Solar balloon

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How a solar balloon works

A solar balloon is a balloon with a dark envelope that is filled with normal ambient air. The shell absorbs the energy of sunlight and thus heats up. It releases part of the thermal energy into the air inside the balloon, which also heats up as a result. Because heated air is less dense than cold air , this creates static buoyancy that allows the balloon to float.

Common designs

Tubular solar balloon
Tetrahedral solar balloon
Teardrop-shaped solar balloon

There are a variety of designs. What they all have in common is that they have a dark shell that is heated by the sun. If the envelope is thin enough for the trapped air volume, almost everything will fly. However, the designs differ greatly in terms of the requirements for producing suitable pieces of film. While the use of adhesive tape to process the film is widespread in self-made solar balloons, the additional mass of the adhesive strips can be avoided by welding techniques.

The simplest design are the tubular solar balloons, also known as solar worms or solar zeppelin. Such solar worms have been available as children's toys for many years. This is simply a matter of a few meters of black tubular film; a worm of any length can also be built using standard black garbage bags. Such solar worms can be 50 meters and longer.

Another design is the tetrahedron. This shape is also easy to build, a tetrahedron only consists of four smooth surfaces, so you can use a large smooth sheet as a starting material.

The ratio of volume to mass of the envelope is greatest with balloons in the form of drops. However, their production is more difficult because they have to be composed of several spindle-shaped paths.

Compared to a hot air balloon

Since solar balloons do not need any fuel, they can fly significantly longer in good weather than hot air balloons , which use up heating gas forcing them to land after just one to two hours. Compared to hot air balloons, solar balloons develop less buoyancy with the same balloon volume. For the same load-bearing capacity, they must therefore be larger. A typical material for the cover of solar balloons is black plastic film, while hot air balloons are made from thermally and mechanically resilient balloon silk.

An obvious disadvantage of solar balloons is their reliance on sunny weather. Their extreme sensitivity to wind is less obvious. Because while the sun heats the shell, the wind cools it down. Hot air balloons avoid windy weather because gusts can deform the balloon and drive it against obstacles. This also applies to solar balloons, but because of their strong influence on buoyancy, solar balloons have to pay more attention to weather with little wind. Therefore, pure solar balloons are not suitable for transporting people, as they quickly lose lift and sink even when the clouds are cloudy. The falling wind that occurs would further intensify the cooling and the sinking process, unless countermeasures can be taken.

Nevertheless, larger solar balloons have also been made in the past, which have also transported people.

history

In 1963 a US patent was applied for claiming a "solar balloon or aerostat" as an invention. It also refers to even earlier US patents in which the idea is already emerging.

Solar Firefly

As early as 1963, the American Tracy Barnes was experimenting with unmanned solar balloons. Ten years later, on May 26, 1973, he soared into the sky with the approximately 5,700 cubic meter, tetrahedral solar balloon Solar Firefly . In the same year he was also recognized by the Ballooning Federation Of America for the development of the solar balloon and the successful flight with it.

Condor I.

In 1977 the author and experimental archaeologist Jim Woodman published the book "Nazca - with the Inca balloon to the sun". As a possible solution to the puzzle of the Nazca Lines , he puts forward the thesis that the Inca in Peru, South America , were already able to build solar balloons and thus possibly even cross the Pacific. Using available materials, traditional legends and with the help of an engineer, he reconstructed a replica, the tetrahedral Condor I , which flew in 1975. On board were Jim Woodman and hot air balloon pilot Julian Nott, who held several records. With the successful flight of the Condor I over the plain of Nazca, he confirmed his thesis. Woodman does not propagate a purely solar balloon, but only the use of a "solar reinforcement" for a normal, but dark-colored, hot air balloon.

Sunstat

On February 6, 1978, the Iranian Fredrick Eshoo carried out another successful manned solar balloon flight with the Sunstat . The Sunstat had the tried and tested teardrop shape of normal hot air balloons, but its shell was partially transparent. The purpose of the transparent surfaces was to absorb the sun's rays only inside the balloon, on the opposite wall of the envelope. This was intended to imitate a solar collector - since a balloon envelope is very thin and the back wall, unlike a good solar collector, was not insulated, the effectiveness of the concept is questionable.

Dominic Michaelis

Dominic Michaelis , a British architect and engineer, had already dealt with solar architecture during his studies. In contrast to the Sunstat, it used a completely transparent outer shell and a black colored inner balloon to absorb the sun's rays. Thus, the inner balloon could give off its heat completely inside and not, as with an outer wall, only half or less. Michaelis realized this improvement in two different ways. His first large solar balloon stretched three vertical black foils inside the completely transparent outer shell, which were offset by 120 degrees. As a second option, he finally designed a large solar balloon with a double envelope. An inner black shell enclosed an air volume of 3000 cubic meters, an outer transparent shell with a volume of 4000 cubic meters shielded the wind from the inner shell. Like the previous one, this solar balloon could carry people and participated in several balloon festivals in the late 1970s. In 1981 this balloon was even used to cross the English Channel, the pilot was none other than Julian Nott, who had also flown in Condor I. Michaelis never flew solely with solar radiation, when landing he needed a burner that was carried for safety.

ARCA

In 2006 the ARCA , a non-governmental Romanian cosmonauts and space travel association, built what is probably the largest solar balloon to date, which on December 2nd, 2006 carried a test payload of around 1000 kilograms to an altitude of 14,700 meters. The stated purpose of this mission was to transport a rocket into the stratosphere , from where it should be able to launch into Earth orbit with less fuel. A second and final successful test of this type took place on September 27, 2007. After that, the unification followed a different direction.

Other solar balloon projects

In 1994 a “Montgolfiere solaire” was registered as an invention in a French patent. In January 2007 Matthias Schlegel presented a radio-controlled 42 cubic meter large solar balloon in spherical shape at the Tegernseer Tal Montgolfiade, which was too small to transport people and therefore more of a solar model balloon .

literature

Web links

Commons : Solar-powered aircraft  - Collection of pictures, videos and audio files

Individual evidence

  1. ^ A b c Ballooning - The Journal Of The Ballooning Federation Of America (1978)
  2. ^ US patent from 1963
  3. Solar Firefly des Tracy Barnes ( Memento of the original from April 19, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot / www.nationalballoonmuseum.com
  4. Pictures of the Condor I
  5. Article on the flight of the Condor I
  6. The solar hot air balloons of Dominic Michaelis (engl.)
  7. The solar hot air balloons of Dominic Michaelis (engl.)
  8. Stabilo-1 mission of the ARCA
  9. ^ French patent application from 1994
  10. Matthias Schlegel's solar balloon ( memento of the original from April 19, 2014 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot / www.modellballon.info