Aeronautics and astronautics – Aircraft control – Stabilizing weights
Reexamination Certificate
1998-06-09
2001-02-06
Barefoot, Galen L. (Department: 3644)
Aeronautics and astronautics
Aircraft control
Stabilizing weights
C244S096000, C244S098000, C244S061000
Reexamination Certificate
active
06182924
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to ballast and ballast substitutes for lighter than air aircraft such as balloons, airships and blimps and particularly to aircraft designed to utilize helium (or other light than air, i.e., nitrogen, gases which can be liquefied, such as hydrogen, ammonia and methane) gas for effective lift and with ballast lift control.
BACKGROUND OF THE INVENTION
Lighter than air aircraft which operate by means of lift afforded by buoyant gas, almost always use a means for controlling the effective lift from the gas. This often entails changing the temperature of the gas (hotter gas provides greater lift and vice versa) or by means of ballast. The ballast, typically in the form of a convenient material such as sand and finely divided metal are commonly used. The ballast, provides a drag or control (i.e., extra weight) for maintaining a desired low altitude with higher altitudes being obtained by the jettisoning thereof since the lighter the aircraft, the greater the effect of the lifting gas and the higher the altitude. Ballast is jettisoned when higher altitude is necessary (when a rapid rise is required or heating of the buoyant gas in not feasible or desired) and buoyant gas is released or cooled (hotter gas occupies greater volume with increased lift) to decrease the buoyancy and to lower the altitude. It may also be desirable to use the ballast to reduce or stop descent to make up for loss in lift that may occur from gas leakage or cooling from decrease in either the amount of incident sunlight or of incident infrared radiation from the surrounding. Control of the aircraft is therefore dependent in some measure on the amount of ballast carried by the aircraft. However, once jettisoned, ballast is lost and not renewable for additional use and control. As a result, effective air loft time or flight time is limited by the amount of available ballast. It is usually prudent to land with some ballast still in the craft to make a controlled and safe landing.
As used herein the term “airship” refers to any craft equipped With propelling means through the surrounding air and which derives at least some of its lift from a lifting gas. This includes blimps and all kinds of non-rigid airships as well as airships with a rigid structure, such as those referred to as Zeppelins or dirigibles which obtain all or most of their lift from a lighter than air gas. It also includes all hybrid craft deriving lift partly from a lighter than air gas and partly by aerodynamic lift generated by moving though an atmosphere. Airships can compensate for changes in lift to some degree by using aerodynamic forces generated by moving though the air. Nevertheless, it is common practice to carry ballast in these craft to land in case of engine failure. It is also often desirable to keep an airship close to equilibrium to minimize power needed to generate aerodynamic forces on the craft.
SUMMARY OF THE INVENTION
It is accordingly an object of the present invention to provide an improved ballast for lighter than air aircraft which increases the per pound effectiveness of ballast, thereby extending its maneuverability or it useful time aloft or both.
Generally the present invention comprises a method for improving the flight control of a lighter than air aircraft by utilization of non-jettisonable improved ballast, comprised of at least one tank of a lighter-than-air gas in liquid form. Lighter than air gases include the preferred helium as well as hydrogen, ammonia and methane. Depending on circumstances and costs other gases, such as hydrogen and ammonia, may be more preferred in locations where helium is very costly. The tank containing the liquefied gas is adapted to maintain the liquefied gas in such state for at least the expected duration of the flight and the attendant handling times or, at the very least for at least a useful part of the flight time, such as in situations where the liquid gas is evaporated well before the end of the flight. The tank is further adapted to be connected to the existing gas lift compartments of the aircraft, whereby, when additional lift is required, a measured portion of the liquefied gas is released into the gas lift compartment and vaporized (vaporization may be effected prior to entry into the gas lift compartment as well). There is no jettisoning of ballast (with possible attendant drop problems) and lift is much greater (up to seven times greater) than that obtainable with prior art dead weight ballast.
Thus, dead weight ballast such as sand bags provides an equivalent pound for pound lift, i.e., jettisoning of one pound of ballast provides one pound of additional lift. With the present invention, not only is the weight of the liquefied gas removed there is a further substantial increase in buoyancy achieved as a result of the additional lighter-than-air gas added to the gas lift compartments.
As an example, existing insulated gas tanks capable of holding liquid helium in liquid form have a dead weight about equal to that of the liquid helium contained therein. A pound of liquid helium when vaporized is capable of lifting 6.2 pounds of weight. Accordingly, by subtracting the dead weight of the helium, one pound of liquid helium provides an ideal ballast increase of 7.2 pounds. In any particular situation a certain amount of weight will be set aside for ballast. The containers for the liquid gas must take up part of the weight. With the prior art container weight taken into account this means that each pound of simple ballast such as sand would be replaced by half a pound of helium and half a pound of container, which still is more than three and a half times that achievable with standard ballast. Greater efficiency in the weight of the holding tanks will provide even greater efficiencies for the liquefied gas ballast. For the ultimate time aloft, in some circumstances it would be possible to drop the containers themselves although this might not often be done for economic reasons since such containers are relatively costly. The containers may also be dropped as emergency ballast, regardless of expense.
This and other objects, features and advantages of the present invention will become more evident from the following discussion and drawings in which:
REFERENCES:
patent: 1035560 (1912-08-01), Erdmann
patent: 1588147 (1926-06-01), Schroder
patent: 1802586 (1931-04-01), Stokes
patent: 4012016 (1977-03-01), Davenport
patent: 4172048 (1979-10-01), Dunlap
patent: 2518946 (1976-11-01), None
Barefoot Galen L.
Greenberg & Traurig, LLP
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