U.S. patent application number 13/636583 was filed with the patent office on 2013-03-14 for aerial vehicle and method of flight.
This patent application is currently assigned to Athene Works Limited. The applicant listed for this patent is Nicholas James Deakin. Invention is credited to Nicholas James Deakin.
Application Number | 20130062457 13/636583 |
Document ID | / |
Family ID | 42228153 |
Filed Date | 2013-03-14 |
United States Patent
Application |
20130062457 |
Kind Code |
A1 |
Deakin; Nicholas James |
March 14, 2013 |
Aerial Vehicle and Method of Flight
Abstract
An aerial vehicle is described which comprises: a first
compartment for holding a lighter than air gas; a second
compartment for holding atmospheric air and having an inlet and an
outlet; a solar panel for converting sunlight into electricity; a
compressor for pumping atmospheric air through the inlet into the
second compartment; control means for controlling the pitch and yaw
of the vehicle; and a controller for controlling the buoyancy of
the vehicle via the compressor and the outlet such that the vehicle
is either lighter than the surrounding air and rising or heavier
than the surrounding air and falling, and for controlling the
control means such that the rising and falling motion includes a
horizontal component. In another embodiment the solar panel is
replaced by an engine and a fuel tank for storing fuel for the
engine is also provided. The aerial vehicle can remain airborne for
extended periods by using buoyancy propulsion. In the embodiments
including a solar panel, a system including a light transmission
station may be provided to supply energy to the solar panel from
the light transmission station rather than relying on the incident
sunlight alone. A method of flight using buoyancy propulsion is
also described.
Inventors: |
Deakin; Nicholas James;
(Leeds, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Deakin; Nicholas James |
Leeds |
|
GB |
|
|
Assignee: |
Athene Works Limited
Leeds
GB
|
Family ID: |
42228153 |
Appl. No.: |
13/636583 |
Filed: |
March 22, 2011 |
PCT Filed: |
March 22, 2011 |
PCT NO: |
PCT/GB11/50562 |
371 Date: |
November 29, 2012 |
Current U.S.
Class: |
244/25 ; 244/97;
343/706 |
Current CPC
Class: |
H01Q 1/36 20130101; B64B
1/02 20130101; B64B 1/64 20130101; B64B 1/08 20130101; B64B 2201/00
20130101; B64C 2201/167 20130101; B64B 1/10 20130101; B64C 2201/101
20130101; B64C 2201/165 20130101; B64B 1/38 20130101; B64B 1/14
20130101; B64C 2201/044 20130101; B64B 1/12 20130101; B64C 2201/122
20130101; B64B 1/20 20130101; B64C 2201/127 20130101; B64C 2201/048
20130101; H01Q 9/27 20130101; B64C 2201/042 20130101 |
Class at
Publication: |
244/25 ; 244/97;
343/706 |
International
Class: |
B64B 1/62 20060101
B64B001/62; H01L 31/0232 20060101 H01L031/0232; H01Q 1/28 20060101
H01Q001/28; B64B 1/20 20060101 B64B001/20 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 23, 2010 |
GB |
1004803.1 |
Claims
1. An aerial vehicle comprising: a first compartment for holding a
lighter than air gas; a second compartment for holding atmospheric
air and having an inlet and an outlet; a solar panel for converting
sunlight into electricity; a compressor for pumping atmospheric air
through the inlet into the second compartment; control means for
controlling the pitch and yaw of the vehicle; and a controller for
controlling the buoyancy of the vehicle via the compressor and the
outlet such that the vehicle is either lighter than the surrounding
air and rising or heavier than the surrounding air and falling, and
for controlling the control means such that the rising and falling
motion includes a horizontal component.
2. An aerial vehicle comprising: a first compartment for holding a
lighter than air gas; a second compartment for holding atmospheric
air and having an inlet and an outlet; an engine; a fuel tank for
storing fuel for use by the engine; a compressor for pumping
atmospheric air through the inlet into the second compartment;
control means for controlling the pitch and yaw of the vehicle; and
a controller for controlling the buoyancy of the vehicle via the
compressor and the outlet such that the vehicle is either lighter
than the surrounding air and rising or heavier than the surrounding
air and falling, and for controlling the control means such that
the rising and falling motion includes a horizontal component.
3. (canceled)
4. An aerial vehicle according to claim 1, wherein the aerial
vehicle creates substantially no aerodynamic lift at a zero degree
angle of attack.
5. An aerial vehicle according to claim 1, wherein the aerial
vehicle further comprises a nacelle, and wherein the first
compartment and the second compartment are both contained within
the nacelle.
6. An aerial vehicle according to claim 5, wherein the nacelle has
an outer surface which defines a body of revolution or an
aerofoil.
7. An aerial vehicle according to claim 5, wherein the nacelle is
transparent and the solar panel is contained within the
nacelle.
8. An aerial vehicle according to claim 5, further comprising a
parabolic mirror associated with the solar panel for focussing
sunlight onto the solar panel.
9. An aerial vehicle according to claim 7, further comprising an
actuator for changing the orientation of the solar panel and/or the
parabolic mirror relative to the vehicle.
10. An aerial vehicle according to claim 1, further comprising at
least one wing.
11. An aerial vehicle according to claim 10, wherein the at least
one wing comprises the solar panel.
12. An aerial vehicle according to claim 11, wherein the solar
panel is positioned on the underside of the at least one wing.
13. An aerial vehicle according to claim 1, wherein the nacelle is
an aerofoil with a ratio of thickness to chord length between
approximately 5% and approximately 35%.
14. An aerial vehicle according to claim 1, wherein a wall of the
first compartment may comprise a barrier layer for limiting loss of
the lighter than air gas through the wall of the compartment.
15. An aerial vehicle according to claim 1, further comprising a
third compartment for holding a refrigerant which can undergo a
reversible phase change from a gas into a liquid.
16. (canceled)
17. An aerial vehicle according to claim 1, further comprising at
least one transmitter and at least one receiver for providing a
wireless communications network.
18. (canceled)
19. An aerial vehicle according to claim 17, wherein the at least
one receiver comprises an antenna formed by a metallised track
having an undulating pattern.
20. (canceled)
21. An aerial vehicle according to claim 1, wherein the control
means comprises a movable mass.
22. An aerial vehicle according to claim 1, further comprising an
electrolyser for electrolysing water into hydrogen and oxygen.
23. (canceled)
24. An aerial vehicle system comprising: an aerial vehicle
according to claim 1; and an electromagnetic radiation source for
emitting electromagnetic radiation for reception by the solar
panel.
25. (canceled)
26. (canceled)
27. A method of flight for an aerial vehicle comprising a first
compartment filled with a lighter than air gas and a second
compartment for holding atmospheric air, the method comprising:
alternately compressing atmospheric air into the second compartment
and then releasing the compressed atmospheric air from the second
compartment, thereby altering the buoyancy of the aerial vehicle
such that it is either heavier than air and falling or lighter than
air and rising; and actuating at least one control surface such
that the rising and falling motion includes a horizontal component.
Description
[0001] The present application relates to an aerial vehicle. More
particularly it relates to an aerial vehicle and method of flight
in which the vehicle is propelled by altering the buoyancy of the
vehicle and using the resulting rising and falling motion to
produce a horizontal motion component.
[0002] Aerial vehicles require some means to maintain their
altitude. At a basic level aerial vehicles can be considered as
those that are lighter than air and those that are heavier than
air. An example of a lighter than air vehicle is a blimp, which
maintains its altitude by buoyancy. An example of a heavier than
air vehicle is a glider, which gains altitude on thermals and then
glides down to lower altitudes using air speed to generate lift
from the passage of air over its wings and control surfaces.
[0003] Unlike powered flight, where fuel must be expended to
generate lift, both blimps and gliders can maintain altitude for
reasonably long periods because no fuel is expended to maintain
lift. Nevertheless, the time that they can spend airborne is still
limited. A glider must find a source of lift such as a thermal,
otherwise it will eventually glide down to the ground. Blimps are
maintained in the air by the buoyancy of a lighter than air gas,
such as helium, in an envelope. Over time the lighter than air gas
will escape from the envelope and the blimp must land to refill the
envelope or refuel to propel the vehicle through wind.
[0004] Recently there has been a desire to develop aerial vehicles
that can remain airborne for long periods: several days and longer.
Such vehicles are useful for gathering reconnaissance and relaying
communications. Conventional aircraft are not suitable for
remaining airborne for several days. A glider cannot remain
airborne long enough to be useful. A blimp has limited longevity in
such applications because the lighter than air gas in its envelope
will gradually escape. The blimp must also be driven by a propeller
to maintain position against winds and air currents and the
required energy and supply of fuel limits the time a position can
be maintained, even if the blimp is still airborne. Although blimps
may be tethered in position this requires access to the ground
under the reconnaissance position, something which may not be
possible.
[0005] Specialist vehicles that can remain airborne for up to three
days are known. For example, QinetiQ has demonstrated the Zephyr
aircraft. The Zephyr is a lightweight, heavier than air, powered
aircraft that uses solar cells on its wings to charge a
rechargeable battery. The Zephyr flies using the thrust from
propellers powered by the battery and the resulting aerodynamic
lift from its wings as it moves through the air. In tests, the
Zephyr has demonstrated a continuous unmanned flight of two
weeks.
[0006] The length of time the Zephyr can remain airborne is
determined by the energy budget--the energy required to power the
propellers to maintain altitude and position versus the energy
generated by the solar cells. To minimise the energy required to
maintain altitude and position, the Zephyr moves at relatively slow
speeds. To minimise drag the solar cells are mounted on the surface
of the wing. However, this introduces a disadvantage because they
may not be orientated in the optimum position towards the sun to
gather the most incident sunlight.
[0007] Buoyancy propelled sea vehicles are known. These include the
Seaglider developed by the University of Washington, the SLOCUM
glider developed by the University of Princeton and the Spray
glider developed with support from the US office of Naval Research.
These vehicles are propelled by changes in their buoyancy causing
them to be alternately heavier than the surrounding water and
sinking or lighter than the surrounding water and rising.
[0008] The density change cycle is powered by the thermal gradient
between deep water and surface water, in other words it is
indirectly powered by the energy input of the sun warming the
surface water. Buoyancy powered sea vehicles can remain in use for
many months, essentially limited by the electrical supply for their
sensors and navigation systems. Existing sea buoyancy powered sea
vehicles cannot easily be adapted for use in air. Atmospheric air
does not demonstrate the same temperature gradient (it is colder
rather than warmer at altitude). There are other problems too, the
increased density of water compared with air means the overall
density of the craft can be much higher for use in water than is
needed for use in air. Known sea vehicles using buoyancy propulsion
may have a mass as high as 50 kg. This helps them to be less
effected by ocean currents than the effect of atmospheric winds on
a lighter than air aerial vehicle. The vehicles also move slowly,
with a horizontal speed of 0.4 m/s, limiting their ability to
traverse distances quickly.
[0009] A buoyancy propelled aerial vehicle is discussed in
WO-A-2005/007506 (Hunt). Hunt proposes to change an aircraft's
density by a phase change technique, changing a gas into a liquid
state and vice versa. However, Hunt's aircraft proposes to generate
the power for this phase change using wind turbines. Although he
discusses that the wind turbines can be used to store energy while
the vehicle is on the ground, once the vehicle is in flight no
additional energy can be input to the system because the energy to
drive the wind turbines comes from the gravitationally driven
motion of the craft. The endurance is determined by the stored
energy from the turbines before the craft takes off. In flight it
is impossible for the gravitational cycle to generate enough energy
to power further gravitational cycles indefinitely without an
external input of energy, otherwise the vehicle would be a
perpetual motion machine.
[0010] It would be desirable to overcome at least one of the
disadvantages with existing aerial vehicles. Accordingly, the
present invention provides an aerial vehicle which is propelled by
changing its buoyancy by compressing atmospheric air into a
compartment of the vehicle. The compressed air acts as ballast so
that the vehicle is either heavier than air and falling or lighter
than air and rising when compressed air is expelled. As it rises
and falls a control mechanism is actuated to create a horizontal
component to the motion, for example through a wing or flight
surfaces. As is discussed below such a method can produce
surprising horizontal speed in air and can be more energy efficient
than generating thrust with a propeller, enabling a longer time in
the air.
According to the present invention, there is provided an aerial
vehicle comprising:
[0011] a first compartment for holding a lighter than air gas;
[0012] a second compartment for holding atmospheric air and having
an inlet and an outlet;
[0013] a solar panel for converting sunlight into electricity;
[0014] a compressor for pumping atmospheric air through the inlet
into the second compartment;
[0015] control means for controlling the pitch and yaw of the
vehicle; and
[0016] a controller for controlling the buoyancy of the vehicle via
the compressor and the outlet such that the vehicle is either
lighter than the surrounding air and rising or heavier than the
surrounding air and falling, and for controlling the control means
such that the rising and falling motion includes a horizontal
component.
[0017] The first compartment filled with lighter than air gas
enables the vehicle to have an overall weight lighter than the
surrounding air (in other words the vehicle weighs less than the
volume of air it displaces). It has been found that for use in air
relatively small changes in the weight of the vehicle can alter its
balance between being lighter than air or heavier than air. Thus,
the buoyancy of the vehicle can be controlled simply by compressing
air into the second compartment. This is simpler and requires less
energy than the phase change technique proposed by Hunt. The
external energy to alter the buoyancy is provided by an external
source, the solar panel. If it is desired for the vehicle to
operate during the night when the sun is not available, batteries
may be included to store the energy for use at night.
[0018] Preferably the horizontal component of the rising and
falling motion is greater than the vertical component. The
horizontal component may be sufficiently large that the overall
motion of the vehicle is substantially horizontal.
[0019] The first and second compartments may be any envelope
suitable for retaining a gas. The solar panel may be any
arrangement suitable for generating electricity from incident
sunlight. Preferably, a solar cell such as photovoltaic cell is
used but other solar energy systems may also be used including the
photoelectric effect and solar furnaces. The compressor may be any
pump suitable for compressing air, for example it may comprise an
air pump driven by an electric motor. The control means can be any
suitable control system for controlling the pitch, roll and yaw of
the vehicle, some non-limiting examples are discussed later in this
specification.
[0020] The controller may be a microprocessor, microcontroller,
field programmable gate array, application specific integrated
circuit, or any other suitable device. The controller preferably
includes interfaces for sensors to allow control of the aircraft,
for example including a position sensor, attitude sensor, compass,
pressure sensors, infrared and/or further sensors. IR sensors can
be orientated in the XYZ axes to determine the orientation using
the property that the IR reading is generally warmer towards the
ground than the sky.
[0021] It has been found that the efficiency of an aerial vehicle
according to the invention is improved, compared with conventional
methods of propulsion such as a propeller. For example, the vehicle
may experience a free lift force of around 7N/s at sea level launch
reducing to 4N/s at the bottom of a typical operating altitude
range (1 km). The force continues to reduce with altitude up to a
buoyancy ceiling, for example 3.5 km. The vehicle may take
typically take 10 minutes to ascend from 1 km to 3 km. The
controller then activates the compressor and air ballast gradually
builds up in the second compartment. For example, this may result
in a constant force of up to 4N arising from gravity during a
gliding descent for a further 10 minutes. When ballast is expelled
a constant freelift force of 4N applies in gliding ascent. The
force reduces over a further 10 mins as the vehicle approaches its
buoyancy ceiling, typically providing 2400N/s of force over this
cycle (averaging 2N). Although the forces are small, the force can
be harnessed to result in unexpectedly fast horizontal motion.
[0022] To give an example, an electric motor may power an air pump
to draw in and compress atmospheric air to create ballast. If the
air pump were to drive a propeller an air speed of around 15 kms/hr
would result. However, with this arrangement an airspeed of around
50 kms/hr may be realised (75 kms/hr at a gliding ascent of
16.degree. ascent, 21.degree. gliding descent) and energy is only
consumed for around half the cycle (around 100 watts while the
motor is in operation to compress air to give ballast for the
descent). This gives sufficient ground speed to penetrate wind
(other than the most extreme winds) to maintain a loitering
position over an operating station.
[0023] A preferred operating altitude range is 1-3 km. This
operating altitude range may be significantly higher in some
embodiments. The vehicle may also operate at a higher operating
range by launching the first compartment semi inflated. As the
density changes, the envelope will become fully inflated at the
required lower operating altitude. A larger first compartment may
also be used. The vehicle may utilise jet-streams at around 10
kms-14 ms altitude to traverse distances more quickly if the wind
offers a useful vector, or alternatively it can circle to utilise
thermals as well as using also ridge lift or wave lift.
[0024] In another aspect of the invention, an aerial vehicle is
provided which comprises:
[0025] a first compartment for holding a lighter than air gas;
[0026] a second compartment for holding atmospheric air and having
an inlet and an outlet;
[0027] an engine;
[0028] a fuel tank for storing fuel for use by the engine;
[0029] a compressor for pumping atmospheric air through the inlet
into the second compartment;
[0030] control means for controlling the pitch and yaw of the
vehicle; and
a controller for controlling the buoyancy of the vehicle via the
compressor and the outlet such that the vehicle is either lighter
than the surrounding air and rising or heavier than the surrounding
air and falling, and for controlling the control means such that
the rising and falling motion includes a horizontal component.
[0031] The construction of this aspect is therefore the same the
first aspect, except that the solar panel is replaced with an
engine and fuel tank. It has been found that the high efficiency of
buoyancy propulsion can be advantageous when the vehicle is
provided with a conventional engine and fuel source. This may allow
carrying of heavier loads than with a solar panel. A buoyancy
propelled aerial vehicle consumes less fuel compared with a lighter
than air blimp or fixed wing aircraft propelled forwards by a
propeller. For example, the buoyancy aerial vehicle may be scaled
to carry an ISO container.
[0032] In both of the above aspects, the aerial vehicle preferably
creates substantially no aerodynamic lift at a zero degree angle of
attack. Ideally, the airframe of the vehicle as a whole has a
coefficient of lift which is between approximately -0.01 and 0.01
based on planform reference area.
[0033] The control means may be further for controlling the roll of
the vehicle.
[0034] The aerial vehicle may further comprise a nacelle, and
wherein the first compartment and the second compartment are both
contained within the nacelle. A nacelle is a streamlined enclosure
that enables the drag of the vehicle to be reduced by housing
components inside the nacelle. As the forces involved are
relatively small, reducing drag can have a significant effect on
the performance of the vehicle.
[0035] Preferably, the nacelle has an outer surface which defines a
body of revolution or an aerofoil. Although the nacelle may have
the shape of an aerofoil, it has been found that, surprisingly, the
performance may be improved if the nacelle is shaped such that no
(or minimal) aerodynamic lift is generated at a zero angle of
attack. A conventional asymmetrical aerofoil commonly used for a
wing, will create vortex induced drag as a result of generating
aerodynamic lift. The induced drag is significant and will
significantly slow the vehicle. The aerodynamic lift from the
aerofoil is not required in a vehicle according to the present
invention, its lift is generated by the buoyancy of the lighter
than air gas in the first compartment. If an asymmetrical aerofoil
is used, performance may be improved by orientating the aerofoil
such that it generates a downward force, rather than a conventional
upward, lift force in gliding ascent.
[0036] It will be appreciated that all the components of the
vehicle, apart from the control surface, could be situated inside
the nacelle, or inside additional nacelles, to further reduce the
drag on the vehicle. In embodiments including a solar panel, it is
particularly advantageous if the nacelle is transparent and the
solar panel is contained within the nacelle. This enables the solar
panel to be oriented more efficiently towards the sun, without
increasing drag.
[0037] The efficiency of the solar panel can be further improved in
one embodiment by providing a parabolic mirror associated with the
solar panel for focussing sunlight onto the solar panel. This has
several advantages. A mirror can weigh less than a solar panel,
allowing more sunlight to be gathered for less weight. The cost of
providing the mirror is also likely to be less than the cost of
solar panels of equivalent area. This embodiment is particularly
effective when the solar panel and mirror are contained within a
transparent nacelle because then the mirror has no effect on the
drag. Any suitable mirrored film can be used for the parabolic
mirror, preferably one that is UV stabilised. In one embodiment 3M
Vikuiti Reflection Film, commercially available from Optical
Systems, 3M, 3M Center, St. Paul, Minn. 55144-1000 USA is used. It
may be manufactured to the required thickness, preferably around 10
.mu.m, and provided with a UV stabilised antireflective coating.
This has a reflectance of 95%.
[0038] The aerial vehicle may further comprise an electric motor
for changing the orientation of the solar panel and/or the
parabolic mirror relative to the vehicle. This allows the solar
panel to track the sun through the sky for improved efficiency and
is particularly advantageous when the solar panel is inside a
transparent nacelle because it then has no effect on drag.
Preferably, the orientation may be altered along an axis running
from the front to the back of the vehicle. The mirror and/or solar
panel may be constructed to have constant distribution of weight
about this axis, so that changing orientation does not alter the
weight distribution of the vehicle. Alternatively, any change in
weight distribution may be compensated through the control surface
or by moving internal components to change the centre of
gravity/buoyancy. The tracking can be implemented simply by
monitoring the output of the solar panel, by using a light sensor
or alternatively by knowledge of the position of the sun to
calculate optimum orientation.
[0039] In another embodiment, the solar panels may comprise one or
more parabolic dishes, held within the first or second chambers.
The one or more parabolic dishes are preferably orientated into sun
light around two rotational axes. The one or more parabolic dishes
may be made of a restraining ring, which is preferably made of
carbon fibre, with mirror film sections that are bonded together to
form a parabolic dish. The shape of the parabolic dish is retained
due to the restraining ring. In this embodiment, light is reflected
by the mirror film and focuses into a small photovoltaic cell.
Ideally, the cell is a triple junction cell with a Indium Gallium
Phosphide (InGaP) junction, Indium Gallium Arsenic (InGaAs)
junction and Germanium (Ge) junction on a substrate Germanium (Ge).
Cells of this type are available from Emcore Corporation,
Albuquerque, USA. Alternatively a four junction cell of GaInNAs,
Cu(In,Ga)Se2 Heterojunction cell, or any other photovoltaic solar
cell may be used.
[0040] The solar panel may comprise Gold Nano Cups latex substrate
that is available from Rice University of Texas. This is created
using a glass substrate and evaporating gold onto nano balls, then
applying an elastizer such as latex. When the latex is removed nano
plano-concaved lens are formed on the latex substrate (they are all
aligned), so that random incidental light, is then made parallel in
a single direction after passing through the latex. Alternatively,
latex may be used as a `former` and if a resin is applied and the
latex `former` removed, nano plano-convex lens may be present on
the resin film (with better optical qualities). Most light passes
through a Photo Voltaic (PV) cell without generating electrical
energy, so use of such a film would bend light along the length of
the PV film, increasing the path of a photon as it passed through
the PV material. This increases the likelihood of the photon
hitting an electron out of orbit to generate additional electrical
power. The nano plano-convex film may be added to any PV cell,
although it is preferred that the PV cell is on a plastic
substrate. NanoSolar of the USA has a demonstrated efficiency of
14.6% commercially available on an aluminium substrate.
Alternatively, a metal backed PV film, such as steel, may be used
or a polymer substrate. Likewise any PV cell may be employed.
[0041] Additional power may be generated in some embodiments by a
Thermal Electrical Generator (TEG). A metal foil section is bonded
into skin of the first and or second compartment or the outer
surfaces of the aerial vehicle. Preferably, the metal foil is a TEG
metal foil, ideally, bismuth telluride with P-N junctions or any
material in the class of Thermal Electrical Generators or
alternatively the TEG is attached to a metal foil such as silver,
gold, copper or aluminium. Waste heat from the solar cells is lost
to the interior of the first and/or second compartments through
convection. The TEG forms part of the chamber (that is heated
through sunlight) and also exposed to colder atmospheric air
outside, the heat differential across the TEG creates electrical
energy that may be used to improve overall efficiency of the aerial
vehicle. A heat sink may be attached to the innermost section of
the TEG to improve thermal conductivity. Preferably the heat sink
is an aluminium honeycomb with high surface area to weight.
[0042] In an alternative embodiment, the heat differential between
the solar cells (first and/or second compartments) and the external
atmosphere may drive a Sterling or Rankine cycle engine to create
additional energy that may either drive the pump directly or a
dynamo to produce additional power. The solar cells may be
thermally connected through a heat conductive flexible wire
(preferably silver wire or carbon filament) or flexible heat pipe
to the TEG or a metal foil section on the chamber or outer surfaces
(across the Sterling or Rankine engine).
[0043] In another embodiment, the aerial vehicle further comprises
at least one wing. It is preferred that the wing is substantially
flat so it generates as little drag as possible. Aerodynamic lift
is not required to be generated by the wing other than to maintain
a glide path, it is instead provided to assist in generation of a
horizontal component from the vertical buoyancy driven motion. The
wing is a `flat plate` film wing, with minimal frontal area exposed
to the air it penetrates. It is maintained by a slim symmetrical
carbon fibre aerofoil section running the length of the wing. A
carbon fibre wingtip section maintains rigidity across the wing.
The film may be sandwiched between two carbon fibre parts.
[0044] In alternate embodiments the wing may be a substantially
symmetrical aerofoil in cross section. In further alternate
embodiments the wing may be an asymmetric aerofoil in cross
section. In the case of an asymmetric aerofoil, preferably
substantially no aerodynamic lift is generated at a zero angle of
attack. Preferably, the asymmetric aerofoil may have a lift
coefficient between approximately -0.01 and 0.01 (based on a
planform reference area)
[0045] In embodiments where the wings are a symmetrical aerofoil
section, they are preferably machined of foam with supporting
carbon fibre parts along the leading and trailing edges and covered
with a heat shrunk film (such as polyester). The ideal thickness of
the wing chord is 3.5% of height to chord length.
[0046] In embodiments including a solar panel, the at least one
wing may comprise the solar panel. For example, a flexible solar
panel may be installed within the wing. In a further embodiment,
one or more actuated parabolic troughs may be installed within the
aperture sections of the wing. The parabolic trough is preferably
made from mirror film that is held in place at each end with a
parabolic section of carbon fibre that is actuated to orientate the
panel into sunlight. The panels may be actuated individually or
together using coupled gears (for example by using a timing
belt).
[0047] Depending on the size of the aerial vehicle, the parabolic
trough may be relatively small in size. In some embodiments
conventional cells would be too large and in that case a solar cell
wire may be used at the focal point. The wire is preferably made of
Germanium with coated layers and a contact for each coated layer.
More preferably triple coatings are used of Indium Gallium
Phosphorus (InGaP), Indium Gallium Arsenic (InGaAs) and Germanium
(Ge) onto a wire or tube substrate (that may be Germanium).
Coatings may be applied by vapour deposition or any industrial
process that may form a metal coating onto the base material. Any
coatings layers and substrates known in the class of photovoltaics
may also be used. Unlike conventional solar cells, in these
embodiments the photovoltaic is applied onto a wire or tubular core
material, for example by using a roller to roller manufacturing
technique. The tubular arrangement of a solar cell wire has the
advantage that a working fluid may be used to draw heat away from
the solar cell. The working fluid may be used in a sealed heat pipe
arrangement to more effectively draw heat away from the solar cell
(so it operates at higher thermal efficiency). Preferably a deep
parabolic trough is used and the focal point is within the trough
(or largely in the centre section) where the solar cell wire is
positioned, so that light is reflected onto all parts of the
wire.
[0048] In an alternative embodiment, the PV cell may be
incorporated onto the surface of the vehicle other than on the
surface of a wing.
[0049] In one embodiment, the nacelle is an aerofoil with a ratio
of thickness to chord length between approximately 5% and
approximately 35%. This gives a significantly more elongated
structure than a conventional blimp, when the first compartment is
incorporated into the nacelle. It has been found that this reduces
drag, improving performance.
[0050] The first compartment has to withstand relatively low
pressures, preferably around 0.3 atm. It may therefore be formed
from any suitable film. However, the time that a vehicle can remain
airborne according to the present invention is limited by the rate
at which gas is lost from the first compartment, because this will
reduce the buoyancy. The film may not be effective at preventing
the loss of gas through it. Preferably, the wall of the first
compartment comprises a barrier layer for limiting loss of the
lighter than air gas through the wall of the compartment. Examples
of suitable barrier layers include EVAL which is commercially
available from Kuraray Co. Ltd. (EVOH), PvdC or PVOH and are
encapsulated between a polymer as the barrier is effected by water
ingress. HOSTAPHAN.RTM. RHBY barrier is commercially available from
Mitsubishi (SiOx) and is preferred because its barrier properties
are unaffected by moisture and it is also optically clear. The
barrier layer may be formed by evaporation onto a substrate in a
vacuum chamber, which may be manufactured by Alcan of Switzerland,
and an additional polymer laminated to the composite by sputtering
adhesive to provide a protective layer. With such a barrier layer
the vehicle may remain airborne for up to 239 days before the lift
gas in the first department is depleted through loss to the
atmosphere, resulting in a 50% loss of free lift.
[0051] The second compartment may have to withstand higher
pressures than the first compartment. There may be a differential
pressure of up to 2 atmospheres with the outside air. To withstand
these pressures the second compartment is preferably made from a
plastic film which can be ultrasonically or radio frequency welded.
Examples include Acetal Co/Homopolymer, Acrylic, Acrylic-Impact
modified, Acrylonitrile Butadiene Styrene, Cellulose Acetate . . .
, Polyamide 6 & 66 (Nylon), Polycarbonate, Polycarbonate/Abs,
Polyester-Thermoplastic, Polyethylene-Low/High Density,
Polyphenylene Oxide, Polyphenylene Sulphide, Polypropylene,
Polystyrene-General Purpose, Polystyrene-High Impact, Polyvinyl
Chloride-Flexible, and Styrene Acrylonitrile.
[0052] In an alternative embodiment the aerial vehicle further
comprises a third compartment for holding a refrigerant which can
undergo a reversible phase change from a gas into a liquid. The
refrigerant may be a refrigerant gas. The third compartment may be
located within the first or second chambers. As the second
compartment is filled with atmospheric air (in some embodiments
this may also displace the lighter-than-air gas held within the
first chamber), the pressure will increase. The pressure change may
then trigger a phase change in the refrigerant from a gas to a
liquid that typically occupies approximately 0.1% of the volume of
the gas. This allows the pump of the compressor to work within a
lower overall pressure regime with higher flow rates, allowing more
air ballast to be accumulated more quickly and improving the aerial
vehicle's overall airspeed performance. Iso-butane, butane or other
refrigeration gas may be used. The total volume of the third
compartment is sufficient to accommodate this gas in its gaseous
state, that the third compartment may be made of a flexible
membrane such as latex or neoprene or a polymer film (previously
described) that deflates when the refrigerant is in a liquid state.
Preferably the refrigerate gas condenses to a liquid state at >1
and <4 ATM absolute pressure at around 0.degree. C.
[0053] Joints on the second compartment may be reinforced with a
glass, plastic, Ultra High Molecular Weight Polyethelene filaments
(such as that sold under the trade name Spectra or Dyneema), or
carbon threads held in place with resin. The material used for the
air ballast chamber may be a composite comprising a matrix held in
a plastic laminate. In a preferable embodiment, Spectra or filament
is used that may be reinforced with carbon fibres in an
encapsulated matrix. This material is known for use in high
performance sail clothing and may be supplied by Cubic Tech
Corporation of Arizona, USA. It is sometimes referred to as Cuben
Cloth.
[0054] In a further embodiment, the second compartment is a
flexible membrane (latex rubber, neoprene or an elastic) or an
inflatable chamber (of a film previously described) held within the
first chamber, that may expand/contract or inflate to accommodate
atmospheric air which is pumped into the second chamber, displacing
the lift gas in the first chamber under pressure. This has the
advantage to reduce the overall volume of the aircraft (reducing
drag) and allows the pump of the compressor to work at a lower
overall pressure range across the cycle. Where the first and second
compartments share a common membrane or film to separate them an
outer ring of carbon fibre is used to maintain the required
aerodynamic shape of the overall envelope. In an alternative
embodiment the second compartment may be separate from the first
compartment.
[0055] The vehicle may further comprise at least one sensor for
aerial reconnaissance or atmospheric monitoring. For example, the
vehicle may include ISR sensors such as optical and IR cameras;
Synthetic aperture RADAR, for example NanoSAR weighs approximately
900 g and is commercially available from IMSAR; an acoustic ranging
and direction sensor, for example for detecting gunfire, that is
commercially available from ROKE/BAE Systems, Thales or QinetiQ.
The vehicle may also include jamming equipment.
[0056] The vehicle may also comprise at least one transmitter and
at least one receiver for providing a wireless communications
network. The transmitter and receiver could be combined in a
transceiver. More than one transmitter or receiver may be provided
to allow communication according to different protocols or for
different purposes. In an advantageous embodiment, a lens can be
used to adjust the Field of view (angle) of the transmitter and/or
receiver (that can be the parabolic mirror described and the
photovoltaic cell may also be the radio receiver). A standard
optical lens, such as is used in a camera, is suitable and the
antenna of the transmitter or received is mounted behind it. This
can either provide a narrow field of view to point at another
receiver for point to point networking at very high speed (for
example speeds of 100 Megabits or greater) or provide a wide angle
to provide multipoint to point networking. To give an example, 15
aerial vehicles could provide a Wi-Fi network covering the whole of
greater London. In this application modest altitude of around 1 km
or higher gives line-of-sight between network nodes that are
preferably placed in a honeycomb formation. The network may be
augmented with surface based radio repeaters to improve the overall
bandwidth across the network.
[0057] The at least one transmitter can be used to transmit any
form of data including reconnaissance data, meterological data, GPS
signals, identification of ocean going vessel and position over
Automated Identification System (AIS), radio data and television
data.
[0058] In embodiments including a solar panel, the at least one
receiver may comprise the solar panel. The solar panel can function
effectively as a component of the receiver, reducing the overall
component count of the aerial vehicle and reducing weight.
[0059] The at least one receiver may comprise an antenna formed by
a metallised track having an undulating or snake-like pattern.
Preferably the undulation is regular, in some embodiments is could
be sinusoidal but a square wave based undulation is preferred. The
distance between tracks of undulations is preferably chosen to be a
multiple of the radio wavelength desired to be received by the
receiver, to improve the antenna performance.
[0060] In another embodiment, the control means may comprise a
member extending from the rear of the vehicle and an articulated
connection between the member and the rear of the vehicle. The
articulated connection enables the member to be angled relative to
the body of vehicle, and preferably angled to the axis of the
nacelle if one is present. The member is preferably generally
cylindrical or rod-like to minimise drag. Surprisingly, such a
member can provide a sufficient force to control the vehicle. The
member may also be configured for rotation relative to the body,
preferably about the axis of the nacelle if one is present. Such a
control member can be used to control just yaw, or all of roll,
pitch and yaw. A tube or paddle may be added to the end of the
member, to increase the deflection into airflow (moment) to
orientate the vehicle.
[0061] In alternate embodiments pitch may be controlled moving
internal masses such as any batteries or pump that may be present,
forward and aft or perpendicular to the main axis to achieve roll
control. Rotational refinement (yaw) may also be achieved by
spinning components, such as the batteries, if they are provided.
Conventional control surfaces, such as a rudder and ailerons and
elevators can also be used in alternate embodiments.
[0062] In some embodiments the control means may comprise a movable
mass. Control of the pitch of the aerial vehicle may then be
achieved by translation of the mass from front to back. Roll may be
controlled by translation of the mass from side to side. Yaw may be
controlled by spinning the mass around an axis. Depending on the
other control means provided, some or all of the control methods
using a movable mass may be implemented.
[0063] Embodiments which include a solar panel may form part of an
aerial vehicle system which further comprises an electromagnetic
radiation source for emitting electromagnetic radiation for
reception by the solar panel. The electromagnetic radiation source
is located remote from the aerial vehicle, for example at a fixed
or mobile location on the ground or sea. The electromagnetic
radiation may be in the visible spectrum, or may be outside of the
visible spectrum, for example in the range 0.01 to 400 nm or 700 to
3000 nm. The electromagnetic radiation source may be a coherent
electromagnetic radiation source, such as laser. In some
embodiments the electromagnetic radiation source has a focal point
which is the aerial vehicle and the aerial vehicle further
comprises means for focusing incident electromagnetic radiation.
The means for defocusing may be a lens or mirror.
[0064] For example, in some embodiments, surfaced based lights may
form part of the air vehicle system. One or more surfaced based
lights may be directed towards the air vehicle when there is less
sunlight available (for example during winter or when in operating
at very northerly or southerly latitudes). This provides additional
power to the solar panels than would otherwise be obtained by
sunlight alone. Ideally, providing additional power before dusk.
The surface based lights may be actuated to direct light towards
the aerial vehicle, using actuators to orientate the light beam
with two degrees of rotational freedom. The lights ideally use a
parabolic reflector or lens to parallelise the light into a beam or
shaft that focuses on the aerial vehicle. The light source may be a
laser. The light may be within the visual wavelength spectrum
(400-700 nanometres wavelength) or ideally outside the visual range
(200-400 nanometers or 700-2000 nanometres). The surface based
lights may be at a fixed land position, on a moving surface vehicle
(4.times.4, ground vehicle or ocean going ship) or mounted on a
buoy for oceanic operation. Lighting apparatus for this purposes is
commercially available and actuation is achievable by those in the
art. The aerial vehicle may transmits its location to the surface
based lights. For fixed location the surface lighting position is
known or, in the case of a moving surface station, position is
obtained by a positioning system such as GPS. The direction from
the surface lighting station to the aerial vehicle is calculated
and the light orientated towards this bearing using actuators. The
solar panels of the aerial vehicle are orientated downwards to this
source of light and additional light energy harvested by the aerial
vehicle. This would not be possible with conventional solar powered
aircraft that incorporate top facing solar panels on a fixed
wing.
[0065] The vehicle may further comprise an electrolyser for
electrolysing water into hydrogen and oxygen. The electrolyser will
produce hydrogen that may replace any lighter than air gas lost
from the first compartment. The hydrogen may also be used as a
fuel. The water for use in the electrolyser is preferably collected
from atmospheric condensation when air is compressed, water will
form in the secondary air ballast chamber and may be pumped to the
electrolyser with a micro liquid pump.
[0066] In a further embodiment, the vehicle further comprises a jet
engine. Excess hydrogen produced by the electrolyser may be stored
to power the jet engine. This allows the vehicle to obtain a new
position more quickly if required.
[0067] Some embodiments may include an outlet at the bottom of the
first compartment. The outlet may be opened to release any air that
is present in the first compartment as the vehicle ascends. More
air will leave via the outlet than the lighter than air gas because
the air is heavier than the gas.
[0068] According to another aspect of the invention, there is
provided a method of flight for an aerial vehicle comprising a
first compartment filled with a lighter than air gas and a second
compartment for holding atmospheric air, the method comprising:
[0069] alternately compressing atmospheric air into the second
compartment and then releasing the compressed atmospheric air from
the second compartment, thereby altering the buoyancy of the
unmanned aerial vehicle such that it is either heavier than air and
falling or lighter than air and rising; and
[0070] actuating at least one control means such that the rising
and falling motion includes a horizontal component.
[0071] Unlike the phase change method proposed by Hunt in
WO-A-2005/007506, it has been found that efficient flight can be
achieved using compressed air as ballast to alter weight of the
vehicle. Controlled flight can be maintained using a fuel or
potentially indefinitely with an external energy source, such as
solar power.
[0072] Embodiments of the invention will now be described with
reference to the accompanying drawings in which:
[0073] FIG. 1 is a perspective view of a diagrammatic
representation of an aerial vehicle according the present
invention.
[0074] FIG. 1A is a detail of a leading edge wing arrangement of
FIG. 1.
[0075] FIG. 1B is a detail of a mid section wing arrangement of
FIG. 1.
[0076] FIG. 1C is a detail of a trailing edge wing arrangement of
FIG. 1.
[0077] FIG. 1D is a detail of a Thermal Electrical Generator foil
insert that may be used with the embodiment of FIG. 1.
[0078] FIG. 2 is a cross section and end view of a solar cell
arrangement for use with the invention.
[0079] FIGS. 3A and 3B depict a diagrammatic representation of a
reinforcing arrangement for use with the vehicle of FIG. 1.
[0080] FIGS. 4A and 4B depict a diagrammatic representation of an
alternate ballast compartment for use with the vehicle of FIG.
1.
[0081] FIGS. 4C and 4D depict cross sections through the ballast
compartments that can be used in the vehicle of FIG. 1.
[0082] FIG. 5 depicts a diagrammatic representation of an optional
third compartment inserted with the ballast compartment.
[0083] FIGS. 6A, 6B, 6C and 6D are a plan views of a diagrammatic
representation of embodiments of a wing with an integrated aerial
for use with the vehicle of FIG. 1.
[0084] FIGS. 7A, 7B and 7C depict a diagrammatic representation of
a cross section through a solar cell for use with the vehicle of
FIG. 1.
[0085] FIG. 8A, 8B, 8C and 8D depict a diagrammatic representation
of an negative refraction index film for use with the vehicle of
FIG. 1.
[0086] FIGS. 9A and 9B depicts a cross section through a film for
use with a compartment of the vehicle of FIG. 1.
[0087] FIGS. 10A, 10B and 10C depict alternative embodiments of
control surfaces that may be used with the vehicle of FIG. 1.
[0088] FIG. 10D depicts a diagrammatic representation of a
symmetrical wing as an alternative embodiment. FIG. 10E depicts a
cross section of a symmetrical wing.
[0089] FIG. 10F depicts an alternative embodiment of a parabolic
solar trough within the symmetrical wing.
[0090] FIGS. 11A, 11B and 11C depict alternative profiles for the
body of the aerial vehicle of FIG. 1. FIG. 11D depicts a
diagrammatic representation of a blended fuselage and wing
configuration.
[0091] FIGS. 12A, 12b, 12C, 12D, 12E and 12F depict plan views of
the wing profiles that may be used in various embodiments of the
invention.
[0092] FIG. 13 depicts an optional wing tip nacelle that may be
used with the vehicle of FIG. 1.
[0093] FIG. 14 is a conceptual diagram showing the arrangement of
control systems, payload and communication systems within the
vehicle of FIG. 1.
[0094] FIGS. 15A and 15B are a conceptual diagrams depicting an
alternative embodiment of the vehicle. FIG. 15A is a conceptual
diagram of a lighting unit for use with FIG. 1 of the vehicle.
[0095] FIGS. 15C, 15E and 15G are conceptual diagrams of
alternative embodiments of the parabolic solar harvesting
apparatus.
[0096] FIGS. 15D, 15F and 15H are cross sections of alternative
embodiments of parabolic mirrors.
[0097] FIG. 16 is a diagrammatic representation of an aerial
vehicle according to a further embodiment of the invention.
[0098] FIGS. 16A and 16B depict cross sections through the solar
cell arrangement and body section of the vehicle of FIG. 16,
respectively.
[0099] FIGS. 17 and 17A is a diagrammatic representation of an
aerial vehicle according to another embodiment of the
invention.
[0100] FIG. 18 is a diagrammatic representation of an aerial
vehicle according to a further embodiment of the invention.
[0101] FIG. 19 is a conceptual diagram illustrating the method of
flight of the present invention.
[0102] FIG. 20 is a graph showing freelift and ground speed versus
altitude for different angles of ascent.
[0103] FIG. 21 is a graph showing ballast and ground speed at
various gliding descent angles.
[0104] FIG. 22 depicts an equilibrium gliding descent.
[0105] FIG. 23 depicts an equilibrium gliding ascent.
[0106] FIG. 24 is a graph of lift and drag coefficients with angle
of attack.
[0107] FIG. 25 depicts a mesh network application.
[0108] FIG. 1 is a diagrammatic representation of a perspective
view of a first embodiment of the present invention. The first
embodiment is an aerial vehicle, considering the vehicle from it's
rear to it's front, it comprises a rudder 1 actuated by a servo 2.
The rudder preferably comprises carbon fibre sheet with an aperture
to reduce weight. Film is draped over frame and attached to the
frame so that the film is taut. The rudder 1 comprises two parts:
top and bottom. The top and bottom parts are attached with a rod.
The rod forms the pivot point and is actuated with the servo 2. The
pivot point is preferably placed at the centre of pressure so the
arrangement is easy to turn with a very small servo.
[0109] The rear of the vehicle also comprises a stabiliser 3.
Preferably, the stabilisers 3 are static. However, in alternative
embodiments, they may be actuated to function as elevators. In that
case the area 4 marked with a dashed line may be removed to allow
them to move and avoid interference with the rudder.
[0110] The rear section of the vehicle, supporting the rudder 1 and
stabiliser 3, comprises a cone 5. It is preferably a carbon fibre
cone with a cap. The cone houses a processor to function as the
autopilot and the autopilot sensors (discussed in more detail
below). An envelope film 13 interfaces with the cone and is held in
place with resin and glass/carbon fibre fabric reinforcement.
[0111] Moving forward from the cone 5, the vehicle comprises a rear
ballast chamber or compartment 6. This is made from either plastic
film or reinforced film. Preferably, a plastic film sandwich is
used comprising Ultra high molecular weight polyethylene (UHMWP) or
UHMWP filaments (such as those sold under the trade names Spectra
or Dyneema). If a filament is used, it is not woven as this would
allow stretch, potentially altering the external surface shape of
the compartment. Alternatively, other thread materials may be added
to form a matrix (e.g. glass or carbon fibre) and may be layered in
different orientations for strength in more than one direction.
[0112] Extending into the rear ballast compartment are
strengthening sections 7. These are provides to maintain the shape
of the interface with the adjacent compartment 13 when the rear
compartment 6 is under pressure. The strengthening sections 7 may
be a UHMWP composite. A divider 8 maintains separation between the
rear ballast compartment 7 and the adjacent compartment 13. It may
also be formed of a carbon or UHMWP composite.
[0113] The adjacent compartment is defined by envelope film 13 and
is filled with a lighter than air gas to provide lift to the
vehicle. Within the envelope is contained a servo 9 to rotate a
solar cell arrangement such that the solar cell arrangement is
preferably oriented towards the sun. Electrical power can be
transferred to the servo through a slip ring and carbon brushes on
the servo connection shaft.
[0114] The solar cell arrangement can also be seen in cross section
in FIG. 2. It comprises an end frame 10, a parabolic strip 18, a
half-pipe length comprising horizontal section 15 and vertical
section 16 and a solar film mount/servo connector 17. The parabolic
strip 18 may be draped over the required profile under heat. The
horizontal section 15 and vertical section 16 are preferably carbon
fibre. The solar cell arrangement also comprises mirror film 11.
The solar film mount/servo connector 17 is also made from carbon
fibre and allows a solar film 12 (at the bottom) and mirror film
(at the top) to be mounted at each end. It also provides a mounting
for the servo which connects the trough to the body. The mirror
film 11 is ideally made of plastic with high optical qualities
(such as acrylic) and metalised. Silver is evaporated onto the film
in the preferred embodiment with a protective coating (of Silicon
or Aluminium to reduce oxidisation) or laminated layer (such as
acrylic). Alternatively aluminium, platinum, gold or another metal
that is highly reflective and ideally inert may be used to metalise
the mirror film 11. Thin Solar film 12 is formed around a mounting
section. A metalised film runs across the top section. The mirror
film 11 reflects sunlight and reduces heat build-up on the rear of
the solar film 12 and helps maintain the profile of the solar film
12 across its length.
[0115] In the preferred embodiment a copper indium gallium
diselenide photovoltaic (PV) panel is used on an aluminium foil
back plate (a stainless steel foil or polymer backplate may also be
used). NanoSolar of San Jose, US manufacture such a film and has an
independently verified efficiency of 14.6% (NREL). A gold nanoball
film (or derivative of this process) may be added onto of the cell
(detailed separately). Any PV thin film may be used including:
amorphous silicon (a-Si), copper indium diselenide (CuInSe.sub.2,
or "CIS"), cadmium telluride (CdTe). Additionally a thin triple
matched junction PV cell may be used, available from Spectralabs
(Boeing), Sylmar, Calif., USA with an efficiency of over 40.7%
under 240 suns or a Inverted Metamorphic Multijunction (IMM) Solar
Cell available from Emcore Corp of Albuquerque, N.M. with an
efficiency of 40.6% under 326 suns. Such cells may be mounted on
both sides of a substrate, for example an aluminium or titanium
plate, to form a panel that is mounted vertically.
[0116] It should be noted that the focal point for the mirror film
11 is not obvious. Light is bent as it moves through materials of
different density. For example as it moved from air to hydrogen,
there will be a slight bending inwards of light. In an embodiment
in which envelope 13 is filled with Hydrogen, the focal point may
be optimised for diffraction through the hydrogen. Likewise, the
focal point may be optimised for whichever lighter than air gas is
used within the envelope 13.
[0117] The envelope 13 defines a compartment for lift gas. It is
made from a transparent barrier film, that is ideally cut into
panels (for example by waterjet CNC or cutting plotter), and then
ultrasonically or RF welded. Alternatively, it may be thermally
bonded or joined with an adhesive. Weldable materials are
preferred, including Acetal Co/Homopolymer, Acrylic, Acrylic-Impact
modified, Acrylonitrile Butadiene Styrene, Cellulose Acetate . . .
, Polyamide 6 & 66 (Nylon), Polycarbonate, Polycarbonate/Abs,
Polyester-Thermoplastic, Polyethylene-Low/High Density,
Polyphenylene Oxide, Polyphenylene Sulphide, Polypropylene,
Polystyrene-General Purpose, Polystyrene-High Impact, Polyvinyl
Chloride-Flexible, and Styrene Acrylonitrile.
[0118] Resins may also be applied to seams and glass/spectra/carbon
cloth reinforced to provide a strong joint. The envelope 13 is
preferably constructed as a sandwich to incorporate a gas barrier
component, normally an adhesive is used to bond the film laminated
parts together. Suitable barriers include PvdC, EVOH (EVAL) or
PVOH. A typical layer for this purpose will be around 10 .mu.m
sandwiched between a 15 .mu.m plastic film (25 .mu.m total). A more
preferable alternative is a ceramic barrier that is vacuum
evaporated onto a substrate film, SiOx or AlOx, for example that is
sold under the trade name Hostaphan. A thin protected film is
normally laminated to the ceramic barrier layer. A combination of
sandwich films may be applied.
[0119] Continuing to move towards the front of the vehicle, a front
ballast chamber or compartment 14 is provided with construction as
described above for the rear ballast compartment 6.
[0120] The operation of the solar cell arrangement is indicated on
FIG. 2. Incident light (indicated by arrow 19) is reflected
(indicated by arrow 20) from the mirror film 11 towards the solar
film 12 and the solar cell.
[0121] Extending from opposite sides of the vehicle is a wing 21.
This may be made of any bondable material and may be metalised to
reflect further light towards the solar cell arrangement. The
leading edge 22 is shown in more detail as a cross section in FIG.
1A. The film is wrapped around a carbon fibre strip and bonded to
itself. The mid section is shown in more detail in the cross
section of FIG. 1B. Two carbon fibre sections are bonded to the
wing 21 to form a symmetrical aerofoil. This is a low profile
aerodynamic structure with little bending. Supports between the
leading and training edge may be provided. The trailing edge 24 is
shown in more detail in FIG. 1C, the construction is the same as
for the leading edge 22. The wing 21 is supported by ring 25 which
is connected to struts 26. The ring 25 may be internal or external
to the envelope 13. A Thermal Electrical Generator (TEG) Foil
insert 13a is position in the chamber 13 as shown in FIG. 1D. A
heat sink 13b thermally conducts heat away from the chamber to the
TEG 13a, that is cooled on its atmospheric air facing side.
[0122] Located within the envelope 13 is a payload 29. A tether
wire 28, preferably a UHMWP filament, extends from the payload 29
to tether anchor points 27. The payload 29 contains an actuator,
such as a winch servo, which can pull the payload along the main
axis of the vehicle for pitch control. The wire 28 may be kept in
tension by a spring.
[0123] The payload 29 typically comprises: batteries, battery
heater, pumps, valves, servo. This is typically a foam container
that incorporates the components with an aperture to allow for the
movement of actuated movable masses (such as batteries in one
embodiment). Electronic components that generate electro-magnetic
fields may be shielded in a Mu metal foil that may also draw heat
away from the component to the outside of the container (this may
reduce interference to any sensors, such as the autopilot). For
example permalloys containing approximately 80% Nickel (Ni), 20%
Iron (Fe) and small amounts of Molybdenum (Mo). A
nickel-iron-molybdenum alloy (permalloy) which offers extremely
high initial permeability and maximum permeability with minimum
hysteresis loss. The foam container is encapsulated in a plastic
film.
[0124] The battery 30 may slide along the secondary axis to achieve
roll control with an actuator that may be a servo with sliding gear
or winch. In some embodiments, the battery may be rotated at speed
for control of yaw. The battery 30 is preferably Lithium Sulphur
with a specific energy exceeding 260 Wh/kg (commercially available
from Sion Power). Carbon nano tube structures may be used as the
electrodes to improve the total surface area so more power can be
pulled from the cell. Other rechargeable technologies may also be
used such as Lithium Polymer and Lithium Ion if larger number of
charge cycles are required before replacement, or any other
suitable technology, such as lithium air battery cells. A high
energy density is preferred to reduce the weight of the
vehicle.
[0125] FIGS. 3A and 3B is a perspective view of a reinforcing
arrangement that may be used for the envelope 13. It depicts only
those parts of the aerial vehicle relevant the reinforcement. It
comprises a receiving sleeve 32 for receiving a reinforcing rib 33.
The sleeve may be welded to the envelope 13. The reinforcing rib 33
is preferably made of carbon fibre. Further support is provided by
O ring 34. The reinforcement is optional. Alternate embodiments may
include addition reinforcement, for example more O rings 34.
[0126] FIGS. 4A and 4B depict an alternative constructions for the
ballast chamber or compartment 35. Optional film sections 38 may
hold the second compartment in position and form a void within the
second compartment 35. This has the advantage compared with a film
envelope which may be crushed. The ballast chamber is held in
tension to maintain a shape (void), so that the chamber does not
need to be pre-inflated before air ballast can be accumulated,
saving energy and increasing performance. The void is a ideally a
bi-pyramid. Preferably an eight sided bi-pyramid is used as shown
in FIG. 4D (cross section) and isolation from the envelope 13. In
other embodiments the bi-pyramid may have more or fewer sides than
eight as illustrated by FIG. 4C. These are contained within the
outer structure for reduced drag. FIG. 5 shows an optional third
compartment 37 in isolation. The third compartment is filled with a
refrigerant gas that when in a gaseous state may occupy the void in
the second compartment 35. When the second compartment is
pressurised, the refrigerant gas changes to a liquid state
(occupying approximately 1000.sup.th of the volume and allows the
pump to work in a lower differential pressure regime with higher
flow over the compression cycle. The third compartment may be
positioned in the first compartment or the second compartment or
between the first and second compartment (not shown).
[0127] An exemplary wing film structure used in alternative
embodiment is depicted in diagrammatic form in FIG. 6A. The wing
structure comprises an aerial 40a, which is a circuit pathway onto
a film substrate, for use with a transmitter and/or a receiver. A
metalised coating may be applied to the film by splutter vapour
disposition. The film may be metalised by the deposition of ideally
silver, aluminium or gold or any material that can be applied using
this method. The circuit pathways are shown for illustrative
purposes only and are not to scale. In the preferred embodiment the
distance between pathways is a multiple of the radio wavelength of
interest. FIG. 6B shows the preferred embodiment that uses a
repeatable pattern 40b, that is applied in the metalisation of
polymer films, using a roller to roller manufacturing technique.
Unwanted parts of the circuit pathway can be removed by acid
etching (for example, as used in circuit board production) and
circuit pathways created with a silver impregnated ink 40c,
protected with a resin top coat to isolate the circuit from the
elements. FIG. 6C shows the repeated pattern in isolation. FIG. 6D
shows an alternative embodiment, with the repeated circuit pattern
40d. Additional circuit pathways 40e are provided in this
repeatable pattern that can be used to independently connect other
electronic devices or antenna circuits. This technique can be
applied to any film parts of the airframe, allowing the entire
airframe structure to become a radio antenna. Additionally this
technique may be applied to sections, such as the wingtips to
create an independent antenna that can be used, for example, for a
Synthetic Aperture Radar antenna, with a wide distance between
stereo antenna.
[0128] FIGS. 7A, 7B and 7C depict diagrammatic representations of a
solar cell for use in the present invention. A Photovoltaic solar
cell is depicted at 41. A transparent nano plano-convex polymer
film 42 is provided on top of the solar cell 41 in FIG. 7A. Light
is bent along the length of the film, so increasing the length of
its passage through the PV material, giving a photon a better
chance of hitting an electron out of orbit (indicated by arrows 43,
showing photon paths). FIG. 7B depicts a transparent nano
plano-concaved polymer film 44. FIG. 7C depicts the shorter path
length when a nano plano-convex or nano plano-concave film 42 or 44
is not used.
[0129] FIG. 8A, 8B, 8C, 8D depicts an alternative embodiment of
films with a negative reflective index used on the wings and
chambers. A transparent nano plano-convex polymer film 42, is
optically bonded to a clear film (typically of higher density) 45.
Light is bent as it passes through the plano-convex film 42 and
enters the second film 45 of typically higher density and bounces
between this film in the same way as light travels down an optical
glass fibre filament, until it hits the PV cell at the end of film
41. FIGS. 8B and 8D shows the passage of light through a
plano-concaved polymer film 44. FIGS. 8C and 8D show the
application of a triple junction coated photovoltaic wire installed
within a polymer film. These configurations represent very light
weight, very high efficiency solar panels that may be installed
into the aerial vehicle. Additionally, the PV cell may be utilised
as an antenna to receive radio wavelengths of interest.
[0130] FIG. 8 depicts a cross section (side view) through the film
that may be used for the first, second or third compartments. The
film comprises two base layers components 46, sandwiched between a
bonding component that may be a gas barrier such as EVOH (trade
name EVAL), PVOH or PvdC and may also comprise further
unidirectional reinforcement filaments 48 (running in the x axis)
and 49 running in the y axis, of carbon, glass, UHMWP or any
reinforcement filament in the class of reinforced plastic
composites may be employed. Additional layers of reinforcement may
also be used, e.g. triaxially orientated with the filaments aligned
at 60.degree., 120.degree. and 180.degree. for strength and/or
flexibility. A plastic film 46 (preferably an ultrasonically or
radio frequency weldable plastic material) forms a base layer. It
has a thickness preferably from 2 to 80 .mu.m. An adhesive layer 47
bonds plastic film 46 to a first barrier component 48. The adhesive
is also a gas barrier component 47 such as PvdC, EVOH (EVAL) or
PVOH at a thickness of 2 to 20 .mu.m. A secondary gas barrier
component 46b is evaporated onto the first base film that also
provides a gas barrier. A second gas barrier component 46b is a
ceramic barrier that is vacuum evaporated onto a substrate base
film of Silicon Oxide or Aluminium Oxide or other gas barrier that
may be applied with this method with a typical thickness of 1
.mu.m. A further layer of adhesive 47 and plastic film 46 are then
added to complete the composite sandwich film. In other embodiments
the barrier layers may not be used, or only one layer used.
However, two layers are preferred to limit loss of lift gas from
compartment 13. FIG. 9 depicts a cross section (end view) through
the composite sandwich film.
[0131] FIGS. 10A, 10B and 10C depict alternative embodiments of
control and stabilising surfaces that may be used with the present
invention. In the embodiment of FIG. 10A, a pole or generally
cylindrical member 54 extends to the rear of the vehicle. The pole
may be tapered and in some embodiments has a paddle or additional
control surface appendage (not shown), The member 54 is articulated
or pivoted where it extends from the rear of the vehicle. An
actuator 55 may move the pole up and down using a linear actuator,
such as a servo driving a threaded bar with a retaining screw
within the member 54. The whole arrangement may also be rotated and
pivoted 56. This allows the member to point in any given direction
and achieve yaw, pitch and roll control with minimal drag when not
in use. An alternative embodiment in FIG. 10B uses a split rudder
57, 58. It is preferable that the pivot is at the centre of
pressure of the stabilising/control surface (e.g. the quarter chord
point from the leading edge), so a smaller actuator can be used.
Alternatively, conventional fixed stabilisers with a separate
actuated rudder(s)/elevators positioned at the trailing edge. The
embodiment in FIG. 10C uses a rudder 59 with elevators 60, 61.
[0132] FIG. 10D shows an alternative embodiment of a wing, using a
symmetrical aerofoil section. Ideally made from a foam core 23b
with sections removed to reduce weight. A reinforced carbon fibre
or composite reinforced leading edge member 22b and trailing edge
member 24b. A Photovoltaic solar panel that is ideally a flexible
film that may be implemented over the entire wing surface (top and
bottom). A clear heat shrunk film is applied 41b, such as
polyester, over the foam core 23b. An optional composite aileron
21c, that is actuated to achieve roll control. A composite wingtip
plate member 21d may be attached to the foam core 23b. The wingtip
plate reduces vortex induced drag on the wing by providing a fence,
so that air cannot roll away from the wing at the wingtip. Unlike a
conventional winglet, the fence reduces vortex induced drag on
gliding accent and descent. In some embodiments a composite tube
member 41c may extent through the main chamber (fuselage) and
extend proud of main chamber--not shown and provide a mounting for
the wings. The foam core 23b has a receiving aperture (not shown)
and wing slide over tube member and attach to the main chamber with
a fixture.
[0133] FIG. 10F is an alternative embodiment of the wing previously
described in FIG. 10E, that instead, uses parabolic mirror film
21e, to reflect light into a small photovoltaic cell 21f, under
concentration. Ideally the PV cell 21f is a triple junction wire
type, described herein, but may be any cell known as a photovoltaic
cell. The parabolic trough may be orientated by a servo (not
shown). One or more parabolic troughs may be orientated together by
a timing belt 21h using a toothed gear 21g. In alternative
embodiments, a simple gear arrangement may be used or the troughs
may be orientated individually using separate actuators (not
shown).
[0134] FIGS. 11A, 11B and 11C depict alternative profiles for the
body of the aerial vehicle (excluding wing). FIG. 11A is the most
preferred profile. It depicts an axi-symmetrical aerofoil body of
revolution. The embodiment of FIG. 11B is an axi-symmetrical Vescia
Piscis body of revolution. FIG. 11C depicts a further embodiment
which has an asymmetric aerofoil. This may generate conventional
lift (top) or be flipped over to generate negative lift (bottom).
Surprisingly, in the embodiment of FIG. 11C, better performance can
be obtained if the aerofoil is arranged to generate negative lift
in gliding ascent (illustrated in the lower part of FIG. 11C), when
energy consumption is considered. More energy is generally
available when the vehicle is ascending due to buoyancy so the
aerofoil can have most effect with this orientation. FIG. 11D,
illustrates how more than one compartment 64 can be implemented to
create a morphed fuselage/wing. A dotted line 65 represents a skin
around the compartments. The profiles in FIGS. 11A, 11B and 11C
apply to the main body or nacelle of the vehicle.
[0135] FIGS. 12A, 12B, 12C 12D, 12E, 12F and 12G depict plan view
of the wing profiles that may be used in various embodiments. For
clarity these are shown with the body profile of FIG. 11A, although
any other body profile may also be used. Next to FIGS. 12A, 12B
12C, 12D, 12E, 12F and 12G are shown diagrammatic representations
of the different vertical positions (in side view) relative to the
body where the wing can be mounted and to the right of this (in
front view). For each is shown a top wing, mid wing (preferred) and
bottom wing respectively. FIG. 12A shows a tapered wing embodiment.
FIG. 12 B shows a straight wing embodiment. FIG. 12C shows a swept
wing embodiment. FIG. 12D shows a delta wing embodiment. FIG. 12E
shows an elliptical wing embodiment. FIG. 12F shows a canard wing
embodiment. For clarity, this can be a plurality of pairs of wings
of any planform, size, type or position In all these embodiments it
is preferred that the wing generates minimal lift and is
substantially flat or symmetrical to maintain a gliding path,
preferably with an angle of attack of .+-.0.5.degree.. In other
embodiments the wing may generate a small amount of lift or have a
more pronounced aerofoil profile.
[0136] FIG. 13 depicts an optional wing tip nacelle 80 that may be
provided if extra lift is required. The nacelle 80 forms a further
compartment for lift gas or ballast with a construction as
described above for the compartments. FIG. 13 represents one or
more additional compartments that may be added to the wing, ideally
this is at the wingtip.
[0137] In a preferred embodiment, for use as an unmanned aerial
vehicle, the main nacelle has a body length of 6.8 m and a
thickness of 15% of chord length. It will be appreciated that
dimensions and chord thickness may be varied depending on the
particular application and payload for the vehicle.
[0138] FIG. 14 is a conceptual diagram showing the arrangement of
control systems and payload within the vehicle. One or more solar
cells 201 generates electrical power from incident light. The solar
cell 201 is connected through a corrective diode 202 to a battery
203. The diode 202 ensures that power is not drawn from the battery
203 by the solar cell 201 at night. The battery may be Lithium
Sulphur supplied by Sion Power with a specific energy of 260 Wh/kg
or a lithium Polymer cell (approximately 200 Wh/kg). Carbon nano
tubes may be used at the electrodes of the battery 203. Power from
the battery 203 is used for the control and electrical systems of
the vehicle. In the preferred embodiment a Lithium Air battery is
used, experimental cells are available from St Andrews University,
Scotland, UK, the theoretical specific energy is as high as 2
kWh/kg.
[0139] Block 208 illustrates a positioning system. Various
positioning systems that may be included in the invention. One or
more of the systems may be included, including more than one system
allows redundancy. GPS system 204 may provide XYZ position, 3 axis
bearing and speed taken at a sampling rate of 0.25 Hz to 1 Hz with
current technology. Alternately a positioning device 205 adhering
to the Long Range Navigation System (LORAN) or LORAN-C standard may
be provided. A positioning device 206 adhering to the SHOrt RAnge
Navigation System (SHORAN) may also be provided. Another
positioning device 207 uses a plurality of either fixed and known
transmission stations with an embedded time code of time of
transmission. Any transmission station transmitting a radio signal
on any bandwidth which embeds its position and time of transmission
may be used. The transmission station may be a surface station.
[0140] The vehicle may remain airborne for several days or longer
and can therefore assume many of the roles of a satellite,
including transmitting a GPS, LORAN-C or SHORAN signal, providing
pseudo-satellite functionality.
[0141] In an alternate embodiment the vehicle may identify fixed
landmarks to establish its own position and then transmit its
position and transmitted time code to allow GPS or other
navigational system devices to operate, should other GPS or other
services be denied. A plurality of aerial vehicles can transmit a
position with embedded time code using the appropriate standard to
receivers in the area, restoring navigational services. This has
the advantage that the signal strength is much stronger compared
with a satellite transmission and significantly more difficult to
disrupt.
[0142] Block 217 illustrates sensor inputs that may be provided.
The vehicle may include one or more of: [0143] a three axis
accelerometer 218; [0144] a three axis infrared sensor 219, which
may be used to determine orientation. The sensors point in all
directions and the airframe orientation relative to the warm earth
and cold sky can be deduced by the relative IR measured. [0145] a
three axis electronic compass 220; [0146] a light meter 221 [0147]
a Hydrometer/humidity sensor 222; [0148] a temperature sensor 223;
[0149] a pressure sensor 224; [0150] a rotary encoder 225 to
establish the rotary position of a motor; [0151] a Power meter 226,
to monitor the status of the battery.
[0152] One or more transmitter/receivers are also provided. For
example a lens corrected radio transmitter receiver/transmitter
227. This may focus a signal specifically at a target. For example,
it may direct a signal directly at another vehicle for high speed
point to point networking or to pickup a weak signal from a
specific ground transmitter. The transmitter may be mounted with
one or more of the parabolic mirrors described and actuated towards
the mirror to change its focal length. One or more transmitter or
receiver 228 may integrated into the film of the wings, for example
using an aerial 40 as discussed above. A unidirectional transmitter
or receiver 229 may also be provided.
[0153] An autopilot 209 receives inputs from the positioning
system(s) 208, the sensors 217 and the transmitters and receivers
227,228,229. These inputs may be analogue or digital. The autopilot
is typically implemented in a microprocessor, ASIC, system-on-chip
or any other system that can receive and process information. It
generates an output to control the vehicle. The functions of the
autopilot are illustrated in graphical form on FIG. 14.
[0154] The autopilot 209 is configured to determine 210 an XYZ
position and orientation in space. This is done by calculating an
expected speed and future position based on a predetermined
aerodynamic model and adjusting these with actual data from the
sensors. For example, the sensors may reveal wind speed and
direction, which may be stored in the Meteorological database
(described below) with time stamp. The autopilot 209 may plot a
route to a loitering position that may include waypoints by
referencing the Meteorological database. The auto pilot may also
receive a target position, used to co-ordinate camera and sensor
gimbals to look at a target position from its current position.
[0155] The autopilot 209 includes an accurate clock 211. Input data
may be time stamped. The autopilot 209 also preferably includes
storage means such as random access memory, which may be
non-volatile such as a flash memory. This storage means can be
loaded with various database such as a 3D map 212 of terrain,
country boundaries and segregated air space type. Building geometry
and other objects of interest may also be included. The autopilot
209 may reference this 3D map to ensure it is not going to collide
with any objects or terrain. It may also be used for determining
right of passage through airspace.
[0156] A meteorological database 213 may also be included. This may
comprise data on: wind speed and direction at various altitudes,
humidity, sunlight intensity, pressure, chemical composition of air
or other meteorological conditions. The meteorological data may be
shared with other vehicles and receiving stations. The vehicle may
receive met data from external sources for route planning Reports
may be transmitted via AIREP (Aircraft Report), encoded according
to the AFMAN manual 15-124 pages 32-35 or any other accepted
Meteorological data reporting standards.
[0157] An object of interest database 214 may be included. These
may include: other aircraft in the vicinity, ships or vehicles.
Ships position are transmitted using the AIS system Automatic
Identification System and are required on all ships with a gross
weight over 300 tons. The sensors may identify small vessels not
equipped with AIS and broadcast these positions across the AIS
network. This could be particularly advantageous if the vehicle is
used for monitoring by the coast guard.
[0158] Aircraft typically transmit their digital position using
ACARS (Aircraft Communications Addressing and Reporting System),
ADS-B and HFDL standards which could be included in object of
interest database 214. Both known positions and sensor feeds may be
used to plot a course to avoid airborne objects and aircraft,
providing `sense and avoid`.
[0159] A datafeed database 215 may also be provided for storing
information from sensors. In addition to the inputs described
above, sensor feeds 250-257 (discussed in more detail below) may be
stored in the datafeed database 215 with an associated geocode for
the position of the feed with an embedded time stamp. Many feeds
may be compared from different angles to reveal geometric shapes.
The raster information relating to a geometric shaped may be
extracted, perceptively corrected and mapped onto the surface of
the shape or face within a 3d model. Many feeds may be compared,
where the raster information is persistent or similar, this denotes
a permanent object. Where a higher resolution source is available
the resolution of the base map may be improved. Many sources may be
used to composite a 3d model of terrain and permanent objects
(buildings and structures). A feed may be compared with the 3d
model with mapped surfaces that may be adjusted to compensate for
the sun's position and intensity as it hits a face in the 3d model
and transitory objects identified as they appear on the base map,
which may be passed to the objects of interest database. This
database 215 may also be stored externally and updated by the
Aerial Vehicle. A subset of the 3d map and related raster
information relating to current operating area may be extracted
from a central external database and stored in this database.
[0160] Another database, setting database 216, may also be
provided. This includes the current setting of the vehicle, for
example the position of servos.
[0161] The autopilot 209 may also include a watchdog system for
checking the health of the autopilot and taking remedial action,
such as restarting it if necessary. Two or more autopilots may be
used in alternate embodiments for redundancy.
[0162] The autopilot 209 is connected to various actuators for
controlling the vehicle. These include optional Mass positioning
servos 234, Control surface servos 235, optional Gyroscope motor
237 (which may be three axis) for maintaining a stable platform for
sensors, optional mirror actuators 238, for stabilising a camera
image, optional Gimbal servos 239 which may be three axis to
orientate sensors, optional Lens camera servos 240, valves 241,
parabolic mirror/solar cell actuators 233b, transmitter/antenna
actuation that may include controlling the focal length (not
shown), Pump 242, optional Water reservoir 243 (water will
accumulate as atmospheric air is compressed and collects in the
water reservoir 243. The water may be purged or converted to
hydrogen to replace lost lift gas through electrolysis), optional
electrolysis unit 246 containing water with anode 244 producing
oxygen (typically expelled 231d) and cathode 245 producing
hydrogen.
[0163] Optional Lamp 233 (a red lamp is presented on the left
(port) side, a green lamp is presented on the right (starboard)
side, a white strobe light is positioned at top and bottom extremes
of the airframe), optional LED 247 with a colour scheme as above.
The lamps/leds 233, 247 may be within the wingtip section. This
would provide sufficient luminosity to meet CAA requirements with
little additional drag, optional Electrical heater 248 for heating
a battery so power can be drawn in cold operating conditions or
heating a refrigerant gas held in the third compartment to change
from a liquid state to a gaseous state. A refrigeration unit (not
shown) for cooling a refrigerant gas from a gaseous to its liquid
state.
[0164] An optional Shielding 249, which is a magnetically shielding
metal or Mu metal foil, may surround the components of the
electrical system.
[0165] The pump 242 is preferably a Diaphragm pump. Any suitable
pump for compressing air may be used in alternative embodiments,
such as scroll, vane, reciprocating, piston, rotary screw,
diagonal, axial flow and centrifugal pumps. A micro pump 242b may
be used to pump hydrogen into the main compartment (that may be
partitioned in it's own chamber). The first compartment may have an
additional chamber 231c that is independent filled with a lighter
than air gas, should control or communications be lost a valve
opened, to vent the lighter then air gas to the atmosphere 231d and
reduce overall buoyancy to force a slow descent.
[0166] Further actuators may be included for the alternative
embodiment including a drogue (described in more detail below with
reference to FIG. 17). These include a solenoid 232 for deploying
the drogue and a winch servo 236.
[0167] Depending on the application of the vehicle, various sensors
may also be included. These include an optical camera 250, that may
be colour or greyscale, CCD, CMOS or line scan. The camera 250 may
be gimbalised and stabilised with gyroscope or mirror gyro, with or
without a zoom lens. Providing more than one camera 250 spaced
apart allows a range to target object to be determined.
[0168] An Infrared camera 251 may be provided, that may be colour
or greyscale, CCD, CMOS or line scan. That IR camera 250 may also
be gimbalised and stabilised with a gyroscope or the image
stabilised with a mirror gyro, with or without a zoom lens. Spacing
two IR cameras apart focusing on a single object allows a range to
be established.
[0169] One or more microphones 252 may be included. Preferably a
number of acoustic sensors are mounted spaced apart to establish a
direction and distance to a source of sound. Microphones are
preferably mounted at the wing tips and front and aft of the
vehicle. The sensors' timing may be compared to establish the
direction. This may be referenced against a 3d map to establish a
point of origin for the source of the sound.
[0170] A RAdio Detection And Ranging sensor 253 may be included.
Suitable types include: Monopulse radar, Bistatic radar, Doppler
radar, Continuous-wave radar or Synthetic Aperture RADAR (SAR--e.g.
A nanoSAR supplied by IMSAR or PicoSAR from Selex). Operating
ranges may include the HF to UWB ranges, passive or active. The
RADAR sensor may be placed at the focal point for the parabolic
trough used for the solar cell.
[0171] A Light Detection and Ranging sensor 254 may be included.
Suitable types include: Elastic backscatter LIDAR, Differential
Absorption LIDAR (DIAL), Raman LIDAR, Doppler LIDAR, Synthetic
Array Heterodyne Detection. A Laser Detection and Ranging module
255 may also be used. The LIDAR sensor may be positioned at the
focal point of the parabolic trough used for the solar cell.
[0172] A Sound navigation and ranging (SONAR) sensor 256 may also
be included. This can be Active (infrasonic to ultrasonic range) or
passive or Synethic aperture sonar, such as a Vision 600 SAS
manufactured by QinetiQ, UK. The sensor may be placed at the bottom
of the airframe. The vehicle may land on a body of water to take a
reading. Preferably the sonar is independent of the airframe and
carried as a payload, within a buoy, the aerial vehicle may drop
the payload at the sampling site and recover it using a skyhook or
Fulton type surface to air recovery system.
[0173] A SODAR (SOnic Detection And Ranging) sensor 257 may also be
included. This is for met measurement of wind. A transducer is
placed in the solar trough that bounces sound into the atmosphere
and returns a sonic signal to the microphones.
[0174] The sensor payload may include a projective laser
spectroscopy sensor (not shown) currently being developed by St
Andrews University, Scotland. This sensor can be used to sample air
for chemicals of interest (detecting less than one part in a
million). The sensor can either take samples from the air ballast
chamber or air that passes over the airframe and in due course may
have sufficient range to penetrate to a surface target of interest
to establish its chemical composition.
[0175] The iconography at the bottom of FIG. 14 showing
communication of the vehicle with other equipment. A ground station
258, may allow many vehicles to be controlled and/or coordinated.
The ground station 258 may receive the current state of the vehicle
settings, receive databases or subsets of the data (212-216),
provide new target co-ordinates and waypoints and specify target
imaging locations for sensors. Intelligence surveillance and
reconnaissance may be provided to the ground station 258. The
ground station may be a small portable device 259, such as a mobile
phone or PDA, authorised users may control the aerial vehicle by
simply specifying a location of interest, the autopilot will then
plot a course to this and provide appropriate feeds from sensors to
the user that may include providing services. Services provided by
the Aerial vehicle may include: data networking, broadcasting it's
location with embedded timecoding for positioning systems,
transmitting the location of objects of interest (e.g. AIS), radio
communication to a required standard. These services may be
provided to a wide area that may be 100 square miles or more for
each aerial vehicle or highly localised, this is achieved with of
one or more parabolic mirrors or lens to alter the transmission to
a wide or narrow coverage area. Additionally, the aerial vehicle
may relay communication at a higher signal strength or utilise
another standard, for example a voice call may be made using a
mobile phone which is then transmitted to a satellite, allowing a
user to access other networks without in this case having to use a
satellite phone. A command and control centre 231e, may direct or
control the vehicle and receive sensor feeds or access the
databases 21 through 216. Additionally the command centre may also
specify that alerts are provided for a given set of conditions, for
example, a motor car that is exceeding the speed limit. A material
with an explosive chemical makeup being identified in the air or a
particular vehicle type entering an area of interest. A Safety
pilot remote control 260 may allow the vehicle to be operated in
civilian airspace or to pilot the vehicle directly from a remote
location. A master vehicle 261 may co-ordinate the positions of one
or more slave vehicle to maintain a honeycomb mesh data network. A
ship 262 may broadcast an AIS signature to the vehicle, that may be
relayed allowing the position of the vessel to be known well beyond
the normal range of a surface based transmitter. Similarly other
vessels that are not equipped with AIS may be identified and their
position broadcast across the AIS network. Air traffic control 263
may direct a vehicle directly or provide updated aircraft
positions. An aircraft 264 may broadcast its position, bearing and
speed to the vehicle.
[0176] A ground based light 231g may be controlled and orientated
by the aerial vehicle to point towards it and the solar cells 201
orientated 233b towards the light source, unusually the solar cells
may be orientated downwards towards earth to receive light from the
ground light. This allows additional energy to be provided to the
vehicle in low lighting conditions such as winter. Typically the
light will be turned on before dusk when light is emitted in the
visual spectrum, but may be turned on when required if transmitting
outside the visual light spectrum.
[0177] FIG. 15 depicts an alternative embodiment of the present
invention. The construction is the same as the embodiment of FIG.
1, apart from the description below. In this embodiment the
actuated control rod 1500, has a cylindrical control surface 1502
that may provide additional force to orientate the vehicle. The
cylindrical control surface 1502 is held in position with struts
1501 that are ideally a symmetrical aerofoil cross section and made
of carbon fibre reinforced composite. A lightning rod 1503 is
provided, ideally made of a carbon fibre reinforced composite tube
with a symmetrical aerofoil cross section into which is placed a
conductive wire of silver. Should lightning strike the vehicle, the
lightning rod is communicated this electrical energy though the
conductor as to not disrupt or damage electrical system operation.
Actuated parabolic mirrors 1504 are provided and described further
in FIG. 15C, 15D, 15E, 15F, 15G and 15H. The parabolic mirrors
1504a may be orientated to receive and transmit a radio
transmission from another station as illustrated by 1505. Similarly
another parabolic mirror 1504b may be orientated towards the ground
to receive light from a ground based light 1506. The vehicle has a
hydrogen storage chamber 1499, that can be presented to a fuel cell
to produce electrical power or used as fuel to power an engine,
such as a wankel or reciprocating engine, to drive the pump 242 or
a conventional method of propulsion to provide bursts of speed to
assume a loitering position (not shown). Conventional methods of
propulsion may include a propeller or jet engine. The hydrogen
storage chamber is preferably cylindrical or spherical and may be
constructed of fibre reinforced polymer composite or light weight
metal or metal alloys, including aluminium or titanium.
[0178] FIG. 15a illustrates the ground based light, that comprises
a light emitter 1509. Light emitted 1509 may be a flood light or an
light emitter beyond the visual spectrum, such as an infrared LED,
that emits light ideally between the 700 to 3000 nanometer range.
The light is directed to the vehicle using a parabolic mirror or
lens to produce a shaft of light. Alternatively a coherent light
source may be used, such as a laser. A megatron that produces light
in the microwave range may also be used (but not preferred). By
example, a 10 kW light source emitting light for 1 hour (assuming
90% optical losses in the atmosphere) is sufficient to sustain the
airframe at a groundspeed (excluding wind) of around 75 kms/hr
throughout the night, in the month of December in London, England.
In the case of a fixed position ground light, the absolute position
of the ground light is known (it may also be transmitted to the
vehicle for movable surface lights) the required orientation is
calculated and transmitted to the light source 1506. Servos 1507
and 1508 orientate the light and emit light 1509 on demand to the
aerial vehicle. These are received by concentrated solar panel
collector on the vehicle 1504b. The light ground station may be
powered by solar power and installed on a buoyant platform that may
be tethered for oceanic applications.
[0179] FIG. 15b shows an alternative embodiment, where the first
lift compartment 1511 is positioned to the front and rear of the
vehicle and secondary ballast compartment 1512 is presented in the
middle of the vehicle around the wing. A lighting rod 1513 is
situated at the mid point (previously described) but extends around
the main fuselage.
[0180] FIG. 15c represents a detailed perspective view of an
alternative embodiment of the solar cell collector 1504 illustrated
on FIG. 15. A film sleeve 1514 is bonded to the outer envelope, a
carbon fibre member 1515 is inserted to hold the mechanism and
houses a pivot 1516. A actuator 1518 rotates an outer carbon fibre
ring 1517 to achieve yaw. A second actuator 1519 achieves pitch to
rotate an inner carbon fibre ring 1520. A parabolic mirror is made
of mirror film (described above), mirror film sections 1522a are
bonded to a centre section 1521 and attached to the inner carbon
fibre ring 1520 with an adhesive. An optional outer mirror film
ring 1523 may be added. The mirror films create a parabolic mirror
1529 as shown in FIG. 15D in cross section. A carbon fibre member
1524 holds a solar cell 1526 and corrective mirror 1525 in
position. Ideally the corrective mirror is a silverised mirror
foil, such as Silver Miro supplied by Alanod of Germany. The solar
cell is ideally a high efficiency concentrator photovoltaic cell
previously described, but may be any PV cell that creates
electrical energy from sunlight. An additional linear actuator 1528
may be used to control the focal point of a radio
transmitter/antenna 1527. FIG. 15D shows incoming light 1530 being
reflected from the parabolic mirror 1529 and a corrective mirror
1525 into the solar cell 1526. FIG. 15E in perspective view and 15F
in cross sectional view show an alternative cassegrain embodiment.
Light 1530 is reflected from the film mirror 1522b onto a secondary
mirror 1525 and into a solar cell 1526. FIG. 15F in perspective
view and 15G in cross sectional view, show an alternative
off-centre parabolic embodiment.
[0181] FIG. 16 depicts an alternative embodiment of the present
invention. The construction is the same as the embodiment of FIG.
1, apart from as described below. In this embodiment the solar cell
arrangement is configured so that the mirror film 1602 can move
independently of the solar cell 1604. FIG. 16A depicts a cross
section through the solar cell arrangement, showing how the solar
cell 1604 is located around the central axis of the vehicle. This
is enabled by a central channel running along the length of the
vehicle along its main axis. The central channel is depicted in the
cross section of FIG. 16B. The mirror film 1602 rotates around the
aperture. The solar cell 1604 rotates independently of the mirror
film 1604 from within the aperture. This allows cooling of the
solar cell.
[0182] FIG. 17 depicts a further embodiment of an aerial vehicle
according to the present invention. The construction is the same as
the embodiment of FIG. 1, expect as described below. This
embodiment includes a drogue or anchor that can be released to drag
in a body of water below the vehicle, for example the sea or a lake
or river. This embodiment is particularly useful to maintain a
position against strong winds, or for applications by the coast
guard or for oceanic operators. The use of the drogue can enable
the vehicle to maintain a height below 60 m--necessary if the
vehicle is used as an unmanned aerial vehicle under an autopilot in
UK airspace. Territorial airspace extends twenty four nautical
miles from the coastline--at that distance a higher altitude can be
used. A conventional propeller 99 may be used to achieve steady,
level flight at low altitude. The drogue creates significant drag
in water to keep the vehicle in position in high wind for oceanic
applications, saving significant energy that would otherwise be
required for propulsion to keep the unit at station. Typically, the
unit drifts with the use of a drogue by 1/30.sup.th the distance
compared to not using the drogue.
[0183] The vehicle comprises an aerodynamic compartment 94
(preferably foam) with plastic film skin. This compartment includes
an actuator that may be a winch servo 95 to retract or deploy the
tether line 100 and an IR emitter 96 for communication with the
drogue 105. Towards the rear is a permanent magnet 97 which mates
with the drogue magnet 102 so that when it is not in use it is
maintained close to the body of the vehicle with a carbon fibre
member 104. When required, the drogue 105 is released by operating
a electromagnet 98.
[0184] This embodiment includes a propeller 99 at the rear of the
vehicle. The propeller is driven by a motor. It is provided to
assist flight at low altitude, for example 60 m or lower, where the
buoyancy method of propulsion cannot be used as efficiently because
of the small vertical range available.
[0185] The drogue 105 is connected to the vehicle by a tether line
100. A drogue control unit 101 is attached to the bottom of the
tether line 100. The outer surface of the control unit 101 is a
solar panel to charge the unit. Drogue unit tether lines 105a
extend from the control unit 101. A retraction line 106 is also
provided. The drogue includes a permanent magnet 102 mounted on a
carbon fibre strip 104 that fits the profile of vehicle when the
drogue is not deployed. The drogue 105 itself is made of a thick
grade of polymer film described above. In FIG. 17 the drogue is
shown deployed below a water level 1700.
[0186] FIG. 17A depicts the control architecture for the drogue
105. It includes a battery 107, IR receiver 108, Winch servo 109
and solar panel body 110.
[0187] Another embodiment of the invention is depicted in FIG. 18.
This embodiment is identical to the embodiment of FIG. 1, except as
described below. In this embodiment a wing extends between two or
more nacelles at each side of the vehicle.
[0188] A wing, which can have profiles as described above, supports
a solar cell 111 on its upper surface (and lower surfaces in some
embodiments). An opening is formed in the solar cell 111 in which
is suspended a symmetrical aerofoil payload section 113 by lines
112. The payload section carries batteries and winch servos that
can move the payload around to move the centre of gravity of the
vehicle to orientate and control the vehicle. As depicted in FIG.
18, the nacelles 1799 at each side of the vehicle do not contain a
solar cell arrangement, although in alternate embodiments this may
be provided instead of or in addition to the solar cell 111. The
nacelles include a pump 114 for filling the ballast chambers.
[0189] The wingspan carbon fibre section used in the embodiment of
FIG. 1 may be used in this configuration on the leading and
trailing edge to reduce bending across the wing (indicated
generally by numeral 115).
[0190] Thus, according to the invention, the vehicle comprises a
main nacelle or nacelles with rudder and elevators. The rudder and
elevators are preferably made of a carbon fibre frame (water-jet
cut sheet), film covers the frame. The rudder is preferably
actuated at the centre of pressure so that a small servo can be
used. The servo is preferably housed in the rear polystyrene
compartment that also houses the control unit, GPS unit,
transmitted/received and other antenna. The polystyrene container
may have a carbon fibre cap with a tail running along the rear
compartment to provide additional stability for the control
surfaces. A film nacelle envelope covers the cap and is preferably
secured with a reinforced composite of fibre and resin to provide
an air tight seal, that may be secured with a fixture.
[0191] The main nacelle is preferably made of EVAL (Ethylene
Vinyl-Alcohol Co-polymer) barrier between one or more polymer films
with an additional ceramic coating. The barrier film composite has
a low demonstrated helium permeability of 160 cc/m.sup.2/atm/24 hrs
without an additional ceramic coating. Eight sections of film make
up the nacelle section, which may be bonded with an
ultrasonic/radio frequency welding machine to provide a good seal.
The seams are reinforced on the reverse of the seal with fibre
reinforced tape to provide a strong joint. EVAL offers 100 times
less helium permeability compared with Mylar. This would result in
helium loss of 6.91 cc/m.sup.2/ATM/hr through the film, or 0.943
l/day for the preferred and exemplary embodiment.
[0192] For the embodiment of FIG. 1, this provides a theoretical
lift endurance of 239 days with a 50% loss of free lift, resulting
in reducing the upper operating altitude from 3 km to around 2
km.
[0193] Solar energy is reflected using a parabolic mirror made of
mirror film in the solar cell arrangement. The film is preferably
adhered to a carbon fibre frame at each end. Servos orientate the
solar trough to harvest available sunlight. Sunlight is
concentrated onto a photovoltaic receiver, facing towards the
mirror film. The photovoltaic cell is attached to the carbon fibre
frame and the top section (not shown) is made of mirror film which
reduces heat build-up on the reverse of the photovoltaic film and
maintains the elliptical profile of solar film across its length.
This arrangement reduces the overall mass of the craft and also
allows the sun's path to be tracked, maximising energy yield.
[0194] The component compartment is preferably made of polystyrene
and encapsulated in Mylar film, it may house a winch servo to move
the component compartment forward and aft, moving the mass along
the main axis of the craft to provide pitch control. A servo moves
the battery in a perpendicular horizontal plane to the main axis,
to provide roll control. The waste heat from the pump keeps the
batteries within operating temperature range. The pump is
preferably also housed within the polystyrene container and
connected to a solenoid valve. Ventilation and a Mu metal foil draw
heat away from the pump when in operation. A pipe draws in
atmospheric air to the pump and two pipes run the length of the
craft to the air ballast chambers.
[0195] As atmospheric air is pumped, water builds up in the feed
pipes. This water is collected in a container attached to the feed
pipes and may either be purged when the valve is switched or
presented to an electrolysis unit for processing into hydrogen to
replace helium lift gas lost through the envelope. To replace 40 cc
of helium lost per hour will require electrolysis of 0.7 cc of
water per day, to liberate hydrogen to replace the lost lift
gas.
[0196] The endurance of the Aerial Buoyancy Glider is unlikely to
be limited by lighter-than-air gas loss, but more likely the
effective battery recharge cycles. Lithium Sulphur batteries are
preferred as they have the highest specific energy per kilogram
(350 Wh/kg, 260 Wh/kg realised at the pack level). However, the
recharge cycles are likely to be only 60-90 cycles. Alternatively,
Lithium Polymer batteries would offer an attractive alternative for
longer term (1000 cycles+, with a lower specific energy of 206
Wh/kg). Other battery technologies may also be used, such as
lithium air that may offer higher specific energies.
[0197] The wings extend from main compartment, but may be combined
in some embodiments
[0198] Having described the construction of various embodiments,
the principle of operation of the present invention will now be
discussed. The present invention derives motion from alternating
upward and downward movements. The vehicle rises under a buoyancy
force resulting from the lift gas contained within the first
compartment. The vehicle falls by increasing its mass by pumping
atmospheric air as ballast into the ballast compartments. It can
then rise by expelling the air compressed in the ballast
chambers.
[0199] During the upward and downward motion the orientation of the
vehicle is controlled such that a horizontal motion component
arises. For example this may arise by force provided by a wing, or
by the shape of the main body of the vehicle itself. The resulting
motion resembles a "zigzag" or "saw tooth" when viewed from the
side. The motion is depicted in FIG. 19.
[0200] The vehicle may alter this gliding path over this cycle to
minimise energy usage (typically a longer gliding inflection with a
longer gliding distance) or increasing airspeed (typically a
shorter gliding inflection with shorter gliding distance). The
gliding angle may also be changed throughout this cycle to maximise
ground speed or energy usage.
[0201] The vehicle operates over an altitude range 1800, which is
typically 2 km or more in a preferred embodiment. The altitude
range has an upper limit 1802 and lower limit 1804 above the ground
level 1806. In a preferred embodiment the upper limit 1820 is 3 km
or more above ground level and the lower limit 1804 is 1 km or less
above ground level. The volume of the main compartment of the
vehicle containing the lift gas will determine the buoyancy of the
vehicle and the overall buoyancy ceiling 1808 where the density of
the vehicle equals the density of the surrounding air. The vehicle
may rise above the buoyancy ceiling by circling on thermals 1810 in
the same way as gliders, if thermals are available.
[0202] The method of the present invention uses buoyancy to
translate a vertical force to horizontal and vertical force
components through the wing giving ground speed. In a preferred
embodiment the overall mass of the vehicle is 1.7 kg with 2.3
m.sup.3 of helium generating free lift of 0.712 kg at sea level. As
the glider rises through the atmosphere, the air density decreases
reducing buoyancy, resulting in free lift of 0.489 kgs at 1000 m
altitude, falling to 0.09 kg of free lift at 3000 m. FIG. 20 shows
ground speeds for various gliding ascent inclinations.
[0203] As the glider ascends, the control surfaces are orientated
and/or internal masses are repositioned to change the centre of
gravity/buoyancy to orientate the craft at the desired glide angle.
At the top of the ascent, a gas pump draws in atmospheric air which
is stored in the air ballast chambers located at the front and rear
of the vehicle.
[0204] The ballast compression chambers have a combined volume of
0.46 m.sup.3 in the preferred embodiment and can withstand a
pressure of up to 3.8 Atm, though typically pressurised to a
differential pressure of 1.5 Atm. A suitable pump may be fabricated
using light weight components with a weight of only 500 grams.
[0205] The pump's performance varies with the differential pressure
between the atmospheric air drawn in and output pressure of the
compression chamber, pumping 120 litres/min at atmospheric
pressure, falling to 40 litres per min under 1.5 Atm differential
pressure. Air ballast may accumulate at a rate of around 100 grams
per minute at the beginning of the gliding descent; however this is
offset by the increase in buoyancy as the craft falls. The pump
must therefore pump sufficient atmospheric air to offset the
increase in buoyancy to maintain a heavier-than-air state to
achieve a gliding descent, as shown in FIG. 21.
[0206] At the bottom of the gliding descent, a valve is opened,
allowing air ballast held in the compression chamber to be
expelled. It is important to note that some pressure is held within
the air compression chamber so that the chamber is fully inflated.
The valve is pulsed to keep the air compression chamber pressure
above atmospheric pressure throughout the ascent glide.
[0207] The preferred embodiment is designed to operate within a 1-3
km altitude range, however if thermals are available, the glider
can circle to obtain greater altitude. Other operating ranges can
also be used, for example changing the mass of the vehicle or
increasing the volume of lift gas to extend this operating altitude
range.
[0208] Should wind offer useful assistance, then it may be
utilised. This is particularly relevant for travelling to a desired
destination. Altitude wind measurements may be gathered and
transmitted to other aerial buoyancy gliders for this purpose.
[0209] The vehicle can attain altitudes considerably higher than
the buoyancy ceiling of 3.5 km by utilising thermals, ridge lift,
or lee waves. This would allow high speed winds to be utilised to
travel considerable distance at speeds beyond the method of
buoyancy propulsion alone, not necessarily a straight line flight
path to the destination. In particular it is envisaged that jet
streams may be utilised in some embodiments.
[0210] The aerodynamic model utilised to control the vehicle of the
invention and the method of flight will now be discussed with
reference to the embodiment of FIG. 1. For the sake of illustration
the lift and drag coefficients for the lift nacelle are taken from
Online Panel Codes for a LWK 100-80, Department of Aeronautics and
Astronautics, Naval Post Graduate School, United States Navy. The
lift and drag coefficients for wing are based on a flat plate.
C.sub.d.alpha.=1.28 sin .alpha.
C.sub.l.alpha.=2.pi..alpha. (1)
[0211] The total drag takes into account vortex/induced drag at
small angles of attack. The aspect ratio for the wing is 6 (with a
0.3 taper ratio) and 0.068 for the nacelle. e is the elliptical
factor, assumed to be 0.95 for the wing (which is a reasonable for
a wing of this aspect ratio and taper) and 1.0 for the nacelle, as
it is a good elliptical shape.
C.sub.D.alpha.=C.sub.d.alpha.+C.sub.di(C.sub.1.sup.2/.pi.eAR)
(2)
[0212] The angle of attack (.alpha.eq) is derived from the
equilibrium glide angle, which varies between 0.07.degree. to
0.00096.degree. for glide angles of 8.8.degree. to 58.degree.,
respectively. FIG. 22 depicts an equilibrium gliding descent and
FIG. 23 depicts and equilibrium gliding ascent.
[0213] The coefficients are based on planform areas of 3.187498
m.sup.2 and 4.68 m.sup.2 for the nacelle and wing, respectively.
The total airframes coefficients are the average of the nacelle and
wing (excludes the control surfaces). The low CD is a result of not
needing to create aerodynamic lift, other than to keep the vehicle
on the glide flight path. FIG. 24 shows the lift and drag
coefficients with angle of attack.
[0214] The minimum glide path angle is achieved at L/Dmax:
tan .gamma. min = - C D .alpha. C L .alpha. = - 0.001235 0.007981 =
0.15478 .thrfore. .gamma. = 8.8 .degree. ( 3 ) ##EQU00001##
[0215] The airspeed is derived at the equilibrium glide angle. In
this case, the minimum glide angle.
V glide = 2 W .rho. 2000 m S 1 C D 2 + C L 2 = 11.02 m / s ( 4 )
##EQU00002##
[0216] The LWK 80-100 is used as a reference aerofoil. Other
aerofoils may also be used. At small angles of attack, little
aerodynamic lift (negative lift on a gliding ascent) is generated
and the associated vortex/induced drag is minimal.
[0217] In summary, the vehicle is a lightweight hybrid aircraft
that uses a buoyancy engine to translate a vertical force to
horizontal and vertical force components through a fixed flat plate
film wing. The glider has sufficient airspeed to penetrate winds
that may be encountered (other than the most extreme winds), offers
a very efficient method of propulsion and may harvest sufficient
solar energy to power on-board systems at most global locations
throughout the year (at an approximate Latitude range
.+-.56.degree.). The unit may effectively operate at latitudes
.+-.57.degree. to .+-.63.degree. for 10 months of the year and
.+-.64.degree. to poles for 6/8 months of the year.
[0218] Possible applications of the vehicle will now be discussed.
The vehicle is an inexpensive platform, with very long endurance
and as such, provides a near permanent aerial platform for Earth
observation and networking.
[0219] The vehicle provides a useful persistent aerial platform for
scientific sensors, meteorological data gathering and imaging
equipment (including; Synthetic Aperture RADAR, high resolution
optical camera and infrared camera). The vehicles may either loiter
over a single location to provide on-going situational awareness or
survey wide areas. Working autonomously, the vehicles do not
necessarily require a manned ground station, can operate for months
at a time, needing minimal support infrastructure and do not
require a landing runway when scheduled maintenance is
required.
[0220] By way of illustration, commercial-off-the-shelf CISCO
equipment can be used to create an aerial IP based network access
point. A number of vehicles may be deployed in a honeycomb
formation as shown in FIG. 25.
[0221] For a high bandwidth network, a distance of 5 km between
vehicles can provide a bandwidth of 48 Mbs. Bandwidth falls off to
11 Mbs at 16 km and 2 Mbs at 25 km distance between nodes.
[0222] By way of example, fifteen vehicles may provide blanket
wi-fi access across Greater London. For oceanic networking, a
persistent over-the-horizon data network would be desirable for
ship-to-ship and ship-to-shore communication that does not require
expensive geo-stationary satellite communication usage.
[0223] Bandwidths can be significantly increased for point-to-point
communication.
[0224] The vehicle's weight is typically 1.7 kgs to 3 kgs packaged
weight (approximately the size of a one-man tent). When the unit is
deployed, the envelope is unfolded, the wingspan sections attached
and the main envelope inflated from a lighter than air gas
canister, such as helium. The vehicle does not require a bulky
launch catapult or runway and may be launched from a small navel
ship or practically anywhere in the field. For advanced deployed
units, it is noted that pressurised helium should not be carried
onboard an aircraft and an off-the-shelf electrolysis unit may be
used to inflate the glider with hydrogen.
[0225] The vehicle typically operates at an altitude of 1-3 km, but
may operate at much higher altitudes by utilising thermals or an
alternative embodiment that generates more freelift. The envelope
and wing are transparent, the solar cell arrangement may be printed
on the reverse to reduce its visual footprint. The unit operates
beyond the range of ground rifle fire. The vehicle flies silently
and offers minimal clues to its presence from the ground. The
vehicle has minimal thermal signature and has `bird-like` radar
signature and flight characteristics.
[0226] A Kestrel autopilot commercially available from Procerus
Technologies, 500 South Geneva Road, Vineyard, Utah 84058, USA may
be used, providing autonomous flight operation with seamless camera
alignment, e.g. the unit does not need to be piloted and aerial
imagery is provided on request by simply specifying a co-ordinate,
the autopilot takes care of the rest.
[0227] An easy field implementation would be to use a wi-fi enabled
`smart phone` to request aerial Intelligence, Surveillance and
Reconnaissance (ISR) with ongoing situational updates provided
on-screen or other services described above, thus an aerial unit
may be under the direct guidance of a small unit. The vehicle
provides the network access point and the ISR. In the context of a
field-wide network, the ISR feed may be provided to command for
further image processing and objects of interest identified and,
where applicable, concise situational updates provided to the
required field personnel.
[0228] If the vehicles operate in non-military airspace, then they
can be piloted. The autopilot allows multiple craft to be operated
by a single pilot. With further development, it is envisaged that
the guidance system could include consideration of:-- [0229]
Dynamic global 3D wind map [0230] Prediction of the likely
occurrence of thermals from the lie of the land and time of day
[0231] Optimise aerial energy sources (thermals, glide path, high
speed winds and solar energy)
[0232] The vehicle has endurance well beyond the current generation
of tactical Unmanned Air Vehicles (UAVs), which require readying,
piloting to a required position to obtain limited ISR, piloting
back to a ground station, recovery and servicing. The vehicle
simply remains at a loitering station providing ongoing ISR and
radio communication services. Other aircraft may be more capable in
terms of airspeed, operating altitude and sensor ranges, however,
they require considerable manpower to operate, have a significantly
higher capital cost, associated running costs and need to be
refuelled and ultimately land for maintenance which can be both
time consuming and costly. Monitoring the routes used by Military
ground vehicles and convoys is a single function the vehicles may
perform amongst many other useful roles.
[0233] The vehicle offers a very low cost, persistent aerial
platform with very long endurance. As the vehicle operates at a low
operating altitude, less power hungry sensors and communication
equipment can be used. Ad hoc aerial networks are known, offering
line-of-sight radio communication to a ground receiving station.
Aerial assets form ad hoc connections between nodes, however, these
networks can only take place if an aircraft is over a particular
location. If there are no aircraft in the sky, there is no network.
The vehicles would allow a planned network to be established over a
very wide area, with consistent bandwidth and access.
[0234] The vehicle is well suited to an IP based network
infrastructure. The vehicles would allow a low-cost field-wide IP
based network to be provided alongside the existing infrastructure
and facilitate a high bandwith global telecommunication
network.
[0235] A unique feature of the vehicle is that the vehicle may land
on a body of water or deploy and recover sensors. For example, make
an active sonar sounding and undertake another sounding elsewhere
without the location of the host control vessel being determined.
Additionally, the vehicle could be used in international waters to
monitor merchant ships and interests, covering a wide patrol area.
There has been an increase in Pirate activity off Somalia (the
significant coastline is around 1000 km), with 93 attacks reported
in 2008. Around 20 vehicles could provide networked surveillance of
this coast, to detect any ships entering the shipping lanes. The
location of all ships could then be passed across the AIS network
to all merchant ships in the area and the position of suspicious
vessels passed to NATO Naval vessels in the vicinity for further
investigation.
* * * * *