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Jet Sail

A high alt.very long range one person soarcraft
  [vote for,


I am new here. I have an engineering background. I like playing with ideas, and finding ways to make them work with existing off the shelf materials.

So: The jetsail

There is a self launch 2 man German made sailplane with fore and aft seating called the Nimbus 4DM. It self launches with a motor driven propeller placed at the top of a extendable pylon. This pylon when raised is right behind the second seat and the one piece side hinged canopy. For ballast the aircraft is built with wing water tanks that allow for up to 320 lbs of water. The aircraft full up loading is about 1808 lbs. Rest of the general specs are listed below. Wing span 26.50 m 86.94 ft Wing area 17.96 m² 193.32 ft² Wing aspect ratio 39.1 39.1 Empty mass (powered) 595 kg 1312 lb Max. all-up mass (powered) 820 kg 1808 lb Max. speed (prop. retr.) 285 km/h 154 kt (177 mph) Best L/D (at 59 kt | 68 mph) ~ 60 ~ 60 Wing loading (full up) 37.5 kg/m² 7.7/ft²

there is more detailed info on the net...

the engine,pylon,and prop assemb. weigh about 75 lbs (more depending on the engine installed with another 25 lbs for fuel (100 lbs)

Full up weight 1808 lbs minus Empty weight powered/wet 1312 lbs equals usefull load 486 lbs remove the power system and fuel tank plus 100lbs more usefull load 586 lbs remove the first and second seats and strip to bare controls. (best quess 58 lbs removed) plus 58 lbs for a total of 674lbs

Now build a light weight one man cockpit that can be pressurized to 20psi with small sideport windows and small front window. Figuring 50% overrun onthe weight using existing of the shelf honeycomb composits and carbon fiber composits the added weight would be 70 lbs using the original controls and avionics. 674 lbs minus 70lbs = 604 lbs Behind the pilots seat place a modified diving rebreather system that has been striped down to only required parts. There is an emerg. breathing system (OSHA approved ) that will let the rebreather function in a static environment. Meaning you don't need to use the mouth piece. This system monitors breathing air, scrubs carbon dioxide and supplies oxygen. Best guess on total weight is 25 to 30 lbs.

604 lbs minus 30 lbs = 574 lbs

(please note: I haven't done the partial pressure calc.'s for system use at sea level but the master diver I questioned said at least 4 hours depending on work preformed. I plan to just sit there.) Also note that the scruber, as a by-product, produces heat and some water vapor.

Now for the power:

There are several companies that produce small jet engines. One is AMT but there are other similar providers.

There are small jet engines in 10 to 15 lb weight range that produce 95lbs to 100 lbs of static thrust. They burn about 160 lbs of standard jet fuel (JP-4) per hour with an oil additive for lub. Note that the engine used here was electric start and the additional weight has been included.

Mount one engine in the old engine compartment. Mount it below the aircraft fore aft centerline with a 5deg positive incident angle. (note that this is a MUCH better thrust coulpe than the old system.) The mounting should be connected to the steel tube frame and the air intakes should be closeable ducts on eather side of and aft of the new cockpit. When cleaned up the new configuration would actually have less parisitic drag than the old one with its engine compartment hatch cover system. The only always open hole is the exhaust outlet and it is 5 " in dia. and faces aft.

In the front of the engine compartment mount a fuel tank and fuel flow control system (there will be three tanks 2 wing and one center) The wing tanks hold 320 lbs of water but only around 300 lbs of fuel at API standard of 60 deg F. The center tank needs to hold about 20 gal. and would be filled to levels according to pilot weight so as not to exceede full up weight.

now include aprox 10 lbs for a composit bottle of NO2 and the bleed control for the intake system

Total engine and fuel system aprox 33 lbs as near as I can figure.


574lbs - 155lbs for the pilot (me with 5 lbs of clothes) equals 541 lbs. minus 33lbs for engine and fuel sys. equals 508 lbs for fuel.

At 160lbs/hour burn at 100 static pounds of thrust the full power burn is 3 hours 10 min. 30 sec..

If you launch and climb to 45,000 using the wing tanks you would get to altitude in 1 hr. 52 min. 30 sec. at 400 ft/min overall climb (I suspect that it climb will be much better.)

This leaves 1hr 18 min. for full burn cruise. the Vne on this aircraft is around 180MPH IAS. But due to the density altitude the ground speed is smoken. Besides at full burn in level flight you would most likely get to Vne in a hurry.

Anyway, you could launch in Colorado and get to the east coast in reeasonable time. And if you had a problem, just shut down the engine, close the intake ports and use the 90 to 1 glide ratio.

The whole project prices in well under $130,000 not counting labor.

So what do you think.


P.S. If you just kept climbing you might get to 76,000 ft depending on how well the nitrus worked to hold engine preformance.

Willlie, Nov 14 2006

U-2 spy plane http://www.area51zo...m/aircraft/u2.shtml
Baked, albeit with two engines. [Vernon, Nov 15 2006]

First link http://www.microjeteng.com/hf100.html
as link [lurch, Nov 20 2006]

Second link http://www.amtjets....ery_real_plain.html
I hope that canopy can handle a grasshopper strike at 150 kts [lurch, Nov 20 2006]


       Welcome, [Willie].   

       If I've got this right, what you want to do is take an existing propellor-driven light aircraft design, replace the engine with a jet and provide a cockpit for high-altitude flight... and the difference from other small jet planes is that it could glide?   

       I'm impressed (however, not being an engineer, I wouldn't be qualified to be unimpressed).
pertinax, Nov 15 2006

       Oh, jeez, Vernon has a cousin!   

       Willie, any chance you could summarise this into one or two paragraphs?
DrCurry, Nov 15 2006

       To Vernon,   

       You are right . But unless I'm wrong the U-2 costs a lot more than $130,000. And you have still have to wear one of those big old pressure suits I believe. And I don't think that Mr. Johnson and the boys at the "Skunk Works" built the U-2 using off the shelf parts. Also I can guess what would happen when the man on the street tried to file a flight plan and listed his aircraft as a U-2.   

Willlie, Nov 16 2006

       [Willie], I wasn't aware that jet engines were so cheap you could include one in the cost that you gave for your jet. Also, I saw a documentary recently that was partly about the U-2, and according to it, the engines were specially modified to be able to work at very high altitude.
Vernon, Nov 16 2006

       DrCurry Sorry. Amd I thought I have cut the thing way down removing a lot of the math.   

       Basic Idea:   

       Take a VERY good 2 man, self launch sailplane, that is powered by a clunky piston engine and propeller on a retractable post system. Throw away the engine and replace it with a 12 lb jet that generates 100lbs of push. Now remove all the stuff in the 2 man cockpit area and replace it with the a smaller 1 man pressurized cockpit made fron the latest composits.   

       Now use all the weight saved plus the wing tanks that normaly carry 320 lbs of ballast water for fuel.   

       There is some other stuff like life support going on here, but thats the general idea.   

       Vernon is correct. The Idea is baked but not at the level that I put forth. The U-2 came out of the Skunk Works as the A-125 back in the 1950's and is still used for high alt testing today. And it costs a lot more than $100 per hour to fly and a whole bunch more than $130,000 to build.   

       What I did was figure a way for the average guy to get around high and fast with off the shelf parts for the cost of a medium priced 182. And you don't need a pressure suit.   

Willlie, Nov 16 2006

       Vernon, There are small jets that weigh around 12 lbs that product 100 lbs of thrust that are Under $12,000.   

       There is a small jet that weighs about 8 lbs and kicks out 45 lbs static thrust that costs about $7500 with all the trimmings. Here is one :   


       and here is another:   

       www.amtjets.com then go to gallery_real_plain.html   

       As to the altitude problem, the nitrus oxide bleed should help and was in fact used on the X prize project I believe. (though i can't swear to that) Even without the nitrus the conventional jets work fairly well at 45,000 ft.   

       With fuel burn off durring climb to say 45,000 ft the aircraft might weigh about 1600 lbs and the thrust to weight ratio would be about 1 to 16...(   

       I have not checked on the thrust to weight ratio for a comercial jet but they go to 40,000 feet plus all the time, have a lift to drag ratio a lot worse than 60 to 1, and have the glide path of a plucked chicken..)   

       You just would not be able to go much higher than say 55,000 ft. But you would really be making considerable ground speed even if the IAS was only 125 MPH due to density altitude.(note the Vne on the sailplane is about 180 MPH   

Willlie, Nov 16 2006

       Nice, Willlie! You make it sound like it's almost finished. Are you going to build it?
jmvw, Nov 17 2006

       Willie, why is there so much ballast in the wings, and would it have an effect when it is gone?
Ling, Nov 17 2006

       Hi Ling   

       The ballast tanks in the wings are to adjust the total weight of the aircraft for competition.(among other things). It allows the leveling of the playing field so that when distance/time contests in various sailplane catagories are held everone starts about equal. There are others reasons but I have been given to understand that is the prime one. Another reason put forth is the effect on the ride in various weather conditions.   

       I find that with already proven (though unauthorized by the factory)modifications for fuel I can use the tanks to great advantage.
Willlie, Nov 18 2006

       TO JMVW   

       I would love to build this. Right now I just can't afford it.   

Willlie, Nov 18 2006

       Have you looked for sponsors/investors?
jmvw, Nov 20 2006

       How much for a picture of a half-eaten croissant atop a plain white plate next to a plain white paper tag reading, in black, 50 cents (allegorical price of the croissant). Under the picture a tagline reading "Number one on the no-fly list" (font and size to be confirmed later). The picture should be below the pilot canopy and about 400 by 400 mm.
methinksnot, Nov 20 2006


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