Is there anything a human traveling at terminal velocity could land on that wouldn't injure them

Factual Questions
1

If terminal velocity tends to be about 120mph, what if anything could a human being land on that would leave them uninjured? I doubt air bags work if so I’m guessing someone would’ve done it by now. I saw a video of someone wearing a wingsuit land into a large bunch of cardboard boxes but I have no idea what his speed was. I’m sure it wasn’t terminal velocity though.

If anyone can also show the math of how that would be calculated that would be good. I took newtonian physics almost 10 years ago, but I have a vague memory of it and would be interested.

I’ve heard the average speed of a landing with an open parachute is only about 10-20mph, which even that can cause knee damage when landing if you don’t roll with your landing.

On a somewhat unrelated subject what animals can survive a fall at their terminal velocity uninjured?

2

A good engineer could certainly design a series of breakaway platforms that would provide a steady, survivable deceleration.

Moviemakers have used big stacks of (empty) cardboard boxes. They crumple just fast enough to cushion the stuntman’s fall, but slowly enough and with enough resistance to stop him from hitting the ground.

ETA: with parachutes, if you “flare” (or is it flair?) just right, you can land at essentially “zero” velocity. Just put your legs down and start walking. I’ve seen this done on tv.

3

Interesting, apparently so.

4

Apparently this (video) is the record highest airbag jump.

I don’t see why an airbag couldn’t be designed to handle a person at 120mph. I suspect the reason it hasn’t been tried is because it takes a lot more distance than you’d think to reach terminal velocity. As wind resistance increases, acceleration drops and it’s not until somewhere around 1800 feet that a person actually reaches terminal velocity. It would be impossible to hit an airbag, or anything else, from that altitude.

5

During World War II, several unlucky guys basically got shot out of their planes and somehow managed to live (ok, in a way i guess that makes them lucky rather than unlucky).

Most notable for the OP was probably Nicholas Alkemade. He was a tail gunner in a British Lancaster bomber that got the crap shot out of it. When the order came to bail out, he looked over and saw that his parachute was in flames. So basically he had a choice. He could stay in the burning wreckage and die a painful death on the way down, or he could jump out and go splat at the end. Finding the prospect of burning to death rather unpleasant, he chose the latter, jumping out of his plane at 18,000 feet. He landed on trees and a bit of snow, and walked away with little more than a few scrapes and scratches and a twisted knee, and that was it. He was captured, and the German Gestapo almost executed him because they didn’t find his story believable. They eventually found the wreckage of his plane, with the remnants of his burnt chute exactly where he said it would be. After that, they treated him fairly well, for a prisoner.

Alan Magee wasn’t quite as lucky, and he ended up fairly badly injured (not quite what the OP is looking for), but his story was pretty remarkable just the same. When his plane got shot apart he was thrown clear of it. He fell 20,000 feet and landed on the roof of the St. Nazair train station. Accounts differ on exactly how he hit. Some accounts say he fell straight through the skylight. Others say he hit an angled part of the roof and rolled into the skylight, then fell through it. Alan couldn’t tell you what happened, as he had passed out from the lack of oxygen on the way down (the same thing happened to Nicholas). He shattered his arm and had other injuries, but lived to tell the tale.

Ivan Chisov was a Russian airman who got shot out of his plane at roughly 20,000 feet. Since there was a raging battle going on around him, he was pretty sure that if he popped his chute he would just make himself an easy target for a pissed off German pilot. So instead what he planned on doing was dropping down below the level of the battle. Then he would pop his chute and land safely. That was the plan, anyway. What actually happened was he passed out on the way down (lack of oxygen, again), never popped his chute, and hit the side of a snowy ravine. He bounced and rolled his way down the side of the ravine, where soldiers who saw him fall rescued him. (ETA) He was injured, but was flying again 3 months later.

There were others, but those are the ones I recall off the top of my head. Mythbusters featured Alan Magee in one of their myths (that a bomb exploded underneath him and the shock wave cushioned the blow - it was busted).

Vesna Vulovic is the current free fall champion, although technically she was more of a wreckage rider than a free faller. She was an airline attendant on a plane that exploded due to a bomb. She rode a piece of the fuselage down from about 33,000 feet and landed in snow. She was badly hurt, but survived.

Alan Magee aside, the rest of these folks all have one thing in common. They all landed in snow. So deep snow seems to kinda fit what the OP is looking for.

6

Most small ones. Mass increases with the cube of the size where air resistance increases with the square of the size. If you are having trouble picturing this, imagine a cube. Now double it in each dimension. You have a 2x2x2 cube, which has 8 times the volume but only 4 times the surface area on its bottom side. Now triple the original cube. Now you’ve got a 3x3x3 which has a volume of 27 but a surface area of only 9 on the bottom side. So as you can see the volume goes up much faster than the surface area of the bottom side. The mass depends on the volume, the air resistance depends more on the surface area. So basically as you scale things up, your weight goes up much faster than your air resistance, which determines your terminal velocity.

That’s why most bigger animals have a fatal terminal velocity, where most smaller ones don’t. Some of it depends on the animal as well. Cats are in the range where their terminal velocity starts to be potentially fatal, but they can often wiggle around and land in such a way that they often (but not always) walk away from those types of falls.

7

I think an airbag could work but it would have to be very large, in all three dimensions. It would have to be tall (or deep) to decelerate the jumper, but also very wide and long to make sure he/she lands on it. A person has to fall over 1000 ft. to reach terminal velocity in a belly-to-earth position. The best way to get that kind of altitude is in an airplane or helicopter.

Obviously an airplane has to be moving so it would be difficult to hit an airbag on the ground unless it was huge. A helicopter can hover, but even so from 1000+ ft. it would not be easy to land on an airbag that wasn’t gigantic.

The guy who landed the wingsuit in the cardboard boxes was traveling at a pretty shallow angle relative to the ground so that dissipated some of his energy. And he was at “terminal velocity” (for the surface area of the wingsuit)- but he wasn’t going 120 mph.

Also, you’ll notice in the video that he did flare just before impact; his body went from parallel to the ground to a head-high position- maybe a 45 degree angle or more.

Well, I see more posts since I started composing this reply. Fubaya said pretty much the same thing I’m saying.

8

A giant silo of whipped cream. Which would probably result in suffocation, but hey, he/she would live a few moments.

9

You could also build a really big slide where the upper segment is near vertical, and gently slopes to horizontal. You could nearly do it on the side of the Sears Tower, although a bit too much of the distance would be taken up just getting to terminal velocity (~1200 feet to 99% of terminal according to various sources).

10

Why did those pilots pass out? You can climb a 20,000 ft mountain without passing out (though you might get a headache if you’re sensitive to altitude). Was something else going on?

11

Silly related questions. I have seen skydivers deliberately assume a ‘head-down’ position while free-falling. Question:

What speed can a skydiver achieve by adopting such a position? Surely much faster than the traditional ‘belly flop’. (I seem to recall a reference to approaching Mach 1). I imagine that as speed and wind-buffeting increased, it would be harder and harder to maintain control - and therefore probably reverting to - well, what is the default position a human body would adopt? Has someone chucked a loose-limbed dummy out of a plane to see what happens?

Also would feet-first (‘pin drop’) be even faster?

12

Just my WAG, but I would think it was caused mainly by the sudden change in the air pressure and the resultant decrease in the percentage of oxygen available to the brain. (Not sure if I’m wording that right.) Climbing a mountain to 20,000 feet, takes time, which gives the body/brain the necessary time to acclimate to the decreased air pressure/oxygen content.
At that altitude, pilots would have been breathing from a pressurized system, if I’m not mistaken.
I’m sure some of the Doper pilots will come along and correct me if I’m wrong. :wink:

13

According to this, you top out at about 150-180mph when doing a head down position (vs 120 for a belly flop position). If done very aerodynamically you can get to 300mph.

14

This wasn’t quite terminal velocity, but would have still been bloody fast. A fall from 15000 feet. The chute came out but was snarled and didn’t open so the drag may have slowed him a little.

So a bunch of blackberry bushes works, he retained consciousness and only broke his ankle.

So the option would be if you were lucky enough to fall into a forested area with lots of skinny branches they would theoretically do the same as the pile of empty cardboard boxes in the stuntman movie trick. Just thick enough that each one slows you down a little without being thick enough to do damage.
Another option that could work (any engineers around to tell me I’m an idiot?) would be a large net strung over a valley or chasm with Bungy cords. So when the person hit the net, they wouldn’t stop but their force would cause the bungy cords to stretch, slowing the deceleration and absorbing the impact.

15

I’ve hit 180 mph in a head-down position. It’s actually easier to maintain control at higher speeds (with practice)- the air flow is smoother and small changes are all that are necessary to produce the desired results (turns etc). Head-first is better than feet-first because your control surfaces (hands, forearms, lower legs, feet) are trailing like a swept-wing airplane.

I remember hearing that the top speed reached in a head-down position is around 300 mph, as Wesley Clark says, but I can’t provide a cite- mostly because I’m too lazy to look.

16

“To the mouse and any smaller animal [ gravity ] presents practically no dangers. You can drop a mouse down a thousand-yard mine shaft; and, on arriving at the bottom, it gets a slight shock and walks away, provided that the ground is fairly soft. A rat is killed, a man is broken, a horse splashes.” -J.B.S. Haldane, On Being The Right Size

17

I recall reading that they not only turn so they land on their feet, but instinctively take a “maximum drag” posture to slow themselves down as well. Also, that cats are actually more likely to suffer major injury or death in relatively short falls, apparently because they don’t have time to assume a proper position.

18

IANAP, but a minor aviation wonk: Most WW2 aircraft weren’t pressurised, but aircrew in those that weren’t would have been breathing from a mask, so you’re functionally correct on that score.

19

Would landing in a deep pile of cotton candy (should someone be fortunate enough to encounter one) be even better than deep snow?

20

Lisa Boyer had a only partly unfurled her reserve chute when she impacted into a sewerage treatment pond. The terminal speed , 125 mph, is terminal (fatal) on impact with water.
The reserve chute may well have slowed her to 80 mph, or maybe it was a bit inbetween and the aerated mushy water was a bit software than clean and still water