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In the battle of Yavin, the Empire wants to destroy a moon that is hidden behind the planet Yavin. They circle around the planet because the moon is hidden. Again: They are on a space station that can destroy planets! Planets! Like the one that is obstructing a clear shot on the rebel base (i.e. the moon).

The only reason I see for them not to simply blow up Yavin is that it may take too long for the Death Star to be able to shoot again. So, is there any information on how long it would take?

As a side note, I have an alternate theory of why they didn't destroy Yavin, maybe those guys'

poor death ray guys

union forbade the Empire to unnecessarily expose them to radiation?

Irregular Webcomic 512

(Source: Irregular Webcomic #512)

DavidW
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bitmask
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    Your initial premise isn't sound. Once they blast Yavin, they don't need to blast the moon with the Rebels on it--- the Rebels are as good as dead anyway. The initial blast would turn the planet into a churning salsa of rocks, magma and superheated gas, all looking for a new gravity well to fall into. That gravity well is going to be the moon with the Rebel base on it, which will be pulverized. – Kyle Jones Feb 09 '12 at 22:38
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    @KyleJones I don't think that is correct. Just because you blow up a planet, you don't drastically reduce its mass. So the mass of the original planet would still be way more that the moon (just all smashed up) so the gravitational pull of the planet on the moon should still be greater than the pull of the moon on the (what was once a) planet. – DQdlM Feb 09 '12 at 22:46
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    @KyleJones That really depends on how much mass they can liberate from Yavin. As I noted in my answer the binding energy of a Jovian planet is huge compared to that of a terrestrial sized body. – dmckee --- ex-moderator kitten Feb 09 '12 at 23:00
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    The same union that won't allow them to have railings: http://www.youtube.com/watch?v=9bSZXucTH4A? – Chris B. Behrens Feb 09 '12 at 23:28
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    @DQ Assuming the planet explodes in all directions, a cone shaped wedge of the planet will be headed straight for the moon. That wedge alone is enough to kill everything. Much smaller impacts have been responsible for extinction level events on Earth. – Kyle Jones Feb 10 '12 at 00:14
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    @KyleJones I'm not saying that blowing up the planet wouldn't majorly eff up the moon. I totally agree with that. I read your original comment to suggest that blowing up the planet would somehow reduce its mass making the moon the principal gravitationl attractor in the system, causing the planetary debris to aggregate on the moon. – DQdlM Feb 10 '12 at 01:22
  • @DQdlM each part of the planet would have a much smaller than the mass of the moon, and would have, at least somewhat, been attracted to the moon. – AncientSwordRage Feb 10 '12 at 09:41
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    Yavin was a gas giant... there's no evidence the laser would have as strong an effect on Yavin as on a rocky-metallic world like Alderaan. – HorusKol Feb 11 '12 at 02:06
  • "maybe those guys' poor death ray guys union forbade the Empire to unnecessarily expose them to radiation?" The Star Wars Technical Journal Vol 2 states "Engineering personnel assigned to monitor the ion vent operations usually wore radiation suits." – BennyMcBenBen Jun 04 '12 at 05:00
  • Relevant: http://youtu.be/zzoeEdW-EDQ – Ellesedil Sep 04 '14 at 14:47
  • The moon could have just flung out in the space. – user931 Nov 30 '15 at 20:02
  • Why didn't the worker's union require safety rails? Somebody could fall into a planet-splitting laser beam! And that would ruin their record for worker related accidents! – RichS Feb 10 '17 at 02:48

4 Answers4

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Well, according to Wookieepedia's entry on the Death Star:

The Death Star's superlaser derived power directly from the hypermatter reactor. Its faceted amplification crystal combined the destructive power of eight separate tributary beams into one single blast with the intensity of a stellar core. After firing a blast, though, the Imperial engineers had to recharge the reactor, which took at least 24 standard hours. Though the energy output of this blast could be scaled to fire at smaller targets such as capital ships, as was the case during the Rebel assault on the second Death Star, the two major instances in which the superlaser was fired were at full power at planetary bodies.

(Emphasis added)

Now, I don't see exactly the source of the information, but most things on Wookieepedia derive from the rather extensive information in the Star Wars Extended Universe publications, which include tech specs and so forth.

I'd take a guess that most of it came from the novel of the same name.

DavidW
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K-H-W
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41

They are on a space station that can destroy terrestrial planets like Alderaan. We don't know how it deals with Jovian planets---and Yavin must be Jovian to have a terrestrial-size moon. From a simple physics point of view, the gravitational binding energy of a Jovian is orders of magnitude larger than that of a terrestrial planet which allows for a number of reason to not do it:

  • They simply don't have the power.
  • They do have the power but the station would be at risk in the aftermath.
  • They do have the power but the recharge time after that shot would be longer than the orbital time to get in position to fire on their real target.

Nor are we told what the cycle time is for the planet buster, but it can't be shorter than the time between Tarkin's ordering the destruction of Alderaan and the accomplishment of the same (around 15 seconds).

dmckee --- ex-moderator kitten
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  • " it can't be shorter than the time between Tarkin's ordering the destruction" Well, it could take days to charge in theory, right? Or he could have told the tech guys that he intends to use it tomorrow ... – bitmask Feb 09 '12 at 21:11
  • That's correct. Though a similar weapon on the second death star could be used on ship sized targets with a cycle time of a few seconds, so I would guess that days are out, though minutes or hours could be in. – dmckee --- ex-moderator kitten Feb 09 '12 at 21:13
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    Although your answer is interesting, note that the question was "how long does it take to charge", not "why didn't they nuke Yavin" (the latter was merely the motivation for the former). – bitmask Feb 09 '12 at 22:08
  • Hmmm...yes. Guilty as charged. – dmckee --- ex-moderator kitten Feb 09 '12 at 23:01
  • Yeah, the station would definitely be at risk. Huge N-body problem. I'd be running before the ray finished firing. – Kyle Jones Feb 10 '12 at 00:16
  • @KyleJones The reason I don't want to be too confident of the risk to the station is that naively you would expect the station to be at risk from a terrestrial planet. I mean they were close enough to Alderaan for it to be an impressive sight and all that mass had to go somewhere. But they didn't seem worried. Dealing with the remains of a Jovian would be a matter of scale--albeit a big scale. – dmckee --- ex-moderator kitten Feb 10 '12 at 19:39
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    A variation on case #2: Jovian planets are mostly hydrogen. This is a beam weapon, the energy density at the point of impact will be incredible. Would blasting a gas giant cause a small nova blast? – Loren Pechtel Feb 10 '12 at 20:52
  • The thing nobody ever seems to think about is RADIANT ENERGY. If you shot the gas giant with the beam, at the energy given, it would, at the very least, become EXTREMELY hot -- probably a million degrees or more. At that point, so much blackbody light is emitted that the moon would evaporate like dry ice in a hot desert. – The_Sympathizer Sep 12 '15 at 23:18
  • You wanna die? Blasting a gas giant has only two possible outcomes: nothing and nova. The force required to disrupt one is many times the force required to compress one to fusion temperature. – Joshua Nov 19 '15 at 02:35
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According to the Star Wars Technical Journal (Volume Two) (1994):

The Death Star's superlaser cannon was once thought to be beyond the capability of Imperial military science. Its faceted amplification crystal combined and intensified eight separate initiator beams into a single laser with all the intensity of a stellar core; the impact of this beam could be controlled and scaled to suit the destruction of any target. A beam of one power level was used against enemy capital ships, while a much greater laser could cause the fracturing and disintegration of a target planet. The superlaser's power had to be recharged between firings and the intensity of each firing determined how many times per day the weapon could be used (from once per minute against spaceborne vessels to once per day against planetary targets). The pinpoint focus necessary for the combining of the superlaser's eight component beam lights limits its range to planetary distances.

According to the Essential Guide to Vehicles and Vessels (1996), the second Death Star contained an improved recharging capability:

This new Death Star's central weapon, the terrifying superlaser, featured substantially increased power, allowing it to be recharged in a matter of minutes, rather than hours. The superlaser's targeting and power-control systems were refined so the weapon could be turned on capital starships.

DavidW
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BennyMcBenBen
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    Always fighting the last war. I suppose Death Star III would have improved targeting for Ewoks and other soft toys. – Oldcat Apr 17 '14 at 22:39
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According the the Stardestroyer.net wiki, the first Death star took 6 hours to reload a planet killing shot, and the second took 5. It was on the official website, but some one took that down.

user78254
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