As I recall, someone here on HLP did a few calculations on the power of FS's beam cannons, and came up with a result that suggests hitting any point on a planet with one would cause an explosion akin to setting off a nuclear bomb in the megaton range. I've never seen a turbolaser do that.
What were the calculations based on? Considering that HP is such an incredible simplification of how damage works, I personally think it might be better to base numbers on the penetrative ability, or the 'beam whack' effect.
For the first, the Lucifer-Orion shot in the intro cutscene, although not exactly true to FS1, provides a nice view of how long it takes for the beam to burn through the ship and burst through the other side. Also, the cbanim showing the ambush of the GTC Vigilant might be useful.
For the second, it's a bit hard considering that the beam whack (at least in retail) was never calculated in a reasonable manner. Also, the fact that a beam is (hypothetically) hottest/most dense/most energetic at the center might make that harder to come up with reliable numbers.
Another thing is the FS1 cbanim of the Lucifer bombarding Vasuda Prime; in that, there definitely is a heck of a big beam hitting the planet, obviously bigger than anything you see in-game.
Really, there's a lot of ways you might come up with numbers for that, and it's silly to argue about crossovers, etc. But, from a FreeSpace campaign/story-writer's point of view, it might be a nice means of coming up with 'subtle' strategies and tactics.
