GB2483993A - Membrane of gas envelopes of airships and balloons - Google Patents

Abstract

Airships and/or balloons having an internal flexible and impermeable membrane, M, within their gas envelopes, E, the lifting gas being contained above the membrane M, while air may be admitted or withdrawn from below the membrane M, preferably by pump P. The variable volume of air contained below the membrane M causing it to rise or to drop as the volume of air is increased or decreased, compressing or decompressing the lifting gas above, so enabling the buoyancy and lifting capacity of an airship, or balloon, to be controlled as appropriate to the payload, operating altitude, rate of ascent or descent, loading and unloading operations and servicing at, or close to ground level. When there is no air in the gas envelope, the membrane is in contact with the lower portion of the gas envelope. The line of attachment, L, of the membrane, M, is horizontal when the airship or balloon is in level flight.

Description

I

A Modification to Gas Envelopes of Airships and Balloons

Description

The gas envelope' of airships and balloons contains the lifting gas'which provides buoyancy, enabling such aircraft to float freely in air without the need for powered assistance.

Variable atmospheric pressure and varying payloads require some means of controlling buoyancy for level flight, ascent and descent.

The modification to the gas envelopes of airships and balloons here described is an impermeable, flexible membrane within the gas envelope to enable controlled variable lift without the need either to jettison and replenish lifting gas, or, alternatively, to compress and store lifting gas aboard the craft, or to carry and jettison ballast. It offers the possibility of replacing hot air to achieve lift for sport' balloons with a safe inert gas economically.

The membrane is attached continuously around its perimeter to the inner surface of the gas envelope along a line which is horizontal when the airship, or balloon, is in level flight, so as to seal the spaces above and below it from each other hermetically. The flexible membrane is shaped so as to conform to the shape of the gas envelope below the line of attachment, so that, when the envelope is completely filled with gas at minimum operating pressure, the flexible membrane is in effect a second, inner, skin to the lower portion of the envelope. This state is achieved by means of a valve located in the lowest region of the envelope, whilst open. In this condition the airship, or balloon, has maximum aerial buoyancy, in excess of that required for take-off at maximum payload, and sufficient to achieve the desired ceiling altitude for safe operation.

An onboard reversible pump (P, Figure 1) enables air from the surrounding atmosphere to be admitted through the afore-mentioned valve between the lower portion of the gas envelope and the underside of the flexible membrane tinder controlled pressure, causing the flexible membrane to rise within the gas envelope, compressing the lifting gas contained within the upper portion of the gas envelope above the line of attachment, so reducing the buoyancy of the airship, or balloon.

When the membrane is raised to its fillest extent, that is, when it is inverted to a position above its line of attachment, mirroring that assumed for maximum buoyancy, aerial buoyancy is at its minimum, and the downward force of gravity upon the airship, or balloon, exceeds the lift due to buoyancy by some desired safe maximum amount.

Whilst on the ground, buoyancy is reduced below the maximum, in order to maintain a safe excess of downward gravitational force upon the airship, or balloon, for secure mooring, servicing, and when loading, or unloading. For take-off, opening the valve and expelling air from the portion of the gas envelope below the membrane increases buoyancy, until the desired rate of ascent is achieved. The rate of expulsion of air may be increased by the use of the pump with reversed flow.

The valve is closed when the airship, or balloon, reaches the desired altitude for level flight.

Equilibrium is maintained by use of the pump and valve to make adjustments to the internal pressure within the gas envelope, as in-flight atmospheric conditions may require.

When air from the surrounding atmosphere is admitted at pressure through the opened valve by means of the onboard pump, the flexible membrane rises as air occupies the space between it and the gas envelope below the membrane's line of attachment, compressing the lifting gas above it within the decreasing volume of the upper region of the gas envelope above the line of attachment. The compressed lifting gas above the membrane increases in density, whilst the air at the same pressure below it has also a density greater than the lifting gas displaced by it, and of the surrounding atmosphere. The buoyancy of the airship, or balloon, relative to the surrounding atmosphere is accordingly reduced.

To descend to a lower altitude, and for landing, the valve is opened, allowing air to be admitted to the gas envelope below the flexible membrane by means of the onboard pump.

The airship, or balloon, therefore descends for as long as the downward force of gravity exceeds, or is just balanced by the airship, or balloon's, buoyancy and the upward drag of the surrounding air upon the surface of the airship, or balloon, the rate of descent being controlled by regulating the rate of in-or outflow of air through the pump.

For ballooning, a membrane as described above should make the use of an inert lifting gas in lieu of heated air, viable. The risk of fire would be removed. Control of landing and take-off should be both easier and safer. For an envelope of comparable lifting capacity, the required area of fabric should be reduced. Fully deflating the balloon for transport and storage would require a separate vessel for storing the lifting gas under pressure.

Figure 1, page 5, illustrates this modification schematically.