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

http://www.origin.popularmechanics.com/science/air_space/4344036.html

by shrike • 16 years ago

129 32 16 years ago

origin.popularmechanics.com

ShabbyDoo5• 16 years 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• 16 years ago

something safer than a parking lot

One of those pools of colored balls at a McDonald's Kids Playland?

ShabbyDoo5• 16 years 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.

mattmaroon3• 16 years ago

I've read previously that you can move up to 12 miles in any direction while falling if you aim for it. Over most of America this gives you ample opportunity to find a tree.

I've also read that you should come down in a sitting position on top of a tree. Haystacks seem like they would be too hard to spot until it's too late. A grain silo might be recognizable and have a thin enough roof to be helpful.

I suppose you could aim for the suburbs and hope someone has one of those obnoxiously large trampolines.

vanschelven• 16 years ago

12 miles in any direction from 22,000 feet (the moment you reach breathable air) seems unlikely to me.

That would imply 2.9 feet horizontal movement for every vertical foot.

Edit: typo in the calculation fixed. (29 => 2.9)

rlpb• 16 years ago

> I've read previously that you can move up to 12 miles in any direction while falling if you aim for it.

Skydiver here. You could manage a mile or two; no more. But both this and changing your body position is quite a bit harder than you might think. You have to push against the air in quite a counter-intuitive manner. A beginner will just flail about and probably start spinning; especially without any tuition.

Raphael• 16 years ago

FTFA:

    Glass hurts, but it gives. So does grass. Haystacks and
    bushes have cushioned surprised-to-be-alive free-fallers.
     Trees aren’t bad, though they tend to skewer. Snow? 
    Absolutely. Swamps? With their mucky, plant-covered 
    surface, even more awesome. Hamilton documents one case of 
    a sky diver who, upon total parachute failure, was saved 
    by bouncing off high-tension wires. Contrary to popular 
    belief, water is an awful choice. Like concrete, liquid 
    doesn’t compress. Hitting the ocean is essentially the 
    same as colliding with a sidewalk, Hamilton explains, 
    except that pavement (perhaps unfortunately) won’t “open 
    up and swallow your shattered body.”

ShabbyDoo5• 16 years ago

My point was that, given the choice between a swamp and a nearby and deep ball pit in the middle of a parking lot, the swamp would be a much better option given the low probability that one could actually hit the ball pit -- an argument not made in the article.

ComputerGuru• 16 years 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• 16 years ago

A lower ratio of body weight to drag force reduces terminal velocity. How's that?

ShabbyDoo5• 16 years 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.

ahi• 16 years 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• 16 years ago

Only in Physics 101 is the article incorrect. Outside of Physics 101, we stop assuming a vacuum.

chrischen• 16 years 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• 16 years 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.

nobody_nowhere2• 16 years 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.

mattmaroon3• 16 years 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_nowhere2• 16 years ago

Well, you could also look at it as taking advice from people with domain expertise in hard landings :)

cromulent• 16 years 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• 16 years 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.h...

electromagnetic3• 16 years 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• 16 years ago

well, if you are going to carry a backpack full of foam just get a parachute instead.

saturnine• 16 years ago

Once removed it doesn't seem likely you'd be able to hold onto your garments in a 120MPH wind. Then again, you just survived the breakup of an airplane traveling 500MPH, so maybe somebody is really fond of you.

georgecmu• 16 years 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• 16 years ago

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

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

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