For anyone who has the book, this story is covered in Chapter 7.2 in Rössler's "Geschichte des Deutschen U-Bootbaus". The main disadvantage of this drive, just like the Walter drive, was limited range. He does not give a range for the design with two 1500 HP engines, but extrapolating from some range figures he gives for the Type XVIIG, we get a range of around 80 - 90 NM @ 22.5 KN. This compares to a teardrop electroboat with extra large battery capacity which could run roughly 50 NM at such a speed. Once the oxygen is gone, you are left with a normal U-boat drive with a very small electric motor. The electroboat could do the same thing again the next day after recharging and the electroboat also looks better at lower speeds since available battery capacity increases with the discharge time.

In principle, all these oxygen based underwater drives are great as long as the oxygen lasts, and after that the U-boat is close to impotent. This is a workable recipe for coastal U-boats, but not for longer range ocean going types. One can argue this idea is better than the Walter drive since one does not have to use hydrogen peroxide, however, Rössler also tells us that the longest endurance with this concept is achieved with hydrogen peroxide instead of oxygen, about 40% longer than with an equal volume of liquid oxygen.

Regards,
SuperKraut