UCS Shadow

[Deepcrush]

Ah, to be good at math. I so wish! HAHAHAHA!

[Thorin]

It's the gravitational binding energy of an Earth sized planet, calculated by using the formula for KE and plugging in the mass of the planet and its escape velocity. I pulled the numbers from here.

If it's using the gravitational binding energy it's probably overdone it a bit in a perfect reaction. As it's using the escape velocity of some 11km/s, it's assumedly used the amount of energy going in to equal the kinetic energy of the mass of the earth all having the velocity at 11km/s - actually with which a quick calculation in my head puts it at about 10E32 ish. But that's to, quite literally, explode the planet so that they end up at an infinite distance away from the start point of the planet (the very definition of escape velocity). However, there are other aspects to take into account - all the energy would not transform into kinetic energy, infact most of it would almost certainly thermal energy. So the first aspect is that if the reaction were perfect, you wouldn't quite need to get to the 11km/s figure - infact enough energy to put a good few cracks would be enough to 'blow it up' - even if they did come back together there'd be nothing there and it'd be more like a few asteroids coming together rather than a planet reforming. The other aspect is that most of the energy would turn to thermal energy, so it'd have to be a lot more than that 10E32 figure. Unless, of course, it was like a huge snooker ball hitting the planet. But just pure beam energy is mainly heat.

Okay, I started babbling...

[Deepcrush]

How dare you say such a thing! No one on this site babbles!

[Captain Seafort]

*snip*

All true, but if you want a rough idea of how much bang you need, 10E32 is a good enough approximation - it is after all only a lower-end figure for the energy required to scatter the planet's mass, not the exact yield of an operational planet-destroying weapon.

[shran]

Could the vaporization of all earth mass be easier? or am I wrong? 9I am NOT good at maths)

[Graham Kennedy]

Actually there's no real point in destroying a planet as such, most of the time. I mean, why bother? What does it accomplish?

The minimum energy needed to destroy Earth would be 80,000,000,000,000,000 megatons. If you fired a blast one billion times smaller than that, it would still be more than sufficient to wreck the surface to the point where the Human species would likely become extinct, or as close to it as makes no real difference.

So why make a weapon that's a billion times more powerful than you need? Sometimes people cite planet busters as terror weapons, that planetary destruction is used because it scares and intimidates people. But that holds little water to me. Is the headline "Entire planetary population wiped out!" really so much less scary than "Planet destroyed!" Is the population you want to scare really going to collectively say "Well yeah, the enemy wiped out the entire population of Planet X the other day. But you know what? The physical ball of rock is still there; frankly I'm not impressed."

Planet busters are only really used because blowing planets up looks cool. But it makes no logical sense.

And yes... I DID come up with a real reason why the Coalition built planet busting weapons.

[Mikey]

Cyclonic torpedoes, perhaps? Exterminatus array?

[Sionnach Glic]

Planet busters can make sense in some situations.
For example, the Death Star was designed to destroy shielded planets, whose shields would otherwise take hours to beat down.

But mostly you're right, in that simply bombing the crap out of the planet will work just as well.

[Graham Kennedy]

Planet busters can make sense in some situations.
For example, the Death Star was designed to destroy shielded planets, whose shields would otherwise take hours to beat down.

Um, and how does it make sense to build something with enough firepower to beat down shields and then still have a billion times the energy needed afterwards?

Or would the DS not destroy a planet if used on one that was shielded?

[Sionnach Glic]

Um, and how does it make sense to build something with enough firepower to beat down shields and then still have a billion times the energy needed afterwards?

Hmm, good point.

Or would the DS not destroy a planet if used on one that was shielded?

No, it would still blow up the planet.

[Graham Kennedy]

Um, and how does it make sense to build something with enough firepower to beat down shields and then still have a billion times the energy needed afterwards?

Hmm, good point.

Then it's worse, not better!

The Death Star was a lovely concept for a movie. But if you give it any thought at all it's quickly apparent that it's a horrible concept for a military unit.

[Sionnach Glic]

Well, it was designed primarily as a terror weapon. Something with the power to blow up a planet a hundred times over would fit that requirement. And it didn't seem to make a noticeable dent in the economy, even the much larger DS2 was built completely in secret by a single shipping company, so it seems like they had the resources to waste on it.
But yeah, as a military unit it's job could've been done by something with a good deal less power.

[Captain Seafort]

It's possible that the firepower demonstrated by the Death Star was required to punch through planetary shields. From the Galaxy's point of view, it's irrelevent whether the planet was destroyed in the extremely violent manner Alderaan was, or whether it was a mare minium 10^32 shot. Given, however, that Alderaan's shield briefly withstood the blast, it's possible that the bare minimum shot wouldn't have got through the shields.

[Thorin]

Could the vaporization of all earth mass be easier? or am I wrong? 9I am NOT good at maths)

It is, actually. After doing some calculations (yes, I'm sad)...
Approximate energy required to explode 1 kilogram of earth: 50 MJ
Approximate energy required to vapourize 1 kilogram of earth: 12 MJ

So actually, by using that 10E32 J figure, you'd probably vapourise the entire planet before it 'explodes'.