Asteroid collision generates heat. Therefore usual result is the entire surface of said planet turning into a lava sea. Not enough power to blow it up entirely. Well, yes, it depends on how big is the asteroid(and how small is the planet). It's not based on any fact, but i'd say one with diameter of few hundread or thousand kilometer.
Using the asteroid impact energy calculator available
here, using 5510 kg/m^3 as the density of the target (average density of Earth, at least as given by Google for the search 'average density of Earth'), assuming an impactor density of 8000 kg/m^3 (iron, roughly), an impact angle of 45 degrees (suggested by the site as the most likely impact angle), and an impact velocity of 17 km/s (suggested by the site as typical for asteroid impacts), the smallest asteroid that I bothered to find that could turn Earth into an asteroid belt was about 11,113 km in diameter; impactors much below 2000km in diameter failed to even melt much of the planet (and at 2000km, the impactor 'only' melts ~3% of the planet), though I'd expect that they'd still have been able to cause large-scale devastation (the asteroid that killed the dinosaurs is thought to have been about 10km in diameter, so I'd expect impactors of roughly that scale would be more than sufficient to count as planet-killing weapons even though they don't completely obliterate the planet). Assuming all other parameters remain the same, changing the target density to 3000 kg/m^2 (suggested by the calculator site for dense rock), the smallest impactor that could turn Earth into an asteroid belt would be around 8570km; changing the target density to 3000 leaves the effects of impactors below ~4000km in diameter largely unchanged and impactors below 2000km again fail to melt any significant fraction of the planet's surface (melting about 3% of the planet's surface for an impactor 2000km in diameter).
Also, while asteroid collisions do generate heat, the 'usual' result is
not turning the entire surface of the planet into a lava sea. You require a significant amount of energy to do that, and the vast majority of asteroid impacts do not provide that; even major impacts like the one that killed off the dinosaurs do not turn any significant fraction of the planet's surface into a lava sea.
As far as what kinds of weapons are available that could do it, how fast can the ships of Starsector move without resorting to 'warped space' or other methods of increasing effective speed without changing real speed? If the sublight drives can propel a ship quickly enough, you might not need a weapon so much as a disposable ship, though since the impact needs to deliver at least ~2.5x10^32 J to an Earthlike target to break the target into pieces, this might not be practical (even a 1e15kg impactor still needs to be moving at ~0.96c before it that much kinetic energy, and I'm more than a little doubtful that even the largest ships of Starsector mass in at trillions of tonnes). Another possibility might be if Opis had significant antimatter stockpiles on its surface for some reason ('significant' as in ~1.5e15kg of antimatter) that all went up at once; depending on exactly how much antimatter one unit of fuel represents, this might not be as unreasonable as it sounds, as even a fairly small fleet can go through hundreds of units of fuel on even short trips, and Askonia is stated to be one of the only locations in the Sector capable of producing fuel; it'd therefore be expected to see relatively heavy ship traffic and it'd need to have significant fuel stockpiles available to load into tankers for export to other areas.
From what we've heard until now the common choice for planetary annihilation is the glassing of the surface, a process which likely requires orders of magnitude less energy.
According to an estimate
here (search 'Base Delta Zero' on the page), the energy required to melt an Earth-sized planet's surface to a depth of 1 meter is approximately 2e24 J (see page for assumptions used). This is about 8 orders of magnitude below the energy required to turn the same target into a debris field, and you can probably add at least an order of magnitude or two to the energy requirement to turn the target into a debris field if you want that to occur quickly, probably several more orders of magnitude to the difference if you're willing to skip uninhabited or lightly-inhabited areas or regions where there is little of any real value when 'glassing' the surface, and perhaps another order of magnitude if you don't require the planet's surface to be melted to the depth of a meter.
Edit:
Having considered this a bit more, it's entirely possible that Opis wasn't a very big moon. Using the numbers from the current version of the game, the combined population of every known inhabited locale isn't more than the low tens of millions. If Opis had a population comparable to even New York City (~8 million; this would give Opis a population similar to Sindria and Volturn, possibly to both combined if both are in the low- or lower-mid-millions rather than upper-mid- or high-millions, and a refugee crisis involving any significant fraction of the population would be a significant problem for the system), you're looking at a location that has a population comparable to the entire population of every inhabited location in the current version of the game combined; if Opis was even as large as Earth's moon, you're looking at something like 3 square kilometers per person, which is an extremely low population density for something described as a 'city moon.' According to Wikipedia, the highest population density of any city on Earth is about 40,000 people per square kilometer; if that were the population density of Opis and the population of Opis was comparable to that of New York City, then Opis could conceivably have been as small as ~4.5 km in radius, and if you built into the moon rather than merely on the moon, you could probably justify Opis being even smaller. This is a much more destroyable target than anything remotely comparable in size to Earth, given the known capabilities of the various factions in the sector, though it's still big enough that destroying it with the weapons available within the game would take a long time (but that's not that much of an issue, regardless; we know that the destruction had to have been either something which occurred relatively slowly or which was foreseen a fair time before the event occurred, as otherwise there wouldn't be much of a refugee crisis).
Also, in light of this, I now think it more likely for Opis to have been a moon of Volturn than of Salus, with its debris forming the ring around Volturn.
Author
Topic: Worldbuilding in the Sector and the aspect of mystery (Read 5945 times)