First to Sail the Jet Stream Around the World 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:

The scenario:



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.
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:



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.