Question about surviving an extremely high fall into water

I did a search and didn’t find anything about this in previous posts, but I have to think it was covered before in a topic or column.

Could you survive a fall from an extremely high place (say a plane) into water (say an ocean or a lake) if you were somehow able to break the surface tension of the water just prior to impact? Let’s say for the sake of the discussion that you have a hand gun and intend to fire it into the water as fast as you could just before impact.

Mythbusters tried it with a hammer, didn’t work. It’s not the surface tension that’ll get you, it’s the massive amount of water you need to displace in a very short time.

It’s nothing to do with surface tension. falling fast into water is injurious because water has significant mass and requires considerable force to be quickly displaced - thus, the force offered by your falling body is quickly spent, and so you decelerate from >100mph to almost zero in a short time, and that’s bad for your body.

It has been argued, however, that contriving for some object to fall into the water just before you impact it might introduce a quantity of compressible air bubbles, which might soften the impact, but this seems a bit too tricky a shot to ever work.

All that being said, people have survived extremely high speed impacts into both water and solid stuff. I used to skydive with a guy who lived through an 80+mph collision with a used-car lot when a stunt went wrong. IIRC there are skydivers who have survived hitting the ground at terminal velocity (~120mph).

So yeah, it’s possible, but as others have said it doesn’t have much to do with the surface tension of the water.

Surface tension of common liquids such as water is typically tens of milliNewtons per meter.. A milliNewton is about 0.0002 pounds of force. If a human being hits a lake at 120 MPH, the impact force will be measured in thousands of pounds. In the scheme of such an event, surface tension effects are vanishingly small, neglible.

Most of the drag on an object is form drag, and is proportional to the density of the fluid through which the object is moving. So if you’re falling at terminal velocity (~120 MPH) through the air, you’re experiencing about 175 pounds of drag force. Water is about 800 times as dense as air, so when you hit the water at that speed, you can expect to immediately experience about 140,000 pounds of drag force, and decelerate at about 800 g’s. For a given impact speed, the only way to decrease this force is to decrease the effective density of the fluid medium through which you’re falling. You can entrain air bubbles in the water, but it would take a LOT of air to reduce the density to the point where the impact forces aren’t fatal. Want a 20-g deceleration event (think “fighter plane ejection seat,” which still hurts)? OK, your fluid density needs to be 1/40th that of water. As they say in Japan, “That could be very difficult.”

Faced with a high-speed vertical impact on water, I’d guess the best approach would be to freefall in the classic skydiver position (on stomach with arms/legs out) to keep the speed as low as possible, and then right before impact transition to a feet-first orientation and point your toes. You’re probably still going to break some bones, but at least your skull won’t implode.

A gun? A GUN!?! How would that be any more effective than your hands, a la cliff diving? Am I missing something here?

Considering that jumping from the Golden Gate Bridge has a near-certain fatality rate, NO. If you jump from the GGB, you’ll hit the water at about 75 MPH and that’s about 200 feet above the water. Those last few seconds after you hit the water, but before you die, are probably pretty painful.

But that got me to wondering …

So, from what height can one jump and have a 50% chance of survival? 99% chance of survival?

Yes – even if it did keep you from dying by hitting the water, I imagine you might end up slamming into the object itself an instant later.

Relevant reading:

Popular Mechanics - How To Survive a Fall from 35,000 Feet

Well, to be fair, part of why the Golden Gate Bridge is such a reliable killer is that if the fall doesn’t kill you, you’re almost certain to drown in the strong currents. The next runner up for suicide bridges, the George Washington Bridge in Seattle (aka the Aurora Bridge) isn’t too much shorter, but people survive suicide attempts off it from time to time because there’s just a shipping canal so if they hit the water (as opposed to the Adobe parking lot) and survive there’s a good chance of them being rescued.

I think Machine Elf is exactly right. If you were free-falling through the air at ~120 mph and the air magically turned into water instantly - meaning surface tension has no effect - you’d slow down due to drag fast enough to cause serious injury.

I remember David Blaine after his time spent in the ice cube saying that he wanted his next stunt to be to jump off the Golden Gate Bridge (and survive, naturally) using the “breaking the surface tension” trick. Pretty telling that he hasn’t done it (and speaking of that, what has he done lately?). Probably watched that episode of Mythbusters. :wink:

There were a few guys who got shot out of their bombers in WWII and managed to survive. Nicholas Alkemade was a tail gunner in a British Lancaster. When the order came to bail out, he found that his chute was on fire. Faced with a choice of jumping to his death or burning to death, he chose to jump. He landed on fir trees, underbrush, and a small bit of snow, but amazingly, he managed to fall about 20,000 feet and his only injury was a twisted knee. Also at an altitude of about 20,000 feet, Alan Magee was thrown from his plane before he could grab his chute. Unlike the other WWII survivors, he didn’t land on anything soft. He ended up coming down through the skylight of the St. Nazaire train station (there’s some uncertainty about whether he bounced off part of the roof first). I wouldn’t exactly say he walked away from his fall since he was very badly injured, but he did live. A Russian named Ivan Chisov bailed out around 22,000 feet. What he hoped to do was drop below the level of the battle and then pop his chute, so that he wouldn’t just be an easy target for a pissed off German fighter pilot to shoot. What he instead did was pass out on the way down and never opened his chute. He was also badly injured but survived.

There are a few more similar stories as well.

Exactly how you hit the water is extremely important. An average Joe who has no training whatsoever will start to see injuries around heights of 50 feet or so. On the other hand, cliff divers routinely dive into water from much greater heights than that. The current high dive record is somewhere around 170 to 180 feet (google gives me different numbers, usually 172 or 177).

As you noted, folks who jump off of the Golden Gate Bridge (approx. 200 feet)
have an almost 100 percent fatality rate, even though that’s not much higher than the current high dive record.

If you’re talking about falls onto the ground, I’ve head that falls from 20 feet up are fatal about 50% of the time. I haven’t heard about similar statistics regarding water.

A pretty interesting website dedicated to freefall survivals.

Interestingly, just an hour ago, someone survived a jump from the Golden Gate Bridge:

I have been trained to jump around the hundred foot mark and it was basically cross your legs, point your toes, cross your arms and plug your nose.

I remember the Mythbusters episode, and found it somewhat unsatisfactory (surprise surprise). In particular it was clear that the dummy completely missed the area of water disturbed by the thrown object. Pretty much rendering the experiment useless.

People jumping off bridges are a problem, in so far as they usually intend killing themselves, they are the least likely to adopt any possible survival activities. As observed above, coming off the Golden Gate is not a good survival activity even without the drop. Indeed the waters are so treacherous that just jumping off a boat under the bridge has a good chance of leading to death. Someone injured, but otherwise alive after jumping, is going to have an uphill battle to say the least.

There are people who dive from very high heights in some well known spots (I believe there’s one such spot in Brazil).

From how high do you have to jump to reach terminal velocity?