winds in access of 300mph???

[potatoman 0]

I am busy building a hot air balloon, and came across a website talking about Jet Streams(winds) between 6 and 9 miles AGL. Wondering if anybody has done a HaLo jump through heavy jet stream, and what was the effect? To me, terminal is not even close to 300mph, so would you be freefalling at say a 45degree angle?

http://www.pbs.org/wgbh/nova/balloon/science/jetstream.html

You have the right to your opinion, and I have the right to tell you how Fu***** stupid it is.
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[CSpenceFLY 1]

If you survived the transition from one airmass to another I think you could track and gain altitude. My initial thought is that going from one air mass to another you would suffer broken limbs or worst.

[denete 2]

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My initial thought is that going from one air mass to another you would suffer broken limbs or worst.

Explain please.

Do you mean that the "air mass" you are talking about has rigid boundaries? There's only one place that I can think of where there is anything close to a rigid boundary and it's around 0' AGL. But even that boundary is not rigid. It's just a point where the neighboring mass is not fluid (or easily influenced by the air current). Bodies of water come in second (more easily influenced).

SCR #14809

"our attitude is the thing most capable of keeping us safe"
(look, grab, look, grab, peel, punch, punch, arch)

[potatoman 0]

rigid? The only part where it would be rigid is the exit, but should not be significantly worse than normal exit, more transition from forward to downward, and in this case forward to sideways, or the way the stream is pushing.

You have the right to your opinion, and I have the right to tell you how Fu***** stupid it is.
Davelepka - "This isn't an x-box, or a Chevy truck forum"
Whatever you do, don't listen to ChrisD.

[denete 2]

Get a really fast plane and you can do a downwind jump run.

SCR #14809

"our attitude is the thing most capable of keeping us safe"
(look, grab, look, grab, peel, punch, punch, arch)

[kevinwhelan 0]

Wouldn't it all be the same? wouldn't the plane be going at the same speed relative to the air around it regardless of what that air is doing, and the same for a person in freefall. no???

"be honest with yourself. Why do I want to go smaller? It is not going to make my penis longer." ~Brian Germain, on downsizing

[jakee 1,254]

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If you survived the transition from one airmass to another I think you could track and gain altitude. My initial thought is that going from one air mass to another you would suffer broken limbs or worst.

Huh?

Do you want to have an ideagasm?

[Andrewwhyte 1]

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If you survived the transition from one air mass to another I think you could track and gain altitude. My initial thought is that going from one air mass to another you would suffer broken limbs or worst.

The term is wind shear. It can tear aircraft apart, but they are crossing the boundary at very slow vertical speeds. A freefaller on the other hand would be less susceptible to differential wind speeds across their body, but would still be susceptible to a delta V of more than 150 mph over a fraction of a second. The big problem is differential reactions to the new wind speed by different parts of the body, i.e. the head will change speed slower than the torso. I think the probability for injury would be high.
This is based upon the assumption that the boundary region is less than 200 ft thick. I don't know whether that is true or not.

[riggerrob 558]

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Wouldn't it all be the same? wouldn't the plane be going at the same speed relative to the air around it regardless of what that air is doing, and the same for a person in freefall. no???

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Correct.

However, your explanation is not nearly as exciting as the original poster hoped for.
Hee!
Hee!

[sundevil777 93]

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My initial thought is that going from one air mass to another you would suffer broken limbs or worst.

Explain please.

Do you mean that the "air mass" you are talking about has rigid boundaries? There's only one place that I can think of where there is anything close to a rigid boundary and it's around 0' AGL. But even that boundary is not rigid. It's just a point where the neighboring mass is not fluid (or easily influenced by the air current). Bodies of water come in second (more easily influenced).

It is common for pilots to get injured during ejection at high speeds. Those injuries are not only due to the acceleration of the seat itself, they are also from the exposure to a sudden high wind. I wonder at what airspeed those type of injuries start happening.

People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am

[billvon 2,381]

> Wondering if anybody has done a HaLo jump through heavy jet
>stream, and what was the effect?

There would be no effect. You'd move pretty fast over the ground, but it would feel like normal freefall.

[kelpdiver 2]

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My initial thought is that going from one air mass to another you would suffer broken limbs or worst.

Explain please.

Do you mean that the "air mass" you are talking about has rigid boundaries? There's only one place that I can think of where there is anything close to a rigid boundary and it's around 0' AGL. But even that boundary is not rigid. It's just a point where the neighboring mass is not fluid (or easily influenced by the air current). Bodies of water come in second (more easily influenced).

My first encounter with wind sheer was under canopy as an AFF student. When your canopy starts bucking at 1500' and you don't know why, it gets your attention. Fortunately it is a short lived barrier.

[Meux 0]

It wasn't a HALO jump, but once on a trans-Pacific flight I observed winds of 218 knots. On the return flight from Tokoyo back to the US we generally put ourselves in the middle of the jetstream to take advantage of the free knots.

Good Luck.

[CSpenceFLY 1]

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If you survived the transition from one air mass to another I think you could track and gain altitude. My initial thought is that going from one air mass to another you would suffer broken limbs or worst.

The term is wind shear. It can tear aircraft apart, but they are crossing the boundary at very slow vertical speeds. A freefaller on the other hand would be less susceptible to differential wind speeds across their body, but would still be susceptible to a delta V of more than 150 mph over a fraction of a second. The big problem is differential reactions to the new wind speed by different parts of the body, i.e. the head will change speed slower than the torso. I think the probability for injury would be high.
This is based upon the assumption that the boundary region is less than 200 ft thick. I don't know whether that is true or not.

What he said.

[mark 102]

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This is based upon the assumption that the boundary region is less than 200 ft thick. I don't know whether that is true or not.

The term is wind shear. It can tear aircraft apart, but they are crossing the boundary at very slow vertical speeds. A freefaller on the other hand would be less susceptible to differential wind speeds across their body, but would still be susceptible to a delta V of more than 150 mph over a fraction of a second. The big problem is differential reactions to the new wind speed by different parts of the body, i.e. the head will change speed slower than the torso. I think the probability for injury would be high.

I've taken the liberty of rearranging your post to put the assumption first. I've tried to find a a source to confirm the assumption, but the best I've been able to get to is a crude cross-section showing isotherms and isotachs, but nothing so detailed as to say "200 feet." How thick would the boundary region need to be for the delta-V to be in the range routinely found in speed skydiving?

Mark

[1969912 0]

Say the jumper's FF speed is ~120 mph = 180 ft/second.

Assume the jumper is falling through completely still air, then passes into the jet stream which is flowing at 300 mph = 440 ft/sec.

Assuming it takes 7 seconds from exit to reach terminal FF speed, the transition layer from still air to the jetstream would need to be ~3,000 ft thick ((440/180)(7)(180)=3,080) for the jumper to experience the same acceleration (1G) as he did after exit.

My guess is that the transition into and out of the jetstream is at least that thick, so the jumper would hardly notice it. A balloonist would probably not even know without instruments.

"Once we got to the point where twenty/something's needed a place on the corner that changed the oil in their cars we were doomed . . ."
-NickDG

[velvetjo 0]

You're completely ignoring any effects of turbulence, and making some big assumptions about: the jet's boundary layer thickness, the drag forces experienced at much higher velocities, and the velocity profile within the jet. Do a little reading about clear air turbulence (CAT) and jetstreams - you might find some stuff that makes you change your opinion.

Lance

[mark 102]

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You're completely ignoring any effects of turbulence, and making some big assumptions about: the jet's boundary layer thickness, the drag forces experienced at much higher velocities, and the velocity profile within the jet. Do a little reading about clear air turbulence (CAT) and jetstreams - you might find some stuff that makes you change your opinion.

I'd like to do a little reading about CAT and jetstreams, as they pertain to objects falling at skydiving speeds. Google has not been my friend. Can you point me to a good reference? Thanks.

Mark

[denete 2]

Get a high lift wingsuit on, and you could use the kick from the faster air to go back up into the slower air. A little like the was an albatross uses dynamic soaring to cover distance with less effort.

By the way, dynamic soaring with rigid wings is amazing over earth ridges.

- David

SCR #14809

"our attitude is the thing most capable of keeping us safe"
(look, grab, look, grab, peel, punch, punch, arch)

[happythoughts 0]

I think that the major difference would be the transition from the dead air inside the plane to the outside.

A first example is doing 150mph jet jumps. Doing 10-way speed linked exits and getting blown apart immediately.

The other is high-speed casa exits. Even during normal jump run speeds, I always keep my arms tucked in for a little after exit. The wind really yanks peoples arms around, rough on the rotator cuff. I know more than a few people who injured their shoulders doing tailgate exits.

People may be able to freefall into a 300mph wind, but I don't think that you could exit an aircraft into one.

It is doubtful that a float exit is possible. You couldn't hang on.
A tailgate exit into 300mph winds would be a massive transition. It would probably dislocate something.

[mark 102]

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People may be able to freefall into a 300mph wind, but I don't think that you could exit an aircraft into one.

It is doubtful that a float exit is possible. You couldn't hang on.
A tailgate exit into 300mph winds would be a massive transition. It would probably dislocate something.

By "wind" we usually mean the speed of the air relative to an observer.

The 300 mph jetstream wind in this discussion is the speed relative to an observer on the ground.

The ease or difficulty of exit from an aircraft is dependent on the airspeed of the aircraft, that is, the wind with respect to an observer in (or on!) the aircraft. If the aircraft airspeed indicator shows 80 knots, then you'd feel 80 knots of wind, and it would feel the same even if you were making a downwind run in a 300 mph jetstream.

Unless, of course, your airplane stalls on a downwind turn, the wind blows on the back of your canopy when you fly downwind, etc.

Mark

[denete 2]

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The 300 mph jetstream wind in this discussion is the speed relative to an observer on the ground.

Thank you (for making the point).

SCR #14809

"our attitude is the thing most capable of keeping us safe"
(look, grab, look, grab, peel, punch, punch, arch)

[bch7773 0]

we are talking altitudes of 31k+, so I really can't see a skydiver actually falling through these. maybe those record breaking high altitude people.


I think it would be perfectly fine, assuming that the boundry layer is thick enough. one thing to remember is that at 30k feet, you wouldn't be falling at 120mph... but much much faster. so the boundry layer would have to be fairly thick.

MB 3528, RB 1182

[virgin-burner 1]

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we are talking altitudes of 31k+, so I really can't see a skydiver actually falling through these. maybe those record breaking high altitude people.


I think it would be perfectly fine, assuming that the boundry layer is thick enough. one thing to remember is that at 30k feet, you wouldn't be falling at 120mph... but much much faster. so the boundry layer would have to be fairly thick.

what he said!

-60° centigrade? you need a couple jumpsuits to survive that..

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