Realistic DET planet destruction

[OmegaGuy]

I notice in a lot of debates and analysis, when there is a planet destroying weapon, people will say stuff like 'the explosions weren't big enough,' or 'the planet took too long to explode' or 'it exploded in the wrong way' so it was a chain reaction.

My question is that if I am making an animation where a planet is destroyed, and I want it to be a DET weapon, what do I make it look like?

The obvious answer, of course, is 'like the Death Star', but that's not what I'm going for. The weapon I'm thinking of is not a beam or blast fired at the planet from space, it's a bomb that explodes on the surface.

So what would be the correct scientific effects of a DET planetbusting bomb detonated on the surface of an earth - like planet?

[Darth Wong]

White-hot ball expanding from a point at somewhere below the speed of light, eventually consuming the entire planet. Given the sheer quantity of energy involved, the initial expansion would probably be high relativistic speed, slowing down as more mass absorbs the energy and the average temperature decreases. And it would obviously be rather lopsided.

Mechanistically, there is a wave moving through the planet at very high velocity, converting everything it touches into white-hot vapour. Behind the wave-front is even higher-pressure, hotter vapour. If there wasn't, then there would be nothing pushing the shock front forward (a common misconception about shock fronts is that they're like ripples in a pond, and they're not; they only propagate as shockwaves rather than regular pressure waves as long as there is enormous pressure driving them forward). As the cloud expands well beyond the original dimensions of the planet, it dissipates and cools so that it eventually stops glowing white-hot.

[Sun Wukung]

I notice in a lot of debates and analysis, when there is a planet destroying weapon, people will say stuff like 'the explosions weren't big enough,' or 'the planet took too long to explode' or 'it exploded in the wrong way' so it was a chain reaction.

My question is that if I am making an animation where a planet is destroyed, and I want it to be a DET weapon, what do I make it look like?

The obvious answer, of course, is 'like the Death Star', but that's not what I'm going for. The weapon I'm thinking of is not a beam or blast fired at the planet from space, it's a bomb that explodes on the surface.

So what would be the correct scientific effects of a DET planetbusting bomb detonated on the surface of an earth - like planet?

The device would need a drilling mechanism and be able to withstand high temperatures (such as the core of the Earth). The idea would be to attack the core and destablize the gravatational binding energy of the planet. That would most likely cause the planet to shatter and would be the most efficent method of attack. To get an idea of what this would be like see the movie Core. In this case you wouldn't need much of what is on the ship in the movie. Most of the cockpit and living quarters would be filled with explosive materiel. Very high tech yet not imposible.

[Batman]

No it wouldn't. If the device is of sufficiently high yield it can absolutely destroy the planet while detonating on the surface.

[OmegaGuy]

Thanks.

[Stark]

The idea would be to attack the core and destablize the gravatational binding energy of the planet. That would most likely cause the planet to shatter and would be the most efficent method of attack.

What. What does it mean to 'destabilise the GPE'. How would this cause the planet to shatter?

[Sun Wukung]

What. What does it mean to 'destabilise the GPE'. How would this cause the planet to shatter?

It would do both disrupt the GBE and blow it up. You want to do both and ensure that nothing is left behind that might clump back toghether and reform the planet. That is if you want to do it cleanly, of course. If you are just out to make it blow up, then it would do what you want it to do.

[Batman]

Why would a weapon intended to prevent the planetary mass from ever reforming again have to be detonated in the core of the planet?
While we're at it why would the weapon be required to leave any solid matter to be left over in the first place? Completely vaporize the planet. Problem solved.
Entirely doable with a surface-detonated DET weapon.

[AdmiralKanos]

What. What does it mean to 'destabilise the GPE'. How would this cause the planet to shatter?

It would do both disrupt the GBE and blow it up. You want to do both and ensure that nothing is left behind that might clump back toghether and reform the planet. That is if you want to do it cleanly, of course. If you are just out to make it blow up, then it would do what you want it to do.

You cannot "disrupt" gravitational binding energy. You can only add enough energy to the system to overcome it.

[Wyrm]

What. What does it mean to 'destabilise the GPE'. How would this cause the planet to shatter?

It would do both disrupt the GBE and blow it up. You want to do both and ensure that nothing is left behind that might clump back toghether and reform the planet. That is if you want to do it cleanly, of course. If you are just out to make it blow up, then it would do what you want it to do.

"Shatter", as picturesque as that word is for describing planetary dissolution, is the wrong word to use for such a process. Planets like the Earth are pretty much held together soley through their self-gravity; the Earth stays together because all its matter is at the bottom of a deep gravitational potential well. The energy you get out when you stick together planet bits together into an Earth-sized planet is its gravitational binding energy (GBE), and when you add that energy back to the planet, planet simply... well, flies apart, and there will be nothing clumping back.

If you only just add back the GBE, then the process is slow, but it will eventually result in planet bits scattered all over creation -- adding more energy only speeds the process up.

"Destablizing the gravitational binding energy" is physical nonsense.

[Surlethe]

The obvious answer, of course, is 'like the Death Star', but that's not what I'm going for. The weapon I'm thinking of is not a beam or blast fired at the planet from space, it's a bomb that explodes on the surface.

Note that the Death Star's destruction of Alderaan is not a "straight-up" DET effect: Alderaan's planetary shield dispersed the Death Star's blast around the planet before it collapsed, so instead of punching through the planet and transferring its energy that way, the Death Star's beam was able to effectively transfer its energy to every point on the surface within a fraction of a second.

There's also the question of whether or not Alderaan was dumping excess heat into the mantle (this arose in a conversation I recently had on the topic), which may have contributed to the explosion.

Finally, this leads to interesting speculation on the Death Star's beam: it was designed to penetrate planetary shields, but by distributing the energy so that it's delivered all around the planet instead of to a single point, is a shield necessary to the Death Star's function by effectively increasing the surface area -- and hence, energy-delivering area -- of the beam?

[Raven]

Wouldn't a planet getting blown up by a giant bomb look like just a blinding white flash obscuring the destruction of the planet? Such an explosion would be more intense than the sun. As the flash eventually fades as the explosion dissipates and cools, you'll begin to make out the shape of a (still brightly glowing) cloud of gas and debris rapidly expanding away from the explosion.

There's also the question of whether or not Alderaan was dumping excess heat into the mantle (this arose in a conversation I recently had on the topic), which may have contributed to the explosion.

You mean the planetary shield was using the mantle as a heat sink? Or do you mean the Death Star heated the crust and mantle (evenly, due to the shield distributing the energy), compressing the core? I think I remember that thread, actually.
Anyway, it's true that the presence of a planetary shield at Alderaan makes its situation a bit different from a normal planet's.

Finally, this leads to interesting speculation on the Death Star's beam: it was designed to penetrate planetary shields, but by distributing the energy so that it's delivered all around the planet instead of to a single point, is a shield necessary to the Death Star's function by effectively increasing the surface area -- and hence, energy-delivering area -- of the beam?

I doubt a shield would be required for the Death Star to function. It's obviously designed with shielded targets in mind, and maybe it's effect on shielded planets, like Alderaan, is working exactly as intended.
An unshielded planet would result in a sloppier explosion, but an exploded planet regardless. Turbolasers don't require their targets to be shielded, after all.

[Winston Blake]

The obvious answer, of course, is 'like the Death Star', but that's not what I'm going for.

Actually the Death Star was way, way overkill. As shown on the main site, having just enough energy to blow up a planet would make it take far longer to scatter. Let's not even mention the rings.

[Admiral Valdemar]

Actually the Death Star was way, way overkill. As shown on the main site, having just enough energy to blow up a planet would make it take far longer to scatter. Let's not even mention the rings.

The DS was also a waste of resources, but for the same reason it was built, that was the reason for Alderaan being obliterated like it was. Simple show of force. We already know the Imperial Navy can slag a planet's lithosphere with ease, which is a planet kill anyway (why bother blowing the thing to pieces and cause another spacial traffic hazard?), but to shock, blowing it up to itty pieces works.

I find that the most realistic and efficient planet buster in most cases is simply the good ol' relativisitic rocket. Even if you could detect it, you'd have outdated data and probably never hit it, but if a rocket doing a good chunk of c and weighing as much as the space shuttle hits Earth, you've got a problem. Just think a similar scenario to that video showing a rifle bullet hitting an apple, but scaled up and with the bullet's KE being efficiently converted to thermal energy and blasting the planet's impact side to molten rock jetting out into space.

[Patrick Degan]

Why would a weapon intended to prevent the planetary mass from ever reforming again have to be detonated in the core of the planet?

Detonate at the surface and half the blast energy will be radiated off into open space for a start.

While we're at it why would the weapon be required to leave any solid matter to be left over in the first place? Completely vaporize the planet. Problem solved.
Entirely doable with a surface-detonated DET weapon.

Entirely undoable. The energy required to vapourise a planetary mass would be many orders of magnitude beyond that required simply to blast it apart.

[Admiral Valdemar]

Vaping an entire planet is just stupid. The most you would go for is simply slagging the crust, since nothing is going to survive that. Do that by mass projectile or beam weapon strikes or causing a nova (supernova being a bit beyond), they'll all sanitise. At the end, you still have a mass of minerals to use. Planets are great resources, so blasting them to pieces is wasteful.

[Il Saggiatore]

My question is that if I am making an animation where a planet is destroyed, and I want it to be a DET weapon, what do I make it look like?

Have a look at the beginning of Akira (alright, it is not the entire planet, but think of scaling it up a bit).

[Lord Zentei]

While we're at it why would the weapon be required to leave any solid matter to be left over in the first place? Completely vaporize the planet. Problem solved.
Entirely doable with a surface-detonated DET weapon.

Entirely undoable. The energy required to vapourise a planetary mass would be many orders of magnitude beyond that required simply to blast it apart.

You sure about that?

[Admiral Valdemar]

Even if you had an AM bomb big enough to vape the planet and plopped it on the surface, the blast would simply vape a continent sized chunk and fragment the rest of the rock and send it careering off into space. There's no way to really vape every cubic metre even with a DS level blast, which still left a massive asteroid field.

[Lord Zentei]

Even if you had an AM bomb big enough to vape the planet and plopped it on the surface, the blast would simply vape a continent sized chunk and fragment the rest of the rock and send it careering off into space. There's no way to really vape every cubic metre even with a DS level blast, which still left a massive asteroid field.

I wasn't arguing that, I was questioning the assertion about the required energy levels.

[Admiral Valdemar]

I'm sure some species could maybe do it, but as I say, it's a waste. Like using a plasma torch on a fly rather than a swatter.

[Lord Zentei]

I'm sure some species could maybe do it, but as I say, it's a waste. Like using a plasma torch on a fly rather than a swatter.

I have no objections to that point.

[Winston Blake]

Even if you had an AM bomb big enough to vape the planet and plopped it on the surface, the blast would simply vape a continent sized chunk and fragment the rest of the rock and send it careering off into space. There's no way to really vape every cubic metre even with a DS level blast, which still left a massive asteroid field.

I wasn't arguing that, I was questioning the assertion about the required energy levels.

Life (Briefly) Near a Supernova

The heat of formation of olivine and enstatite from
the elements implies it would take on the order of 10^32
joules to vaporize the Earth.

Curtis Saxton's estimate for the destruction of Earth is 2.4E32 J. So yeah, oddly enough they're about the same.