From an email response posted to Baen's Bar BuShips dated August 11, 2004:

Energy torpedos in a defensive role

    The possibility of using energy torpedo launchers as a point defense weapon has been bruited about. How does the mass/volume requirement of an energy torpedo launcher compared to that of a standard point defense laser cluster? Which would be more effective against incoming missiles? And, if it's not too much trouble, could you, in your copious free time, explain how point defense clusters work and the nature of the targeting environment they face? ;- )

     

    Jeez, Richard!

    Short answer: no. Longer answer (though probably not as long as the one you wanted, you greedy bastard) follows.

    Energy torpedo launchers are much less massive than anti-shipping energy weapons; they are much more massive than point defense laser clusters. Point defense clusters have different numbers of emitters, depending on the size of the ship which mounts them. In the Royal Manticoran Navy, for example, heavy cruisers have (on average) eight emitters per cluster. If I remember correctly (and I'm speaking from memory here) light cruisers and destroyers have six emitters and wallers have up to twelve emitters per cluster. The greater the number of emitters, the more rapid the cluster's combined rate of fire becomes, and a point defense laser, which is much lighter than an anti-shipping energy weapon, already has a very high rate of fire compared to the aforesaid anti-shipping weapon.

    Now, an energy torpedo launcher also has a very high rate of fire… compared to a standard antishipping energy weapon. It does not have a particularly high rate of fire compared to a point defense laser, and is certainly far less rapid-firing than an entire cluster of them. You will get many more shots from a laser cluster, even aboard a smaller warship, then you will from an energy torpedo launcher. This has many implications, of course, but one particularly significant one stems from the fact that, unlike counter-missiles, neither energy torpedoes nor lasers are guided weapons. The higher rate of fire of a point defense laser and the fact that a laser travels at the speed of light whereas an energy torpedo moves appreciably slower than the speed of light, makes a laser inherently more accurate and allows it more shots at a target in a given time window.

    I suppose that under some circumstances a sort of "barrage" defense, firing timed-detonation energy torpedoes, might be thrown up as some sort of last-ditch interdiction defense, sort of a "wall of fire" in space. I do not think it would be incredibly effective, however, and I suspect it would create all sorts of fire control problems, not to mention interference with the firing ship's sensor capabilities. The greater objection to a defense of this sort, however, would be that the probability of the kill at the ranges at which laser heads need to be stopped would be significantly lower on a per-shot basis for an energy torpedo launcher as compared to even the smallest point defense cluster, and you could fit many fewer of them into the same tonnage and volume. The very rare circumstances under which the energy torpedo point defense concept might prove more valuable than the existing laser cluster concept, combined with the lower number of targets you would be able to engage, would combined to make the energy torpedo system unacceptable on a cost-benefit basis to almost any admiralty I can think of. That's not to say that a ship which mounted energy torpedo launchers anyway might not try to use them in a point defense role in a moment of maximum desperation, but it is not something which anyone will adopt as standard doctrine.

    As for the targeting environment, Richard, go read the books. :-p