The Wikipedia article has a reference to the 40 knot figure from Clay Blair's Silent Victory. I had missed this earlier when reviewing the Wiki article. I pulled my copy and verified that it is in the book just like Wiki said. Blair is a very reliable source, but remember even the best author is only as good as his sources. Never in all my time researching have I ever come across anything that backs up his assertion that the Mk-18 speed was increased to 40 knots. Therefore, I would tend to question this account.
Blair explains it by stating that work done on the batteries increased the speed to as high as 40 knots, depending on the water temperature (which effected the electrical output of the battery). I can verify this. Water temp did effect the battery and this was one of the prime weaknesses of this weapon. Imagine the difficulty of determining a correct firing solution if you did not know precisely how fast the weapon was moving! So, yes, the speed of the Mk-18 tended to be slightly variable, but I have never come across another account which put it as high as 40 knots.
Blair was a very thorough researcher and maybe he came across a little known source that no one else had. This is entirely possible, but it stretches believability a little. I say the jury is out on this one for now.
BTW, the rest of the Wiki article on the Mk-18 is spot on.
|