5 ms·

I feel like it's missing the whole question of what to do if you'll be hitting water instead of dirt, trees or snow. I've heard speculation that you could impro

by m12k 5y ago

I feel like it's missing the whole question of what to do if you'll be hitting water instead of dirt, trees or snow. I've heard speculation that you could improve your odds of surviving by e.g. throwing down a pair of keys or similar to break the surface tension right before you hit the water, but I'd like to see that investigated further. Also, no matter the landing zone, it seems like you should try to minimize your landing speed by maximizing drag until the last moment, then switch to a position from which to execute a five-point-landing (or going through the water surface with feet first) - I'd be interested in strategies for how to successfully execute that.

AnIdiotOnTheNet 5y ago
> I've heard speculation that you could improve your odds of surviving by e.g. throwing down a pair of keys or similar to break the surface tension right before you hit the water, but I'd like to see that investigated further. Mythbusters did it, it didn't help. https://mythresults.com/episode5 https://mythresults.com/episode5
fennecfoxen 5y ago
The harm from impacting water is mostly due to the bulk of water which is in your way, which is neither very compressible, nor can able to instantaneously displace itself so that it is out of your way. It is not from the 0.07275 joules per square metre of surface tension.
dahart 5y ago
There’s a pretty good chance your keys would just float up past you if you tried to throw them, and hit the water long after you. I think humans have a higher weight to surface area ratio. But if you found a waterfall, you might try to land in the area that’s bubbling up. That could conceivably improve your chances when hitting water, which are very slim - hitting water in free fall is not that much better than hitting concrete. Trying to execute a stand-up 2 or 3 seconds before impact might help you survive, I could buy that. I’d guess this is something that’s difficult to do without having tried it before, it usually takes a few tries to do without flopping back to flat.
- LorenPechtel 5y ago
  Would changing your orientation even matter? Wouldn't you just reach the new terminal velocity by the time you entered? It's not like your a Starship that can flip at the last moment and has a big difference between sideways and vertical terminal velocity.
  - dahart 5y ago
    I think orientation does matter, and that a water entry might be more survivable with a vertical entry. Think about diving from a high-dive versus a belly flop. At terminal, you’re still likely to break legs or die from entry in a vertical position, but the surface area hitting the water is a lot less if you’re feet first, plus you’d have shoes on, etc. Check out the world record cliff jump https://www.dailymotion.com/video/x32e3od https://www.dailymotion.com/video/x32e3od Terminal in stand-up is indeed much higher than terminal in the flat position. A perfect stand-up / head-down is around 180mph typically, while flat is around 120mph, give or take depending on body shape & density. But it takes time to accelerate, long enough that I think if you stood up quickly you’d still be around the flat-position velocity. The maximum you can theoretically accelerate is about 22 mph/s, but you’re starting from terminal with tons of drag, so I think it would take 5-10 seconds to reach 180mph, and you can go from flat to stand-up in 1-2 seconds.
LorenPechtel 5y ago
Water landings you want to go in feet first but not perfectly vertical. Walking away is possible if your angle of entry is perfect--but even then you might be knocked unconscious and even if you're not you might not make it back to the surface before you run out of air.

by m12k 5y ago

AnIdiotOnTheNet 5y ago

> I've heard speculation that you could improve your odds of surviving by e.g. throwing down a pair of keys or similar to break the surface tension right before you hit the water, but I'd like to see that investigated further. Mythbusters did it, it didn't help. https://mythresults.com/episode5 https://mythresults.com/episode5

fennecfoxen 5y ago

The harm from impacting water is mostly due to the bulk of water which is in your way, which is neither very compressible, nor can able to instantaneously displace itself so that it is out of your way. It is not from the 0.07275 joules per square metre of surface tension.

dahart 5y ago

There’s a pretty good chance your keys would just float up past you if you tried to throw them, and hit the water long after you. I think humans have a higher weight to surface area ratio. But if you found a waterfall, you might try to land in the area that’s bubbling up. That could conceivably improve your chances when hitting water, which are very slim - hitting water in free fall is not that much better than hitting concrete. Trying to execute a stand-up 2 or 3 seconds before impact might help you survive, I could buy that. I’d guess this is something that’s difficult to do without having tried it before, it usually takes a few tries to do without flopping back to flat.

LorenPechtel 5y ago
Would changing your orientation even matter? Wouldn't you just reach the new terminal velocity by the time you entered? It's not like your a Starship that can flip at the last moment and has a big difference between sideways and vertical terminal velocity.
- dahart 5y ago
  I think orientation does matter, and that a water entry might be more survivable with a vertical entry. Think about diving from a high-dive versus a belly flop. At terminal, you’re still likely to break legs or die from entry in a vertical position, but the surface area hitting the water is a lot less if you’re feet first, plus you’d have shoes on, etc. Check out the world record cliff jump https://www.dailymotion.com/video/x32e3od https://www.dailymotion.com/video/x32e3od Terminal in stand-up is indeed much higher than terminal in the flat position. A perfect stand-up / head-down is around 180mph typically, while flat is around 120mph, give or take depending on body shape & density. But it takes time to accelerate, long enough that I think if you stood up quickly you’d still be around the flat-position velocity. The maximum you can theoretically accelerate is about 22 mph/s, but you’re starting from terminal with tons of drag, so I think it would take 5-10 seconds to reach 180mph, and you can go from flat to stand-up in 1-2 seconds.

LorenPechtel 5y ago

Water landings you want to go in feet first but not perfectly vertical. Walking away is possible if your angle of entry is perfect--but even then you might be knocked unconscious and even if you're not you might not make it back to the surface before you run out of air.