5 ms·

Just in case you fall out of a plane without your 'chute

129 points by shrike 17y ago

ComputerGuru 17y ago
While very nicely written and a good read, I too was taken aback by "Lower body weight reduces terminal velocity" - Physics 101 anybody?
- sketerpot 17y ago
  A lower ratio of body weight to drag force reduces terminal velocity. How's that?
- ShabbyDoo 17y ago
  If your surface area to weight ratio is higher, then yes. Small women end up strapping on 10+ pounds of lead weight if they want to fly with the boys.
- deleted 17y ago
  [deleted]
- ahi 17y ago
  All objects have the same acceleration (g) but not the same gravitational force. Terminal velocity is reached when Fdrag = Fgravity. Remember F=ma, so Fgravity is (mass * gravitational acceleration).
- carbocation 17y ago
  Only in Physics 101 is the article incorrect. Outside of Physics 101, we stop assuming a vacuum.
- chrischen 17y ago
  Less mass means less force exhibited by the earth on the baby. This means less force the wind exhibits on the baby has to overcome to match the force of gravity on baby. It also means less impact force. Think dropping an ant from a plane. It's terminal velocity would prbably be very small, and the force it feels on landing likewise.
- prewett 17y ago
  Gravitational acceleration (acting "down") is proportional to mass. Air friction (acting "up") is proportional to the velocity of the object. Terminal velocity is reached when the force of air friction equals the force of gravitational acceleration: gm = nv^2. Since g, n are constants, if m decreases, v decreases.
ShabbyDoo 17y ago
"To slow your descent, emulate a sky diver. Spread your arms and legs, present your chest to the ground, and arch your back and head upward." You will fall slightly (5MPH-ish) slower if you instead arch your back and arms in the opposite way, as if attempting to hug a large beachball. This position is slightly less stable though, so you risk flailing around and increasing your speed. What the article did not discuss was any attempt at horizontal movement as a way of plummeting into something safer than a parking lot.
- wensing 17y ago
  something safer than a parking lot One of those pools of colored balls at a McDonald's Kids Playland?
  - ShabbyDoo 17y ago
    That's the thing...unless you're a very experienced skydiver, you could not land under with a parachute inside something that small much less by flying your body at 120MPH. So, I think you'd be best off aiming for something big and kinda good -- like a bunch of scrub brush or a marsh.
    - electromagnetic 17y ago
      Agreed, even aiming for trees is a better prospect than concrete. You may run the risk of impalement, however you run a greater chance of catching a ton of weak branches and landing in a bed of mulch a foot thick. Again a corn field would be better than concrete, especially if you had horizontal momentum. Water is a bad idea, as stated in the article. If you're lucky, hitting a waterfall could possibly allow you to survive unharmed, although your targeting would have to be world-class. Landing mid-stream of a waterfall (that's not over rocks) would allow you to land in aerated water, which is essentially a giant cushion. Similarly, if you're over sea you'd either want to follow down a piece of your plane, or pray a major ocean liner just went down, because you'd want to hit the aerated water they'll leave behind. Also note: If you're over Venezuela, don't target any tall waterfalls. Hitting Angel falls is pointless, the water that hits the ground (not much does, most turns into vapor) is falling at its own terminal velocity . . . so you'll just hit wet stone at 120MPH. Concrete + Water, both things you're told to avoid.
nobody_nowhere 17y ago
The mantra I've heard among BASE jumpers is "if the chute fails, go in head first" -- e.g., if the shit's going to go down, finish it quick instead of ending up a mangled vegetable.
- mattmaroon 17y ago
  If someone's hobby is throwing themselves off of high cliffs and buildings, I think that would prevent me from ever accepting their advice about anything.
  - nobody_nowhere 17y ago
    Well, you could also look at it as taking advice from people with domain expertise in hard landings :)
    - staunch 17y ago
      Or they had a hard landing as a child and have been trying to recapture the experience ever since...
  - cromulent 17y ago
    Because they engage in a high-risk activity on purpose? Hardly unusual. You might be surprised at how thoughtful and considered the advice that you receive from BASE jumpers is (apart from perhaps the comment above). Certainly, the successful execution of a BASE jump, especially on a closed site, requires much forethought, planning, skill, knowledge, and also good execution. Most serious BASE jumpers are not at all foolhardy. They will have several contingency plans and also have set predetermined safety parameters outside which the jump will not take place. In the case you are forced to jump from anything, with or without anything, a BASE jumpers advice may be the best you can get.
hendler 17y ago
I've always wondered what I'd do. I imagined ripping off some clothes (pants in particular, if I still had them) and creating just enough of a "parachute" or flying squirrel effect that I'd be able to slow down to about 60mph and hit the ground at 45 degrees instead of 90 degrees. Inspired by, e.g. http://news.nationalgeographic.com/news/bigphotos/21240738.html http://news.nationalgeographic.com/news/bigphotos/21240738.h...
- electromagnetic 17y ago
  Agreed, I imagine I'd remove my pants and attach them around my waist with my belt, tying the ankles shut. Similarly I'd tie off the wrists of my shit (I always wear a long-sleeved t-shirt when I fly, I'm naturally warm so a jacket makes me hot and a regular t-shirt makes me cold) and hold that. As another poster said, falling like you're hugging the top of a giant ball can reduce your terminal velocity by an extra 5MPH, but it's unstable. However with your pants acting like a drogue, you might be able to stay stable enough to use it's effect. I'd agree with you however, gaining lateral velocity instead of vertical is perhaps key because 'tuck and roll' could probably save your life. It's also worth remembering that the human body can survive more g-force through their back than their front, so the 'tuck and roll' landing increases your odds. Although carrying a backpack full of foam would be preferable if you wanted to try the 'tuck and roll' landing.
  - vl 17y ago
    well, if you are going to carry a backpack full of foam just get a parachute instead.
    - electromagnetic 17y ago
      Foam is easier to explain to security than a bag full of high-tension wires and masses of canvas, which all could be damaged by debris and be rendered useless where as foam still works. Plus, where's the fun?
      - mct 17y ago
tomjen2 17y ago
And if you do survive, please do sue the airline company for putting a "Flotation device" under your seat and not a parachute. It is about time somebody stop this madness.
georgecmu 17y ago
I've read about quite a few documented survival cases of shot down pilots during WWII landing without a parachute. Pretty much all of them had the same scenario: landing site was a steep slope covered in snow. Snow helped cushion the initial impact, and the rest of the kinetic energy was dissipated during the roll to the bottom of the slope.
mdasen 17y ago
There's a similar post from a while back: http://www.greenharbor.com/fffolder/carkeet.html http://www.greenharbor.com/fffolder/carkeet.html (also at http://www.modernhumorist.com/mh/0103/freefall/ http://www.modernhumorist.com/mh/0103/freefall/).

129 points by shrike 17y ago

While very nicely written and a good read, I too was taken aback by "Lower body weight reduces terminal velocity" - Physics 101 anybody?

sketerpot 17y ago
A lower ratio of body weight to drag force reduces terminal velocity. How's that?
ShabbyDoo 17y ago
If your surface area to weight ratio is higher, then yes. Small women end up strapping on 10+ pounds of lead weight if they want to fly with the boys.
deleted 17y ago
[deleted]
ahi 17y ago
All objects have the same acceleration (g) but not the same gravitational force. Terminal velocity is reached when Fdrag = Fgravity. Remember F=ma, so Fgravity is (mass * gravitational acceleration).
carbocation 17y ago
Only in Physics 101 is the article incorrect. Outside of Physics 101, we stop assuming a vacuum.
chrischen 17y ago
Less mass means less force exhibited by the earth on the baby. This means less force the wind exhibits on the baby has to overcome to match the force of gravity on baby. It also means less impact force. Think dropping an ant from a plane. It's terminal velocity would prbably be very small, and the force it feels on landing likewise.
prewett 17y ago
Gravitational acceleration (acting "down") is proportional to mass. Air friction (acting "up") is proportional to the velocity of the object. Terminal velocity is reached when the force of air friction equals the force of gravitational acceleration: gm = nv^2. Since g, n are constants, if m decreases, v decreases.

ShabbyDoo 17y ago

"To slow your descent, emulate a sky diver. Spread your arms and legs, present your chest to the ground, and arch your back and head upward." You will fall slightly (5MPH-ish) slower if you instead arch your back and arms in the opposite way, as if attempting to hug a large beachball. This position is slightly less stable though, so you risk flailing around and increasing your speed. What the article did not discuss was any attempt at horizontal movement as a way of plummeting into something safer than a parking lot.

wensing 17y ago
something safer than a parking lot One of those pools of colored balls at a McDonald's Kids Playland?
- ShabbyDoo 17y ago
  That's the thing...unless you're a very experienced skydiver, you could not land under with a parachute inside something that small much less by flying your body at 120MPH. So, I think you'd be best off aiming for something big and kinda good -- like a bunch of scrub brush or a marsh.
  - electromagnetic 17y ago
    Agreed, even aiming for trees is a better prospect than concrete. You may run the risk of impalement, however you run a greater chance of catching a ton of weak branches and landing in a bed of mulch a foot thick. Again a corn field would be better than concrete, especially if you had horizontal momentum. Water is a bad idea, as stated in the article. If you're lucky, hitting a waterfall could possibly allow you to survive unharmed, although your targeting would have to be world-class. Landing mid-stream of a waterfall (that's not over rocks) would allow you to land in aerated water, which is essentially a giant cushion. Similarly, if you're over sea you'd either want to follow down a piece of your plane, or pray a major ocean liner just went down, because you'd want to hit the aerated water they'll leave behind. Also note: If you're over Venezuela, don't target any tall waterfalls. Hitting Angel falls is pointless, the water that hits the ground (not much does, most turns into vapor) is falling at its own terminal velocity . . . so you'll just hit wet stone at 120MPH. Concrete + Water, both things you're told to avoid.

nobody_nowhere 17y ago

The mantra I've heard among BASE jumpers is "if the chute fails, go in head first" -- e.g., if the shit's going to go down, finish it quick instead of ending up a mangled vegetable.

mattmaroon 17y ago
If someone's hobby is throwing themselves off of high cliffs and buildings, I think that would prevent me from ever accepting their advice about anything.
- nobody_nowhere 17y ago
  Well, you could also look at it as taking advice from people with domain expertise in hard landings :)
  - staunch 17y ago
    Or they had a hard landing as a child and have been trying to recapture the experience ever since...
- cromulent 17y ago
  Because they engage in a high-risk activity on purpose? Hardly unusual. You might be surprised at how thoughtful and considered the advice that you receive from BASE jumpers is (apart from perhaps the comment above). Certainly, the successful execution of a BASE jump, especially on a closed site, requires much forethought, planning, skill, knowledge, and also good execution. Most serious BASE jumpers are not at all foolhardy. They will have several contingency plans and also have set predetermined safety parameters outside which the jump will not take place. In the case you are forced to jump from anything, with or without anything, a BASE jumpers advice may be the best you can get.

hendler 17y ago

I've always wondered what I'd do. I imagined ripping off some clothes (pants in particular, if I still had them) and creating just enough of a "parachute" or flying squirrel effect that I'd be able to slow down to about 60mph and hit the ground at 45 degrees instead of 90 degrees. Inspired by, e.g. http://news.nationalgeographic.com/news/bigphotos/21240738.html http://news.nationalgeographic.com/news/bigphotos/21240738.h...

electromagnetic 17y ago
Agreed, I imagine I'd remove my pants and attach them around my waist with my belt, tying the ankles shut. Similarly I'd tie off the wrists of my shit (I always wear a long-sleeved t-shirt when I fly, I'm naturally warm so a jacket makes me hot and a regular t-shirt makes me cold) and hold that. As another poster said, falling like you're hugging the top of a giant ball can reduce your terminal velocity by an extra 5MPH, but it's unstable. However with your pants acting like a drogue, you might be able to stay stable enough to use it's effect. I'd agree with you however, gaining lateral velocity instead of vertical is perhaps key because 'tuck and roll' could probably save your life. It's also worth remembering that the human body can survive more g-force through their back than their front, so the 'tuck and roll' landing increases your odds. Although carrying a backpack full of foam would be preferable if you wanted to try the 'tuck and roll' landing.
- vl 17y ago
  well, if you are going to carry a backpack full of foam just get a parachute instead.
  - electromagnetic 17y ago
    Foam is easier to explain to security than a bag full of high-tension wires and masses of canvas, which all could be damaged by debris and be rendered useless where as foam still works. Plus, where's the fun?
    - mct 17y ago

tomjen2 17y ago

And if you do survive, please do sue the airline company for putting a "Flotation device" under your seat and not a parachute. It is about time somebody stop this madness.

georgecmu 17y ago

I've read about quite a few documented survival cases of shot down pilots during WWII landing without a parachute. Pretty much all of them had the same scenario: landing site was a steep slope covered in snow. Snow helped cushion the initial impact, and the rest of the kinetic energy was dissipated during the roll to the bottom of the slope.

mdasen 17y ago

There's a similar post from a while back: http://www.greenharbor.com/fffolder/carkeet.html http://www.greenharbor.com/fffolder/carkeet.html (also at http://www.modernhumorist.com/mh/0103/freefall/ http://www.modernhumorist.com/mh/0103/freefall/).