What does that matter? How is that supposed to change the impulse calculations?
Once again:
Critiques must be substantiated. Why and how would the representations change the impulse calculations?
Yep. No response. Figures.
Well, let's look at his original objections:
I see he likes to add the fuel's mass and density to the wing, but I don't see where he calculates the fuel's stress against the wing at impact. Wouldn't the fuel push against the inside of the wing on impact? Where are those calculations?
The predominant factors here are mass and velocity. So what effect is the "stress against the wing at impact/push agasint the inside of the wing on impact" supposed to have? Is that supposed to matter? Is it supposed to take away so much energy that the wings and fuel slugs cannot fail the columns?
Remember NIST's pressure-impulse failure curves, and what information we can glean from them:
Ryan Mackey noted in his presentation that above 800 PSI on impact, at least some exterior columns are expected to fail. The corollary of that is that below that figure, they're expected to survive. As he worked out, that critical velocity ends up being 270 ft/s (185 MPH). That would make the critical "failure" impulse be around 6,500 lbf-s (check my math, people; I'm using the figures in the presentation Ryan gave)?
So, if all it takes is 800 PSI, 6500 lbf-s of impulse, 270 ft/s, and we have 4,600 PSI (AA11)/6800 PSI (UA175), 15,900/19300 lbf-s impulse, 650/790 ft/s velocity, you can say there is certainly
more than enough mass, velocity, force, energy, whatever you want to use to cause column failure. The mass and velocities of the jets were far in excess of what was needed.
Now, I don't know what the losses from the wing failures would be (the
"stress against the wing at impact/push agasint the inside of the wing on impact" ). I don't know how to even begin calculating that. But, if the claim is that they're significant - and why else ask the question if that's not the claim? - then there's the way for yankee451 to respond: Show that the wing strength was sufficient enough to significantly decrease the impact-induced impulse.
But stop and take a good, long look at how much excess force is available given the velocities involved first, before doing that.
Also:
No, of course not, but that's because above the 50th floors (roughly) of each tower, the core columns (which is what the pressure-impulse failure calculations for Figure 10-5 above were based on) were wide-flanged ones, not box columns. So Yankee451 didn't do his homework either in posting the wrong picture for the topic being discussed. But still, let's try to answer the spirit of the question despite his error and ask whether the general representation of columns for the calculations were accurately represented. And the answer is: Of course. The failure curves (NCSTAR1-2B, figure 10-5, p 376) are based on more than just isolated, individual columns material properties. It's based on
loading as well, and if there's one thing truthers continually keep on ignoring when discussing column properties, it's the fact that they're being loaded by the floors above. That simply cannot be ignored. Figure 10-5 takes that into account.
Now, was it accurately modeled in Ryan's calculations? Again, of course. His "model" was merely using the columns to determine an impact area so as to calculate force and impulse. Given that he cited the correct figure - 14 inches - in his presentation (slide 19), and given that the figure Yankee451 showed says the same, then yes, he most definitely, demonstrably did accurately model it. He wasn't trying to model every minute characteristic - the NIST curves took that into account - he was merely determining the width. And he got it right. Confirmable by Yankee's own image.
Now (out of order):
Why does he represent the aircraft wing as a slug of uniform density in this slide? Is a wing a slug of uniform density?
Probably not, but again, see above: Whatever differences in distribution exist
would not affect the impulse calculations significantly. If that's wrong, prove otherwise.
