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What would be the effects of the Death Star's superlaser on a typical gas giant planet, based on the canon calculations of Alderaan's destruction? I'm asking this because of what I read a while ago in a question and answer section on the official site, which I can't link to because I've forgotten where it is or whether it's still up. Basically, the question was why the Death Star had to circle around Yavin to fire on its moon, when it could have just destroyed Yavin itself, something that would not have been good for anyone on its moon. The official answer was that the superlaser was powerful, but not powerful enough to destroy gas giants. Do the canon calculations refute this?

Actually, I think the general consensus is that if they do blow up Yavin to get at Yavin IV, they would have to wait around all day to charge up the superlaser back to planet-killer level. Tarkin wanted his crush the Rebellion in one stroke in style.

Tossing thousands of Yottantons of energy into a planets atomsphere is a BAD thing for the Planet

Best way to kill a Gas Giant is to aim at the Core and Fire Quater Power Shots, Evenutaly you will burn away most of the gases in the Atmosphere, plus don't forget the 5000 or So Gigaton leve weapons you can use as well

From Saxton's on Yavin:

Compared to Jupiter, it is about 2.79 times as massive and 1.35 times as wide. Its surface gravity is about 3.89 times Earth's, vs 2.54 for Jupiter.

Jupiter: mass: 1.900e27 kg, diameter: 142,984 km (equatorial) (this took forever to load from Brittanica, from a page I had a link to anyway. Doooh )
So for Yavin we get: (5,30e27kg), 3,89g & 1,93e5km.

Inputting this into Wongs Planetary Parameter Calculator we get:
Death Star yield LL (J): 1.176E+37 & Death Star yield UL (J): 2.479E+45

So Yavin would blow up if shot, but would would disperse at a speed on the order of the escape velocity (85.8 km/s), so the problem of circling Yavin would just get worse as the planet slowly blooms.
The smart thing to do therefore, regardless of the recharge/cooling rate of the DS1, is not to shoot but to circle the planet.

And guess what: the DS crew were not Trekkies, so they took the most efficient path to their target.

The problem with employing a superlaser against a gas giant planet would be density. At this point in our own astronomical knowledge, we can't be certain if a gas giant planet even has a solid core, and from the surveys of our own solar system's Jovians, the densities of gas giant planets can vary considerably. Jupiter has a planetary density only 1.33 times that of Earth, while Saturn's is only 0.69 Earth density. A superlaser might disrupt the core mass and atmosphere through the path of its passage, but in terms of effective destruction, it would probably be like shooting a bullet through a large mass of cotton candy

Firing on Yavin would have been a waste of energy. Therefore, it was the better decision to orbit Yavin to intercept Yavin-D.

Patrick Degan wrote:The problem with employing a superlaser against a gas giant planet would be density. At this point in our own astronomical knowledge, we can't be certain if a gas giant planet even has a solid core, and from the surveys of our own solar system's Jovians, the densities of gas giant planets can vary considerably. Jupiter has a planetary density only 1.33 times that of Earth, while Saturn's is only 0.69 Earth density. A superlaser might disrupt the core mass and atmosphere through the path of its passage, but in terms of effective destruction, it would probably be like shooting a bullet through a large mass of cotton candy

Firing on Yavin would have been a waste of energy. Therefore, it was the better decision to orbit Yavin to intercept Yavin-D.

But then the question is, "why not just shoot through Yavin to hit the moon?" Perhaps the gas disperses the beam?

Patrick Degan wrote:The problem with employing a superlaser against a gas giant planet would be density. At this point in our own astronomical knowledge, we can't be certain if a gas giant planet even has a solid core, and from the surveys of our own solar system's Jovians, the densities of gas giant planets can vary considerably. Jupiter has a planetary density only 1.33 times that of Earth, while Saturn's is only 0.69 Earth density. A superlaser might disrupt the core mass and atmosphere through the path of its passage, but in terms of effective destruction, it would probably be like shooting a bullet through a large mass of cotton candy

Firing on Yavin would have been a waste of energy. Therefore, it was the better decision to orbit Yavin to intercept Yavin-D.

But then the question is, "why not just shoot through Yavin to hit the moon?" Perhaps the gas disperses the beam?

Hell, shooting Yavin should have caused enough damage to destroy the Yavin base anyway.

Dramatics agian, Dramatics

They were stymied by the mere fact that they couldn't be sure what would happen.

Think about it: if it takes a day to recharge, you'd damned well better not waste that shot! So maybe they're not 100% sure what will happen if they shoot the gas giant, and that uncertainty alone is more than enough justification to simply whip around the obstruction and get a clear shot.

I contest your claim that they wouldn't know, Mike.

1) ANH Opening Crawl: The Death Star is stated to be able to destroy any planet in the Empire. Yavin and Bespin, both gas giants, are in the Empire.

2) Firepower from Canon(1e38J scaling from debris) is sufficient to blow away Yavin, stated in an earlier post.

3) Firepower derived from West End Games(The statement the DS beam will vaporize a planet that isn't shielded) pegs it at ~1e42 if my math is right, even safer into the realms of blasting a gas giant.

From this I conclude that they could have destroyed Yavin, and yes it would have wrecked Yavin 4. However:

1) This would take more time than a one-shot-one-kill after orbiting. The slowly expanding gas giant would give the Rebels time to escape.

2) Tarkin invented rule-by-fear, and thus wanted to be dramatic in approaching with his nigh-invincible battlestation.

From this I conclude that they would, of course, orbit the planet.

Could it be that Tarkin was just plain stupid..

Look at the fact, blowing up Yavin instead of moon would truly have been impressive. ( hell anything that Vaporized Jupiter would impress me )

Failing to launch Tie fighters when told that the Turbolaser batteries where having problem targeting the rebel Snub fighters....

Or abandoning the station when it became plain what the rebels were out to do. Not that he survive the Emperor tender mercy after that, but he could have made a run for unknown space..

Or maybe there were other forces at work.. Remember that Ben while dead was still able to advise Luke, maybe he was able to do more and Tarkin could have had a weak mind easily influence by the force....

Wouldn't it be funny that he did not fire on the gas giant Yavin, because he was afraid that opponents of the Empire ( and critics of whole DS project) would accuse the DS of using a trick to blow up planets..

imagine some troll of a rebel spreading the following rumor:

" Of cause it destroy the Rebel base on Yavin, as every one knows it cause all to Hydrogen in the gas giant to under go a fusion reaction, causing the planet to blow and other instant it was a defenseless planet without shield, in that case the oceans were chock full of fusionable material"..

Sure, they could have used the massed turbolaser batterys to totally dominate Yavin 4 after a shot into Yavin, they could have stood over the rebel base and blasted anything that left until the SL was recharged or blasted the rebel base itself. However, the debris from Yavin would have complicated things. Easiest, quickest way to kill the rebel base was a superlaser shot to Yavin 4.

There would be a number of reasons for not attempting to fire a superlaser blast through a gas giant in order to hit a target behind it. For a start: beam attenuation. The atmospheric envelope would absorb part of the beam or act in the same manner as a scattering prism, disrupting beam cohesion and reducing the power of the strike. If, for example, Yavin-D had a planetary shield protecting it and the superlaser beam's power was reduced in propagating through Yavin's atmosphere, it may not have been strong enough to overcome the moon's defence and destroy it. This is in addition to the fact that you don't have a clear sighting on the target to begin with. Lacking continuous data on Yavin-D's orbital movement, calculations as to the moon's position at a given point would not take into account minor pertubations induced by tidal forces, other gravitational influences from the other moons orbiting Yavin, or those pertubations induced by the influence of other bodies in the star system: a lack of information which induces a degree of uncertaintly and inaccuracy in a blind targeting calculation.

Disrupting Yavin would not produce an impact upon Yavin-D's planetary shield sufficent to ensure the moon's destruction —this assuming that Yavin would be so disrupted that the planet would "break apart" in an expanding wave of superheated gasses (there would certainly not be any solid debris field).

The simplest targeting solution is the one where you have a clear line-of-sight on Yavin-D and can employ the full power of the superlaser directly against the Rebel moon itself.

SirNitram wrote:I contest your claim that they wouldn't know, Mike.

1) ANH Opening Crawl: The Death Star is stated to be able to destroy any planet in the Empire. Yavin and Bespin, both gas giants, are in the Empire.

During the battle, Rebel spies managed
to steal secret plans to the Empire's
ultimate weapon, the Death Star, an
armored space station with enough
power to destroy an entire planet.

Read: an entire planet. Not "any planet in the Empire", not "a planet of any size and composition" and not "any kind of planet with the same exact efficiency".

This doesn't prove that they CAN'T, but only invalidates your reference.

2) Firepower from Canon(1e38J scaling from debris) is sufficient to blow away Yavin, stated in an earlier post.

The problem isn't that the power is or not enough. The point is that the planet is composed of gas and maybe not even a solid core. Maybe it will start burning from the inside, maybe the atmosphere will boil off slowly, maybe 99% of the superlaser will go right past thru it, or maybe it would be refracted all around its surface evenly in every possible direction, or maybe just change direction (and miss the moon if that's what they were aiming for)

From this I conclude that they could have destroyed Yavin, and yes it would have wrecked Yavin 4. However:

1) This would take more time than a one-shot-one-kill after orbiting. The slowly expanding gas giant would give the Rebels time to escape.

2) Tarkin invented rule-by-fear, and thus wanted to be dramatic in approaching with his nigh-invincible battlestation.

From this I conclude that they would, of course, orbit the planet.

I agree with these final points, also (in the event that they can destroy the giant)

That or maybe Mini-Me was humping the 'laser'.