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


migrated from physics.stackexchange.com Dec 28 '15 at 4:10

This question came from our site for active researchers, academics and students of physics.


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.

  • 1
    $\begingroup$ Crash landing won't be so bad if you loose wind. thanks so much!!! $\endgroup$ – Muze Dec 27 '15 at 3:47
  • $\begingroup$ "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
  • 2
    $\begingroup$ @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
  • 2
    $\begingroup$ @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

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

  • $\begingroup$ 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

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.

  • 3
    $\begingroup$ 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

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.