Realistic Falling Damage

[Koningkrush]

I think I found a way to model falling damage more accurately in terms of certain death for falling into the ground at terminal velocity. I used the whiplash and collision rules for the brain and vitals since the body is a vehicle transporting them.

Joe is excited to take part in an experiment, especially since he was given this fancy space armor (DR of 150/90). They direct him to the end of the plane where he awaits his orders. They tell him to close his eyes, which he does, and suddenly finds himself falling from a couple of miles up in the sky. After panicking and screaming while looking for a nonexistent parachute, he slams into either the streets or a body of water.

Scenario 1: Joe slams into the pavement which should be certain death.
Joe has 10 HP and collides with a hard, immovable surface at 60 Yards per Second.
((10x2)60)/100 = 12d crushing damage.
Assuming an average damage of 42.
The armor takes the full impact without problem; it’s all absorbed.
Joe’s entire body smashes against the interior of the armor, dealing 8 points of blunt trauma to his body.
Now for Joe’s internal organs and brain which are riding as passengers in a vehicle known as Joe’s body. Both get 5 DR for the seatbelt (connective tissue) and 10 DR for the airbag (liquid cushioning) for a total of 15 DR.
The brain takes 27x4 (108) damage as it is turned into liquefied mush against the front of Joe’s skull.
The vital organs take 27 damage as they take severe trauma from the deceleration.
Joe takes a total of 143 crushing damage altogether from falling at terminal velocity into the pavement. Joe is below -10xHP which means his body is totally destroyed within the unfazed space armor.

Scenario 2: Joe gets really lucky and lands into some water. There should be a chance of survival.
Joe has 10 HP and collides with a soft, immovable object at an angle at 60 Yards per Second.
(10x60)/100 = 6d crushing damage.
Assuming an average damage of 21.
The armor takes the full impact without problem; it’s all absorbed.
Joe’s entire body smashes against the interior of the armor, dealing 4 points of blunt trauma to his body.
Now for Joe’s internal organs and brain which are riding as passengers in a vehicle known as Joe’s body. Both get 5 DR for the seatbelt (connective tissue) and 10 DR for the airbag (liquid cushioning) for a total of 15 DR.
The brain takes 6x4 damage (24) as it receives a major concussion smashing into the side of the skull.
The vital organs take 6 damage as they receive some moderate trauma.
Joe takes a total of 34 damage from falling at terminal velocity into a body of water.
Joe is at -24 HP which means, with 10 HT, he has a 25% chance of survival.

[Koningkrush]

Joe falls out of a 5 story building window and has a velocity of 20 Yards per Second. He has just the clothes on his back to protect him as he hits the street below.
Joe takes (20x20)/100 = 4d of crushing damage.
Assuming an average of 14 damage, he takes 14 crushing damage to his body (assuming he lands on his back).
The brain has DR 15. From blunt trauma, it takes 2x4 (8) damage from a decent concussion.
The vitals have DR 15. From blunt trauma, they take 2 damage.
Joe took 30 damage from falling out of a 5 story building and landing on his back against the pavement below. He has a 25% chance of survival.
I don’t know if this is realistic or not. If it is too deadly than it would be in reality, you could remove blunt trauma which means Joe would just go unconscious at worst along with some likely broken bones.

If Joe had fallen into water in this accident, he would have taken, including blunt trauma for brain and vitals, 10 damage which could possibly knock him unconscious from the shock. This would be bad since he would drown.

[Flyndaran]

Few people are killed instantly from falls. Almost always they bleed to death from internal damage.

[Humabout]

How does this affect insanely lucky people who manage to fall feet-first at terminal velocity into a soft surface and somehow survive (with swvere leg injuries)?

[Eukie]

If you want to do this GURPS Vehicles 2e-style, research into falling deaths has showed that the mortality rate from falls is equivalent to pedestrian deaths from being hit by a car moving at the same velocity. According to a Swedish road safety paper, the mortality-rate can be given by:

P(death) = 1/(1+e^(6.9-0.09*v))

Where v is the velocity in kilometers per hour. This is of course an incredibly awkward equation to use with GURPS, but let's try an amusing approach. Each time you pass -1xHT, you have to roll 3d6 against HT to survive; for most people, a 50% chance of survival. The loss of 10 HP then represents a 50% chance of death, so we can convert freely between probabilities and HP:

HP = 10*log(1-P(death))/log(0.5)

Which gives

HP_loss = 10*log(1/(1+e^(6.9-0.09*v)))/log(0.5)

We want this in dice, so:

Xd | X = (10*log(1/(1+e^(6.9-0.09*v)))/log(0.5))/3.5

Which gives the following table:

<1.2 m [no damage]
<8 m 1d-3
<11 m 1d-2
<15 m 1d-1
<20 m 1d
<23 m 2d
<26 m 3d
<29 m 4d
<32 m 5d
<34 m 6d
<36 m 7d
<39 m 8d
<42 m 9d
<44 m 10d
<46 m 11d
<48 m 12d
<51 m 13d
<53 m 14d
<57 m 15d
<59 m 16d
<61 m 17d
<64 m 18d
<67 m 19d
<70 m 20d
<80 m 25d
<90 m 28d
<100 m 31d

I think I'll stop there. I'm not calculating drag effects here, since they depend on factors like size and drag coefficient, which can be modified by everything from clothing to skill at falling controlled, so the table is somewhat inaccurate anyway.

A very quick rule-of-thumb is that fall damage starts at 20 meters, and you add 1d for each 3 meters of fall after that, up to a maximum of 46 dice.

[Bruno]

Originally Posted by Flyndaran

Few people are killed instantly from falls. Almost always they bleed to death from internal damage.

The ones that die "instantly", in an ER sense not an RPG sense, die within a few minutes because breathing or circulation are no longer possible (not necessarily from the blood falling out either). Or from just plain old head-smashed-in. Big causes here are neck fractures and brainstem trauma, but landing particularly badly and taking it on the chest would suck; This would probably require falling onto a not-flat surface - a pile of rubble, an ibeam on the ground, across a branch, whatever. Otherwise you'd be more immediately concerned with the inevitable face-into-ground problem which again causes brain and neck injury.

But that just highlights one of the problems - most ground isn't perfectly flat and clear (possible exception of sidewalks, but they still have stuff in and around them - and most times you fall off a building, you're going to fall away from it, not just straight down). Also, most people falling to their doom didn't go into it with much control over their orientation, and unlike cats we don't have a righting reflex. Whether someone lands on their feet (relatively good), butt (not great), back or side (bad), belly (terrible), or head (worst case) has a huge impact (har har) on the results.

Landing on your feet from a great height may break both your feet, ankles, shins, knees, femurs, and/or pelvis, which would suck, but presuming you don't bleed to death from torn vessels in your thighs you'd be "relatively" OK. Landing on your head from falling off a chair can kill you.

I've come to the conclusion that "realistic" falling damage is too complicated for me to care about in most cases in game. It's like sweating weapon damage too finely - just roll some dice and handwave variation coming down to how incredibly complicated the situation is.

[Koningkrush]

Originally Posted by Humabout

How does this affect insanely lucky people who manage to fall feet-first at terminal velocity into a soft surface and somehow survive (with swvere leg injuries)?

Well, if you rolled a 1 on every dice, or just really low, you could still survive. At that point, I would have to say that a series of miraculous events slowed your descent or softened your landing.

[Koningkrush]

Eukie, your 46d maximum comes up to an average of 161 which is a bit larger than what I got at terminal. If air drag was factored in, the damage from your system would probably more or less end up really close to mine.

The reason I thought of all this is that I don't think GURPS factors in internal injury when it comes to deceleration. The reason the damage is so low by RAW is because it only calculates the actual impact, not the extreme trauma from going 60 yards per second to 0 yards per second in a fraction of a second. Sure, your face caved in from the fall, but your brain isn't just going to stop, it wants to hit the ground too.

This makes it possible for beings without vitals or a central brain to survive falls quite easily. A robot, for example, would still be really messed up from the fall and need extreme repairs, but he has a much higher chance of survival than a person.

[Flyndaran]

Originally Posted by Bruno

...
But that just highlights one of the problems - most ground isn't perfectly flat and clear (possible exception of sidewalks, but they still have stuff in and around them - and most times you fall off a building, you're going to fall away from it, not just straight down). Also, most people falling to their doom didn't go into it with much control over their orientation, and unlike cats we don't have a righting reflex. Whether someone lands on their feet (relatively good), butt (not great), back or side (bad), belly (terrible), or head (worst case) has a huge impact (har har) on the results.

Landing on your feet from a great height may break both your feet, ankles, shins, knees, femurs, and/or pelvis, which would suck, but presuming you don't bleed to death from torn vessels in your thighs you'd be "relatively" OK. Landing on your head from falling off a chair can kill you.
....

As a child, I fell from around two stories flat onto my chest and "only" had the wind knocked out of me for 1/2 hour. After staying calm and waiting, I recovered perfectly fine in that time.
In basic training, my brother sleep walked out a second story window feet first. He still has pins where they had to fix his messed up bones.

But I would consider that landing in such a way as to concentrate injury to one body part. That of course can endanger life in ways that taking the shock spread out onto the entire body wouldn't. OR allow survival using said parts as "crumple zones" to absorb damage that would ensure death if taken by the entire body.
The point at which it changes from one to the other is horribly variable.

[Flyndaran]

Originally Posted by Koningkrush

Eukie, your 46d maximum comes up to an average of 161 which is a bit larger than what I got at terminal. If air drag was factored in, the damage from your system would probably more or less end up really close to mine.
....

Terminal velocity is different for different volume to surface area ratios. There isn't much variability for humans except for falling position, but in Gurps one could easily have all sorts of character forms.