub commanders would have liked to have done to the responsible people in the Bureau of Ordnance.

The contact exploders on American torpedoes were so bad that they were most likely to fail with a perfect setup, a shot perpendicular to the hull of the target.