Torpedos, extreme range and accuracy

Von Due · 08-07-12, 01:02 PM

I am looking at the possibility of shots at extreme range, 5,000-10,000 metres with a reasonable probability of a hit and have done some calculations and looked at methods for getting target speed and heading, setting up for a plain 90* shots.

Needless to say, the accuracy needed is really touching on the limits of what can be achieved but here are some thoughts so far. Please chime in if you spot flaws etc!

Speed is if possible even more crucial to get just right and the 3.15 rule is, imo, too rough to give that exact speed for those ranges. I am looking at 730 metres per knot per 23 minutes 39 seconds. The time and distance per knot would have sufficient resolution to determine speed with a high level of accuracy, even in rough sea where target speed is yoyo-ing over short distances.

About target heading. I have looked at speeds of 7.5 knot and 12.5 knots range to impact point 10,000 metres, torpedo speed 30 knots. The way I reasoned and do correct me here if I'm wrong:

First, I calculated the time T in seconds it takes the 30 kts torpedo to travel 10,000 metres to the ideal impact point P. This is the ideal situation where I somehow managed to get target heading accurate and am on a perfect perpendicular course.

For a 12.5 kts target starting at torpedo fireing point A, in that same time, it will travel T x 12.5 x 1.852 / 3.6 metres.

I now have a triangle with two sides of 10,000 and T x 12.5 x 1.852 / 3.6 metres.

Now if I got the target heading wrong by +- 1*, that would mean the distance from P to true impact point P+ or P- is
T x 12.5 x 1.852 / 3.6 x tan 1*and the true distance traveled is
10,000 +- T x 12.5 x 1.852 / 3.6 x tan 1*

I now need the time it takes the torpedo to travel those distances, T+ and T- and I calculate how far the ship will travel in the same time.

By comparing true impact points to where the ship would actually be, I find that I will miss the aiming point by some 30 metres. The actual distance would vary depending on whether I missed by -1* or +1* but roughly 30 metres will do.

That means I should not attempt long range shots at targets at around 60 metres in length or less but for a ship or 100 metres or more, I should have a good chance of hitting if I aim at center.

For target speed of 7.5 knots, the possible error would be around +- 11 metres, meaning if the target is moving slow, I should be able to hit a 50 metres or more long target if I aim at center.

All this of course rely on accurate heading and speed calculations but the bottom line is, even if I get the heading wrong by 1 degree either way, I still stand a good chance of hitting at 10,000 metres.

Any inputs and corrections greatly appreciated!

08-07-12, 01:02 PM	#1
Von Due Sea Lord Join Date: Jul 2012 Posts: 1,690 Downloads: 30 Uploads: 0	Torpedos, extreme range and accuracy I am looking at the possibility of shots at extreme range, 5,000-10,000 metres with a reasonable probability of a hit and have done some calculations and looked at methods for getting target speed and heading, setting up for a plain 90* shots. Needless to say, the accuracy needed is really touching on the limits of what can be achieved but here are some thoughts so far. Please chime in if you spot flaws etc! Speed is if possible even more crucial to get just right and the 3.15 rule is, imo, too rough to give that exact speed for those ranges. I am looking at 730 metres per knot per 23 minutes 39 seconds. The time and distance per knot would have sufficient resolution to determine speed with a high level of accuracy, even in rough sea where target speed is yoyo-ing over short distances. About target heading. I have looked at speeds of 7.5 knot and 12.5 knots range to impact point 10,000 metres, torpedo speed 30 knots. The way I reasoned and do correct me here if I'm wrong: First, I calculated the time T in seconds it takes the 30 kts torpedo to travel 10,000 metres to the ideal impact point P. This is the ideal situation where I somehow managed to get target heading accurate and am on a perfect perpendicular course. For a 12.5 kts target starting at torpedo fireing point A, in that same time, it will travel T x 12.5 x 1.852 / 3.6 metres. I now have a triangle with two sides of 10,000 and T x 12.5 x 1.852 / 3.6 metres. Now if I got the target heading wrong by +- 1, that would mean the distance from P to true impact point P+ or P- is T x 12.5 x 1.852 / 3.6 x tan 1and the true distance traveled is 10,000 +- T x 12.5 x 1.852 / 3.6 x tan 1* I now need the time it takes the torpedo to travel those distances, T+ and T- and I calculate how far the ship will travel in the same time. By comparing true impact points to where the ship would actually be, I find that I will miss the aiming point by some 30 metres. The actual distance would vary depending on whether I missed by -1* or +1* but roughly 30 metres will do. That means I should not attempt long range shots at targets at around 60 metres in length or less but for a ship or 100 metres or more, I should have a good chance of hitting if I aim at center. For target speed of 7.5 knots, the possible error would be around +- 11 metres, meaning if the target is moving slow, I should be able to hit a 50 metres or more long target if I aim at center. All this of course rely on accurate heading and speed calculations but the bottom line is, even if I get the heading wrong by 1 degree either way, I still stand a good chance of hitting at 10,000 metres. Any inputs and corrections greatly appreciated!