Ammunition and explosives – Fuel air explosive
Reexamination Certificate
2000-08-11
2001-12-04
Jordan, Charles T. (Department: 3641)
Ammunition and explosives
Fuel air explosive
C102S301000, C102S324000
Reexamination Certificate
active
06324982
ABSTRACT:
FIELD OF THE INVENTION
The invention involves a process for artificially triggering an avalanche and more generally a process for artificial triggering of a natural phenomenon in which one or several explosions of a fluid are triggered in a predetermined zone where this phenomenon is to be triggered.
The invention can be applied in all areas where a phenomenon can be triggered or started with local overpressure of the atmosphere above the zone affected by the phenomenon.
The invention is typically applied to artificial triggering of avalanches of snow at winter sport resorts and at sites where there is a potential risk to people such as ski trails, mechanical lifts, roads, mountain railroads and, in general, public and private constructions and developments.
The invention also involves a device for applying this process including the means to trigger at least one explosion of a fluid in a predetermined area where the aforesaid phenomenon is to be triggered.
STATE OF THE ART
Several means now exist for artificially triggering an avalanche from a predetermined zone, by causing local overpressure of the atmosphere in the aforesaid zone.
For example, one of these means involves placing or throwing explosive charges such as TNT and then triggering the explosion of these charges. The explosion creates a blast which sweeps the surface of the blanket of snow in the avalanche zone, and a shock wave which shakes the base of this blanket and triggers an avalanche.
The handling of these explosive changes is a risky operation regardless of the precautions taken by the users. These charges are also generally polluting.
Another means is the system marketed under the name GAZEX. This means is described in patent application FR-A-2 636 729. It involves using a device including a cannon or metallic tube with a closed bottom, and a frontal mouth opening in the direction of the blanket of snow. This device also includes a combustive gas supply circuit from a first source and a fuel gas supply circuit from a second source. Nozzles for filling the cannon with these gases are arranged in various places along the length of this cannon and an ignition device is mounted at the rear of the cannon. A gaseous mixture is formed within the cannon, for example a mixture of propane and oxygen, and the explosion of this mixture is triggered in the cannon by the ignition device.
The frontal mouth of the cannon diffuses the blast and the shock wave caused by the explosion on the surface of the snow blanket, thus triggering the avalanche.
While this approach has proven effective in many facilities, it has a certain number of drawbacks. The cannon is heavy, it can weigh several hundred kilograms, it is hard to move, unattractive and expensive. In addition, this system uses electronic valves to make the explosive gas mixture and thus requires numerous adjustments and verifications.
BRIEF DESCRIPTION OF THE INVENTION
This invention precisely aims to overcome the aforementioned drawbacks with a process for artificially triggering an avalanche by at least one explosion of an explosive fluid in a predetermined zone, the aforesaid process including a first step of filling at least one flexible envelope with an explosive fluid and a second step of triggering an explosion of the aforesaid fluid within each envelope, each envelope being destroyed by the explosion of the fluid.
The fluid can be inserted in the envelope by means of a diffuser, the diffuser being connected to a source of gas by means of a gas supply tube.
The flexible envelope can be directly attached to the diffuser which can then act as a fixed support for the flexible envelope during filling.
According to the invention process, the fluid can be an explosive gaseous mixture of a combustive and a fuel.
According to the invention, a combustible gas is used as a gaseous fuel. This combustible gas may be chosen from among the group of substances including hydrogen, petrol residues (such as tetraine commercialized by the French company Air Liquid), acetylene, propane, butane, or a mixture of these substances, but preferably hydrogen.
The combustive used can be, oxygen, ozone, air, or air enriched with oxygen or ozone, but preferably air.
According to the invention process, the fluid within each flexible envelope can be at a pressure equal to the atmospheric pressure or it may be substantially higher than it when the envelope(s) is (are) filled.
According to the invention process, each flexible envelope used must be made of a material which can be destroyed by the explosion of the fluid which it contains. The material of the flexible envelope and the thickness of this material must be chosen so that it releases the overpressure wave created by the explosion of the fluid that it contains, without presenting too much resistance to this explosion. This material must also be able to contain the fluid until the time of the explosion and it must be sealed.
According to a preferred embodiment of the invention, the flexible envelope can be made of a light material such that for a gaseous mixture forming a fluid which is lighter that the surrounding air, for example an explosive mixture of hydrogen and air, the envelope is held in a vertical position above the blanket of snow. This envelope could advantageously be bio-degradable to avoid polluting the environment.
An example of a flexible envelope with all of the previously-mentioned characteristics is an envelope made of a material chosen from the group including butyl rubber. The thickness of the material which makes up the envelope could be for example about 100 to 200 &mgr;m.
The envelope could be a balloon of the type used for weather balloons.
This flexible envelope must have a volume such that it can contain a sufficient volume of the fluid, at atmospheric pressure or at a slightly higher pressure, so that the explosion of this fluid triggers the avalanche. When the fluid is a mixture of hydrogen and air for example, the minimum volume of the envelope can be determined by the following reasoning, considering that the fluid in the envelope is at atmospheric pressure.
It is generally accepted that a force equivalent to the explosion of at least 3 kg of TNT is needed to trigger an avalanche in normal conditions, i.e. when there is a risk of a natural avalanche.
The following equation (I) is the chemical equation for the explosion of a mixture of H
2
/oxygen in the air:
H
2
+½O
2
→H
2
O (I)
This equation (I) shows that the stoichiometric mixture for the explosion in normal temperature and pressure conditions (273° Kelvin, and 101 325 Pa) includes two volumes of H
2
for one volume of O
2
. When the fluid is a hydrogen/air mixture, this corresponds to 30% hydrogen and 70% air by volume. The explosion of 2 g of H
2
(1 mole of H
2
) according to equation (I) supplies 57,800 calories, or about 60,000 calories, and the explosion of 1 g of TNT supplies 1000 calories, 1 g of H
2
thus being the equivalent of 30 g of TNT in terms of power. The density of hydrogen being 90 g/m
3
, 1 m
3
of hydrogen is equivalent to 2700 g of TNT. Considering that for various reasons such as the quality of the gaseous mixture, the temperature, etc. the yield of the explosion is not equal to 1 but to 0.5, 1 m
3
of hydrogen can supply an energy equivalent to an explosion of 1.35 kg of TNT. It is therefore preferable to use a volume of hydrogen of 2.2 m
3
so that the detonation power is sufficient, i.e. equivalent to the explosion of 3 kg of TNT, to trigger the avalanche. This volume of hydrogen would then require a volume of air of 6.8 m
3
to obtain a stoichiometrically detonating mixture.
The minimum preferable volume of the envelope for the H
2
/air mixture is thus 8.9 m
3
when the fluid filling the envelope is at atmospheric pressure.
According to the invention process, the volume of the envelope is thus chosen so as to be suitable for a volume of explosive fluid sufficient to trigger an avalanche and thus also depending on the nature of the fluid.
This process is thus adaptable because envelopes with differen
Berlandis Jean-Pierre
Eybert-Berard Andre
Taillandier Jean-Michel
Burns Doane , Swecker, Mathis LLP
Commissariat A l'Energie Atomique
Jordan Charles T.
Thomson M.
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