Silent Hunter 5 : Wolves of Steel Mod Submarine Commander ′ s Guide Version 0.21 Patrick Doolittle July 31, 2023 Contents 1 Introduction 2 2 U-Boat Operation 3 3 Strategy 6 4 Tactics 8 5 Target Motion Analysis 9 5.1 Foundations . . . . . . . . . . . . . . . . . . . . . 9 5.2 Three Bearing Method . . . . . . . . . . . . . . . 12 5.3 Four Bearing Method . . . . . . . . . . . . . . . 14 6 Torpedo Firing Solutions 15 6.1 RAOBF Guide . . . . . . . . . . . . . . . . . . . 16 6.2 Speed Finding . . . . . . . . . . . . . . . . . . . . 17 6.3 Range Finding . . . . . . . . . . . . . . . . . . . 18 6.4 Angle on Bow (AOB) Finding . . . . . . . . . . . 18 7 Attack Disc 19 8 Stadimeter 20 9 Glossary 20 1 1 Introduction Silent Hunter 5 is a game released by ubisoft that puts the player in charge of a World War II German submarine. The game takes place in several theaters from the North Sea, East Atlantic, Mediterranean, and the open ocean over the span of the outbreak of the war in September 1939 to it’s end in May 1945. Your goal as the U-Boat commander is to direct your crew and operate the submarine’s mechanisms to sink enemy vessels both alone and as part of multi-submarine ”wolf packs”. As the war progresses the technology available to you in terms of your submarine, instruments, and torpedos will improve. The response of the enemy over time will also continually increase, until by the late war there will be significant risk in making any submarine patrol. Wolves of Steel is a mod to Silent Hunter 5 that provides modifications to the original game that make it more realistic. Although the original game is playable on it’s own, Wolves of Steel adds to the quality of the game as well as making the game a lot easier to play. 2 2 U-Boat Operation The U-Boat is a diesel-electric submarine. In Silent Hunter 5 we use various iterations of the German Type VII U-Boat. The Type A U-Boat at full power will do 17 knots on the surface and 6 knots submerged, with later versions being slightly faster. The crush depth of the Type VII was around 200 meters, while the Type C/41 had increased hull strength and could dive even deeper. The batteries on the U-Boat do not have to capacity to permit long distance travel while submerged. In later years U-Boats are equipped with a snorkel , a tube extending from a submerged submarine to the surface that permits running the 3 diesel engine without exposing the submarine to visual detec- tion. The Type A is armed with 10 bow torpedos and one that fires from the stern. Type B and later U-Boats instead feature 4 stern torpedos for a total of 14. The U-Boat is also often armed with an 88mm or 105mm deck gun with both armor-piercing and high-explosive ammunition capable of sinking other vessels. However the U-Boat is very vulnerable to cannon fire itself. It is also armed with a single 20mm cannon for deterring air attacks, although in most situations diving when an aircraft is spotted is ideal. In late war U-Boat commanders ditch the deck gun in favor of more anti-aircraft weaponry as merchant vessels began to arm themselves and aircraft began to become a serious threat to U-Boat operations. U-Boat torpedos come with either electric or steam propul- sion. Early models of electric torpedo suffered from very low reliability, but their lack of a wake made them invaluable as steam torpedos could be spotted while in transit and avoided. Torpedos are triggered by either an impact or magnetic fuse. The magnetic fuse suffered from lack of reliability as well, but could be used to strike vessels from below where the torpedo warhead would cause fatal damage. The low silhouette of the U-Boat allows it to make visual contact with other vessels first and maintain the element of sur- prise by diving before they are spotted. Two periscopes allow the submarine to spot enemy vessels and collect data for the tor- 4 pedo computer while submerged. The U-Boat is also equipped with a hydrophone that in quiet ambient conditions can hear enemy vessels’ propellers at up to 20 kilometers away. In later years U-Boats are equipped with surface radars for detecting hostile vessels as well. The U-Boats torpedos have internal gyroscopes for allowing them to maintain a set course upon release. This gyroscope is set with help by a torpedo computer called the TDC , fed with data attained by the periscope in conjuction with the RAOBF, Stadimeter, or by other methods. The TDC calculates the cor- rect trajectory for an intercept course and sets the torpedo’s gyroscope so that it follows this course. 5 3 Strategy The U-Boat is far outgunned and outpaced by other warships. The fastest enemy warship found often on the open sea is the smallest class of warship, the Destroyer , and Destroyer Es- cort . The destroyer is fast and heavily gunned for it’s size. It is also equipped to destroy submarines with depth charges, hy- drophones, and sonar. Depth charges are bombs that are set to explode under the surface at the same depth as a subma- rine to destroy it, and sonar is an active detection device that can find submarines at several km away even when they are not 6 completely silent to hydrophones. For this reason it is advisable to avoid confrontation with hostile destroyers at all costs. De- stroyer Escorts are small vessels specifically designed for dealing with submarines, which accompany convoys of merchant vessels on long range voyages. Destroyer Escorts are also armed with anti submarine equipment and are even faster and more numer- ous than Destroyers. Another arguably more dangerous adversary of the U-Boat is the enemy anti-submarine plane. Small single-engine planes will strafe and potentially even bomb U-Boats, but longer range twin-engine bombers are more often used for hunting submarines. Enemy anti-submarine bombers will spot the submarine and quickly line up a depth charge bombing run giving you little time to react. For this reason a submarine commander should dive if an enemy aircraft is spotted at long range, and poten- tially use the 20mm cannon to destroy it if it is too late to dive safely. In areas where attacks by enemy aircraft are common, extreme caution is advised. The primary target of the U-Boat commander will be very large enemy freighters or troop transports. Vessels in excess of 10,000 tons will be the ideal target. A single well-placed torpedo has the power to cripple or sink even the largest vessels and with the high likelihood of misses or duds the value of the ships being fired on should be maximized. Using your limited supply of torpedos on high value targets will maximize the effectiveness of each patrol you make. If you see high value warships such as cruisers, battleships, and especially aircraft carriers, it may be 7 worth making an attack. 4 Tactics Large enemy coal or oil burning vessels such as warships and freighters will create smoke columns visible from many miles away. In good conditions they can also be detected by hy- drophone at even longer ranges. The hydrophone can be used to determine the propeller speed of the contact. Slow moving propellers indicate slow moving vessels such as freighters. Con- versely, destroyers moving at high speed will have a high pro- peller frequency. The size and number of enemy ships should be estimated. Using bearing-interception methods to determine the course of the target is advised, as getting within visual range 8 risks being spotted by the target. Since the submarine cannot move very quickly while submerged the best tactic is to use high engine power (full speed or flanking speed) to get ahead of the enemy group while at long range where the U-Boat cannot be detected visually. The contact’s course should be estimated and the U-Boat should submerge in a position where it can lie in wait to launch an attack on the target undetected. 5 Target Motion Analysis Ideally, you should be able to find your targets distance and course from beyond visual range. However beyond visual range you only have access to the target’s bearing through smoke trails or by hydrophone. By recording the bearing to the target at regular intervals, you can gather enough information about the target to find an approximation of the target’s distance and course. This is all likely under the assumption that the target is traveling at a constant speed and bearing however. 5.1 Foundations The target vessel will be assumed to be following a linear course , meaning that it does not change course over time. The target will likely be following a waypoint navigation plan, and will change course at certain points. However within the window of interception it is likely that the target will follow a linear course. 9 Bearing Rate The bearing only Target Motion Analysis methods rely on the concept of bearing rate to determine the target’s course. Bear- ing rate is the ratio between the difference in bearing and the difference in time ∆ B ∆ t B 1 B 2 B 3 Note that in the above diagram, the angle between bearings B 1 and B 2 is greater than B 2 and B 3. ∆ B 12 > ∆ B 23 If the difference in time ∆ t between bearings ( B 1, B 2) and ( B 2, B 3) are equal, then the bearing rate has decreased over time. ∆ B 12 ∆ t > ∆ B 23 ∆ t Under the assumption that the target is maintaining it’s course and speed, we can deduce that if the bearing rate is decreasing that the target is moving away from us. If the bearing rate is increasing it is moving towards us. Finally if the bearing rate is nearly constant, the target is moving approximately tangentially to us. Conjecture 1. For a target on a linear course and constant speed, if the bearing rate decreases over time the target is moving away, if it increases the target is getting closer. 10 Proof. From the observer’s perspective we can represent the tar- get as following a straight line on a plane. Align the target’s motion with the x axis. We can represent the target’s position by the point ( x, y ). The angle θ of the target clockwise from the positive x axis is found using the tangent function: tan ( θ ) = y x We apply the inverse tangent function tan − 1 to both sides to get θ θ = tan − 1 ( y x ) Bearing rate is equivalent to the rate of change of θ with respect to time dθ dt . We make the supposition that the target is traveling at a constant speed and direction so y will be constant with respect to time as well as the rate that x changes dx dt or velocity v . We will treat the angle θ as a function of time implicitly and differentiate. dθ dt = d dt ( tan − 1 ( y x )) dθ dt = 1 1 + ( y x ) 2 d dt ( y x ) dθ dt = − y (1 + ( y x ) 2 )( x 2 ) dx dt 11 dθ dt = − yv x 2 + y 2 Notice that the only variable on the right side is x . Since y is constant the target will be at the point of closest approach where x is zero. There the bearing rate dθ dt will be at it’s maximum, − v y . As the target gets farther away and x grows, bearing rate dθ dt will start to shrink. ( x a , y ) θ y 5.2 Three Bearing Method When the submarine is not moving, the three bearing method can be used to get a rough estimate of the target’s course by tak- ing three bearing measurements at equal time interval. While this method will get you the direction the target is traveling in, it won’t tell you how far away the contact is. It also will not be accurate when the submarine is under way. The procedure is as follows: 1. Ensure that the submarine is almost completely still in the water. 12 2. Take three bearing measurements ( B 1 , B 2 and B 3) at equal time intervals O B 1 B 2 B 3 3. Choose an arbitrary point P along the middle bearing B 2. 4. Draw lines which are along the bearings B 1 and B 3 pass- ing through P . Again, they are parallel to the other two bearings but they intercept P on B 2. The line parallel to B 1 is B 1 ′ and the line parallel to B 3 is B 3 ′ 5. Find where B 1 intersects B 3 ′ and where B 3 intercepts B 1 ′ and mark them. 6. The target vessel will be traveling roughly parallel to the line that passes through these two marks. 13 O B 1 B 2 B 3 P B 1 ′ B 3 ′ C 5.3 Four Bearing Method In reality a ship at sea is never truly stationary. We can develop a method for fixing target position from a moving vessel. For simplification of calculations we will assume bearing measure- ments are taken at equal intervals. 1. To be added. 14 6 Torpedo Firing Solutions To effectively intercept and destroy hostile ships that are un- derway from distances of 1-12km, the torpedo is equipped with an internal gyroscope and maneuvering fins that allow it to travel along trajectories that are not parallel to the submarine. This gyroscope is set prior to firing either manually or fed with data from the ships instruments such as the stadimeter and the periscope. You can gather all the data you need to manually configure the torpedo using the RAOBF. Most torpedo attacks are made either directly to the port or starboard (left or right) side of the enemy vessel. The larger 15 profile from the side provides a larger target, but you must com- pensate for it’s speed. It will also be very difficult for the enemy to evade a torpedo attack from the side, and the torpedo will strike at a steep angle which is required for reliable detonation. The data required to make a torpedo firing solution is as follows: 1. Target Speed: At range the target vessel may travel it’s own length several times before the torpedo is able to intercept it. 2. Range: The farther a target vessel is from the U-Boat at the time of launch, the farther the torpedo will need to lead the target vessel to account for it’s motion. 3. Angle On Bow (AOB): The Angle-On-Bow measure- ment tells you your relative bearing from the tar- get’s perspective. This is will allow you to determine the target’s course. You can tell what the target’s relative bearing using the periscope or hydrophone, but to find your relative heading you need to plot their course or use the RAOBF within visual range. 6.1 RAOBF Guide The RAOBF is an instrument that allows gathering all the data required for a firing solution just using optical measurements of the target vessel. 16 6.2 Speed Finding 1. Measure the time it takes the vessel to cross the reticule from bow to stern in seconds using stopwatch. 2. Rotate the middle wheel until the number of seconds on the outer guide of the middle wheel aligns with the refer- ence vessel length on the outer wheel. 3. Read off the vessel’s speed on the 1:30 o’ clock red marker line on the inner guide of the middle wheel. 17 6.3 Range Finding 1. Measure the optical height of the target vessel in number of reticule ticks. 2. Rotate the middle wheel of the RAOBF until the point on the inner guide of the middle wheel corresponding to the optical height is aligned with the vertical red marker. 3. Find the mark on the outer wheel that corresponds to the reference mast height of the target vessel. The mark on the outer guide of the middle wheel adjacent will provide you the target range in hundreds of meters 6.4 Angle on Bow (AOB) Finding 1. Measure the optical length of the target vessel in number of reticule ticks. 2. Align the middle wheel until the mark on the outer guide of the middle wheel corresponding to the target range that was previously found using the range-finding method points to the mark on the outer wheel corresponding to the ship reference length (Now the outer guide corre- sponds to ship length in m , not mast height in m ). 3. View Angle-on-Bow (AOB) from the point where the inner wheel meets the corresponding optical length on the inner guide of the middle wheel. 18 7 Attack Disc 1. Use main switch to automatically align the middle wheel with your own vessel’s heading. 2. Align bearing pointer (pointer with red/green scale) to the target direction on outermost wheel. 3. Use the scale on bearing pointer to align one-sided vessel pointer to the target’s bearing using AOB measurements as deflection from target direction using the innermost wheel. 19