Yes, we can only assume that the planet killer suspended its attack at some point and thus provided the opportunity to abandon the ship before it resumed the attack with only Decker remaining aboard.
We also have to postulate that during that brief lull, 429 people decided it would be a good idea to beam down to a planet to escape a planet killer.
It must have been an
extremely good idea, one that provided real hope of long-term survival. What we can rule out right away is the idea that the crew would beam down to the planet
in panic, without considering the risks and disaster scenarios. A panicking crew could not beam down - the operation depends on perfect coordination. Moreover, a panicking crew's first instinct would not be to abandon ship. The ship would have been their only means of survival for months or years, and everybody would not just intellectually but instinctively know that "not inside ship" = "death". Starship crews have never been known to attempt anything even remotely like abandoning ship, not unless the CO gives an explicit order (and even then, he's often disobeyed). Yet here 429 people do beam down, in good order.
We must also accept that everybody involved knew that planets were deathtraps as long as the DDM was around. Decker's crew had located the beast by following a trail of eaten star systems. Everybody who had been on the bridge during the supposedly multi-day chase would be well informed, and would have to agree with the beam-down decision before it could proceed. Moreover, everybody on the bridge when the DDM was finally spotted would know exactly what it did to planets, as Decker says this is the very thing they saw happen.
So, what could this brilliant idea be?
The episode itself provides a pretty good answer: Decker had the same idea all along. Since the hides of the beast are invulnerable, ram something down the throat of the damn thing! If Decker had engaged the beast in combat already (and this is suggested by his "We couldn't run!" - he wouldn't try to run without trying something more proactive first), he would know he's out of other options. If Decker had lost phasers (and this happened before the beamdown, he says as much), he would know he's out of other opinions. So what he tells could be literally true after all.
1) Evacuate the crew. This calls for the ability to maneuver to within transporter range of a planet, so the ship is still maneuverable at that point, even though she can't "run" (with antimatter deactivated, warp drive is probably dead, but impulse here is explicitly a different matter).
2) Ram the beast. This turns the planet from a deathtrap to a survival shelter, even though it costs Decker his own life. And ramming speed is not an issue, as we later find out; limping in would suffice.
Too bad that the second part failed because the DDM attacked a second time, and totally destroyed the
Constellation's ability to move and thus ram. Scotty ascertains that the ship is now immobile, whereas the beam-down event itself verifies the ship was still mobile moments before the beam-down.
Of course, after the total failure, Decker is hell-bent on exhausting all other options when handed a fully functional, armed starship... But eventually he goes back to his original idea anyway.
Six transporter pads, 430 crewman
We never learn what the total transporter capacity of the
Enterprise is. We see something like four distinct configurations for the transporter set during the course of the show, some very distinct. We could safely assume at least two transporters, because one is in the saucer, near Deck 7 highlights such as Sickbay, but another is down near Deck 14 ("Dagger of the Mind"). But we could just as well assume six. Or twelve, or whatever.
We never see a single transporter room go down anyway. In "The Enemy Within", transporters first fail inexplicably, so they must all be declared unusable until the mystery is solved; after that, Evil Kirk destroys a central resource rather than something specific to a single room. In all other episodes where transporters become unusable, they do so because of some phenomenon that affects the overall machinery, not because a single room would be damaged or hexed or jinxed or whatever. So there is no particular reason to believe that the ship would not have more than one room. (Naturally, whichever room our heroes use becomes "
The transporter room" in dialogue. They only ever use one at a time, after all, there only being so many of our heroes!)
Timo Saloniemi