But lets back up a bit, and consider a few things.. Let us start but a few things that arn't in dispute...
The episode opens with Kirk saying he is investigating the disappearance of Several planets
So first fact, while we do not have a time fram, we know that at the very MOST< it destroyed SEVEN planets within a year, and it may have been far less time then that. We also have the following.SULU: Sir, we're now within the limits of System L-370, but I can't seem to locate
SPOCK: Captain, sensors show this entire solar system has been destroyed. Nothing left but rubble and asteroids.
KIRK: But that's incredible. The star in this system is still intact. Only a nova could destroy like that.
SPOCK: Nonetheless, Captain, sensors show nothing but debris where we charted seven planets last year.
Along with:KIRK: Matt, your log stated that the fourth planet was breaking up. You went in to investigate.
DECKER: We saw this thing hovering over the planet, slicing out chunks of it with a force beam.
Now while it is never said in the episode, it is recorded that the episode takes place at StarDate 4202.9 So once more, at the very least it was able to destroy the Fourth planet within a matter of a few days. Also Decker visibly observed it "slicing chinks" out of the planet, this implies that the process is at least fast enough that you can observe it quite easily. It also seems to have no trouble dismantling planets as well.ECKER [OC]: Captain's log, stardate 4202.1. We are now entering system L-374. Science Officer Masada reports the fourth planet seems to be breaking up. We are going to investigate.
Now let us pause a moment. According to various Scifi sites, the Doomsday Weapon is "about" 2700 meters. In the grand sense of things, this is ridiculous small... Several Trek built ships pass the 1000 meter size and a few get up to 1500 meters. So, we have another indisputable fact... This ship, which is barley larger then an ISD, puts out enough Energy to "Slice chunks" form a planet and eventually reduce it to rubble. The time frame for destroying a single planet may also be as little as Eight to Nine days, for a 2700 (or so) meter ship, that is DAMNED impressive.
Now let us move on.
Let us discuss the Beam in question... Decker refers to it as "Pure Anti Protons" Now then, this is where I may be putting my foot in it... Put that to me seems to be describing basically, an Anti-matter gun... Protons are found in every Atom in the universe, logical, if you had a Beam that fired Anti-Protons, it would result in mutual annihilation of Any Mater it came in contact with. Putting this into perspective with the effect it would have upon a Planet would make it ideal for indeed 'slicing chunks' form it.. A beam that continuously annihilates mater in all its forms would blast easily through the rock and magma of planets.
So, so far, considering the above observations and logical assumptions, Thus far the Doomsday Machine is rather impressive one would say. However we come to the Nut of the problem. Once agin, a fact that cannot be in dispute is that the explosion of a Small starships core was enough to disable it. Further more, the "Anti Proton Beam" fired on both the Enterprise as well as the Constellation and did minimal damage, with the Constellation having at the worst, Hull damage to parts of the saucer and Engine nacelles. These item has been the primary cause of Scorn and Derision to the Machine for quite some time. My own personal belief is simply the Machine was old, Very Very old, and that it's internal machinery was in a state where the explosion was enough to disable it. As for the ships? ll I can say is plot, perhaps the shields in Trek are able to neutralize such a beam, perhaps under normal circumstances such ships would have been annihilated, but Writers fiat and Chairchter shields prevented such an occurrence.
however the Machine may eventually deal with Starships, it's effectiveness at Destroying planets cannot be questioned, and perhaps deserves mre credit and respect then it other wise gets.
Thank you.