[Sailor Steve]

Originally Posted by SubConscious

1. A wire-controlled decoy: My thought here is to have a small electrically powered unmanned mini-sub attached outside the pressure hull. When being hunted by escorts, the U-boat Kaleun would order the release this mini-sub which would move well away from the U-Boat and commence a terrible racket, the goal being to disrupt ASDIC return signals. Alternately, it could return a fake ping signal, ideally distracting the escorts.

Not something they could do at that time. As for return pings, they would have to coincide precisely with the original ping, and be on the same frequency, or else the operator would know immediately what was going on.

2. Defensive mines: Have a number of small magnetic mines stored outside the pressure hull which could be released either singly or en masse. The goal here is to slow the escorts down and disrupt their hunting patterns.

Would create a huge amount of drag until released, cutting your speed way down. Also a lot of extra weight, plus the complexity of the release mechanisms and more holes in the pressure hull to route the release controls.

3. Oil/Debris decoy: I'd like a container of floating debris and oil affixed outside the pressure hull to simulate a destroyed U-boat.

'Bold'? Not oil but bubbles, but available later in the war. In The Enemy Below Kurt Jurgens released oil to fool the destroyer. Not sure they could do it in real life.

4. Anti-aircraft rockets: My thought here is to affix rocket tubes vertically around the conning tower. When an aircraft is sighted, the rockets would fire up in a bloom pattern, fanning out in all directions. Each would go up to a prescribed altitude and jettison a parachute and a long thin steel cable with an explosive charge on the end, set with a contact fuse. The end result is that the charge would slowly float downward, but if an aircraft struck one of the cables, it would pull the charge up to the aircraft before detonation. The goal here is to give the boat time to crash dive, forcing the plane to veer off on its initial attack run. I think the British had something similar to this, though I don't know if they deployed it.

Weight, drag, space, complexity, hazard to the bridge crew when fired...

5. Smoke screen: If all else fails, I'd like the ability to produce a very rapid and large smoke screen to disrupt aircraft attacks.

Smoke screens don't work against aircraft. They simply bomb the start of the smoke trail.

6. Variable size dive planes: This might not be practical, but I'm envisioning a segmented dive plane that could be fanned out to make it larger. The intent is to allow for faster depth changes.

Not only impractical, but enormously complex and prone to breakage.

7. Retractable deck gun and/or flak guns: Again, this might not be practical or add too much weight to the boat, but my thought is having the deck gun on a mechanism that folds into the forward deck, streamlining the boat for underwater maneuvers.

Again hugely complex, plus the need for the extra space to stow the gun would make the boat larger, slower to dive, require more or larger ballast tanks, all for one extra knot submerged.

8. Bow Rudder: It seems to me that the boat could turn faster if it had an additional rudder mounted in the bow.

The Germans had these on their destroyers in WW1. Didn't help, and needed extra space and added extra weight for the control chains.

9. Variable pitch propeller / larger propellers: My hope here is to cut down on cavitation noise and increase the speed & efficiency of the boat.

Not possible on propellors of that size at the time.

10. Underwater boosters: These would be one-time use underwater rockets to the hull in such a way that they could be jettisoned after use. The goal is to provide a surge of emergency speed to propel the boat away from a depth charge attack.

What kind of rockets? Solid fuel? Firing mechanism would have to pass through the pressure hull, and against the pressure underwater would have to be several magnitudes larger than their airborn counterparts. Liquid fuel? Not practical, given that you have to store sub-freezing liquid oxygen and add it to the mix immediately prior to firing. Hydrogen peroxide? Again must be stored frozen and added just before firing. And there's that whole "very good chance of exploding" thing, and the part where if it gets loose it kills everyone it comes into contact with.

Please feel free to constructively criticize these ideas. I'm curious if any of these musings have merit.

Not so constructively, it sounds to me like turning a reasonable sim/game into a fantasy realm.