Looking for Hindu members

[Dan Neely]

Even at a very oblique angle a big rock is going to make it down intact http://impact.ese.ic.ac.uk/cgi-bin/crater.cgi?dist=100&diam=10000&pdens=1500&pdens_select=0&vel=17&theta=1&tdens=1000&tdens_select=1000[^] Even with porus rock a 10km impactor is going to deliver 20,000,000 megatons. With something that big the only thing an extremely low inclination will do is to enlarge the scorch zone as it enters the atmosphere.

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[Gregory Gadow]

That will be very helpful in figuring things out, thanks! As I put in the OP, though, the asteroid breaks up when it hits the atmosphere and most of it ricochets back out into space; what actually impacts is a much smaller (but still sizeable) fragment. From what you and Dave (thank you too) have said, I need to decrease the size of that fragment and increase the amount of damage it does. To make future events track as planned, I need to frighten the planet half to death, not actually kill it. Writing plausable science fiction is a bit of a challenge. :laugh:

[Dan Neely]

Part of my point was that it's not likely to breakup the way you want. Most calculators will report breakups when they happen although I didn't explicitly test this one; but the ones that do so have only ever done it with much smaller rocks. Something this big is going to stay in one piece, and the friction from grazing the atmosphere is going to incinerate anything below it even it it doesn't make contact. Unfortunately I'm not aware of any calculators, but have read that an extinction level impactor would incinerate anyone close enough to the entry path to see anything (and IIRC well outside it to hundreds of miles as well).

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[Gregory Gadow]

The great thing about future history is that it is remarkably fluid ;P So a minor adjustment: the second attempt to deflect the asteroid did fracture it, just not enough to separate all the pieces. The three largest pieces were still heading towards Earth, and two of them bounced. Most of the damage cause by the impact would have been from the atmospheric collision and not the hit itself, although the piece that did land would have been made... er... quite an impact.