A kite balloon combines a lifting gas with active lift structures like wings to fly in all conditions. A good design may solve the common difficulty of flying in light winds, which makes balloon mapping difficult, but still falls short of kite-flying weather. It may also help reduce helium use, and therefore price.
Developments thus far:
Mylar and EVOH are the materials we're experimenting with now because they are gas barriers, unlike Polyethylene (HDPE/LDPE/LLDPE). Like Polyethylene, EVOH can be heat seamed. Mylar must be glued.
Mylar should be glued with UHU Power Stic in lap joints according to forum discussion on RC Groups. UHU Power Stic doesn't appear to be for sale in the USA, but can be found on Ebay.
Tests Tests are occurring on configurations of mylar sleeping bags at the Gowanus Canal site in January 2011:
A successful flight mapping flight based on Leif's and Liz Barry's design. Notes from flight?
and in Lima PeruJanuary 2011:
The Black Knight, by Jeffrey Warren, Oliver Yeh, and Reid Beels, April 2010 This kite had structural problems in its construction and broke quickly. It is an attempt at a helium sled kite. Other problems: material- it was made from polyethylene, which is not a gas barrier. Otherwise, a fine early flight and prototype.
A blimp-style kite balloon from Grassroots Mapping's NuVu Studio workshop April, 2010: This balloon was also lost, owing to a knot. Problems: Balloon does not hold its shape in pressure due to dispersion and lack of rigid structures. Material is polyethylene, which does not retain helium well.
Sled Kites Sled kites with balloon re-enforcements on the sides inspired Jeffery and Leif's designs. They have a high active lift (wing lift) to static lift (gas lift) ratio. Helium here is a means of lifting a kite into higher winds at higher altitude. More ram/sled kites here. This technology was invented by Domina Jalbert, who also experimented with small kite balloons in the 1940's. Ram-air structures also appear on the early Parseval-Sigsfeld balloon.
Lifting Bodies Lifting bodies are high-volume shapes that produce active lift like wings do. They would be good compromise shapes for a kite balloon, allowing a high volume of lifting gas and aerodynamic stability Examples of kites using lifting bodies can be seen in lenticular kite balloon designs, like the commercial Southern Balloon Works Kingfisher and Allsopp Helikite.
Bowed Kites Traditional Asian bowed kites are very stable. They are also curved like the underside of a balloon. Features of Bowed kites can be seen in the Allsopp Helikite, detailed below under "Alternatives to the blimp shape."
History of Kite Balloon Designs
Early kite balloons were used for artillery observation, and had to be manned. Large balloons have different design constraints, but similar functions to small kite balloons. From discussions with users of contemporary small kite balloons, it appears that these cigar, sausage, or "blimp" style balloons (sometimes called photoblimps) aren't particularly stable below 15ft long. That said, early designs show the basics of kite balloon structure, strategies to maintain rigidity, and rigging concepts that we can probably learn from. In terms of shapes to pursue in development, see "Alternatives to the blimp shape" below and "Inspirations" above.
Large Kite Balloons 1896-Present Designed during 1895 and 1896, the Parseval-Sigsfeld kite ballon (Drachenballoon, or colloquially, "sausage balloon") was the first observational balloon integrated into regular military field service. Its ability to climb into the wind and maintain its shape were due to a balloonet (listed as a diaphragm in the illustration) in the back that was inflated by a wind rushing into duct underneath, similar to the structural members of a rammed air sled kite. here is a diagram of the Parseval-Sigsfeld balloon:
Early experimental versions had a drag sail on the back instead of a duct. This same means of stabilization is used in the contemporary Southern Balloon Works "Kingfisher". Here is a terribly low-res image of an early experimental Parseval-Sigsfeld design:
Parseval-Sigsfeld style balloons first saw battle during the Russo-Japanese War (1903-1905), and were notably well integrated with mobile artillery by the Belgians during 1914's German invasion.
Here is a Japanese version of the Parseval-Sigsfeld balloon from the Russo Japanese War:
During World War I, the Parseval-Sigsfeld was replaced by the more blimp-formed Caquot Type R (which looks more like a blimp), whose design evolved into the the streamlined barrage balloon style still used today for radar domes. Later Caquot-style models used a fan to forcibly pressurize their balloonet. This is "Fat Albert" a broadcast tower and radar dome used to watch Cuban airspace from the Florida Keys: The balloonet & duct system is also used to control lift and rigidity in blimps. This diagram of the Goodyear Blimp accurately represents how the balloonets work on simpler kite balloons:
Small Kite Balloons: 1940's to present
Amateur Radio Operators began looking for a good way to put up antennas, renewing interest in kite balloon development. Domina Jalbert Patented a kite balloon in the mid-1940's, and his design is similar to the "blimp" style Caquot balloons. His patent describes the design rather well. Jalbert used pressure and rigid structures only to maintain his kite balloon's shape, rather than rammed air ducting. All the small kite balloons I've seen do the same.
Contemporary Plastic Caquot Style balloon, often sold as "photo blimps." I'm not sure what brand this is:
Alternatives to the Blimp Shape
Recently, lenticular (lens-shaped) kite balloons have emerged. From discussions with users of "photo blimps", I (mathew) have heard that at below 10-15 feet long the design is not particularly stable. The lenticular shape appears to be more stable, and it aught to be more space-efficient, having a higher volume than the blimp shape. Lenticular objects are a form of lifting body (see "Inspirations" below) and may perform as active (wing-like) lift structures.
The Helikite, manufactured by Allsopp in the UK, apparently flies in up to 40 knot winds, and yet is only 6 ft long. It is notable that as well as being lenticular, the Helikite's wing structure shares features with the Japanese Rokkaku, or bowed kite (see "Inspirations" below) Southern Balloon Works manufactures a kite balloon called the Kingfisher that is lenticular, but uses a sail in the back for stability, like the early 1895 experimental Parseval-Sigsfeld balloon. This is curious, why use a stability strategy 115 years out of date? One of the GRM participants has used the kingfisher and says it's kind of a pain. (CITE)
The Southern Balloon Work Kingfisher: