Question about the asteroid vaporization page

[DarthPooky]

Ok so on the empire strikes back asteroid vaporization page on the main site Wong comes to the conclusion that the light pint defence guns have a minimum energy of 22,500 TW. So how can it be in Terawatts when turbo lasers fire in bolts and not beams shouldn't it be in Terajoulse?

[Imperial528]

He's getting a power output estimate based on the observed fire rate.

[DarthPooky]

I see so just to make sure I understand he's basing the Terawatts on shots per second. There's something thing else though he averages silicon and iron in the asteroid and gets 1500 TJ and then gets the 22,500 estimate but in the unit calculators iv found on the internet shows 1500 TJ is 1500 TW so what am I missing hear?

[Imperial528]

1500 TW is 1500 TJ/s

The figures he gets are higher as it takes under a second for the asteroid to be vaporized.

It turns out I was wrong earlier, he does not do it off of fire rate, it is entirely due to the reason I stated above, having looked the page over again.

He explains as much in the footnotes:

Conclusions

By averaging the silicon and iron-based estimates, we can derive a 1500 TJ figure for the minimum energy requirements of vaporizing 40m asteroids which may be either silicaceous or stony-iron. This leads to a lower limit of 22,500 TW for a Star Destroyer's small point-defense trench-mount turbolasers. If size is proportional to power (an unsubstantiated but not unreasonable assumption), then the heavy dorsal turbolasers must therefore output at least 2.8 million TW.

Figures for ice are included only to inform and amuse. The TESB asteroids were clearly not ice. These figures are highly conservative for three reasons:

The fact that the asteroids were vaporized so quickly and completely is indicative of energy input greatly in excess of the minimum. The equations of state for the liquid-gas phase transition mean that significant kinetic energy was added to the mass as well as the aforementioned thermal energy. The fact that the entire energy input occurred in a mere 1/15-second, and that the energy propagated through the asteroid's body in 1/3 to 1/4-second, indicate that this quantity of energy should definitely be significant.

In reality there are a huge variety of process inefficiencies which would raise the energy requirement further. Heat transfer inside the asteroid body is negatively impacted by the non-homogeneous nature of the asteroid's chemical composition (which sets up countless heat transfer boundary conditions). Heat conduction through real-world substances is not instantaneous or even relativistic. The facing side of the asteroid will vaporize first, thus deflecting incoming energy and most likely causing the back half of the asteroid to vaporize through convective heating via contact with the superheated vaporized matter from the front side. All of these factors will tend to increase the actual energy requirement.

In nature, both iron and silicon tend to exist as ceramic compounds (hematite and silicon dioxide) rather than pure elemental metals. These ceramic compounds have much higher specific heats and much lower thermal conductivity than their pure-metal forms. For example, the specific heat for silicon dioxide is more than 60% larger than the specific heat for elemental silicon, and the thermal conductivity for silicon dioxide is 0.9% of the thermal conductivity for elemental silicon. Furthermore, these compounds decompose at high temperatures into their constituent elements, thus the equations governing elemental iron and silicon will still control the latent heats of evaporation.

[DarthPooky]

Ok I see the 1500 terajules is the most conservative number for the vaporization while the visuals are consistent with the 22,500. After reading the quote however I still don't understand how he goes from terajules to terawatts with a pulse weapon again what am I missing?

[Batman]

Those pulses have a duration. Yes, they're short, but not infinitely short. They impart the energy over time. A really really short time but it still takes time, hence energy per time. J/s doesn't stop translating into W just because the pulse didn't last an entire second. It just ups the wattage.

[Eternal_Freedom]

The energy required is 1500 TJ. If the energy was delivered in one second the power would be 1500 TW (or 1500 TJ/s). Since the energy is delivered in less than one second (substantially so) the per-second power is much higher.

Think of it as (something like) speed. Traveling at, say, 100 m/s means in one second you travel 100 metres. If you only travel for 0.1 seconds you only travel 10 metres. Your speed in both cases is the same but the distance traveled is not.

[Lord Revan]

Just to warn that this will be quite "nerdy" but 1W=1J/s=1 Nm/s=1 kgm2/s3.

That said there's 2 ways to deal with "power" for energy weapons with bolts, first (and the most common) is to look at the average rate of fire and the energy per bolt and get an estimate of average power second is to look at how fast is the energy delivered and get a "per bolt" power so to speak though is can be somewhat unrelible for long term if you don't take the average rate of fire into account (since some weapons might be bursty with a relatively long cooldown period betwen the bursts so the overall rate of fire might low even if they have high rate of fire during the burst).

[DarthPooky]

I think I understand now thanks for the info.

[texanmarauder]

the issue I have is that we only see like 3 asteroids "vaporized". the rest of his screenshots that claim "this asteroid was this big" were the flak burst effect from the laser impacts to the shields of the falcon. we see it from TIESs outside the asteroid field before they enter as well as from the Avenger after they exit the field. yet wong claimed they were asteroids. I have the blu ray edition and slow motion and zoom confirm that the only asteroids destroyed were the 3? that the Avenger popped while the falcon was in the exogorth. and there is no way to know exactly how big they were. seems pretty shady to me. plus, in his turbolaser power page, didn't he state that the medium turbolasers were used, NOT the light PDTs?