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My questions are related to a scenario discussed on Earth Science: A huge (heavier-than-air) kite sailing in and out of the jet streams.

The kite:

Kite Image

The scenario:

enter image description here

enter image description here

Earth Jet Stream model

The assumptions:

  • Such an airship exists and there is a person aboard, with an oxygen mask.
  • The person is thermally insulated to keep the heat inside.
  • The jet streams are at an altitude around 9–12 km (30,000–39,000 ft) .

The Questions:

  • Can a kite like the one in the picture be built to hold a person?
  • Does the human body require pressurization as well as oxygen and insulation? ANSWER
  • Is it possible using the jet stream systems to go around the world?
  • Can the kite fly at speeds around 80-150 km/h related to the ground?
  • Can it sustain a free fall from its cruising altitude around 9–12 km so that the pilot can land maybe using a parachute?

Possible Solutions:

Launch Considering the altitude is up around 9–12 km then air would be thinner the size of it will have to be much larger to compensate. Use a cable and boat to lift the UltraKite into the Jet Stream. At preferred altitude cable then can be mechanically released from connected drag section of the kite. A drone or balloons could replace boat and then dropped. Maybe the person could ride in the drag section.

Long Term Altitude with Ultralights Gliders on Record.

The current 15460-meter glider height record was made with pressurized suits. But it is only 500 meters higher than Harris' previous record from 1986, which was done with just an oxygen mask. – Martin Argerami in a comment in Turbulent Jet Streams on Ultralights

As commented by @Jan Hudec: This is supposed to be a kite, but instead of being fixed to the ground as normal kite, it would have just a cabin with a braking parachute flying below the jet stream and the kite flying in the jet stream, so the whole thing would move at some speed between the slow speed of the wind at low altitude and the high speed of the jet stream.

enter image description here

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    $\begingroup$ It's an old question, but I still think it should be removed. The assumptions carry quite an implicit load. Basically, the assumptions and comments by the questioner are roughly forcing the notion that the endeavor is possible. Asking if circumnavigation is possible in a real-world jet stream should require that a craft doing the navigating satisfy all the engineering requirements for the task. Biosupport, drag anchor function, structural integrity, sufficient lift, anchor line weight all must be considered in a solution, so one must PROVE, not presume, a suitable craft exists! $\endgroup$
    – Bruzote
    Oct 25 at 16:43
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As your diagram shows, the jet stream actually has two circulating components: one is "around the earth" (which is why the transatlantic crossing is so much faster going East than going West), while the second is more like a vortex, with a circulating flow "around" the main direction. This circulating flow is vertical in two places: North of the jet stream it is downwards, and South of the jet stream it is upwards.

That makes for an "almost endless" lift - and you could in principle hover there. It would be very uncomfortable, as the winds in that region are quite strong and turbulent.

It reminds me of something I have seen near the beach: when the wind comes in from the sea, it is lifted up by the dunes; and people with hanggliders can jump off the dune, catch the wind, and literally stay in the air as long as they want (and as long as the wind stays up). If they "miss" the updraft when they first jump off the top of the dune, they are on the beach within five seconds; if they succeed, they fly for an hour or more. Right alongside the sea gulls who discovered the same trick many years ago. Example source:

enter image description here

I don't think you can prevent yourself from traveling around the globe when you do this - in other words, you would have to be content to travel in a mostly Easterly direction. I suspect (but do not know for sure) that the currents are too strong to allow you to traverse in the Westerly direction by ducking in and out of the Jet.

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    $\begingroup$ Crash landing won't be so bad if you loose wind. thanks so much!!! $\endgroup$
    – Muze
    Dec 27 '15 at 3:47
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    $\begingroup$ "Endless lift": synoptic scale lift will be around 5 cm/hour (as you can see here www1.wetter3.de/Animation_06_UTC/00_6.gif) and even if you go to smaller scales the lift will be around 20 cm/hour (12 km grid modellzentrale.de/WRF/00Z/06h/VV500_eu.png), which is much less than in your example (~1m/s) $\endgroup$
    – Lukas
    Jan 6 '16 at 12:49
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    $\begingroup$ @Lukas how does the scale in the diagram (hPa/hr) convert to cm/hr? I thought pressure drop is about 1 hPa/10 m at ground level, and less as you get higher. Could you elaborate your interpretation of the data? Is it taken at the altitude of the jet stream? After all that's what we are talking about here - "surfing" the jet stream. $\endgroup$
    – Floris
    Jan 6 '16 at 13:03
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    $\begingroup$ @Floris, you are correct, I don't know what I calculated. Hydrostatic: $\frac{-dp}{g \rho}=dz$, 1 hPa=100 Pa, g=9.81 m/s^2, ideal gas law, 240K at 500 hPa. 100 hPa/h gives 39 cm per second wolframalpha.com/input/?i=10000+%2F9.81+*%28287*240%29%2F50000+*+1%2F3600 $\endgroup$
    – Lukas
    Jan 6 '16 at 14:38
  • $\begingroup$ @Floris - Regarding vertical motion/lift vs vertical pressure gradients at the synoptic scale, synoptic-scale lift is a matter of dynamics, not just a static situation. Momentum/kinetic energy matters as well as gradients. $\endgroup$
    – Bruzote
    Oct 25 at 16:11
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Keep in mind that your jetstream map is only a schematic description. In reality you will experience shear (strong wind along jet axis, decreasing outwards).

enter image description here

Assuming that the airship would drift with the wind, the shear would throw you off the jetstream and you would sooner or later been taken to convergent areas in the upper troposphere (poles, or subsidence areas at 30° N/S)

A keyword for online search would be: (Forward/Backward) Trajectories

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  • $\begingroup$ I would build it light enough to only need some of the jet stream. $\endgroup$
    – Muze
    Dec 28 '15 at 0:53
  • $\begingroup$ Like sail boats as long as they have wind they can sail against it. I edited your picture to show a possible flight plan , but on the maiden voyage I would suggest the easiest path. $\endgroup$
    – Muze
    Dec 28 '15 at 0:55
  • $\begingroup$ @Muze - Sailboats have an ocean that is effectively static and capable of infinite reactive force to the control surfaces of the moving sailboat. Your kite craft would be using a lower atmosphere that is moving and not fully reactive. That is, if the kite had a anchor or rudder in the lower atmosphere, the force vectors it could generate would result in the anchor or rudder slipping through the atmosphere significantly more than a ship's keel or rudder. In other words, the kite craft would be navigating both the upper AND lower atmospheres. That's a very difficult challenge indeed. $\endgroup$
    – Bruzote
    Oct 25 at 16:25
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In theory, maybe you could do it, but some of the jet stream loops are even tighter than in Aabaakawad's examples. The wind shear and associated turbulence in and around the jet stream's are so severe that no 'light plane' could survive. Any glider-like aircraft would break up almost immediately.

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    $\begingroup$ While you can find turbulence in the periphery of the jet (particularly on the polar side) you can also find smooth rides. My experience is in a ~22,000 kg airplane, but in general I wouldn't be adverse to taking a light airplane up there (among the few light airplanes that could actually make it up there). $\endgroup$
    – casey
    Jan 6 '16 at 17:13
  • $\begingroup$ @Casey, sooner or later, a discontinuity will be encountered where to go from one smooth flow section to another, you will traverse a section that is turbulent. At that point, you need a robust craft. I suppose it doesn't matter. After all, the initial question PRESUMES that a suitable craft exists that can handle the requirements of circumnavigating, then the same questions asks if circumnavigation is possible. That's like saying , "I have a magic solution. Does a solution exist?" Well, yeah, actually, if you say so. ;-) The assumptions already answered the question. $\endgroup$
    – Bruzote
    Oct 25 at 16:36
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It can't be done. That is my guess. I think you would need a pressure suit or cabin.

I am a former USAF weather officer with flight experience. I have a Masters Degree in Meteorology and a BS in Space Physics. I have working experience in analyzing the jet stream and also using data for vertical airspeed (or omega, as some call it). That does not give me magic powers or even make me generally correct at any time, but I think it provides me with a rough familiarity to review the question and mention the key issues it raises. I ask for your trust in my meteorology and flight experience when I say that you should not assume you have good reason to trust in your idea just because some of the answers got a lot of thumbs up or seem like they good answers. Based on my training and experience, none of the answers that predate mine have justified your idea. The point of that is to keep you skeptical, not to conduct ad hominem attacks to support my own answer. I don't care if I get one up vote.

I think with a pressurized suit of some sort and a massive soaring aircraft, some day a circumnavigation will be completed. It's almost inevitable, but how and when is the question.

I think your idea won't work unless you use dynamic soaring. Period. You seem to be under the impression a trip might succeed using the vertical velocity of the atmosphere for lift. However, across broad areas where lift would be needed, the atmosphere would rise at only a few cm/s. For scale analysis, let's pick a number and say 3 cm/s. As the air would be rising and bringing your craft with it, your kite would only maintain altitude with a descent rate not exceeding 3 cm/s. (In reality, due to other issues, probably MUCH less than 3 cm/s would be required!). How achievable is a 3 cm/s descent rate? Well, let's look at a glide slope ratio analysis and compare the result to existing soaring aircraft.

Slope Analysis: If your kite is extremely efficient, you will probably not have a very fast forward air speed. After all, the aircraft's drag goes up with the square of velocity (assuming constant drag coefficient) so you would probably travel with low air speed. Let's say you are traveling forward at just 60 knots, which is close to 30 m/s. That is also 3000 cm/s forward air speed. If you had a descent rate of 3 cm/s, your ratio of forward speed to vertical speed would be 3000 cm/s to 3 cm/s, or 1000:1. How does that glide ratio compare to world-class sailplanes? Well, an extremely efficient open-class glider might have a glide ratio of 70:1, so your design would have to get FOURTEEN times more distance out of the glide slope of the best aircraft. Put another way, you are trying to be FOURTEEN TIMES MORE EFFICIENT at utilizing energy. That may be possible, but you are talking about a massive change in design technology.

All of this scale analysis assumes you are always in an area of robust uplift. Unfortunately, the atmosphere is not like that, not even on the south side of "THE" jet stream. In fact, where the jet stream speeds up, those sections are called "jet streaks" and they have descending air in two of the four quadrants that surround them (and likewise for jet sinks). So, it's not some easy picture as a simplified schematic suggests. Your aircraft would constantly go through places of descending air as well. So, it seems to me that your aircraft would need tens of times better glide slope than an efficient glider. That's not a very easy path to success.

Instead of using rising air, I think you would need to copy the technique of countless seabirds who use dynamic soaring. They are able to travel much farther and more quickly than birds that only depend on updrafts. It's a simple analysis, but nature seems to be pointing the way!

Dynamic soaring around the globe would require a nearly continuous trail of highly differential shear. Where the continuity is broken, you would be losing altitude until you found another location of differential shear. Above the tropopause, perhaps that is possible with a sufficiently advanced aircraft. I doubt it is possible below the tropopause, where areas of no lift and occasional turbulence would both be enemies of your kite. So, I leave a scale analysis for dynamic soaring possibilities to someone else. I suspect it would be a more likely path to success, but still it would require massive improvement in soaring efficiency as well as highly detailed knowledge of where the differential shear is located.

Also, I think you would definitely need pressurization or else you would need a lot of specialized breathing training and still take on a lot of risk to your life and limb. Without cabin or full suit pressurization, you would need to breathe pressurized oxygen, which means forcibly breathing out against HIGH positive pressure on EVERY breath for days on end. Your mask would be crushed against your face. Goodness knows how your eyeballs and other body parts would eventually react. I have done some of the positive pressure breathing in a USAF pressure chamber (Peterson AFB). It didn't seem sustainable. I have seen videos of this positive pressure breathing in actual aircrew exercises. It looks quite challenging! And that is only at altitudes that might not be high enough for your kite idea to succeed.

Breathing out against this pressure for long periods of time causes health problems and is exhausting. I even wonder if such a long period of positive-pressure breathing could kill you through embolism or some other form of respiratory-related injury. Even with sufficiemt positive pressure to drive up the partial pressure of oxygen in your blood, if you got too far above the tropopause, no amount of positive pressure would even keep you alive. So, your flight would be limited to areas below 40,000 feet, which means you could not circumnavigate close to the equator where the tropopause exceeds that altitude.

As for your general understanding of a physical path to gliding 'round the globe, "THE" jet stream is ALWAYS just a term for RELATIVE velocity distribution. What looks like a continuous jet stream around the world might be a stream with 300 knots over Alaska but then only 60 knots over the Atlantic! That's why looking at numbers and not just colors and lines is important. Likewise, the horizontal and vertical gradients of the "horizontal" velocity would vary widely, as would vertical velocity. I can definitively say that in all my of days doing manual analysis of the jet stream (before computers were left to do it alone), I found it unusual to find a continuous jet across the Western Northern hemisphere, let alone fully around the globe in either the Northern OR Southern Hemisphere. Now imagine looking for a jet stream AND significant differential shear along the jet. It would be quite an endeavor. It may be possible, but the idea would require in-depth study of the wind patterns, not just for theoretical feasibility but likelihood it would be feasible to find necessary and sustained conditions on the special day an aircraft would be ready for launch.

The idea of circumnavigation by natural power alone is an old one. However, there is always room for more achievement. I think someday someone might circumnavigate the globe in a special gliding craft, but I do think they will use a pressure suit or cabin.

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