Supersonic Freefall

[C]

Where did they get their 1000mph from? He plans to go supersonic, not 1000mph jusdging by the article...

...or is that the level of intelligence on needs to work for the Telegraph nowadays. Research ability = 0.

I'd be surprised if they've planned to go much faster than 500mph. Looking at the weather the Saskatchewan plains look relatively cool compared to the rest of the North American continent, which again would lower the speed of sound.

[born_2_fly]

If it is just him in a suit jumping from the balloon, I don't see how he thinks he can achieve supersonic velocity.

A falling object has a terminal velocity, when the forces acting apon it are balanced the the object is neither accelerating, nor decelerating. I always believed the maximum Terminal velocity for a Human was around 54-56 m/s.

As far as I know, there is nothing anyone can do to increase their terminal velocity, as it depends on the mass of the object falling, and so although you can take steps to ensure you achieve your terminal velocity (more aerodynamic) but unless you increase your mass or introduce propulsion you cannot.

Am I missing something here?  :-?

[Xyn_Air]

If it is just him in a suit jumping from the balloon, I don't see how he thinks he can achieve supersonic velocity.

A falling object has a terminal velocity, when the forces acting apon it are balanced the the object is neither accelerating, nor decelerating. I always believed the maximum Terminal velocity for a Human was around 54-56 m/s.

As far as I know, there is nothing anyone can do to increase their terminal velocity, as it depends on the mass of the object falling, and so although you can take steps to ensure you achieve your terminal velocity (more aerodynamic) but unless you increase your mass or introduce propulsion you cannot.

Am I missing something here? :-?

Only the human will to strive towards ever more fantastic ways to remove oneself from the gene pool.  ;)

[Hagar]

[quote]Am I missing something here?

[born_2_fly]

Am I missing something here?  :-?

I think the altitude has something to do with it.

I originally thought the same as you but it has apparently been done before.

Hmm I suppose the air density would play a factor.

I'm just wondering how he is going to slow down, as any sudden movements at the speed would be bone shattering, even moving to the horizontal from the vertical must have some effect when he head is moved from the vertically down position.

Only the human will to strive towards ever more fantastic ways to remove oneself from the gene pool.  

LOL!

"Only two things are infinite, Human Stupidity and the Universe, and I'm not too sure about the Universe"  :P

A cookie for whoever can tell me said that?  :)

[Hagar]

I'm just wondering how he is going to slow down, as any sudden movements at the speed would be bone shattering, even moving to the horizontal from the vertical must have some effect when he head is moved from the vertically down position.

Did you read the article from my PS?

I don't see anywhere in that Daily Telegraph report that Mr Fournier will be falling head first.  According to reports Capt Kittinger did it in the sitting position to simulate ejecting from aircraft at extremely high altitudes.

[born_2_fly]

I'm just wondering how he is going to slow down, as any sudden movements at the speed would be bone shattering, even moving to the horizontal from the vertical must have some effect when he head is moved from the vertically down position.

Did you read the article from my PS?

I don't see anywhere in that Daily Telegraph report that Mr Fournier will be falling head first.  According to reports Capt Kittinger did it in the sitting position to simulate ejecting from aircraft at extremely high altitudes.

Ahh true, sorry Hagar, I missed that PS  :-[

I suppose the air density must be a huge factor if he managed to reach such speeds in a sitting position. I assumed (wrongly) that he might have gone head first to be more Aerodynamic.

[Hagar]

I'm just wondering how he is going to slow down, as any sudden movements at the speed would be bone shattering, even moving to the horizontal from the vertical must have some effect when he head is moved from the vertically down position.

Did you read the article from my PS?

I don't see anywhere in that Daily Telegraph report that Mr Fournier will be falling head first.

[beaky]

Fozzer is right- mach is dependent on  air pressure as well as velocity (because it references the velocity relative to the speed of sound in the medium in question), so even in Kittinger's case, the freefall cannot really be described as "supersonic". At the moment that velocity was recorded, there wasn't enough air present for it to really be "+1.0 Mach", because there wasn't enough air for sound waves to propogate.
And there would be no sonic boom. Neither of these jumpers, had they been foolish enough to remove a glove or the helmet, would have felt any relative wind on their skin, despite their tremendous velocity (although the exposed flesh would freeze-dry almost instantly). As they fell into thicker air, they immediately decelerated. The fastest relative wind a free-falling skydiver could ever feel is a little over the human body's "terminal velocity", or  about 200 mph, if they tucked their arms in to dive in freefall. In thinner air, the relative wind is lower, although the atual velocity, say as recorded by an inertial-type instrument, is the same.  That's why airplanes show lower and lower IAS at a given power setting as altitude increases, even if their groundspeed is the same or higher.
What we call "The speed of sound" (@ 770 mph) is the velocity of sound waves in typical air of standard pressure and humidity at sea level.

http://en.wikipedia.org/wiki/Mach_number

Not that these jumps are not impressive... but if you want to consider actually going transonic without a vehicle to protect you- that is, with a relative wind of over 700mph hitting your unprotected body, read the story of this pilot, who punched out of an F-100 in a full-power dive with an IAS of +1 Mach at about 6,000 feet MSL:



http://www.time.com/time/magazine/artic ... -1,00.html

[Ravang]

I can just picture it now.  ;D

So can I...on he's way down a 747 hits him, the pilot says...He jumped out in front of me , who has the right-of-way the 361276 pound plane or a 170 pound man :-/

[ozzy72]

Speaking as a reasonably experienced parachutist (did my first jump 17 years ago ) and keen aviation enthusiast I can confidently say that in the upper levels of the atmosphere he can indeed go supersonic. In the lower levels as air density increases he will be naturally slowed some.
The terminal velocity of 120 Mph is often quoted and is WRONG! There are a group known as the Lawn Darts who do terminal dive speeds from aircraft at 14,000 feet of up to 320 Mph! They use special rubber suits and all their kit is aerodynamic in an attempt to increase speed. They're mad (and this is me saying it!) but they've proved that the often quoted stuff is journalistic BS. A normal jumper in standard kit and in the frog position will reach a terminal speed of 120-140 Mph but that isn't THE limit

[Hagar]

Not that these jumps are not impressive... but if you want to consider actually going transonic without a vehicle to protect you- that is, with a relative wind of over 700mph hitting your unprotected body, read the story of this pilot, who punched out of an F-100 in a full-power dive with an IAS of +1 Mach at about 6,000 feet MSL:



http://www.time.com/time/magazine/artic ... -1,00.html

That reminds me. The late 'Ben' Gunn, chief test pilot for Boulton Paul Aircraft Ltd, held the world record for the highest "live" ejection for many years. On 28 August 1952, the tiny P.120 research delta broke up round him as he was approaching Mach 1.0 at high altitude. http://en.wikipedia.org/wiki/Boulton_Paul_P.120

Like many ejectees he injured his back & was no longer able to fly high performance aircraft. After a stint as test pilot for Beagle Aircraft during the 1960s he became airport manager at Shoreham Airport.

[Mushroom_Farmer]

So what is the approximate maximum altitude or minimum air density, and speed needed, to create a sonic wave strong enough to create a sonic boom?

[beaky]

So what is the approximate maximum altitude or minimum air density, and speed needed, to create a sonic wave strong enough to create a sonic boom?

That is an excellent question. I know sound pretty well, but that's out there... I'd imagine there's a theoretical limit for sound-friendly air density, but there would be many variables, including the volume of air involved in the shock wave.

[beaky]

Speaking as a reasonably experienced parachutist (did my first jump 17 years ago ) and keen aviation enthusiast I can confidently say that in the upper levels of the atmosphere he can indeed go supersonic. In the lower levels as air density increases he will be naturally slowed some.
The terminal velocity of 120 Mph is often quoted and is WRONG! There are a group known as the Lawn Darts who do terminal dive speeds from aircraft at 14,000 feet of up to 320 Mph! They use special rubber suits and all their kit is aerodynamic in an attempt to increase speed. They're mad (and this is me saying it!) but they've proved that the often quoted stuff is journalistic BS. A normal jumper in standard kit and in the frog position will reach a terminal speed of 120-140 Mph but that isn't THE limit

OK, I'm all wet on the terminal velocity thing.
 But I only said "not supersonic" because there seemed to be some notion that these upper-stratospheric freefallers  experience transonic buffeting and the release of pressure that creates the "boom" , but they don't, because there just ain't enough air around them when they reach that velocity. The balloons used at those altitudes are barley lifting, even with pure helium at, i guess, ambient pressure.
so in other words, if some lunatic in a spacesuit reaches a velocity of over 760 mph while falling from 100, 000 feet, he does not make a sound, even if someone is there to hear it.

This video footage, from the gondola and his pack, gives a pretty good idea of just how little air there is up there (and how fast he fell!! Whoa!!). And no, he diodn't go surfing afterwards; no idea what that's doing there.

http://www.youtube.com/watch?v=9MkB6NkQ ... ed&search=

Assuming standard conditions, air density is at about 50% of sea level pressure (which is 1000 millibars, or about 15 lbs./sq. in.) at 18,000 feet, and by the time you're at 100,000 feet, the pressure is about 1% of standard sea level pressure (about 10 millibars, or .15 lbs/ sq. in.). Not sure how far apart the various gas molecules are at that pressure, but you could probably catch some in a gallon bucket and easily count them, if you could see them.  ;)
I could be wrong, but I don't think even a man-sized transonic shock wave would sound like much of anything in such conditions, and I don't think the jumper would notice the pressure buildup at all.

I don't see the point in referencing the speed of sound when describing acceleration in near-vacuum, that's all. Nobody uses Mach numbers to describe orbital velocities, for example... although sometimes the terminology is used to describe the speed of spacecraft and missiles re-entering the Earth's atmosphere (once they reach the lower stratosphere).

 I'm pretty familiar with Kittinger's account of his jump, and if I remember it right, he said he experienced no sensation of speed at all at his highest velocity, and certainly no transonic buffeting. But as he looked up briefly, he was astounded at how rapidly the balloon was receding from view as he fell... must have been quite a ride!!  

As for Fournier: good luck to him, and I hope he brings a camera!!