Below is an image that was a bonus from the Star Wars Resistance Season 1 DVD. We see this again in Season 2, Episode 2. That’s a big hole that the Mandator IV-class siege dreadnought Fulminatrix made when she blasted the Resistance base on D’Qar.
You can also see that an area for seemingly several hundred kilometres from the blast crater on all sides has been devastated.
Devastated area diameter is nearly 1300 km according to some quick pixel scaling I did. This would mean that the Fulminatrix flattened an area more than double the land area of France (which is not a small country) and 40% the area of India (which is a large country) with a four round burst.
Crater size
Crater diameter
What is important for the sake of this calc is the crater itself. Let’s find out how large it is, shall we?
Red circle = 510 px = 10,400 km (D’Qar official diameter)
Green line = 11 px = 224.31 km
Purple line = 11.31 px = 230.64 km
I’m just going to go with the 11 px and ~224 km estimate here as a safe low end.
Crater depth
I’m not even going to bother. Zooming in and pixel-scaling to try and get crater depth is a gigantic pain in the ass.
What about yield?
Well there are three methods we can go with here:
Comparison to the Chicxulub crater
The Chicxulub Impact Event produced a crater estimated to be at least 150 to 200 km in diameter and 20 km deep (Reference link).
Now, while it is true that some recent evidence puts this crater at 300 km, and that the 150 to 200 km ring is just an inner wall of the larger crater, the current estimates of the impact energies are for the 150 to 200 km crater.
The National Geographic link on the Chicxulub impact event profile here states that the impactor struck with kinetic energy equivalent to 100 Teratons of TNT. This is baseline High 6-B (Large Country level). If we go with this estimate, then that means that the Fulminatrix blasted the Resistance base on D’Qar with energy greater than 100 Teratons. This would put each shot well into the 6-B (Country level) range, which is consistent with the feat and rating of the Onager-class Star Destroyer.
However, according to more recent estimates (refer this link) the energy of the Chicxulub impactor may have been far greater. According to that link, which is what the Wikipedia article on the Chicxulub impact crater now uses as a reference, the impactor’s kinetic energy was in the range of 1.3e24 J to 5.8e25 J. That’s ~310 Teratons to ~13.8 Petatons. And keep in mind that these estimates are for a crater 180 to 200 km in diameter, whereas the Fulminatrix carved out a slightly larger crater on D’Qar.
Using asteroid impact calculators
For this I used two impact calculators:
By playing around with the values in the first one, I get a yield of 308 to 557 Teratons for carving out a crater 224 km in diameter and less than a couple of kilometres in depth.
By playing around with the values in the second one, I get a yield of 4.45 Petatons for carving out a crater 224 km in diameter and 56 km in depth.
The first one gave results in line with the low end of the impactor kinetic energy assessments in this link. The problem with this one is that the final crater depth is too shallow, meaning that this is actually a low-balled yield estimate.
The problem with the second one is that the crater depth would go down into the mantle, assuming D’Qar has similar crust thickness to Earth. And I think it’s safe to say that the Petaton level estimate is just a hilarious high-ball.
Crater melting and vaporization method
One method is to assume crater depth of 22.4 km (10% of crater width estimate), calculate its volume, and calculate the yield needed to melt and vaporize that volume of planetary crust.
There are three pieces of evidence to support vaporization:
1. Just look at the crater. The crater is still so freaking hot that it’s visible like a giant red burst pimple pit from thousands to tens of thousand of kilometres away in orbit. And, no, I am not apologizing for giving you that pussy visual.
2. The plethora of vaporization feats detailed in this blog for much weaker weapons. Hell, there are even a few atomization statements and feats in there.
3. This quote from The Last Jedi novelization about the Fulminatrix’s orbital autocannons:
A single shot could obliterate planetary shields as if they were an afterthought and turn a hundred cubic metres of crust into vapor and slag.
~ The Last Jedi: Expanded Edition
Obviously, that hundred cubic metre thing is just a case of the trope Writers Cannot do Maths and shouldn’t be taken seriously.
The actual calculation:
Using this spherical cap calculator (because I don’t know how else to calculate crater volume) and plugging in 224000 metres for Chord AB (crater diameter) and 22400 metres for Cap Height (crater depth):
Volume = 4.4726e+14 m^3
Assuming slagging (refer this thread):
Yield 1 = 4.4726e+14*4350*10^6/4.184e21 = 465 Teratons
Per shot yield would be 116.25 Teratons, which is High 6-B (Large Country level).
Yield 2 = 4.4726e+14*25700*10^6/4.184e21 = 2.747 Petatons
Per shot yield would be 686.75 Teratons, which is High 6-B (Large Country level+).
Edit suggested by DMUA
I've been conversing with DMUA on his message wall. He suggested using the crater dimensions I got in all three of the calculations using this impact calculator, and then applying vaporization. He agreed that the final crater dimensions obtained were quite consistent.
Using this spherical cap calculator and plugging in 224000 metres for Chord AB (crater diameter) and 1510 metres for Cap Height (crater depth):
Volume = 2.9755e+13 m^3
Yield = 2.9755e+13*25700*10^6/4.184e21 = 182.77 Teratons
Per shot yield would be 45.69 Teratons, which is solid 6-B (Country level)
Conclusion
I am not here asking that these figures be considered to upgrade the Mandator IV-class siege dreadnought to Large Country level or Continent level per shot (especially not the latter).
However, I believe there is sufficient evidence to support the current Country level per shot rating, or even a slight upgrade to Country level+ per shot.
Assuming the 100+ Teraton estimate for carving out a 150 to 200 km crater (in the National Geographic link) is correct, then per shot yield would be in the range of 25+ Teratons.
Assuming the lowest end of the impactor estimates of 308 Teratons; which, by the way, is very consistent with the low end impactor energy estimate of 310 Teratons given in the Wikipedia article on the Chicxulub impact event and this link, then per shot yield would be in the range of 77 Teratons. I would also, once again, like to point out that given the low crater depth estimates here, this is actually a low-balled yield estimate.
Proposals
- Keep the current 6-B (Country level) per shot rating for the Mandator IV-class’s orbital autocannons and add an “At least” before this rating.
- Slight upgrade to higher end of 6-B i.e. Country level+ per shot rating for the Mandator IV-class’s orbital autocannons and ignore addition of “At least” before this rating.
- New proposal: We go with the new edit suggested by DMUA, which gives ~45 Teratons per shot. This is hilariously consistent with the accepted end of this calculation.
That reminds me. Someone should make a content revision thread about updating the Chicxulub Impact Event profile on here, based on the new information. I think “At least High 6-B (Large Country level) with the 310 Teraton low end estimate on the Wikipedia page makes sense.