ASVS's First Topic--Federation vs Covenant

Did a related website in the community go down? Come back up? Relocate to a new address? Install pop-up advertisements?

This forum is for discussion of these sorts of issues.
User avatar
Mr. Oragahn
Admiral
Posts: 6865
Joined: Sun Dec 03, 2006 11:58 am
Location: Paradise Mountain

Re: ASVS's First Topic--Federation vs Covenant

Post by Mr. Oragahn » Wed Mar 03, 2010 11:35 pm

Roondar wrote:
Mr. Oragahn wrote:Considering what a single buried 10 MT nuke does, and considering we don't need to go there, and that you must use a couple more surface impacts to obtain similar effects, I don't see how we'd burst out of the allowed margin that sits between half of the torpedo complement and nearly all of it.
I'm pretty darned certain that you can't compare centrally buried explosives with non burried ones. It's a downright unfair comparisom.
That I know. That's why I didn't do it. Otherwise I'd say just add one nuke at the surface to get the same results. Which I didn't do.
Just for starters: you lose half the yield with a surface detonation.
And thats not counting (because I have no real data on this) that the effectiveness of subsurface detonations is known to be 'rather more effective' than surface ones.

The 'science' in Armageddon is seriously flawed, but they did get that bit mostly right - surface explosion means expanding gasses go where they like, which is away from the rock, not towards it.
Nothing I say goes against it. It's literally in my post, and found in parts you quoted.
See, Mike is correct in that adding 1 KM to the asteroid means those torpedoes will have to target multiple cubic KM's of extra rock to get rid of.
Which are grouped into blocks. That makes them easy to target, and anything that's big enough to be part of the ship in question has to be shot at again.
Since the ship is ought to tougher than typical space rock, the rock in question will be gone before the Pegasus is destroyed, which just makes the targetting even easier once the target is even clearer.
Yeah, but Riker didn't say it would take most of their torpedoes to blow the asteroid in progressively smaller chunks until they destroyed the Pegasus - he eyeballed the thing and said it would take most torpedoes they carried to destroy the asteroid -and conveniently the Pegasus with it-, knowing full well his career was on the line. He'd want to overkill, not underkill.[/quote]

He couldn't avoid fragmentation, and the ship couldn't fire half its torp in one go. It could only fire salvo after salvo, and even if it's measured in under a minute, which I highly doubt, it would already be too long to avoid fragmentation. So no matter what happens, he's going to have to chase the chunks.
Besides, this doesn't change the fact that blowing up an extra couple of cubic KM at the kind of yields your advocating is not 'a couple more' but rather 'a whole lot more'.
When the point is to cause considerable fragmentation, it's a couple more. I remember reading that even surface 1 kt nukes are considered to be capable of cracking open non porous 1 km asteroids.
There's also a source that provides a less generous, albeit interesting take on blasting asteroids. It's rather old (1992) and at that time, asteroid related concerns were rarely adressed from the perspective of complicated masses of dusts, porous, and rubble piles, but instead threated as hard lumps of rock.
Figure 2 of this document (PDF page 1) showed that, it was estimated that a 10^2 KT standoff nuclear detonation could fragment and remove 10^10 kg of matter in the form of ejected fragments accelerated beyond escape velocity, for an asteroid greater than 1 km wide.
Likewise, a 10^4 KT detonation, still at a distance, can remove 10^12 kg (10^9 tons) of mass under the form of high speed ejecta, on a 10 km wide asteroid, roughly spherical.
This last figure provides an ejecta that masses between a hundredth and a thousandth of an 9 km wide asteroid, totally spherical with no cavities at all.

Let's also remember that for those who often like to think the ENT torp that is capable of putting a 3 km wide crater into the surface of an asteroid, and peg it at 50 MT, a few dozens of them would be completely overkill to deal with a ~9 km long asteroid. :)
Or that you haven't actually managed to establish that the simulation you've quoted can be upscaled the way you are doing now - we have no real way of knowing if using low-mt near-surface explosions will crack an asteroid that is a whole lot bigger into pieces like that.
It's cavernous and certainly not one big ball. It will break up. Besides, the explosions will not be a few meters standoff explosions. If anything, torpedoes will still smash into the surface, making them contact detonations, if not slightly half buried ones, which is always that taken.
In my view it's just as likely it'll open a fissure at the 'weakest spot' to 'let off steam' as it where - like 'smaller' explosions tend to do inside enclosures when used on earth.
It's quite possible indeed that a torp may strike near a "fault line" that would split a chunk off the main body. In the end, it would offer more angles of attack on that new bit.
Besides: your yields assume that the torpedoes bury themselves, right?
No, but if I wanted to be nastier, I could since we know torps can do such a thing. :]
It would make the destruction even faster and much more efficient. What low kiloton nukes buried under a few hundred feets can do to a ground in a 1g environment is rather impressive.
I dunno, you seem to be basing your figures on results of a simulation of a centrally burried explosive going off inside an asteroid. And you seem to use those results to claim a lowest-possible destroy explanation on the asteroid as you could possibly make fit.
Aside from your error on understanding my claims, is there anything bad into establishing a low end that's different than what Mike touts?
And yes, burried low KT nukes are quite impressive - yet show nowhere near the kind of effects what we'd need here to destroy the asteroid in under 250 odd blasts.
They're very good to fragment big chunks though. But I didn't claim that torpedoes were rated at low kiloton torps. It just gave a perspective on how a mess that asteroid would become the moment one would start shooting at it.
(BTW, the effects of lower gravity on crater sizes and the like I've seen so far seem to be based on kinetic impacts - do you have figures for explosive charges instead?)
I would have to dig up some files I have about impactors uses against asteroids. They are surely the most effective mean of expending most of the energy into cratering.
Modern "air blast" nukes, not so much. Nukes with heavy casings would be much more efficient for concussion effects, but well below impactors. You just can't really beat an impactor's momentum and the way it delivers its energy.
It's still better than anything because the energy can only radiate towards the "outside", so it's still more efficient, plus when firing inside a cavern, there's no chance that energy will be wasted, as there will always be a wall to meet for each particle.
Of course it's better than the other options (even though you are wrong - the exit is also a valid direction for particles to go so there will be plenty of wasted energy) but it's far, far less efficient than burried charges. As in orders of magnitude less.
The cavern in question seems deep and tortuous enough to seem to offer no direct LOS into space for anyone located deep inside it. So in my opinion there would always be a wall for each particle, but gases will behave just like in a giant a thruster.
A buried enough detonation is obviously better, assuming it got deep enough towards the asteroid core. A detonation inside a large cavern comes second, and a surfacic impact on the outside comes last.
Quite true, but a detonation inside the cave is not a close second - it'll deliver several orders of magnitude less energy to any specific spot other than the ones quite close to point of impact. Yields requirements will still rise dramatically as a result. I'm pretty much convinced (considering the size of the caverns and that it has openings to the outside) that the difference between surface detonation and in-cave detonation are much smaller than you're thinking. There is really quite a lot of open space to carry vapor not to mention that radiation intensity will go down really, really fast with expanding distances.
I actually agree with that part.

Post Reply