The solar hot air balloons of Dominic Michaelis

last changed : 04.01.2006

At the completion of his architects formation, Dominic Michaelis had already written a thesis on the solar house. This was back in 1964 !
In 1970 he is leading a team of architects and engineers specialized in the use of solar energies. This international consulting group was called "Solar Energy Developments" and had broad centers of interest.
Dominic Michaelis realized a project : a 50 yard diameter solar dome for the movie "Human" directed by Jérôme Lapérousaz with Jeanne Moreau, Terence Stamp and Frédéric van Pallandt.

ballon michaelis

Dominic Michaelis believed that a hot air balloon can fly with solar energy alone.
To confirm this, he built a small balloon (1 cubic meter) with a double skin envelope. The results were encouraging. The temperature difference betaken inside and outside was about 27°C, which corresponds to a lift of approximately 100 grams per m³.
Then after building a few small balloons, he build a large one (diameter 10 meters) that was able to lift his son Stéphane (30 kg) who so became the first solar balloon human pilot ! (captive flight). But one day the balloon broke loose from its moorings and disappeared into the Oxfordshire skies.

In 1972 Dominic Michaelis built a huge balloon of 22 meter diameter (more than 5000 cubic meter or 180'000 cubic feet) with a 12 micron transparent polyester film (Melinex® - Mylar® of DuPont Polyester Films).
Inside the balloon where 3 vertical black screens with 120° between each, forming a trefoil.
The air inside the balloon is heated by greenhouse effect and the black screens pick up the energy that has gone through the transparent polyester film.
The envelope is reinforced by vertical and horizontal adhesive tapes (J-Lar910® or J-Larii®). These tapes define 240 panels and limit the possible tearing to a maximum length of 50 cm (0,5 yards).
The balloon is fitted with a aluminum honeycomb basket (very stiff and light). This balloon easily lifted one adult man. The test flights were conducted tethered to a Land Rover.

Human free flight

For manned solar free flight, Dominic Michaelis chose to build a balloon with a double envelope : Dominic Michaelis commissioned Cameron Balloons in Bristol to make for him :
- a black balloon 3000 cubic meter (104'000 cubic foot) built of polyester (Dacron®),
- a transparent balloon 4000 cubic meter (140'000 cubic foot) made of double layer transparent (Melinex®). The transparent outer skin consists of two transparent films with, inserted between them, a layer of glue coated reinforcing mesh. Each hole in the mesh defines an air bubble. These air bubbles increase the insulation.
The transparent balloon produces the greenhouse effect while the inner black envelope picks up the trapped solar radiation and transfers this energy to the air enclosed within it. The thermal looses by convection of the black balloon are totally recovered for the lifting of the transparent envelope.

The twin envelopes are attached to the basket in a hangar (photo above).

A gas burner is fitted to ease the inflation, or to cope with the possibility of cloud cover during the flight.
The altitude control is done by the opening or closing of horizontal panels located at the balloon equator.
The deflation is possible with irreversible rip panels at the balloon crowns.

This balloon (number G-BAVU) participated in some hot air balloon festivals in England from 1976 to 1980. The flights where usually performed during the late evening in such a way that, assuming a valve failure, the uncontrollable balloon would not rise too high !

The Channel Crossing

During the international ISES meeting about solar energy that was held in Brighton in 1981, Julian NOTT (with hot air balloon altitude world record 1980 : 55000 feet) decided to attempt the channel crossing with Dominic Michaelis's solar balloon.
The lift-off took place at 7h 30 am on 22 August 1981 to the North West of Dover. After a silent crossing without any trouble the landing was made at Tournehem sur la Hem in the Pas-de-Calais.
During the flight J. NOTT used the burner only once : during the landing. He had some difficulty to deflate the balloon because the valves were not working well that day.
The envelope is at the British Balloon Museum now.
In the mid 70's, Tracy BARNES in the states also made some solar flights under a tetrahedral single skin solar balloon.
MICHAELIS is still involved in solar energy : he is producing solar ovens (www.solarenergyltd.net) and he still has a lot of projects in mind....

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