Historically, the Type XVIII never saw the light of day. Construction was halted halfway through in favor of the Type XXI. The Type XVIII is sort of a not-so-hidden Easter egg and a "what if" scenario. However, it is no long range boat. Its diesel endurance is comparable to a Type VIIB with its most fuel efficient speed being around 7.5 knots. 12 knots is not the most fuel efficient speed. The Walter Drive is necessary to maintain depth below 180m. The e-machines are less effective and consume too much battery power to maintain for very long.
What the Type XVIII excels at is submerged high speed approach and high speed submerged evasion. The drive may be extremely noisy, but with a flank speed rate of 28kts, escorts really cannot do much other than run around desperately trying to get a fix before they have to accelerate past washout speed to follow. Even if the escorts are all over you, depth charges do not fall fast enough. The odds of a hit are slim, if you are Johhny-on-the-Spot.
Good thing, too. Historically, the 80% H2O2 fuel is obnoxiously volatile and equally corrosive. A good hit to a fuel cell would rupture it and you would blow yourself up. This reality and the expense of the fuel is why the XXI boat came into being. Germany could not afford to make this thing work fast enough.
|