StarDestroyer.Net BBS

TESB Asteroid Vapourization Energy Footnotes wrote: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.