Model for UA93: Weight buried in solid ground after fall (Veritasium)

Oystein

Senior Member
Veritasium's latest YouTube video is on kinetic energy weapons. They are experimentally dropping heavy, slender weights from a helicopter to see what happens on the ground.

Their first preliminary experiment, with a concrete "rod" of 100 kg dropped from a height of 500 m results in this:

Source: https://www.youtube.com/watch?v=J_n1FZaKzF8&t=560s


Veritasium_dropped_rod_screenshot_YT J_n1FZaKzF8 9m26s.jpg

They go on to say:
Falling from 50 meters, the rod accelerated for 10 seconds, and, even accounting for air resistance, it hit the ground going about 350 kilometers per hour. At that speed, with a mass of a hundred kg, it was carrying nearly half a million Joules of kinetic energy.

The point of me posting this is that this is a nice demonstration of what happens to a fast object hitting solid ground at high speed: A smallish crater, but the object ends up being mostly buried below the crater, deep inside the ground (what you see in the screenshot above is merely the rope with which they dangled the rod from the helicopter prior to release. I imagine that the tail rope incidentally helped to keep the rod vertical and keep it from rotating chaotically.

Compare this to the impact of Flight United Airlines 93 as it impacted the ground in a field near Shanksville, a former strip mine refilled with what has to be relatively loose soil.
 

FatPhil

Senior Member.
My goodness, they did almost everything wrong; everything from design and planning to execution. No fins? No small trials to work out what issues there would be - which was the greater cause of inaccuracy, the wind, the swinging, or simple the GPS itself? Without that, you've got no hope of estimating a CEP, and knowing how it would scale. Which is probably why they were so wildly out pretty much the whole time. Amusingly, you can rent cherry-pickers that are taller than some of their helicopter-based drops.

They even shipped a champion sandcastle-building team out to the desert and had them build an elaborate sandcastle city *before* they'd worked out whether they'd be able to hit it or not. If that isn't hubris putting the cart before the horse, I don't know what is.

But the most painful thing was hearing him repeatedly say "drop" and "fall" when talking about the orbital weapons: if you drop something from orbit, it remains in that same orbit, it doesn't fall towards the ground, because, as it was in orbit, it was already in freefall. The energy required to reduce the sideways motion of your orbit is huge.

[Imagine a Picard facepalm meme here.]
 

Henkka

Banned
Banned
I do agree that the lack of plane debris at Shanksville is not a particularly convincing argument... With most plane crashes, the pilots are trying to land the plane, so they're going much slower than UA93. What happens in incredibly high speed, high energy collisions can be unintuitive.

I also don't really understand the implication of saying UA93 didn't really crash in Shanksville... Like sure, maybe the crater is a bit strange, but there is still a smoking crater there. Did someone blow up a bomb, and then deep state agents with shovels went in and made the hole look more like a plane? Or what? This is a pretty frustrating part in the documentary New Pearl Harbour, where they point at all these strange anomalies in Shanksville, but don't really give an alternative theory of what happened.
 

Ann K

Senior Member.
Their sand castle city...hah! it's pretty obvious that when dropping something into sand, the shock is well absorbed by the flexibility of grains that can move separately from each other. That's why sandbags have long been used as protection in military conflicts. Even in medieval times, earth-filled wicker gabions were effectively used to stop projectiles. The efficacy of dropping an object as a weapon is highly dependent on the geology of the surface upon which it falls, and that usually requires detailed study of the target area.
 

MapperGuy

Member
Please when posting something like this don't just tell us to "check this out". Tell us what you think this is demonstrating. Does this confirm UA93 crashed in Shanksville, or does this prove that it did not crash in Shanksville? I am not very good at reading minds.

I had never heard of Veritasium before, and from this, and from checking out other things posted on their website, they seem quite amateurish. No fins on the rod, a large suspension rope that might help stabilize it but could also slow its fall, did they check the weather and try to find a windless day (or time of day)? Dropping things on sand what did they expect to happen. The original rods-from-god was intended to be used against hardened bunkers, or those built into solid rock. A rod hitting solid rock would create a shock wave that would propagate through the rock, that shock wave (essentially a local earthquake) would damage or destroy the buried facility. And this is the first I have heard of trying to use them to stop ICBM's, silly idea, kinetic kill vehicles to use against warheads would not be huge rods, they would be a couple of pounds or less, they just need to get themselves in front of the warhead and let it hit them, the collision would do the rest.

And on the subject of plane crashes, too many people expect to see the back half of the airplane sticking up from the crater, that is not what happens. Check wikipedia or google Images for the ValueJet 592 crash in the Everglades, a high speed crash, nothing sticking up through the few feet of mud and water, total disintegration of the aircraft. Not even a visible crater, just an area where the vegetation had been blasted away. No two crashes of an airliner sized aircraft will ever look the same of course, speed, angle of descent, ground material will all have their effect. There is no one "how a crash should look", they are all a little bit different.
 

Landru

Moderator
Staff member
Please when posting something like this don't just tell us to "check this out". Tell us what you think this is demonstrating. Does this confirm UA93 crashed in Shanksville, or does this prove that it did not crash in Shanksville? I am not very good at reading minds.

I had never heard of Veritasium before, and from this, and from checking out other things posted on their website, they seem quite amateurish. No fins on the rod, a large suspension rope that might help stabilize it but could also slow its fall, did they check the weather and try to find a windless day (or time of day)? Dropping things on sand what did they expect to happen. The original rods-from-god was intended to be used against hardened bunkers, or those built into solid rock. A rod hitting solid rock would create a shock wave that would propagate through the rock, that shock wave (essentially a local earthquake) would damage or destroy the buried facility. And this is the first I have heard of trying to use them to stop ICBM's, silly idea, kinetic kill vehicles to use against warheads would not be huge rods, they would be a couple of pounds or less, they just need to get themselves in front of the warhead and let it hit them, the collision would do the rest.

And on the subject of plane crashes, too many people expect to see the back half of the airplane sticking up from the crater, that is not what happens. Check wikipedia or google Images for the ValueJet 592 crash in the Everglades, a high speed crash, nothing sticking up through the few feet of mud and water, total disintegration of the aircraft. Not even a visible crater, just an area where the vegetation had been blasted away. No two crashes of an airliner sized aircraft will ever look the same of course, speed, angle of descent, ground material will all have their effect. There is no one "how a crash should look", they are all a little bit different.
When responding to a post please use the reply button so we can see what you are replying to.
 

FatPhil

Senior Member.
I had never heard of Veritasium before, and from this, and from checking out other things posted on their website, they seem quite amateurish.
He's normally pretty good, he's given me several "everything I know is wrong" moments over the years, but he literally dropped the ball on this one. I presume the presence of Adam Savage, and their biggest budget ever, meant that there were external influences that he's normally able to avoid. Bigger isn't always better.
 

Oystein

Senior Member
Please when posting something like this don't just tell us to "check this out". Tell us what you think this is demonstrating. Does this confirm UA93 crashed in Shanksville, or does this prove that it did not crash in Shanksville? I am not very good at reading minds.
...
Really? You had troubke parsing this? Urrr... You just need to read what I wrote in my opening post:
The point of me posting this is that this is a nice demonstration of what happens to a fast object hitting solid ground at high speed: A smallish crater, but the object ends up being mostly buried below the crater, deep inside the ground ....

Compare this to the impact of Flight United Airlines 93 as it impacted the ground in a field near Shanksville, a former strip mine refilled with what has to be relatively loose soil.
I assume that anyone who knows at all what Flight United Airlines 93 is, also knows what the impact site looked like: A smallish crater, but the object ends up being mostly buried below the crater, deep inside the ground.

So the point is, of course, that the Veritasium experiment demonstrates the plausibility of the kinetics of how UA93 would in fact crash, creat a shallow crater, and end up mostly beneath the crater, buried in the ground.

I posted this so people can link to either the YT video, with time stamp, or to this thread here, when they encounter in the wild a Truther who posts the iconic photo of the UA93 crater and askes "and where is the plane?" Answer: "Buried in the ground beneath the crater; see, here is a video that shows you how that sort of thing actually happens."
 

FatPhil

Senior Member.
So the point is, of course, that the Veritasium experiment demonstrates the plausibility of the kinetics of how UA93 would in fact crash, creat a shallow crater, and end up mostly beneath the crater, buried in the ground.

If UA93 was composed of solid dense matter known for its hardness, toughness, and strength. Was UA93 composed of solid dense matter known for its hardness, toughness, and strength?
 

Oystein

Senior Member
If UA93 was composed of solid dense matter known for its hardness, toughness, and strength. Was UA93 composed of solid dense matter known for its hardness, toughness, and strength?
I reject your question out of hand.

You forget to remember that we are here looking at completely different scales of mass, momentum and kinetic energy. So if you want to actually model the plane crash with a view to experimentally proving a point, we'd have to compute carefully the dimensions of our "model plane". I would expect that it would have to be an extremely thin-walled tube, but of far higher overall density, than the original plane (two design objectives that are very difficult to marry, I admit). As for the properties of the ground, I do not even start to have an intuition of how that would have to be to stand is as a fair model for the Shanksville refilled mine pit.

So, my point is merely to demonstrate that long, heavy things crashing at high speed and at a very steep trajectory can and do bury themselves beneath their own impact crater. Demonstrate, not prove this for UA93, particularly. It's to give the Truther who denies this could happen a visual that it CAN happen - and then the ball is back in their court to construct an argument why this rod could, while the plane could not.

However, have you considered that the plane is far longer than the rod in the Veritasium experiment? The longer it is, the more mass it puts behind the impact area. This plays a major role.

However, the rod being "hard" and "tough" probably plays a very minor role - its mass and its density are far more important. See, they used lead for shotgun projectiles forever not because lead is particularly hard (it's known for being an unusually soft metal), but because it is dense - you can project more mass onto a given target area with a lead bullet than with, say, an iron or stone bullet. But you can also project more mass by making the impactor longer, and that way heavier.

A 757-200 has a fuselage that is 47 m long.
I cannot find immediately a value for the cross section area of the fuselage - I'll leave this open and call it "A square meters". So the volume of the fuselage is approximately A*47 cubic meters.
A plane like this swims easily on water. I am pretty sure that the density of the fuselage is only a fraction that of water, let's say 0.2 tons per cubic meter. Then the mass of the fuselage would be 47*A*0.2 tons. The mass projected onto the ground area as the fuselage crashes is then (47*A*0.2)/A tons per square meter - A cancels out, and so UA93 projected a mass of about 10 tons per square meter onto the soil.

The rods in Veritasium's experiment - 100 kg, they say. They don't tell us the length nor diameter of their rods, nor their density. In a couple of shots, it appears that the rod is shorter than a man, but longer than half a man, so let's say about 1.2 meters long. The density of concrete is usually given as 2.4 tons per cubic meter. 100 kg or 0.1 tons of concrete thus have a volume of 0.1/2.4 = 0.041666 cubic meters. A rod of that volume and length 1.2 m then has a cross section area of 0.0347222 square meters. 0.1 tons projected onto 0.0347222 square meters is 28.8 tons per square meter. Roughly 3 times the mass per area than a 757/200. We are in the correct ball park with that number!

Now the rod impacted, so they say, at 350 km/h. UA93 impacted at 906 km/h according to NTSNB estimate, that's a factor of 2.6 for the momentum (both rod and plane hit with roughly equal momentum per unit of area), and a factor of 6.7 for kinetic energy (i.e. the plane projected more than twice as much energy on a unit of area).

Had both hit the same kind of ground, then I would expect that the rod would bury itself deeper (relative to their respective own lengths) in Shanksville, or that there'd be visible plane debris on the surface in the desert.

But te two did not hit the same ground: The denser object hit harder soil, the less dense object hit looser soil.

The quality of the ground plays a major role: The ground near Shanksville was relatively soft, with the soil being composed of finer particulates and probably a substantial proportion of water stored in it - you can probably easily shovel away that soil, many yards deep. The ground in the Veritasium experiment is probably also of a fine particulate, but evidently dry, and thus would resist a shovel much more. How exactly those differences affect a high-speed impact I can only guess.

----

So, considering all that, I remain satisfied that the Veritasium experiment is a good-enough demonstration of what happened at Shanksville - a proof-of-concept, if you will, given that the per-area values are in the same ball park, and the soils are similar enough in quality, with the intuitively "right" kind of difference in loosenes, given the characteristics of plane and model.
 

Ann K

Senior Member.
If UA93 was composed of solid dense matter known for its hardness, toughness, and strength. Was UA93 composed of solid dense matter known for its hardness, toughness, and strength?
No, of course not, but coming in at hundreds of miles per hour, it had momentum. The shock of the impact, of course, caused huge damage to the plane (about a third of it was scattered over the landscape; it was not all buried) just as the plane caused damage to the ground. We are not talking about a hard, tough, strong object that might bury itself without receiving much damage.

My parents lived near the disastrous Xenia tornado in the 1970s, and saw fragile pine needles that had been driven deeply into the trunks of solid trees. They had momentum, although they themselves were not hard, tough, or strong.
 

Mick West

Administrator
Staff member
You don't really need models when we have actual planes to compare with.

Ethiopian 302:
https://www.metabunk.org/threads/ethiopian.10552/
Comparison.jpg


Flight 5735
https://www.metabunk.org/threads/crash-of-china-eastern-airlines-flight-5735-mu5735-ces5735.12350/
West-Flight-5735.jpg


A B-24
https://www.dailymail.co.uk/news/ar...ssex-field-Air-Force-B-24-bomber-crashed.html
Article:
Speaking to authorities in June 2017, farmer John Sellers recounted the crash he witnessed as a schoolboy. He said: 'At about 9pm [on on June 22, 1944] I had started to get ready for bed when there was a thunderous scream of a plane in a power dive then bump of it hitting the ground.

'About 15 minutes later I slipped out and went behind the farm buildings to where I could see the crash site (some 300 yards away). The fireball was long gone out, the only sign was the scorched area of ripening barley in the next field. There was little sign of debris in the grass field, only the dirt around five craters.


And likely many others.
 

FatPhil

Senior Member.
No, of course not, but coming in at hundreds of miles per hour, it had momentum. The shock of the impact, of course, caused huge damage to the plane (about a third of it was scattered over the landscape; it was not all buried) just as the plane caused damage to the ground. We are not talking about a hard, tough, strong object that might bury itself without receiving much damage.

But he *was* talking about a hard tough strong object that might bury itself without receiving damage - that was the entirety of the video. (And "he" being @Oystein, he was talking about that video, and its contents, and so was talking about the same things). That is *specifically* what I am objecting to - this is not comparing like with like. The density of a fully-laden plane is less than 1/100th that of a tungsten rod. Apples to oranges.

My parents lived near the disastrous Xenia tornado in the 1970s, and saw fragile pine needles that had been driven deeply into the trunks of solid trees. They had momentum, although they themselves were not hard, tough, or strong.

Pine needles are not fragile. They have a comparable density, and strength, to wood. Their densest part is also their sharpest part. This is just xylem hitting xylem. No 100x density difference here, there's no equivalence between this and hollow planes crashing. Additionally, the fact that you see the ones that penetrate the wood is pure selection bias - you don't, can't, count the ones that destroyed themselves on impact.

From the laws of mechanics, as we now understand them from special relativity - those needles think they're stationary, and that they've been hit by an incredibly high momentum tree. If your "had momentum" argument has teeth, then it must apply even more to these incredibly high momentum solid trees and their ability to do damage to stationary fragile pine needles.

You're being swayed by your feelings of how impressive the results looked, and not stepping back and just looking at the numbers, and how mundane the explanation is.
 

FatPhil

Senior Member.
I reject your question out of hand.

You forget to remember that we are here looking at completely different scales of mass, momentum and kinetic energy.

You reject me questioning why you think the two cases you have brought up are similar because the two cases you brought up are not in any way similar? That's an odd way to express agreement, but I'll take it. However, so that it doesn't clutter the discussion for future readers of the the thread, perhaps you could remove the irrelevant material from your earlier post now we're all agreed it's not useful for any kind of comparison or analogy?
 

Oystein

Senior Member
You reject me questioning why you think the two cases you have brought up are similar because the two cases you brought up are not in any way similar?
That's not what I explained in my first response to you.
It's the opposite:
I explained to you that the two ARE similar, when you take into account the necessities of scaling models.

That's an odd way to express agreement, but I'll take it. However, so that it doesn't clutter the discussion for future readers of the the thread, perhaps you could remove the irrelevant material from your earlier post now we're all agreed it's not useful for any kind of comparison or analogy?
No.
 

deirdre

Senior Member.
Was UA93 composed of solid dense matter
it is once it hits the ground.
Article:
The National Transportation Safety Board investigation determined the plane was traveling upside down at more than 560 mpg — full flight speed — when its nose and right wing hit the ground. More than 5,500 gallons of fuel exploded with the impact.

.....
Anything heavy, including the plane’s cockpit, was drilled “full-throttle” into layers of soil, silt and coal, while lighter materials, including aluminum sheet metal, were expelled up to 150 feet into the air, according to McCall, an FBI section chief who helped supervise the Oklahoma City bombing investigation six years before 9/11.


(although i agree, the op video doesnt convince me personally of anything. the rod is too slender for me to visualize a comparison.

although....i do always grab a "steak knife" when i hear a sound in the house vs a butcher knife like they do in the movies. i imagine a butcher knife would be too hard to stick into a rapist with my lack of upper body strength. I wonder if i had 3x the force, like ua93 had 3x the force...if it would be then be smarter to grab a butcher knife? How's that for an analogy.)
 

FatPhil

Senior Member.
That's not what I explained in my first response to you.
It's the opposite:
I explained to you that the two ARE similar, when you take into account the necessities of scaling models.

Scaling invalidates any imagined equivalence, as different properties scale with differnet numbers of dimensions. Please restrict your arguments to comparing like with like.
 

FatPhil

Senior Member.
it is once it hits the ground.
Article:
The National Transportation Safety Board investigation determined the plane was traveling upside down at more than 560 mpg — full flight speed — when its nose and right wing hit the ground. More than 5,500 gallons of fuel exploded with the impact.

.....
Anything heavy, including the plane’s cockpit, was drilled “full-throttle” into layers of soil, silt and coal, while lighter materials, including aluminum sheet metal, were expelled up to 150 feet into the air, according to McCall, an FBI section chief who helped supervise the Oklahoma City bombing investigation six years before 9/11.


(although i agree, the op video doesnt convince me personally of anything. the rod is too slender for me to visualize a comparison.

The heavier denser bits drill into the ground because the weaker hollow bits collapses and even break apart. Dense rods/cubes of course don't have weaker hollow bits, and won't fly 150 feet into the air.

A fuel explosion further reduces the equivalence.

Isolate the landing gear, for example, and the rods become a much better analogue, but most of the plane isn't the landing gear.
 
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