Tests were conducted in May/June of 1942 using a standard army issue
Wurfgerat 41 launcher and rockets from 21 to 30cm. The tests proved that it was not only feasable, but that the rockets could be fired
from depths up to 15 meters below the surface, without effecting the normal flight path. The sequence of photos below show an actual launch from U-511.
see :
http://www.prinzeugen.com/V2.htm
Loon :
http://www.pbs.org/wgbh/nova/lostsub/hist1945.html
This last one is the model I wanna use for the FliggendeTorpedo.
keltos