IMPERIAL PATENT OFFICE

Published on 2 October 1909

PATENT SPECIFICATION No. 214019; Class 77h. GROUP 3.

Dr. HUGO ERDMANN, CHARLOTTENBURG

Filling Gas for Aircraft

Patented in the German Reich from 14 August 1908 onward.

This invention relates to a filling gas for aircraft, and consists of the use of superheated steam, for example in the relaxed state (at ambient pressure?), at a temperature of more than 100C, or mixtures thereof with other gases.

The materials to which the airships owe their lift and their buoyancy, which have been used in the past, can be divided into two groups. On the one hand combustible gases of low specific gravities have been utilized, and on the other hand heated air. Both methods entail substantial fire danger, as experience has shown, because light materials, such as animal and vegetable fibers and skins, rubber, and light alloys will always have to be used for the design of the balloons or lifting portions of the airship. All such materials are however easily ignited, burnt, or melted. The use of a fireproof filling gas for airships must therefore appear to be very favourable. Among light gases which are not combustible or at least not dangerously inflammable, like helium or ammonia, some are barred because of their difficulty of production and some by their acid characteristics. Steam which is not superheated condenses very quickly, which is not the case, as is later shown, with superheated steam, especially in mixtures with other gases.

The filling gas introduced by this invention can be used with advantage in rigid airships. The multiple covers used in any case with airships work here to prevent radiant emission, since the still air layers, present between the covers, serve as insulation. This insulation effect can be further amplified by including some well-known insulation material, e.g. eiderdown. In addition to fire safety, the use of steam offers the substantial advantage that the refilling can be easily performed in any location; and the airship operator does not first have to wait for the procurement of hydrogen or coal gas. The necessity to shroud the balloon in multiple covers, eiderdown and the like makes the airship at the same time less sensitive to solar radiation and shadowing by clouds, as well as more resistant against impacts (birds, projectiles, or similar), which in some circumstances may be of importance.

Example 1.

A balloon of 1000 m3 volume is filled with unpressurized, dry steam at 105C temperature. The lift provided by this content is 700 kg. In order to maintain the lift during travel, it is only necessary to replace the heat lost by radiation. This replacement can be implemented by direct injection of superheated steam.

According to circumstances, it could be wise to mix the steam with hydrogen, illuminating gas, nitrogen or atmospheric air. The advantage obtained is, for example, that, due to the gas expansion and steam tension, a large balloon can be filled with a relatively small quantity of hydrogen gas, and the lift of the gas can be enormously increased without substantial extra cost; on the other hand during flight such a mixture may be allowed to cool down substantially under 100C, without the danger of water condensation.

Example 2.

A balloon of 2000 m3 volume is filled at the same time with 1000 m3 of hydrogen gas and with the steam from 270 kg of water. The steam is heated before the filling so strongly that the temperature of the mixture in the balloon is about 140C. This will achieve a lift of 2200 kg, which is only around 8 per cent less than when the whole balloon is filled with pure hydrogen gas.

Example 3.

Into a balloon filled with 5000 m3 of air, the steam developed from 600 kg water is injected by a nozzle, so strongly heated that the temperature of the thus mixed contents of the balloon is about 95C. The lift will be almost 2000 kg.

PATENT CLAIMS:

1. Superheated steam as filling gas for aircraft.

2. Filling gas according to Claim 1, characterized in that other gases or gas mixtures are mixed with the superheated steam.

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