Aeronautics and astronautics – Aircraft – lighter-than-air – Airships
Reexamination Certificate
2001-01-18
2002-08-06
Swiatek, Robert P. (Department: 3644)
Aeronautics and astronautics
Aircraft, lighter-than-air
Airships
C244S127000, C244S128000
Reexamination Certificate
active
06427943
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an airship, and more particularly to a stratospheric airship having a gas envelope which is divided by a diaphragm into a buoyant gas compartment containing a buoyant gas therein and an air compartment containing air therein.
Airships are typically used at low altitudes (on the order of kilometer or less) where there is a relatively small change in atmospheric pressure for the purposes of advertisement, relay broadcasting of events, monitoring, security guarding, transportation, sightseeing, etc. For airships used at such low altitudes, the flight altitude control is relatively easy because the flight altitude does not have to be changed over a wide range. Specifically, for such an airship, the volume of the gas envelope is determined so that it can withstand flight at the maximum altitude. After takeoff, the airship is allowed to ascend by throwing ballasts away. After the airship reaches the maximum altitude, the buoyant gas is partially exchanged to the air so as to allow the airship to descend.
In order for an airship to ascend to a high altitude, called the “stratosphere” (e.g., 17 to 22 Km in altitude), where the atmosphere density is diluted to about {fraction (1/14)} to {fraction (1/15)} of that in the vicinity of the sea level, it is indispensable to provide the airship with a mechanism capable of substantially varying the volume of the buoyant gas for producing a buoyancy such as a helium gas by 14 to 15 folds.
A type of a volume varying mechanism is disclosed in, for example, Japanese Patent Laid-Open Publication No. Sho 54-70597. According to the disclosure, an airship is allowed to descend by winding up the hull of the gas envelope (where the buoyant gas is contained) by means of a roller or by retracting the hull of the gas envelope while squeezing the gas envelope by means of a plurality of rollers opposing one another, so as to reduce the volume of the gas envelope and increase the internal pressure thereof, thereby reducing the static buoyancy. The airship is allowed to ascend by drawing out the hull so as to increase the volume of the gas envelope and reduce the internal pressure, thereby increasing the static buoyancy.
With such a mechanism, however, since the volume of the gas envelope is varied to control the altitude of the airship, the outer shape of the airship changes substantially. This also substantially changes the aerodynamic characteristics of the airship, thereby preventing the airship from ascending with a stable attitude.
FIG. 9
is a schematic side view illustrating another airship in the prior art which addresses this problem.
FIG. 10
, FIG.
11
and
FIG. 12
are cross-sectional views illustrating the same taken along line V—V, line VI—VI and line VII—VII in
FIG. 9
, respectively. Referring to
FIG. 10
, the airship has a gas envelope
101
defined by a balloon-shaped ship hull
102
, and the gas envelope
101
is divided by a diaphragm
103
, which acts as a diaphragm, into a buoyant gas compartment
104
containing a buoyant gas therein and an air compartment
105
containing air therein.
Referring to
FIG. 11
, a thin film buoyant gas tank
106
is provided in an upper portion of the buoyant gas compartment
104
. Referring to
FIG. 9
, ballonets
107
are provided in a front and a rear portion of the air compartment
105
for maintaining the shape of the ship hull
102
, i.e., the shape of the gas envelope
101
, and for keeping the balance of the airship. Moreover, a solar battery module
108
is provided on the upper surface of the gas envelope
101
, and a load
109
including equipment, a storage battery, a fuel cell, mission payload equipment, etc., is suspended from the bottom of the gas envelope
101
. The solar battery module
108
and the storage battery, etc., are connected to each other via power cables
110
provided therebetween along the outer surface of the gas envelope
101
.
Referring to FIG.
11
and
FIG. 12
, while the airship is still on the ground before takeoff, a buoyant gas, e.g., a helium gas, is introduced via a buoyant gas inlet
111
into the thin film buoyant gas tank
106
, and the valve of the buoyant gas inlet ill is closed. Then, the ambient air is introduced via an air blower
112
into the air compartment
105
so as to pressurize the air compartment
105
to maintain the shape of the ship hull
102
. At this time, an air vent valve
113
of the air compartment
105
is closed, and the diaphragm
103
is pushed up, whereby the thin film buoyant gas tank
106
and the buoyant gas supplied from the thin film buoyant gas tank
106
into the buoyant gas compartment
104
are pressurized, as illustrated in FIG.
12
.
The airship starts ascending by an excessive buoyancy which is equal to the buoyancy provided by the buoyant gas in the buoyant gas compartment
104
and the thin film buoyant gas tank
106
minus the total weight of the airship including the equipment. As the airship ascends, the atmospheric pressure gradually decreases. Along with the decrease in the atmospheric pressure, the difference between the internal pressure of the gas envelope
101
and the atmospheric pressure gradually increases. In order to keep the pressure difference within a predetermined limit, the air vent valve
113
is opened so as to discharge the air from the air compartment
105
and to reduce and adjust the volume of air therein. The adjustment of the volume of air causes a difference between the pressure in the thin film buoyant gas tank
106
and that in the buoyant gas compartment
104
. In order to keep the pressure difference at or below a predetermined pressure, a buoyant gas bent valve
114
is opened so as to transfer the buoyant gas from the thin film buoyant gas tank
106
into the buoyant gas compartment
104
.
The buoyant gas transferred into the buoyant gas compartment
104
expands, thereby ensuring a sufficient excessive buoyancy for the airship to continue to ascend, and compensates for the reduction in the volume of air due to the discharge of air, thereby constantly maintaining the volume within the ship hull
102
and thus substantially constantly maintaining the outer shape of the gas envelope
101
.
After the airship has ascended into the stratosphere, the airship keeps a station in the air, with the gas envelope
101
being in a state as illustrated in FIG.
13
. The volume of air in the air compartment
105
has been substantially reduced, and the diaphragm
103
has been pushed down by the expanded buoyant gas in the buoyant gas compartment
104
while the airship keeps a station in the stratosphere.
With the conventional airship as described above, the difference between the internal pressure of the gas envelope
101
and the atmospheric pressure which is caused by the atmospheric pressure decreasing along with the ascent of the airship is accommodated by reducing and adjusting the volume of air in the air compartment
105
so as to allow the buoyant gas to expand, thereby ensuring a sufficient excessive buoyancy. Moreover, the reduced volume of air is compensated for by the increased volume of the buoyant gas, thereby constantly maintaining the volume of the gas envelope
101
. Thus, the outer shape of the gas envelope
101
, i.e., the outer shape of the airship is substantially constantly maintained.
However, the diaphragm
103
for partitioning the buoyant gas compartment
104
and the air compartment
105
from each other is a very large sheet of film which is coupled along its periphery to the ship hull
102
. Therefore, it is difficult for the diaphragm
103
to smoothly change its shape to closely follow the increase in the volume of the buoyant gas occurring along with the decrease in the volume of air in the air compartment
105
. For example, as illustrated in
FIG. 14
, the diaphragm
103
may experience “sloshing” (i.e., a phenomenon in which the diaphragm
103
takes a wavy shape), thereby causing an asymmetric distribution of the buoyant gas in the gas envelope
101
. The asymmetric distribution of the buoyant gas may
Kimura Jun-ichi
Komatsu Keiji
Sano Masaaki
Yokomaku Yoshio
Farber Martin A.
Fuji Jukogyo Kabushiki Kaisha
Swiatek Robert P.
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