What do you think...

[tinman]

...the overall effect of a loaded supertanker falling from 2km onto a large city would be?

I'm having a hard time wrapping my head around this one.

Clearly the impact alone would be tremendous, but what about the oil? There would certainly be enough heat generated to ignite the oil, but would it be dissipated enough by the impact to actually explode or would it simply spread and burn?

Secondary fire sources (burst gas mains, flammable buildings, asphalt, etc.) would likely spread the fire well beyond the initial zone of effect, but would a firestorm be likely to develop?

What about the downwind effects from that much smoke and particulate?

What would be the best way to model this kind of event in HERO terms?

[Cancer]

It's not supersonic at impact; the velocity is only about 200 m/s.

Drawing numbers from here, posit 200,000 tons of oil on a ship with an empty mass of 200,000 tons. The ship is 350m long by 55 m wide by 35 m deep. That's the "footprint" of the falling object. Very crudely, that makes for 20 tons per square meter fallling, with that 200 m/s velocity, in the impact footprint. You can probably turn that into Hero-style KA damage.

You'll also have tsunami-like damage done by all that liquid (with its density of about 0.9 tons per cubic meter) being bounced away from the impact as the tanker structure is crushed.

The impression I have (from reading discussions of the firestorms resulting from WW2 strategic bombing) is that firestorms don't really come from a single big fire. To get one going, you need lots of lesser fires over a large fuel-rich area. I don't think this will make a firestorm. It'll be a very large nasty fire, but not a firestorm.

If you were to spread the oil out in a layer 1 m deep, then that makes a circle about 250 m in radius. If you make that 10 cm deep, then it's about an 800 m radius. So that's probably about the size of the area directly covered with the burning oil.

The big tankers carry crude, which isn't going to explode, and isn't as flammable as its refined products (gasoline). It also doesn't burn as cleanly, so you'll have yucky black smoke from the oil fire. I would look to descriptions of being downwind of the oilfield fires in Kuwait after the Iraqi invasion in 1990 (or '91, I forget) for that. The wind matters, both for smoke, and for the progress of the "collateral damage" fires that break out after impact.

Offhand, I'd say total destruction for a 1-kilometer radius around the center of the impact, and severe damage for another kilometer.

[Black Lotus]

It'd crush whatever structures/ vehicles/ creatures it fell on, create a respectable indentation in the concrete, cause a small localized earthqquake, send debris shooting around when it lands, and cause a mighty large dust cloud. I'm guessing it'd also be crushed and break up, sending pieces of itself spinning about.

It's be moving at 250 ft/s or so after a 2 km fall, somewhere terminal velocity for sure.

[NuSoardGraphite]

Oooh, Good scenario!

I'd treat it as a really big explosion, then beyond the effects of the explosion, a continuous RKA thats spreading.

I would use the secondary fire effects (gas mains exploding etc) as distractions to add tension to an already tense situation....they happen at dramatically important moments of course (the fire seems to be under control, then BOOM)

What dastardly villian is planning an attack of this magnitude on our heroes city???

Thats pretty ruthless!

[NuSoardGraphite]

am I mistaken in thinking that 400 thousand tons at 200 meters per second can generate somewhere on the order of 16 Trillion Joules of impact energy?

If so, thats about a 35 DC attack (using an exponential scale of X2, starting with 100 Joules = 1 DC) or 11 1/2D6K. Large enough to be considered on an Atomic scale. (a 1 Kiloton nuke comes out to about 13D6K or thereabouts)

The base damage should be localized in the Area of Effect the size of the Tanker itself. Beyond those hexes, it should be treated as an Explosion (maybe -1DC per 2 hexes instead of -1/1")

[tinman]

What dastardly villian is planning an attack of this magnitude on our heroes city???

Thats pretty ruthless!

Actually, it already occurred, but I had to wing it and I'm not sure I got the scale or effects of the devastation right.

Essentially the scenario was that a group of metahuman supremacists were staging a protest which included holding the tanker above Manhattan as a means of instilling fear and awe in the "lesser beings". They never intended to actually drop it, merely use it to make a point.

When the PC's rushed to intervene a struggle ensued and the telekinetic who was actually holding the tanker got taken out. The PC's had figured that between them they could easily carry it to safety, but they were about two orders of magnitude off in their calculations.

It honestly never occurred to me that the PC's would take that route, I figured they would defuse such a hair-trigger situation through diplomacy. As a result I hadn't really put much thought into the outcome if the tanker actually fell.

[Cancer]

If you're going to do this, you might do some thinking about what superhero PCs might be able to do about it before impact.

If you just materialize the tanker 2 km up, then the answer is "not much". There'll be 20 seconds of free-fall time before impact.

Trying to lift the thing back up, or deflect it, isn't going to work, if you do the Superman-style fly up to it and catch it in your hands. The tanker doesn't have the strength to support its own weight. The STR you compute for moving that 400,000 tons has to be applied approximately uniformly over the whole tanker surface, or you'll just break the tanker apart; the pieces other than the one in Superman's hands will keep falling, and now they fall slightly away from each other, widening the zone of destruction. If that happens high enough up, then the oil will disperse over a much larger area. If you have a way of igniting it after that (it won't ignite on impact by itself), that could give your the widely dispersed fires you need to start a firestorm.

[Hawksmoor]

Shows you what most heroes think about situations they get in.

Punch first, rescue bystanders second.

This I believe comes from the fact that HERO evolved very strongly from table top wargaming (disagree? look at the movement and combat systems...HERO can be played as a WH2K game) and thus there are few systems for interaction resolution and XPs are not expressly awarded to motivate more peaceful methods.

I would have the characters really, really examine the impact of their actions as they certainly doubled or tripled the impact of a 9/11 type event on a major city.

Hawksmoor

[Cancer]

Woof, you've done it already. Ooooh. Man, the authorities are gonna be after the PCs now. The cure was much worse than the disease.

I like it. "Neutral evil gamemasters have the most fun."

[tinman]

am I mistaken in thinking that 400 thousand tons at 200 meters per second can generate somewhere on the order of 16 Trillion Joules of impact energy?

If so, thats about a 35 DC attack (using an exponential scale of X2, starting with 100 Joules = 1 DC) or 11 1/2D6K. Large enough to be considered on an Atomic scale. (a 1 Kiloton nuke comes out to about 13D6K or thereabouts)

The base damage should be localized in the Area of Effect the size of the Tanker itself. Beyond those hexes, it should be treated as an Explosion (maybe -1DC per 2 hexes instead of -1/1")

Unless I'm off by a decimal place, that seems about equal to a magnitude 5 earthquake...

[Hawksmoor]

If you're going to do this, you might do some thinking about what superhero PCs might be able to do about it before impact.

If you just materialize the tanker 2 km up, then the answer is "not much". There'll be 20 seconds of free-fall time before impact.

Trying to lift the thing back up, or deflect it, isn't going to work, if you do the Superman-style fly up to it and catch it in your hands. The tanker doesn't have the strength to support its own weight. The STR you compute for moving that 400,000 tons has to be applied approximately uniformly over the whole tanker surface, or you'll just break the tanker apart; the pieces other than the one in Superman's hands will keep falling, and now they fall slightly away from each other, widening the zone of destruction. If that happens high enough up, then the oil will disperse over a much larger area. If you have a way of igniting it after that (it won't ignite on impact by itself), that could give your the widely dispersed fires you need to start a firestorm.

Ah...real world physics.

But these are the comics of super action heroes (and the RPG that portrays them) thus the tanker slows down, its fall is arrested and moving slowly under the vast bulk the hero flies the laden tanker to the harbor setting it down past the Coast Guard cordon where clean up crews are already being dispatched.

That is comic book physics.

Of course Comic Book Physics also have the tanker detonating and taking out half of downtown and covering the rest in burning crude sludge.

Hawksmoor

[tinman]

Shows you what most heroes think about situations they get in.

Punch first, rescue bystanders second.

This I believe comes from the fact that HERO evolved very strongly from table top wargaming (disagree? look at the movement and combat systems...HERO can be played as a WH2K game) and thus there are few systems for interaction resolution and XPs are not expressly awarded to motivate more peaceful methods.

I would have the characters really, really examine the impact of their actions as they certainly doubled or tripled the impact of a 9/11 type event on a major city.

Hawksmoor

Considering the political fallout from 9/11 it would probably be safe to say that this event will be at the heart of government policy concerning metahumans for at least the next few decades, and not just in the US.

[Hawksmoor]

And suddenly the PCs are either told to retire (a la the Incredibles) or are forced to by an adminstration that has to been seen as cracking down on dangerous Metahumans.

Hawksmoor

[tinman]

Between them the PC's had the combined might of 60 STR, 40 STR, 70 STR and 35 STR TK. The PC with 60 STR was able to use it to affect an entire object (indirect).

The NPC holding the tanker had 120 STR TK and was visibly straining. In the past she had hit them with up to 20d6 worth of Turtle-style smack-down.

I can't believe they thought they could hold it up.

[Cancer]

Considering the political fallout from 9/11 it would probably be safe to say that this event will be at the heart of government policy concerning metahumans for at least the next few decades, and not just in the US.

Absolutely! I imagine most places will just go for the "Final Solution" to the "metahuman question" after that incident. And the PCs did it purely to themselves! Absolutely glorious! GM Brilliance of the first magnitude. Time to lean on the rep button.