Discussions de vol libre au Québec

From: BARCLAY Ian

Sent: Wednesday, June 18, 1997 11:40 AM

To: hang-gliding@lists.utah.edu

Subject: Jetstream Riding Paraglider

> I've been working on this to try to figure what kind of mountain I'd

> need for a PG 100-miler. In theory, a 78 thousand-footer would do, but

> the fall-off in glide performance at altitude means it would take more

> like a 129 thousand foot launch. This means that Everest is only 100 k

> short. I'm still working on this problem....

> Penguin

> The Day that a Paraglider Pilot

> can Claim a distance Record over 300 Miles is the day that I quit Hang

> Gliding.

> David Vincent

The admirable attempts by Penguin to do a PG 100 miler are to be

encouraged but I am afraid 78000ft hills and 2100mph tailwinds are

somewhat rare. The way to do not only 100 miles, not only 300 miles, not

only smash the existing paragliding record but also the hang gliding,

sailplane and possibly even Voyagers circumnavigation record is to build

a Jetstream Riding paraglider (JRPG). This would harness the power of

the atmospheric jetstreams to soar thousands of miles across the oceans

and continents. So what would this wing look like and how would it work?

The wing would be a vast 6000ft2 (560m2) canopy of 250ft (76m) span. The

suspension lines would be 5000ft (1500m) long. The pilot would sit

within a pressurised pod (with sealed openings to allow him to stick his

legs out for that all important foot launching and landing capability).

Attached to the pilot pod would be a round drag parachute of about

1000ft2.

LE TE

___________________

\_________________| Canopy

\ / /|\

\ / |

\ / |

\ / Suspension |

\ / Lines 5000 ft

\ / |

\ / |

\_/ |

Drag Chute (-----------|_| Pilot Pod \|/

----- Direction of Travel ----->

And how would it work? The canopy could perhaps be foot launched from

the summit of Everest or more practically from an aerotow to 35000ft

(say behind a small turboprop) or from a balloon launch. After release

the pilot would descend through the 120mph winds of the jetstream that

exist between 25000ft and 45000ft. He would then level out with the

canopy facing directly into the fastest moving airstream. The pilot

would then deploy the round drag chute. With the canopy flying at an

airspeed of say 25 mph with a headwind of about 120mph the JRPG would be

blown backwards at 95 mph groundspeed. The pod however, being 3000ft

lower down and outside the jetstream itself, would be travelling in wind

speeds of maybe only 70 mph. With the groundspeed of 95mph backwards it

would see an airspeed of 25mph in the opposite direction to that seen by

the canopy. The drag chute would be sized such that its drag matched

that of the canopy but would be in the opposite direction. The JPRG

would therefore have a total drag of zero and would then cruise along

with an infinite glide angle.

Before you dismiss this as a load of complete bollocks think it through

carefully and check the greatly simplified maths (+ is taken in the

direction of travel of the JRPG over the ground) :

Altitude Wind Speed Airspeed Groundspeed Drag

Canopy 33000ft +120mph +25mph +95mph +250lbf

Pod + 28000ft +70mph -25mph +95mph -250lbf

Drag chute

-------------

Total Drag = 0 lbf

This is no magic, no perpetual motion machine. It is all good physics (I

think). It simply harnesses the power of nature by spanning a wind

gradient.

Practical problems are numerous : launching, landing, dynamic behaviour

of canopy/pod/canopy system, turbulence in jetstream, canopy control,

pod systems, etc and these are just back of the envelope numbers.

However much of the technology and many of the problems are the same as

those for balloon circumnavigation which is not too far away from being

achieved. Crazy? Sure it is crazy? Any takers?

p.s. theoretically it would also work in the much weaker wind gradient

caused by the ground. Which paraglider pilot is going to try that with

their regular canopy and reserve chute? Come on Penguin; 100 miles,

backwards, at an altitude of 3ft; that would be something!

Ian Barclay

Toulouse, France

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The BCHPA's Site Guide pushes 272 pages and includes sites from the East

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The cost for the Site Guide is

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The Site Guide is produced as a fund raiser for the BCHPA, our the Clubs

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Pour tous ceux qui auraient envis de voler au Mont Washington, voici quelques

renseignements intéressants:

Le décollage est orienté sud-est

Les décollages doivent être entre 10:00 am et 5:00 pm.

Les décollages s'effectuent près des réservoirs d'eau

Niveau 4

Nous devons payer les frais de remontée pour la route

La météo peut changer très rapidement

L'atterrissage se trouve au sud du batiment de péage.

Le site est volable environ 10 fois par année (Les hautes pressions sont favorables)

Bonne chance à ceux qui veulent s'attaquer au plus haut sommet à l'est de l'amérique

du nord.

MecFly