Solar balloon

The solar balloon is a Aérostat similar to the Montgolfière except which it does not use of burner, nor no other excluded source of heat that provided by the sun. Like the others Airship S, the solar balloon is in lift thanks to the Poussée of Archimedes.

General information

The solar balloon generally is built and used by amateurs. The objectives of a solar flight of balloon are very varied. That can go from the simple pleasure of seeing it flying, until the experiment embarked with radio-transmission of the data and follow-up of the balloon by GPS, while passing by traditional air photography. Certain people use even their balloon to rise in the airs.

Advantages of the solar balloon

There are several advantages to build a solar balloon, among them:

the cost, it is not necessary to have a burner nor to use gas
the weight, the absence of burner makes it possible to decrease the mass of the payload
the description of the possibilities of solar energy utilization

Disadvantages

Such a device has its disadvantages of course:

requires conditions weather favorable (not or few clouds, room temperature not too high)
a flight must of course be made of day (presence of sun) and for this reason it has one limited duration (disadvantage in the case of a device intended to steal several days).

Dimension of a solar balloon

Dimensions of a solar balloon depend on the use for which it is intended. One in general seeks to transport to a payload of definite mass. To raise this mass, it is necessary that the volume of the balloon is sufficiently important.

To find this volume minimal, one applies the formula of the Poussée of Archimedes. It is necessary to be based on a difference in densities between the air inside the balloon and the ambient air. If it makes 20°C moreover in the balloon that outside, then the difference in densities will be of envion 80g/m ³.

Types of flight

One distinguishes two types of flight:

the captive flight, the balloon is attached on the ground by a solid cord connected to a sufficiently important mass to retain the balloon
the coasting flight, the balloon is not retained. Its trajectory is subjected to the environmental conditions

A flight in solar balloon can be inhabited or not. In the case of a manned flight all the precautions must be implemented for an unfolding without encumbers.

Inflation of the balloon

All depends on the size of the balloon, here some techniques of inflation:

manual Inflation: to put themselves in front of the opening of the balloon, to maintain the bottom of the opening against the ground with the knees and to hold the top of the opening with the hands. To insert of the air in the balloon by highly shaking from top to bottom hands. Thus of the air enters the balloon and inflates it.
With a ventilator, it is enough to put the ventilator in the opening of the balloon and to inflate it.

Once the inflated balloon, it should be waited until it is heated sufficiently to fly away.

Warming of the air of the balloon

The air of the balloon is heated by the radiations of the sun.

The envelope of the balloon is a fine film of black Polyéthylène which collects the solar heat of the radiations what causes to heat the air in the balloon.

Composition of the balloon

A solar balloon is relatively simple, therefore the construction of a reasonable model of size is with the range of any motivated person.

The envelope of the balloon

The envelope of the balloon must imperatively be black in order to collect the solar heat of the radiations. One uses a polyethylene film a thickness from 15 to 20 microns. Thickness a 30 microns or more gives to the envelope a too large mass to have satisfactory performances.

For balloons of modest size, bags dustbins blacks are often used (attention with their thickness). For larger balloon, one uses a broad film polyethylene reel in order to limit the quantity of connections to be made between the panels.

There exist various more or less resistant techniques of connections of the panels:

connection by adhesive tape (attention with the quality of the ribbon), that increases the cost and the mass of the balloon
by thermosoldering, inexpensive but more difficult to control. A bad thermosoldering can lead to the tear of the envelope. Various apparatuses can be used (soldering iron, hair drier, cut-cord,…)

The payload

The main feature of the payload is masses. Its contents will depend on what the user wishes to do. The following devices are often embarked:

camera or camera (often numerical)
pressure pick-ups and temperature
transmitting/receiving radio operator
Receiving GPS

It is possible to imagine any kind of embarked experiment on board balloon. But always think of safety and the regulation.

See too

Internal bonds

External bonds

the solar balloon is an extra-light montgolfier
TRANSPOL' AIR - the solar balloon with the service of the polar adventure
Some explanations, photographs and constructions on the balloons solar

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