If I were to jump from an altitude of 10,000 ft and streamline my body for maximum speed I read that I might reach about 220 mph. Would that be enough speed to generate sufficient lift if I were to change my body position for maximum drag, to break the fall more than if I just jumped and tried to maintain maximum drag the entire trip down?
Is your question the same as whether a sky diver who goes at top speed and then pulls the parachute will go slower than a sky diver who pulls the parachute right away?
I think the answer is no – an object that’s falling fast and then changes its wind resistance will slow down to the terminal velocity for that new resistance. That is, I don’t think terminal velocity for a given shape/density/cross-section is dependent upon the previous velocity.
If anything, maybe you might end up going marginally faster if you start out really fast, since you may only asymptotically reach terminal velocity?
I was wondering if the added speed might be enough to create lift, theoretically if timed properly for a softer landing with a less severe angle of impact.
Some kind of squirrel suit idea, I guess. I don’t really know anything about those, but I’m pretty sure they deploy a parachute at the end. Hopefully someone with more knowledge will chime in.
What I expect you’re trying to do is a flare–gain speed so that you have enough lift to maintain altitude (which you want to be 0), and then progressively increase your angle of attack until you stall and are forced to land. You have negligible vertical velocity and probably a high amount of remaining horizontal velocity.
Apparently, people in wingsuits can flare to some extent. I’d be surprised if a human in ordinary clothes could pull it off. And you still have the problem of the horizontal velocity, though maybe you could land on an iced-over lake or something to bleed off the speed.
Human bodies can create lift. Watch any ski jumper. And yeah, skydivers assume the same position as ski jumpers when they want to ‘fly’. But that’s just maximizing downrange distance a bit. A human body can’t create enough lift to substantially slow them down more than terminal velocity. Even wingsuited skydivers are plummeting towards the ground at 90mph. They can just do more lateral traversing while plummeting, and plummet just a little bit slower.
My guess is that if you were going 220 and tried to assume a shape for maximum lift you’d eventually slow down to terminal velocity for your lifting shape, and that’s about it. I don’t think there’s enough lift or reserve of energy to temporarily halt your descent.
You can create some lift with just your body. Your descent will change from totally vertical to slightly horizontal leaving a slightly different mark on the ground when you die from the impact.
That’s not the whole story, though. If you gain speed in advance, you can then use that excess lift to reduce vertical velocity below the steady-state case–possibly even to zero.
That’s why airplanes can land gently even with no engine thrust. They arrive at zero altitude with horizontal velocity above their stall speed. They then shed this velocity to halt their descent, and either land then, or more likely shed even more speed, further increasing their angle of attack. At some point they decide to land, or are forced to as the plane stalls (in small planes, often considered the ideal outcome).
You can’t slow the rate of descent of a human body unaided to that extent in any real world situation.
I agree, but it’s a matter of degree. It can (possibly) be done in a wingsuit. But what about Hammer pants?
Then you deserve to die.
It’s not commonly known that the wingsuit was invented after a passenger survived a forcible ejection from a plane for crimes against fashion.
Wheres the Like button?
Lift is by definition a force that acts in a direction perpendicular to your path of travel. Skydivers who are falling straight down are not creating lift, they are creating drag. But skydivers certainly can create lift; it’s how they are able to move laterally during their freefall, to the point where they can steer clear of each other and/or carefully come together to make interesting formations. This page says that skilled skydivers without a wingsuit can achieve a glide ratio of 1:1 - that is, they can move one foot horizontally for every foot of altitude they fall:
By tracking in this manner, you can reduce your vertical speed from the typical 120 MPH seen during face-down freefall to 90 MPH. That’s roughly the same vertical speed that suicidal people achieve when they jump from the Golden Gate Bridge; most of these jumpers die from blunt trauma, not from drowning.
Bottom line, a 1:1 glideslope won’t save you from almost-certain death.
Suppose that instead of a sustained 1:1 glide, you adopt a head-down posture to build your speed up to ~200 MPH, and then use this speed to try to pull out of the dive and achieve a glideslope shallower than 1:1. The challenge here is that you need to create a lot more lift during the transition from vertical freefall to gliding, same as a plane that’s trying to pull out of a dive. During that period, you’ll also be creating a lot more drag, bleeding off your speed along the way. Difficult to say for sure, but I’d wager that by the time you achieved a stable glide angle, you’d have bled away pretty much all of your excess speed and achieved nothing much better than the aforementioned 1:1 glideslope.
Note also that in gliding, you attain a pretty substantial horizontal velocity. a skydiver on a 1:1 glideslope has 90 MPH of vertical speed, but also 90 MPH of horizontal speed. Just for the sake of discussion, let’s assume you could flare to a very shallow glideslope while preserving your total speed of ~120 MPH. Unless you’ve got wheels and a glassy smooth runway to set down on, you’re going to tumble violently as soon as you touch down. Motorcycle racers on tracks survive crashes at these speeds, but they’re wearing full leathers, body armor, and a full-face helmet, and the track has been cleared of obstacles they might otherwise collide with. Skydivers wear cordura suits with no armor; if they wear a helmet, it’s much lighter and less sturdy than a motorcycle helmet. I would guess 120 MPH of horizontal speed, even with zero vertical speed at touchdown, is very probably fatal for a skydiver.
For comparison, wingsuits enable a glide ratio of 3:1. The Wikipedia article claims that a vertical speed of 25 MPH has been achieved with a wingsuit (though there’s no cite), but even this is likely to be devastating; it’s the equivalent of falling face-down from a height of 20 feet, and that doesn’t even consider the additional effects of the 60-MPH horizontal velocity.
Or just aim for the net.
@Machine_Elf: Great post overall there. Thank you.
As to this bit:
That suggests to me that a wingsuit landing into water would be readily survivable and maybe a coinflip on injured vs uninjured. Not much worse than a speed-waterskier crashing.
My two cents on the OP:
Ultimately all talk of flaring a landing at the end assumes / requires that you can create enough lift at whatever speed to more than support your weight. That is, enough lift to climb, trading decreasing airspeed for increasing altitude.
A wing-suited human doesn’t come close. A human under a conventional sport parachute gets close albeit only very briefly. A human Paragliding - Wikipedia can do that readily. But that is the least size and sophistication of wing necessary to pull off a complete flare.
Holy christ. From his wiki page, people do like to do crazy things.
Although several news articles headlines describe Aikins achievement by focusing on the fact that he jumped and went to freefall without parachute, many others have jumped from aircraft without having a parachute when they departed the plane – they were either handed a parachute by a fellow jumper while in freefall or maneuvered to a container carrying a parachute, with first successes dating back to 1965.[19] Others have jumped out of an aircraft and returned to the same or another aircraft without making use of parachute.[20][21]
There is no human idea so stupid that some other human can’t be persuaded to try it. Or so stupid that no other humans will want to try it for thrills, lulz, or fame.
Before you try wingsuit flying check out this list of fatalities. Remember how your mother asked “If everybody was jumping off a bridge would you jump too?”.