Breaking surface tension of water to survive high fall [closed]

Question

I'm writing a sci-fi story where a character has to jump off the top of a 140m (459ft) tall building, and fall into the sea. I think it's pretty obvious that no one could survive such a fall, so my question is, if this character would throw something before him that would break the surface tension of the water (or something to move away the water right before he would hit it), would he have a chance to survive the impact? Or is there an alternative to the situation in question?

Thanks in advance :D

Answer 1

They likely will not survive.

This is a common myth about jumping into water from very high. It was tested by Mythbusters and shown to be false.

Eventually, they managed consistent drops (mostly just below 300 g), finding that the hammer reduced the impact slightly, but the 150-foot (46 m) fall would still be lethal.

Up to about 450m, a falling human will most likely still be accelerating to terminal velocity. So your character would still be accelerating and suffer far more damage than the Mythbusters experiments showed.

It's not the surface tension that kills, it's the change in acceleration. That can't be prevented or slowed by affecting the surface. Unless you can somehow get the density to change from air to water over several tens of meters.

To make the fall more survivable, the change in acceleration needs to occur over a longer period of time. There are a few ideas on how to survive a long fall, if the character can do that while drunk (inebriated individuals have a disproportionate survival rate), it may improve their odds of surviving the fall.

Answer 2

Best alternative I can come up with here is made use of in diving, however this is assuming 10m not 140m.

When an in training Olympic diver is giving their first attempts off a 10m board, an aerator under the pool shoots bubbles to the surface. If you've ever seen it, it looks like a massive underwater volcano bubbling to the surface. This has two effects...the first is surface tension as you mention with an object dropped before the fall. This doesn't have the biggest effect in your case, although your diver in training doesn't get the harsh slap a belly flop receives, losing the surface tension doesn't help much as far as lessening the impact of the rapid deceleration that ultimately kills (the fall doesn't kill, it's the rapid deceleration at the end that does). From this stand point, breaking the surface tension does little.

However there is a second effect that the bubbles might make a difference on...force is mass times acceleration, and acceleration has a time component to it. If you increase the amount of time that you are decelerating over, then the force on your characters body is lower (despite being over a larger period of time). Enter bubbles...if the bubbling is heavy enough, you actually effect the density of the water that you are falling into and you fall further into the water giving yourself a longer time to decelerate and a better chance of surviving. Of course this might not be enough to make it survivable...but best chance I can come up with.

Unfortunately you are not going to get bubbles to the degree you need by simply dropping off a rock or other large object before you go yourself...rapid little bubbles are better than a single massive one for this. It's quite doable in an artificial setup like a giant aerator at the bottom of a dive pool, but outside of these lab like conditions it's quite difficult to generate the bubbles you need. Any chance there's a two ton alka-seltzer tablet available to your hero before he jumps? More bubbles = lower density = longer time to decelerate = better chance of survival.

And as a final barely worth mentioning point...cold water is higher density and is a quicker stop while warm water is a little less dense and has a bit more give to it (same effect, you fall further into warm water and increase the distance you decelerate over)...but the effects here are very minimal, less than a percent difference.

Answer 3

It could, but only if the object was really big.

Also, surface tension wouldn't be what it would help him survive.

The goal here would be to reduce the rate that the faller decelerated when hitting the water. Kayakers survive large falls by doing this, though in their case, the thing hitting the water before them is water. The impact of the water (or large object) on the lower body of water both creates a localized downward current and aerates the water. The downward moving water reduces the velocity differential between the faller and the water, which in turn reduces the force exerted by the water on the faller. Aeration reduces the effective density of the fluid, which also reduces the force of the water on the faller. (In essence, the faller has to move less water out of the way per unit distance travelled if some of the water is replaced by air.)

If you're dropping a large object in front of you, you need to also account for the fact that, if the object slows down too fast, the faller will smack into it, which could kill them even if the water doesn't. Ideally, the faller would obtain a heavy, streamlined object which won't decelerate quickly and stand on the back of it when jumping off the building. Something like a torpedo would do nicely. This would possibly stop the impact from killing the faller, but would also probably drag the faller down deep under the water with the falling torpedo, at which point drowning would start to become a serious potential problem.

A parachute would be a better solution.

Answer 4

It has nothing to do with surface tension, and I don't see what people were thinking when advancing the myth. Without mis-using terminology, what are you supposing happens?

The splash could have an effect, but as shown on Mythbusters it is too small to matter. Consider if a plume of water existed, not as a solid block but ropes of fountain-flow or foamy breakers: that would be hit first. How deep is it and how much resistance does it offer? Nothing from a previous dropped hammer.

How about an explosion? Throw a plume up 40 feet right as you reach the top of it. The "loose" water can get out of the way so it's not behaving like concrete, and you have a foam of water and air.

Imagine a fire-hose fountain: also on Mythbusters they levitated a car (sans engine) with firehoses, and there is a waterski-hover-jet thing for people. If the jet was tall enough it could "catch" you and slow your fall as gradually as desired.

Your best realistic bet is to use a liferaft as a parachute. That worked on Mythbusters.

For something along the lines you're asking, try a grenade not a hammer. Or if it's like the Batman TV show with Adam West, he would have some compact pills in his utility belt that would act like mega-seltzer.

Answer 5

If your character threw something high-tech (magical) before him that caused a large whirlpool, it he could survive. He or she could conceivably "slide down" the inner surface/side/wall of the whirlpool. That would minimize his angle of impact, since the water isn't level and perpendicular to his direction of travel (straight down).

The water on the edges of the whirlpool is moving downwards too, so your hero's velocity relative to it would be greatly reduced. In other words, if the water is travelling downwards at 60 MPH, and your character is travelling at terminal velocity (about 120 MPH, I think), then your character is only travelling at 60 MPH relative to the water.

He would need to worry about drowning, of course. But that's a separate question.

What would he throw down there? Possibly a super-fast pump that would eject a geyser of water out of a nearby spot on the ocean. Or a small, short-lived, controllable micro black hole. (Not likely.) Or a bomb that shot to the floor of the ocean floor and exploded, opening up a heretofore unknown cavern hidden underneath, which would start pulling water down into it. (These are all pretty far fetched. I just like the idea of a whirlpool to save his life after the fall.)