[HN Gopher] Unplanned Freefall? Some Survival Tips (2001)
___________________________________________________________________
Unplanned Freefall? Some Survival Tips (2001)
Author : Tomte
Score : 121 points
Date : 2021-09-15 11:18 UTC (11 hours ago)
(HTM) web link (www.greenharbor.com)
(TXT) w3m dump (www.greenharbor.com)
| m12k wrote:
| 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.
| LorenPechtel wrote:
| 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.
| fennecfoxen wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| 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
|
| 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.
| AnIdiotOnTheNet wrote:
| > 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
| Someone wrote:
| _"Look around for a proportionate personal vehicle--some large,
| flat, aerodynamically suitable piece of wreckage. Mount it and
| ride, cowboy"_
|
| Given that you woke up after falling 20,000 feet, anything that
| in itself is "aerodynamically suitable" will be high above you by
| now (1) or, if it dropped of before you started falling, be miles
| behind you. Even that tightly packed parachute likely has lower
| terminal velocity, and will be out of reach by now.
|
| I guess your best (not one with good odds, but still best) bet is
| an airplane door with an uninflated glide that you can tie
| yourself to, remove from the door, and then inflate.
|
| (1) you can see that with rain showers: it's the smaller droplets
| that hit the ground last
| gus_massa wrote:
| I mostly agree, but a nice flat surface would rotate/rock/wave
| [1] like a sheet of paper. When it's horizontal it will go
| slowly, but when it's vertical it will go faster than a person.
| I'm not sure about the average.
|
| Note: This is a nice experiment for ~12 year old students that
| are learning to measure things in the laboratory. Just get two
| sheets of paper and make a ball with one of them, and measure
| the time when they fall from a fixed height.
|
| The time of the ball of paper will have a nice distribution.
| You can probably measure the time 5 times and have a good idea
| of the average and dispersion. Moreover, most of the dispersion
| in the time is due to the problems to start and stop the
| stopwatch, and perhaps some problems to release the ball.
|
| The flat sheet will dance randomly while falling, and the time
| will be very inconsistent. I don't remember the details, but
| you should repeat the experiment like 20 times to get an idea
| of the distribution. The average changes, but the dispersion is
| a lot higher an impossible to avoid.
|
| [1] I'm not sure which is the correct word in English.
| sophacles wrote:
| I'm putting this paper experiment in my list of things to do
| with my nephew when he's a bit older. Neat idea, thanks!
|
| About the correct word: I have no idea what the best word is,
| but the way you wrote it certainly brought images to my mind
| of various ways I've seen falling debris act. I honestly
| wonder if using the "best word" would have been less useful
| to my comprehension - but I'm in general a big fan of the
| word1/word2/.../wordN way of describing multi-
| faceted/ambiguous/complex statements.
| whoopdedo wrote:
| > I'm not sure which is the correct word in English.
|
| "Flutter", perhaps?
| I_complete_me wrote:
| > I'm not sure which is the correct word in English.
|
| would fall like an autumn leaf
| abcd_f wrote:
| That's your top nitpick across all points presented in this
| survival guide?
| LorenPechtel wrote:
| Hadn't thought of that, it's certainly going to reduce your
| terminal velocity even if it goes vertical as it probably
| would.
| arwhatever wrote:
| "If you go parachuting, and your parachute doesn't open, and you
| friends are all watching you fall, I think a funny gag would be
| to pretend you were swimming."
|
| Deep Thoughts by Jack Handey
| dahart wrote:
| > Let's say your jet blows apart at 35,000 feet. You exit the
| aircraft, and you begin to descend independently. Now what? First
| of all, you're starting off a full mile higher than Everest, so
| after a few gulps of disappointing air you're going to black out.
|
| Not mentioned is the fact that at 35k feet, the average temp is
| around -40 to -55 degrees Celsius. I don't know if it would kill
| you, but you'd probably freeze some skin, and if you try to look
| you might freeze your eyeballs. It will be hard to move muscles
| after sixty seconds of 120mph freezing wind.
|
| I'm curious if the passing out part is true. It certainly might
| be. My experience skydiving is that I would get light headed and
| seeing stars at 18k feet unpressurized, and the instant I jumped
| out of the plane, everything got better. Seemed like the force of
| the air in my face somehow packed all the oxygen I needed. 35k is
| _very_ different from 18k, obviously.
|
| * Oh yeah, and speaking from experience, I know it's hard to see
| straight without wearing goggles when in free fall. I forgot to
| put them on once before jumping. Never forgot again after that.
| interestica wrote:
| >I don't know if it would kill you, but you'd probably freeze
| some skin, and if you try to look you might freeze your
| eyeballs. It will be hard to move muscles after sixty seconds
| of 120mph freezing wind.
|
| https://youtu.be/6SI2V_DbCTw
|
| If you haven't seen it, watch it from beginning.
| dahart wrote:
| Thanks, what a crazy story! I started it, and they mention
| this incident happened at 17k feet, so isn't subject to the
| kind of freezing temps you'd see at cruising altitude, right?
| People skydive from 18k feet all the time. Haven't finished
| yet because it's long, but does it say something later about
| surviving cold at higher altitudes? (Edit I did hear now that
| it was -17C at the start before they dove lower... wild!!)
| LorenPechtel wrote:
| https://www.skybrary.aero/index.php/Time_of_Useful_Conscious...
|
| You have 30-60 seconds at 35k. At 18k you'll feel it but you'll
| be down long before it's serious. (Although if it was
| unpressurized for the climb I wonder how much of the time you
| used up that way.)
|
| Real world data--a guy punched at such altitudes and lost his
| oxygen in the process. Blacked out, came to on the way down.
| Amazing survival--he was supersonic at the time and punched
| without blowing the canopy.
| cecilpl2 wrote:
| > 120 divided by 5 = 24. Not bad! 24 mph is only a bit faster
| than the speed at which experienced parachutists land. There will
| be some bruising and breakage but no loss of consciousness to
| delay your press conference. Just be sure to apportion the
| 120-mph blow in equal fifths. Concentrate!
|
| Sadly this is not how it works. Kinetic energy is proportional to
| the square of velocity, and so if you can equally split the
| impact energy 5 ways, it's as though each impact is at 54mph. A
| bit harder to absorb.
| LorenPechtel wrote:
| And it's not something the untrained person is going to have
| any hope of pulling off. There is a grain of truth in the
| assertion--if the surface hit isn't too hard and the landing
| fall is executed perfectly survival is possible. Done correctly
| the energy is dissipated in breaking a whole bunch of bones but
| the truly vital areas aren't subjected to lethal force.
| dspillett wrote:
| To paraphrase THHGTTG:
|
| What to do if you find yourself falling from a great height:
| consider how lucky you are that life has been kind to you so far.
| If life hasn't been kind to you so far, which is not unlikely
| given your current circumstances, consider how lucky you are that
| it won't be bothering you much longer.
| 14 wrote:
| Feel silly I had to look up what THHGTTG was. The Hitchhiker's
| Guide To The Galaxy
| Fnoord wrote:
| You are Number Six.
| 14 wrote:
| Actually I am Number 14
| sandworm101 wrote:
| Aim for the whale, not the petunias. They are already having a
| worse day than you.
| bryanrasmussen wrote:
| about halfway down remember to shout "so far so good!" in case
| anyone is listening.
| h4waii wrote:
| La Haine? Subtle, I like it.
| tobr wrote:
| And about 90% of the way down, I would suggest "So long, and
| thanks for all the fish!"
| sleavey wrote:
| I wonder why the advice if you're still on a row of seats is to
| ditch it. Whilst heavier, it may also be wider. I guess it's the
| ratio of mass to surface area (x drag coefficient) that matters,
| and if the thing you're attached to's mass-to-surface-area ratio
| is lower, you should keep holding onto it _.
|
| _ As long as holding onto it doesn't result in you orienting your
| body away from presenting the most area to the oncoming air.
| Don't hold onto a beach ball for example.
| Symmetry wrote:
| Given a constant shape and density, terminal velocity goes up
| proportionally to the square root of the length of the object.
| Unless the object your grabbing is noticeably less dense than
| you are, which I'd guess wouldn't be true for the seat row,
| you're better off separated.
| OminousWeapons wrote:
| Naively I would assume that one risk might be the seat itself
| causing you damage upon impact. At those speeds could there be
| a risk of the entire seat coming apart on impact and impaling
| you with metal shards?
| Someone wrote:
| I don't see any advice as to that. FTA:
|
| _"If thus connected, you have some questions to address. Is
| your new conveyance air-worthy? [...] If you choose to go it
| alone"_
|
| Also, even if it is dropping faster, it may be worth it to stay
| in your seat _if you can use it as a crumple zone_
| rozab wrote:
| This article isn't meant to be serious, I don't think.
|
| Juliane Koepcke, one of the only people to survive such a fall,
| did it strapped into a row of seats. And when she landed she
| was in good enough shape to survive 11 days in the Amazon
| rainforest (!!!) and make her own way to safety. So I'd say
| statistically, it's about the best thing you can do.
|
| https://en.wikipedia.org/wiki/Juliane_Koepcke
| stavros wrote:
| > Whilst heavier, it may also be wider
|
| Weight/mass doesn't matter, as all objects of the same shape
| above a certain density fall with the same speed. So literally
| just pick the widest object you can find, no matter how heavy
| it is, and ride it.
| bluGill wrote:
| You want something that will act as a crumple zone and slow
| your final crash. So seats would be better than a wide sheet
| of iron of the same mass. At the last moment (and not before)
| stand on the seat and follow the roll the crash up your body
| advice.
| stavros wrote:
| Yes, but the GP was talking about drag, so I responded to
| that.
| Enginerrrd wrote:
| That's not how that works at all.
|
| Terminal velocity occurs when the drag force balances the
| gravitational force. So F_d = F_g
|
| F_d is proportional to the area of the object and the
| velocity squared.
|
| F_g is proportional to the mass.
|
| So, for constant area, at terminal velocity we have v^2 ~ m
| or v ~ m^(1/2) where "~" denotes a proportional relation.
|
| Thus a heavier object falls at a higher terminal velocity
| than a lighter one.
| stavros wrote:
| Ah, you are right, I was thinking acceleration.
| godshatter wrote:
| If by some chance the row of seats is not spinning wildly and
| is just falling in it's normal (pre-accident) orientation then
| you should see if you're butt is being pressed into the seat or
| if you are lifting up constrained only by your seatbelt. Butt
| into seat, stay. Constrained by seatbelt, unlatch.
| LorenPechtel wrote:
| Why unstrap? Having the seat underneath you gives you a bit
| of crumple and some protection from landing on something
| sticking up. In her case I suspect it had a lot to do with
| her survival--since she came down in rainforest I suspect the
| seat hit a lot of branches.
| dTal wrote:
| Note that your terminal velocity is not an intrinsic
| property, but a consequence of air resistance on your body -
| air resistance you will not be feeling when enveloped by a
| row of airline seats. Even if the seat row has a higher
| terminal velocity than you would by yourself, its wake will
| take you with it.
|
| Which isn't to say you won't feel your seatbelt tugging on
| you. You will likely be straining painfully against it. But
| that's because you'll be tumbling wildly, the entire assembly
| battered and buffeted by huge forces.
| shadowgovt wrote:
| Good summary. It left out the benefits of always wearing a
| Mjolnir Mark VI power armor with an active microfusion core; the
| hydrostatic gel layer and surface-range energy shielding can
| protect the wearer from phenomenal kinetic impacts, while the
| armor-lock system guards the joints and other sensitive anatomic
| structure from contusion or rupture. Plus, the built-in
| transponder will minimize the time for emergency first-response /
| evac forces to locate the crash site and assist in resuscitation
| and vertical recalibration (always oddly necessary in those
| suits; I don't know why they don't just put some glue on that
| vertical toggle switch to keep it from flipping so often).
|
| Don't leave home without it.
| wiradikusuma wrote:
| In summary few things you can do to increase the odds of
| surviving.
|
| I can't help but feeling panic and hopeless if I were in that
| situation because THERE'S NO UNDO BUTTON / CANT SAVE-AND-RELOAD,
| you have to do it right at first attempt! Can slide to forest?
| Whoops I just missed it.
| jmvoodoo wrote:
| As someone with significant skydiving experience, good luck doing
| any of these things your first time out of a plane. Chances are
| you'll end up on your back, spinning out of control. If you are
| lucky you'll end up on your belly, spinning out of control.
|
| If you want to learn how to do any of these things, go to your
| local wind tunnel and practice. Without that practice, you should
| just enjoy the minute or so of spectacular views before you go
| splat.
|
| Also, even with that experience, you'll probably go splat. Best
| case your aorta will disconnect and you'll bleed out after a few
| seconds. This is common even when people are stopped by the
| harness (e.g. by hitting trees). Human body just wasn't designed
| to accelerate (decelerate) that quickly.
| stronglikedan wrote:
| > enjoy the minute or so of spectacular views before you go
| splat
|
| This is what I've always said. The only time I'll skydive is if
| I already find myself falling out of a plane. Then I'll cross
| it off my bucket list as I go splat.
| m3kw9 wrote:
| Or pretend you are superman that is about to thrust himself
| into a planet. Like do the fist thing downwards.
| tomxor wrote:
| :D I have to remember this one. Someone should write an
| accompanying article:
|
| "Awesome or hilarious poses to choose from on your decent
| towards massive and permanent deceleration".
| sleavey wrote:
| I wonder if someone will make a computer game akin to Bridge
| Designer, but for surviving falls. Levels could have various
| objects released along with your body, and various targets on the
| ground to aim for, and you can try to survive.
| xkeysc0re wrote:
| Such a game does exist - check out the Pilotwings series for
| SNES and N64
| tomxor wrote:
| The worlds smallest parachute is 3.25m square [0]
|
| This is only possible because it's behaving like a wing and
| generating lift if you look at the shape closely... probably out
| of luck to find a piece of debris that is going to behave like an
| airfoil well enough, but this parachute user can land with zero
| injuries, if you only want to survive, perhaps some concessions
| can be made, and this made me wonder:
|
| If you found such a flat and light enough piece of material with
| a useful surface area - how best to use it? even if it's not the
| right shape to generate significant lift, there are different
| ways to use it, and one of them causes the smallest terminal
| velocity - the obvious use is directly against the airflow like a
| flat parachute - but would it work better if you tried to convert
| your downward force into a horizontal one by deflecting the air
| into one direction? (like a really bad glider, or those wingman
| suits). My instinct says yes, but without lift I can't explain
| why, I suppose because I can see where the force is going
| (horizontal) rather than just "dissipating" through turbulence.
|
| I suppose at the minimum, by directing the flow to one side you
| provide yourself with significantly more horizontal mobility for
| choice of landing site.
|
| https://www.guinnessworldrecords.com/world-records/88729-sma...
| raxxorrax wrote:
| The usefulness is questionable, but it still is an entertaining
| read.
| davidwritesbugs wrote:
| And you'll be reading it for the rest of your life.
| gumby wrote:
| Make sure you bookmark it so you can consult it at 15,000:feet!
| kwertyoowiyop wrote:
| And mark it for Offline Reading, since your reception will be
| pretty poor until you're closer to the ground.
| jl6 wrote:
| Best to store it in GNU Info format.
|
| https://xkcd.com/912/
| pietromenna wrote:
| done! Is there a way to put an auto reminder to read it just
| a minute before the accident happens?
| sleavey wrote:
| Setting up some trigger to open the page based on your
| phone's accelerometer would probably work.
| kwertyoowiyop wrote:
| IFTTT?
| cjonas wrote:
| The author missed a very important strategy. Look for a
| transition.
|
| If you manage to land on a nice slope, catching the transition
| will vastly reduced the peak force. The angle and composition of
| the slope will determine your outcome. Soft spring snow is
| probably best. Powder snow would have a much lower impact force,
| but most like you'll become deeply embedded and suffocate. Grass,
| shrubs or loose soil would be the next choice. If it's rocky or
| trees terrain you're probably toast
| angrais wrote:
| What do you mean by transition? Like where the snow meets the
| mountain?
| TrainedMonkey wrote:
| I think he means transition between vertical and
| sloped/horizontal surface. Targeting such a landing area
| would be pretty hard.
| daniel_iversen wrote:
| Why on earth does such a simple text-only page not have "Reader
| View" on iOS safari!?
| red_trumpet wrote:
| Probably because each paragraph is a table row :D
| trampi wrote:
| Oh god, I hoped you were kidding. But you were not ...
| daniel_iversen wrote:
| Oh the sweet 90s and early 2000s :-)
| neomantra wrote:
| My father was a survivor of China Airlines Flight 006, which in
| 1985 fell 30,000 feet over 2.5 minutes and corrected tens of
| seconds before impact with the Pacific. The incident was caused
| by human error, but also recovered by the skill of the same
| Captain; after it, the FAA made new guidelines about crew
| schedules and mandatory rest times.
|
| Stephen passed away January 2021 from COVID (but had an amazing
| 85-year life) and I was just reading his diary from the incident.
| The gist:
|
| There was still an hour left before an emergency landing at SFO.
| The cabin was festering with vomit and tears, but there was a
| profound sense of love and connectedness and compassion among
| every passenger. Every one felt touched by a Divine Grace.
|
| However, after a only few hours at the terminal and people could
| finally leave, it was every person for themselves as they
| physically and verbally harassed each over to get to where they
| were going. So quickly back to being selfish humans...
|
| My Mom said she would drive from Los Angeles to get him, but he
| said that if he didn't get on a plane right then, he would never
| be able to fly again. So he courageously flew SFO->LAX right
| away, one of many flights he would continue to take throughout
| his life.
|
| [1] https://en.wikipedia.org/wiki/China_Airlines_Flight_006
| avh02 wrote:
| holy crap - i've read about that flight so many times - it's
| one of the stories that keeps me relatively calm in turbulence*
| (along with the video of the famous 777 wing failure test) -
| they both give me solace in how much a plane is built to
| survive (yet, i read a lot about plane crashes, and also know
| what small things/mistakes/flaws lead to the opposite outcome)
|
| * (obvi unfortunate that it happened and people had to
| experience that)
|
| and sorry to hear about your father.
| logshipper wrote:
| I am somewhat interested in reading about plane crashes and
| such. Are there any books/resources you can recommend to me?
| mardifoufs wrote:
| There's a guy on reddit making a written series on air
| crashes, with articles every Saturday and it's been going
| for a few years now.
|
| https://www.old.reddit.com/r/AdmiralCloudberg/
|
| It's obviously not extremely technical (though a lot more
| than I'd have thought), and it's probably nothing you can't
| get from more in depth websites but it's neatly organized,
| well written and the articles are getting better and
| better. I like that he keeps conjecture to a minimum too
| but still points out what lessons can be learnt from the
| tragedies.
|
| The only thing is that I'd recommend reading it through the
| Medium link he posts in the comments instead of the linked
| imgur albums. It's a much better experience
| randycupertino wrote:
| The youtube video of the guy hangliding which took off
| without him strapped in is pretty incredible. He survived
| by holding on, only ended up breaking his wrist:
| https://www.youtube.com/watch?v=dLBJA8SlH2w
| ohdannyboy wrote:
| If you like documentaries there is a whole genre on Youtube
| that covers air incidents. Lots exist but the ones I follow
| are Mentour Pilot (technical / crew focused analysis from
| an airline pilot), Wonder (more TV style focused on the
| passengers and stories), Air Safety Institute and FlyWire-
| scott perdue (small-time incident analysis geared towards
| educating private pilots).
| avh02 wrote:
| Personally I just go through Wikipedia articles, some are a
| little short on details but will often enough link you to
| more I'm depth information.
|
| I end up just jumping from one article to another through
| the "see also" links and similar accidents
|
| Edit: occasionally you'd also find a podcast episode
| covering a particular crash or documentaries like air crash
| investigation or similar
| interestica wrote:
| More than just the accidents, you can keep up with all the
| random incidents that are reported (and could potentially
| have been worse).
|
| Eg last month "Screwdriver tip left in engine during
| maintenance results in engine failure on take-off"
|
| https://aviation-safety.net/
| e40 wrote:
| _fell 30,000 feet over 2.5 minutes and corrected tens of
| seconds before impact with the Pacific_
|
| What does "corrected tens of seconds before impact" mean here?
| Thanks.
| bombcar wrote:
| If they hadn't leveled out and stopped descending, in a few
| more seconds they would have impacted the Pacific Ocean.
| neomantra wrote:
| Correct, that's what I meant, thanks.
| heliodor wrote:
| "Tens of seconds" versus "a few seconds" is quite
| different in this scenario.
| kaliszad wrote:
| Quite morbid for a Do It Yourself guide ;-)
|
| Fun fact, Vesna [0] from Serbia came down in Srbska (Serbian)
| Kamenice a small village in Czechoslowakia. What a coincidence.
| Btw. there was an article about this incident just this year [1]
| with some pictures.
|
| [0] https://en.wikipedia.org/wiki/Vesna_Vulovi%C4%87
|
| [1] https://zpravy.aktualne.cz/pred-49-lety-roky-teroristicky-
| ut...
| haolez wrote:
| This made me remember a Myth Busters episode where they were
| testing if Indiana Jones could survive a fall from a tall
| building into an awning (happens in one of the movies). They were
| pretty sure that it was impossible, but the crash dummy survived
| with a bruised rib :)
| gonzo41 wrote:
| The life raft was also possible, but it has to be a giant one.
| raxxorrax wrote:
| So did anyone test the nuke and the fridge?
| jackcviers3 wrote:
| Reel Physics concluded from frame analysis that is possible
| [1].
|
| https://youtu.be/foUn_6W9N-Y
| dcchambers wrote:
| I guess we all owe George Lucas an apology for that one.
| short_sells_poo wrote:
| Not the fridge specifically, but there's the famous case of
| the (apocryphally) fastest man made object, which is
| supposedly a large manhole cover that was blasted into
| space by an underground nuclear test detonated in a shaft
| 150m below it: https://www.zmescience.com/science/news-
| science/fastest-manm...
|
| Now obviously the shaft here functioned nearly like a gun
| barrel so the manhole cover could've reached 5-6x the
| escape velocity (according to the scientists), but even
| just being accelerated to 10% of escape velocity in the
| span of milliseconds would've turned the hapless Mr. Jones
| into a fine red paste. Assuming he resided in a metal
| fridge at the time, he would've become what can only be
| described as a flat tin can of pate.
| Rooster61 wrote:
| Hang on, wouldn't this make that manhole cover also the
| furthest manmade object from Earth? Voyager 1, even after
| all of its slingshots, is traveling at about 38k mph.
| That manhole cover is traveling several times faster, and
| was launched decades before Voyager even thought about
| taking off.
|
| Edit: And before anyone mentions the fact that Brownlee's
| calculation did not take into consideration atmospheric
| forces (which probably disintegrated the cap before it
| got to space), at least some molecules of the cap
| probably did go that far, and would still remain the
| fastest, and possibly furthest object from Earth
| (assuming it did not get caught in the gravity well of
| another object on its way out).
| short_sells_poo wrote:
| You are probably right. Although I'd assume that given
| the cover was very close to the epicenter of the
| detonation, it would've been almost instantly vaporized
| and turned into plasma even before air resistance
| would've done the job.
| LorenPechtel wrote:
| The manhole cover *did* survive the detonation--it's
| visible one *one* frame of film. Unfortunately, only one
| so there's no way to figure out it's velocity. All they
| can conclude is a minimum velocity based on the fact that
| it's not on two frames.
|
| There have been objects placed even closer to nukes that
| have survived and note Project Orion--not only objects
| near a bomb, but the plan was to put a crew near bombs.
| Obviously, they would catch some radiation but that's
| going to happen anyway in deep space flight and back then
| they didn't realize the cancer risk.
|
| The basic physics of protecting the ship and crew from
| the nearby detonations is clear. There is some question
| about whether it could actually be used to take off from
| Earth, though--it's not so certain if the pusher plate
| could be kept cool enough during the ride to orbit. Deep
| space doesn't require such sustained thrust, it's no
| problem. EMP from near-Earth detonations is a big issue,
| though.
| LorenPechtel wrote:
| Why would any molecules make it out of the atmosphere?
| The mean free path at low altitude is very short.
| jayess wrote:
| I'm reminded of the story of the girl who survived, somehow, a
| fall from a plane in the Amazon while strapped in to her seat.
| The theory is that the row seats spun like one of those seed pods
| and slowed her down when hitting some trees.
|
| https://www.nytimes.com/2021/06/18/science/koepcke-diller-pa...
|
| I've often thought about this topic since the explosive
| decompression of Malaysia flight 17 over Ukraine. The anti-
| aircraft missile apparently caused an instant, explosive
| decompression of the plane. Assuming you weren't hit by one of
| the projectiles, you would have found yourself suddenly free-
| falling.
| LorenPechtel wrote:
| I don't even think it would matter if it spun. She went into
| trees. Lighter tree branches are about your ideal landing.
|
| There is one case of a guy who apparently hit a pine tree
| perfectly, then a snow bank *and walked away*, with no injuries
| that were obviously from the landing. No aiming or anything,
| pure luck. (The injury situation is uncertain because he was
| injured when he jumped and hadn't had time to take stock of his
| injuries.)
| yardie wrote:
| > Thirty feet is the cutoff for fatality in a fall. That is, most
| who fall from thirty feet or higher die.
|
| And to think my friends and I used to jump off a 2nd story
| balcony for shits and giggles. Even after one of us broke an arm
| doing it. Just 2/3 of the way towards certain death!
| jacquesm wrote:
| At a guess you were a lot lighter back then. The speed of
| impact would be the same but the total energy to dissipate a
| fraction of what it would be today. So better not to try that
| particular trick again.
| Symmetry wrote:
| "You can drop a mouse down a thousand-yard mine shaft and, on
| arriving at the bottom, it gets a slight shock and walks
| away. A rat is killed, a man is broken, a horse splashes."
| yardie wrote:
| Oh to have the resiliance and cartilage of a teenage boy!
| Pretty sure if I did that those stunts at my age I'd win a
| Darwin award.
| jacquesm wrote:
| I used that particular trick as my escape route during tag.
| We would play on this structure made from wooden rolls, it
| spiraled upwards, about 3.5 meters high at the top and I
| found that I could easily jump down as long as I bent
| through my knees upon landing and touched down afterwards
| with my arms. Magic :)
| LorenPechtel wrote:
| Yup. As small kids we would jump from a tree that I wouldn't
| consider doing as an adult. I don't think terminal velocity
| is important at that scale but square-cube certainly is. You
| landed pretty hard but I never heard of anyone getting hurt.
| aerique wrote:
| Shouldn't the speed ramp up quite a bit in that last 1/3?
| wyager wrote:
| Less than 1/3rd of the velocity will come from the last 1/3rd
| of the fall.
|
| If you're going X speed after 2 stories, you'd be going
| sqrt(3/2)X = 1.22X after the last 1/3rd, ignoring drag.
|
| Energy increases linearly with fall height though, and energy
| is probably what mostly kills you. (Again ignoring drag.)
| ReactiveJelly wrote:
| Ah, because after that first 2/3rds, you're going too fast
| to have time to accelerate much more.
| DuskStar wrote:
| The first quarter of the fall distance takes half of the
| time.
| gibspaulding wrote:
| Wouldn't a second story balcony be in line with the floor of
| the second story, not the roof, so ~10 or 12', not 20.
| machawinka wrote:
| Seriously, this reminds me of a question I have always being
| afraid to ask due to morality reasons. Was there any chance for
| the 911 jumpers to survive in any way, no matter how minimal?
| LorenPechtel wrote:
| Hard surface landing--nope, nobody has ever survived free fall
| into something hard. No survival unless they could rig some
| sort of parachute.
| rob74 wrote:
| Not to detract from another great "What If?" article, but I think
| the biggest gotcha is right at the beginning:
|
| > _Let 's say your jet blows apart at 35,000 feet. You exit the
| aircraft, and you begin to descend independently._
|
| As far as I know, most airplanes don't do that nowadays. They
| tend to descend more or less in one piece (or several big pieces)
| to ground level and "blow apart" there. If they do blow apart at
| high altitude, it's probably due to an explosion which is apt to
| drastically reduce the chances of passengers being conscious (or
| alive) during the free-fall phase.
| LorenPechtel wrote:
| Terrorist bombs normally do not actually blow up planes.
| Rather, a successful bombing damages the skin enough that the
| wind shreds the plane. Thus it's quite possible to survive the
| bombing. Surviving the plane disintegrating around you,
| though...
| simonebrunozzi wrote:
| > As you go down 15,000 feet, you can also go sideways two-thirds
| of that distance--that's two miles! Choose your landing zone. You
| be the boss.
|
| Pretty interesting. I wouldn't have imagined you could do this.
| abcd_f wrote:
| Probably depends on whether you are in boxers or in a speedo.
| KineticLensman wrote:
| Tracking [0] is frequently used by skydivers after close
| freefall formation manoeuvring ('relative work') to increase
| their horizontal separation before deploying their canopies.
|
| https://en.wikipedia.org/wiki/Tracking_(skydiving)
| huseyinkeles wrote:
| A very entertaining video about the subject:
| https://www.youtube.com/watch?v=dy5xLVx2NGY
| diffuse_l wrote:
| Reminds me of this: https://youtu.be/oZIzreiseMk
|
| I'm not sure if their analysis is accurate, but it's sure fun to
| watch :)
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