WO1999024315A2

WO1999024315A2 - Partially buoyant aerial vehicle

Info

Publication number: WO1999024315A2
Application number: PCT/US1998/023494
Authority: WO
Inventors: Edsel R. Glasgow; Grant E. Carichner
Original assignee: Lockheed Martin Corporation
Priority date: 1997-11-06
Filing date: 1998-11-04
Publication date: 1999-05-20
Also published as: WO1999024315A3; AU1518999A

Abstract

An ultra large, partially buoyant, aerial vehicle (10) capable of carrying up to one million pounds of cargo for a distance of up to 4000 nautical miles before landing or needing to refuel. The vehicle (10) comprises a lifting body (11) having a thick airfoil configuration further defining a lifting body shape, and includes structural support members held in tension by cable members (22), a skin (24) extending over the support members (21) to define an internal volume for storing cargo, flight stabilization apparatus at a center rear portion of the lifting body, propulsion apparatus (12) supported on various locations of the lifting body, and flexible compartments containing lighter than air gas to provide lift assisting capability, the compartments being carried within the lifting body.

Description

PARTIALLY BUOYANT AERIAL VEHICLE

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to aircraft, and more particularly to a

partially buoyant aerial vehicle having a thick airfoil configuration further

defining a lifting body shape capable of carrying up to one million pounds

of cargo for a distance of up to 4000 nautical miles or at least 10,000

nautical miles without cargo before landing or needing to refuel.

2. Description of the Related Art

In recent years, air vehicles designed for transporting passengers

and cargo have undergone many changes. Driven by rapidly developing

new technologies and the influx of many new companies into global

commerce, various body and engine designs and modifications have been

developed resulting in aircraft capable of carrying greater passenger and

cargo payloads for greater distances and for longer times.

Some well-known "large" aircraft include the B-747 and the C-5B,

both of which are expensive to develop, produce and operate. Productivity

improvements have been made to transport aircraft over the years by

increasing engine efficiencies, wing aerodynamics and vehicle size. Such

improvements are expected to provide limited gains in the future. And the

idea of developing still larger aircraft in the near future is not likely, as they

would be very expensive and probably not compatible with existing ground

infrastructure.

Other vehicles for transporting large payloads in a global capacity

include container ships. These vehicles are able to carry tremendous

cargo loads for long distances, but travel at relatively slow speeds. Higher

speed ships are possible but require tremendous amounts of power to

propel the vehicle through the water. Adding to the water transit time are

the other land based modes of transportation required for door-to-door

delivery.

The cost of airborne transport vehicles can be reduced significantly

by designing for lower speed and altitude, and using buoyant lift to replace

the aerodynamic lift produced by wings which are expensive-to-build and

expensive-to-fly. The size of the vehicle and its associated payload

capacity must be large enough, however, to compensate for the slower

cruise speed.

US Patent No. 4,052,025 to Clark et al. discloses an airborne vehicle

of a type that uses buoyant cells pressurized to augment the crafts lift.

But the majority of its lift is produced by the wings attached to the

aerodynamically shaped fuselage. The body shape creates additional

aerodynamic lift to the vehicle when in flight with a minimum of

aerodynamic drag. The body of the vehicle is a rigid exoskeleton consisting

of a web of tension members helically wrapped around the fuselage.

Propulsion is provided by a combination of jet engines and turboprop

engines.

Other aircraft are known that use buoyant cells to augment lift

produced predominantly by wings include US Patent No. 5,425,515 to

Hirose, US Patent No. 3,907,218 to Miller, US Patent No. 3,913,871 to

Miller, US Patent No. 4,889,297 to Ikeda, US Patent No. 3,032,298 to

Callahan, and US Patent No. 3,856,238 to Malvestuto, Jr.

Examples of aircraft in which lift is predominantly produced by

buoyant cells or balloons include US Patent No. 3,120,932 to Stahmer, US

Patent No. 5,005,783 to Taylor, and US Patent No. 4,366,936 to Ferguson.

Against this background of known technology, the applicants have

developed a new ultra-large, multi-purpose hybrid aerial vehicle which is a

cross between a conventional aircraft and an airship. This "aerocraff is

partially buoyant and is capable of short takeoff and landing (STOL) using

a conventional 10,000 foot runway. The aerocraft is designed to carry

about one million (1 ,000,000) pounds of payload for approximately 4,000

nautical miles at a speed of about 150 knots and at an altitude of

approximately 4,000 feet. It is further contemplated that varied

configurations of aerocraft will be capable of short takeoffs and vertical

landings (STOVL) and vertical takeoffs and landings (VTOL).

OBJECTS AND SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a novel

aerial vehicle which will allow global transport of extremely large and heavy

weight payloads at speeds much faster than ocean-going ships and at a

cost much less than conventional aircraft, while overcoming many of the

disadvantages and drawbacks of similar vehicles known in the art.

Another object of the present invention is to provide a craft that is

partially buoyant, capable of short takeoff and landing (STOL) using a

conventional 10,000 foot runway and has the ability to carry about one

million (1 ,000,000) pounds of payload for approximately 4,000 nautical

miles at a speed of about 150 knots and at an altitude of approximately

4,000 feet.

It is yet another object of the present invention to provide a vehicle

that is capable of short takeoffs and vertical landings and vertical takeoffs

and landings.

Still another object of the present invention is to provide an aerial

vehicle with first and second separate internal compartments, the first

compartment for carrying a payload and the second for carrying a lighter-

than-air gas to provide buoyancy of the vehicle at the start, during, and at

the end of flight.

Yet another object of the present invention is to provide an aerial

vehicle with an internal variable volume of a lighter-than-air gas to provide

buoyancy for the aerial vehicle, and buoyancy management means to

enable take-off, flight and landing regardless of weather conditions, while

optimizing propulsion fuel usage.

Yet another object of the present invention is to provide an aerial

vehicle having an internal volume outfitted to carry extremely large

payloads, on the order of 1-1.5 million pounds, and provided with all the

characteristics of a conventional aircraft, including among other things,

propulsion means, lift-augmentation means, steering means, and attitude

altering means.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a front end view of a preferred embodiment of the

aerocraft of the present invention;

Figure 2 is a side view of the aerocraft shown in Figure 1 ;

Figure 3 is a top overhead view of the aerocraft shown in Figure 1 ;

Figure 4 is a cross-sectional view of the aerocraft taken along section

line 4-4 in Figure 3;

Figure 5 is a cross-sectional view of the aerocraft taken along section

line 5-5 in Figure 3;

Figure 6 is a cross-sectional view of the aerocraft taken along section

line 6-6 in Figure 2; and

Figure 7 is a partial perspective view of landing gear of the type that

are contemplated for use with the aerocraft of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The following description is provided to enable any person skilled in

the art to make and use the invention and sets forth the best modes

contemplated by the inventor of carrying out his invention. Various

modifications, however, will remain readily apparent to those skilled in the

art, since the generic principles of the present invention have been defined

herein specifically to provide an ultra large, yet novel, aerial vehicle that

encompasses many long sought after features that make transport of

extremely large payloads easier and less expensive.

The aircraft of the present invention is an ultra-large, partially

buoyant, multi-purpose aerial vehicle which is capable of a short take-off

and landing (STOL) from a conventional runway (typically on the order of

200-300 feet wide and about 10,000 feet long). It is additionally

contemplated that the vehicle of the present invention will be capable of a

short takeoff and vertical landing (STOVL) at reduced payload weights and

a vertical takeoff and landing (VTOL) at reduced fuel and/or payload

weight.

The basic design is a hybrid between an aircraft and an airship, and

is designed to carry about one million (1 ,000,000) pounds of payload for

approximately 4,000 nautical miles at a speed of about 150 knots and at an

altitude of approximately 4,000 feet. In contrast with an aircraft, the vehicle

of the present invention has substantial payload volume which allows for

outsized or large volume cargo to be carried.

Referring now to Figures 1-3, the vehicle 10 of the present invention

has a thick airfoil configuration further defining a lifting body shape 11 ,

propulsion means 12 located on fore and aft lateral portions of the lifting

body, horizontally extensive fins 13 at a rear portion of the body, vertically

arranged fins 14, one or more trailing edge body flaps 15, and an aileron

16 associated with each horizontal fin 13, rudders 17 associated with each

vertical fin 14, vertically, flight and crew station 18, and landing gear 19.

The lifting body 11 has an airfoil cross-section for efficiently

producing lift while maximizing the volume available for the lifting gas. The

airfoil is quite thick to obtain desired cargo and lifting gas volume

requirements.

The shape of the lifting body defining an airfoil configuration was

selected to provide the best aspect ratio, and therefore the lowest drag due

to lift which results in the lowest fuel weight and propulsion power

requirements. The horizontal fins 13 on the aft portion of the body provide

a shift in the aerodynamic center of the vehicle and increases the aspect

ratio by increasing vehicle span without a large weight penalty. The

vertical fins 14 at the ends of horizontal fins 13 help make the tip of the

horizontal fins more aerodynamically efficient. Aerodynamic stability and

control is provided by the vertical fins, rudder, trailing edge body flaps and

ailerons.

In a preferred embodiment of the present invention, the total

internal volume would be approximately 30 million cubic feet. This large

volume would be required to fly with a million pounds of payload using

internal lift from a lighter-than-air gas, such as helium, and external

aerodynamic lift produced by the flow of ambient air over the body and the

horizontal fins.

The vehicle in its preferred embodiment would be on the order of 740

feet long, 480 feet wide, and 220 feet high, and would have a takeoff mass

of about 3 million pounds split almost equally between empty weight, fuel

weight, and payload. As a result of the buoyancy produced by the lighter-

than-air gas, the weight on the landing gear would be only about half of the

takeoff mass, or on the order of 1.5 million pounds.

The flight and crew station 18 is positioned at or near the nose of the

vehicle. This allows for good visibility within the forward quadrant of the

vehicle. It is located above the payload bay so that in a crash, it would not

be damaged by the payload shifting forward. Also, if the vehicle were to

come down in the ocean, the flight and crew station would remain above

water.

The vehicle includes turboprop engines 12 located on lateral

portions, fore and aft, of the center of gravity of the lifting body 11. These

engines (only four of which have been shown for purposes of illustration)

enable limited pitch vectoring for low speed stability and control during

STOL operation. For STOVL and VTOL capability, pitch vectoring from

about -110 degrees to + 110 degrees would be required.

In a preferred embodiment, the propulsion system design of the

present invention consists of a turboshaft engine which drives a large (for

example, 50 to 60 foot diameter) fan or multi-bladed propeller through one

or more reducing gearboxes. In another preferred embodiment, the engine

could be located directly behind the propeller where the entire system

could rotate to provide pitch vectoring. In yet another preferred

embodiment, the engine could be located in a support pylon, where only

the propeller and one 90 degree gearbox would rotate to provide thrust

vectoring. And it is also possible that a shrouded fan could be used

instead of a propeller.

Propulsive lift and control during vertical operation are achievable by

a combination of engine throttle position and thrust vector angle. With the

loss of an engine, the engine located diagonally across from the failed

engine could be shut down, thus eliminating any power and/or control

imbalance, and the loss of lift would be partially offset by increasing the

power on the two remaining engines using an emergency time-limited

rating. To reduce the lift loss, two additional engines could be added to

either side of the vehicle on or near the vehicle center of gravity. With six

engines, the size of each engine would be less so that the total thrust

would be the same as that for the four-engine configuration.

Referring to Figures 1 and 7, the landing gear 19 is a conventional

type with the outermost wheels located approximately 100 feet apart. A

total of 36 wheels should be used so that the bearing stress on the runway

is the same as for current large aircraft. Preferably, the landing gear will

be retractable, although non-retractable landing gear could also be used

with appropriate aerodynamic fairings. Gear retraction would be

accomplished with a vertical motion which also allows the vehicle to lower

itself on the ground to improve compatibility with ground support

equipment. This height flexibility will enable reduction in cargo loading and

unloading time.

The internal structure of the vehicle is shown more clearly in the

cross-sectional views of Figures 4-6. As shown, the body comprises a

rigid shell in which both the internal structure and the outer skin carry the

aerodynamic and structural loads. The body 11 comprises a frame

consisting of a plurality of structural members 21 , cables 22, longerons 23,

and an outer skin 24. The structural members 21 define a geodesic

skeleton. The frames of the body are made rigid by means of the cables

22, which are non-metallic and always in tension. The longerons are used

to interconnect the frames and provide longitudinal stiffening to resist body

bending. The outer skin of the vehicle comprises a multi-ply soft laminate

consisting of two or three plies of a light denier (200d) scrim held together

by a polyurethane resin and coated with an outer film for protection against

ultraviolet rays. The scrim is laminated using a modified rip stop weave

architecture. The outer skin is attached to the structural frames using a

series of longitudinal gores 25 which are then seamed together or

individual panels between the frames and longerons.

A payload bay 28 is located at the bottom of the vehicle with the

geometric center of the bay at or near the vehicle center of gravity. The

payload bay is preferably about 250 feet long and 260 feet wide. However,

bays as small as 100 feet wide are feasible. The floor is strengthened

along a plurality of longitudinal extents or runs 30. Preferably, eight such

runs are used, each approximately 20 feet wide.

Cargo and equipment can be loaded onto the payload bay through

doors located at the forward and aft ends of each run. Rollers are

available in the floor to accommodate cargo containers and pallets. The

payload can be loaded and unloaded quickly due to the simultaneous roll

on and roll off capability along the payload runs.

The vehicle buoyancy system includes a plurality of helium filled bags

arranged inside the lifting body 11 on each side of the body between the

frames. The bags are constructed from a film material which has low

helium permeability. The fore and aft helium bags can be interconnected

so that vehicle trim is obtained by transferring helium back and forth.

Vehicle trim can also be accomplished by transferring fuel back and forth.

Having multiple helium bags also reduces the vulnerability of the vehicle to

threat systems.

The amount of helium to be used in the vehicle depends on various

considerations, including the atmospheric pressure and temperature

expected to be encountered in flight. At takeoff, the helium bags are

partially filled so that the helium has room to expand when the vehicle

gains altitude. The additional volume is required because the atmospheric

pressure decreases with increasing altitude and temperature, and the

helium bag would become overstressed if the helium were not allowed to

expand. The vehicle is at "pressure altitude" when the helium bag is fully

expanded. Flights above pressure altitude would require that helium be

vented to the atmosphere so as not to damage the helium bags. Venting

helium increases operating costs considerably and would only be done in

emergencies. For usual flight, the pressure altitude is expected to be 5000

feet which is 1000 feet above the nominal cruise altitude of 4000 feet. The

payload weight would need to be lowered from one million pounds if a

pressure altitude above 5000 feet is required.

The present invention contemplates use of a buoyancy management

system to insure that the vehicle is sufficiently heavy to land with adequate

control during adverse weather conditions. The vehicle design is expected

to use up its operating fuel after traveling 4000 nautical miles, and can land

with a weight on wheels of about 500,000 pounds. To keep from becoming

lighter than air on the ground, fuel or other ballast weight would need to be

added before half of the one million pounds of payload is removed. If a

vehicle range of 6000 nautical miles was desired for the same vehicle

volume and payload, a larger propulsion system would be required to

insure takeoff within 10,000 feet of runway with a heavier fuel load. For

this situation, the vehicle would be heavier than air even after removing the

payload at the end of the trip.

The vehicle of the present invention has exceptional operational

versatility. During STOL operation, with a full fuel load, one million pounds

of payload can be carried 4000 nautical miles. The range can be doubled

by stopping and refueling once or by carrying less payload and more fuel.

VTOL operation is possible if the combined weight of the fuel and payload

is within the expected thrust vectoring capabilities.

Those skilled in the art will appreciate that various adoptions and

modifications of the invention as described above can be configured

without departing from the scope and spirit of the invention. Therefore, it is

to be understood that, within the scope of the appended claims, the

invention may be practiced other than as specifically described herein.

Claims

WHAT I CLAIM IS:

1. An ultra large, partially buoyant, aerocraft capable of transporting up

to one million pounds of cargo, said aerocraft comprising:

a lifting body with an exterior airfoil configuration, said body including

structural support members held in tension by non-metallic cable members

to define a substantially geodesic skeleton, and skin means extending over

said skeleton to define an internal volume for storing the cargo,

propulsion means supported on said lifting body,

flight stabilization means at a rear portion of said lifting body, and

lift assisting means carried within said internal volume.

2. The ultra large aerocraft claim 1 , wherein said propulsion means is

disposed on opposite sides of said lifting body at fore and aft locations.

3. The ultra large aerocraft of claim 2, wherein said propulsion means

includes turboprop engines with pitch vectoring capability.

4. The ultra large aerocraft of claim 2, wherein said propulsion means

includes two engines installed far forward of the aerocraft center of gravity

and two engines installed far rearward of the aerocraft center of gravity.

5. The ultra large aerocraft of claim 4, and further including two

additional engines located at or near the center of gravity of the aerocraft.

6. The ultra large aerocraft of claim 1 , wherein said internal volume of

said lifting body has an upper portion and a lower portion for said cargo,

said lift assisting means comprising flexible bags housing a lighter-than-air

gas and being disposed atop said internal volume.

7. The ultra large aerocraft of claim 6, wherein said gas is helium.

8. The ultra large aerocraft of claim 6, and further including frame

means arranged parallel with one another and defining compartments, a

respective one of said bags being secured in each of said compartments.

9. The ultra large aerocraft of claim 1 , wherein said flight stabilization

means comprises fin means, rudder means, trailing edge body flap means,

and aileron means.

10. The ultra large aerocraft of claim 9, wherein said fin means

comprises horizontal portions.

11. The ultra large aerocraft of claim 10, wherein said fin means further

comprises vertical portions disposed at free ends of said horizontal

portions.

12. The ultra large aerocraft of claim 1 , wherein said lifting body has an

overall airfoil configuration.

13. The ultra large aerocraft of claim 1 , and further including a flight and

crew station in the vicinity of the forward portion of said lifting body.

14. The ultra large aerocraft of claim 1 , wherein said skin means

comprises a thin layer of composite material.

15. The ultra large aerocraft of claim 1 , wherein said internal volume for

storing cargo comprises a reinforced floor and access openings at fore and

aft regions of said lifting body.

16. The ultra large aerocraft of claim 15, wherein said internal volume is

located in the vicinity of the center of gravity of said lifting body.

17. The ultra large aerocraft of claim 1 , wherein said lift assisting means

comprises an array of compartments containing bags housing a lighter

than air gas, and buoyancy management means for shifting the center of

gravity of said lifting body as needed.

18. The ultra large aerocraft of claim 17, wherein said buoyancy

management means comprises pressure balancing means wherein said

bags are free to expand and contract to compensate for changes in

atmospheric pressure and temperature.

19. The ultra large aerocraft of claim 1 , wherein said craft is capable of

operation in VTOL, STOVL and STOL modes.

20. The ultra large aerocraft of claim 1 , wherein said craft has a range of

up to 4000 nautical miles.

21. The ultra large aerocraft of claim 1 , wherein said aerocraft has a

range of at least 10,000 nautical miles when operated without a payload.

22. The ultra large aerocraft of claim 1 , wherein said aerocraft has a

range of between 4,000 nautical miles and 10,000 nautical miles when

operated in a limited payload mode.