The Glade 4.0

{Crap, I hate this. I posted this about an hour ago, but I just hit Submit and went to eat dinner. Came back, and it was waiting for my response, since others had posted while I was typing. Kind of less relevant now.}

Do you all really think the difference is so great between what the guy did in 1960 and what this guy proposes to do? Kittinger hit 614 mph, dressed in layers of clothing and a pressure suit. This guy has the advantage of 50 years of technology, and the empirical evidence that it's possible to do this and survive.

Plus, that article in the OP is really poorly written. The guy's gonna be going down head first (if the accompanying photos are any indication), yet ""for Felix it's in an almost standing position." I think a "prone" position would be a better description.

And, the writer has apparently never heard of Kittinger: "No one else has tried to use a pressurized suit as Baumgartner plans to; they're typically used to protect jet pilots who eject from their seats -- not skydivers who plan to travel faster than sound." Kittinger used a pressure suit, albeit in a sitting position. What's odd is that Kittinger is advising Baumgartner on this jump, according to the Wikipedia article on Kittinger.

The real novelty of this jump seems to be that he'll be going down head first, really. As for exceeding the speed of sound, people thought that Chuck Yeager's head was gonna explode when he attempted to crack the sound barrier. Heck, people in the early 1900s thought that it would be physically impossible for a human to withstand the shock of going 100 mph in a car. This guy will be fine.

_________________
This cold and dark tormented hell
Is all I`ll ever know
So when you get to heaven
May the devil be the judge

I hope something unexpected and cool happens when he hits the sound barrier.

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Ron Paul 2012

Chuck Yeager was inside a box, and was not creating shock waves with his own body. There is a physical difference between what he did, and what this jumper is trying to do.

You might think of it as a cup of coffee sitting in a room. The ambient temperature of the room is terminal velocity, while the cup of coffee is our diver. Any adult should know that the coffee cup will cool down until it's the same temperature as the rest of the room - a diver's speed works the same way.

Terminal velocity is a phenomenon that arises from moving through a fluid environment. (Both gases and liquids qualify as fluids). As you move through a fluid, there are particles striking you, creating mostly elastic collisions that rob you of momentum. Each individual particle doesn't steal much, but there are a lot of particles. The faster you move, the more particles you run into. What this means is that the air resistance you encounter increases with your speed.

There is also friction between your body and the surrounding environment, although friction gets sort of wacky. It increases as your speed increases, but there is also a sharp drop-off at high temperatures as the boundary layer of your body behaves more like a liquid than a solid.

For an object in free-fall, there is only one force causing them to go faster - gravity.

At this point, I feel obligated to bring up the word "decelerate." This is not a useful word. It doesn't actually describe what is happening. We sometimes use it in our day to day language because we think accelerate means "speed up" and that "slow down" should have a different prefix - this is false, despite definitions the two words have in the dictionary. (Remember, dictionaries are written by English majors). Acceleration is defined as the rate of change for velocity with respect to time, and is a vector quantity having both a size and a direction. An object that is slowing down is still accelerating, it just has an acceleration that's pointing in a direction opposite it's velocity. This is an important distinction because acceleration is caused by forces.

Terminal velocity is the equilibrium solution for the speed at which all of the forces (friction, air resistance, and gravity) on your body are equal to zero. If you are above terminal velocity, friction and air resistance are stronger than gravity. There is a net force pushing up, which creates an acceleration upward. If you are below terminal velocity, gravity is stronger, there is a net force pulling down, and thus, an acceleration downward.

Because the atmosphere is thinner at very high altitudes, there is less air resistance regardless of your speed, and therefore a higher terminal velocity. As you plummet toward the Earth, the air gets thicker. Terminal velocity goes down, because now there is more air pushing against you and it's easier for air resistance to overcome gravity. The diver will be slowing down almost the whole way in. This is a good thing, because if he opens his parachute going 700mph, it's likely to rip apart when it creates extra drag for him.

_________________
Buckle your pants or they might fall down.

I would imagine he has some sort of multi-stage chute deployment so he could theoretically halt himself from speeds an ordinary chute would provide breakneck acceleration.

_________________
"It's real, grew up in trife life, the times of white lines
The hype vice, murderous nighttimes and knife fights invite crimes" - Nasir Jones

I don't know if this is an awesome pun or not... :p

I think the Apollo command modules actually did have multi-stage chutes.

After reading about the equilibrium of forces that makes more sense but obviously if you're going above a certain speed in the first place the drag from air resistance could never slow you to terminal velocity before you hit the ground.. hence the enormous meteor craters in some places.

Obviously the diver is nowhere near as fast as the meteor, but...

_________________
"Hysterical children shrieking about right-wing anything need to go sit in the corner and be quiet while the adults are talking."

I just thought of something. Freefall velocity is largely a function of drag, because gravitational force is a function of the product of the masses and the square of the distance of seperation. Because the mass of the earth is so gargantuan, we can basically neglect the mass of the object being attracted as having any difference since the mass of even the largest madmade structure compared to a single person is negligible when you compare it to the mass of Earth. In addition, the distance of separation (i.e. altitude of the falling object) has a negligible impact at any made-made vehicle or suit that is built to operate within the atmosphere - the distance is simply not very great.

So that means the drag (if we ignore compressibility, which is a decent assumption, but not great since this suit wants to attain near sonic velocity) of the parachute being deployed is only a function of fall velocity and air density. The other factors are relatively constant for a given parachute.

At higher altitudes, higher speeds are possible, because the drag is lower from lower atmospheric density. However, that means the chute's drag is lower too, which means it doesn't exert nearly as much acceleration (decceleration). This relationship probably isn't perfectly offsetting, but it indicates a parachute might be more valid for a greater range of altitudes and entry/re-entry velocities that initial intuition might suggest.

I am willing bet bank that Aerospace engineers have some sort of special relationship predetermined describing this performance metric given you can describe the chute's aerodynamic characteristics, which says how constant a parachute retardation is over a range of altitudes.

_________________
"It's real, grew up in trife life, the times of white lines
The hype vice, murderous nighttimes and knife fights invite crimes" - Nasir Jones

It is possible to conceptualize such a speed. It would depend on the distance to the ground, and the shape and density of the falling object.

A few things to remember:

Air resistance is proportional to the square of your velocity. Near the speed of sound, you would have an absolutely massive upward acceleration because the force pushing you up is very big. The faster you're going, the faster you slow down. Actually, the entire function of a parachute is to lower your terminal velocity (which causes you to slow down that much faster).

Meteors don't have to be going as fast as you might think to make those enormous craters. Terminal velocity for a human being is still pretty fast, and a big rock that hits the ground at that speed is going to be impressive. They can also have a higher terminal velocity than a human being due to being more dense and more aerodynamic (assuming a person falling spread-eagled, rather than diving).

Meteors are also responsible for the first documented thermo-nuclear explosions on Earth. Sometimes bits of meteor get a boost part-way down when the whole thing explodes.

_________________
Buckle your pants or they might fall down.

I don't think anyone was discounting the earlier jumps, and you certainly don't need to do that to appreciate the balls this guy has, even with 50 years of tech advancement.

Personally, I think the hard part would be the ride up... sitting alone in a gondola, strapped to the bottom of a weather balloon, going up 23 miles. I don't know the rate of climb of these things, but I'm guessing he will have more than a few minutes to think about opening the door and looking from the edge of space, and jumping...

Oh, no, didn't mean to deny the ballsiness of this jump at all. It's just that we're talking about him getting his arms ripped off, etc., when I think a bunch of those questions have been answered. But, maybe it's all just tongue in cheek. Or, maybe there is a quantitative difference between the two, but I'm not getting it from that article.

But, yeah, given that he's only the second guy in history to give this a shot, yeah, I'd say it's pretty ballsy.

_________________
This cold and dark tormented hell
Is all I`ll ever know
So when you get to heaven
May the devil be the judge

_________________
Buckle your pants or they might fall down.

Sorry, missed that the first time. I wasn't comparing him and Yeager; I was comparing the fear of this guy getting injured breaking the speed of sound, and fears that people had early in this century about the effects of breaking various speed milestones. I guess I see what you're saying, but still, Yeager was in a pressurized cabin, right? And this guy is using a pressurized suit ... I dunno, just finding it hard to get worked up about him getting injured just by breaking the sound barrier.

_________________
This cold and dark tormented hell
Is all I`ll ever know
So when you get to heaven
May the devil be the judge

The cabin of the X-1 was a rigid structure, so Yeager's body wasn't exposed directly to the forces of the air. A suit isn't rigid; his body will be far more exposed to the effects of the air.

_________________
"Hysterical children shrieking about right-wing anything need to go sit in the corner and be quiet while the adults are talking."