Patent Publication Number: US-2011062289-A1

Title: Envelope With Gas Management System For Lighter-Than-Air Aircraft

Description:
BACKGROUND OF THE INVENTION 
     Lighter-than-air aircraft take many forms and have a variety of uses. Primary uses for unmanned high altitude lighter-than-air aircraft are for surveillance and communications. Often, it is desirable that these aircraft maintain their position, or station keep. 
     Traditionally, these high altitude aircraft fly below 70,000 feet. It would be greatly advantageous to fly above 70,000 feet to be above atmospheric turbulence and disruptive weather, and to deconflict from commercial, private, and military fixed wing aircraft. However, at altitudes above 70,000 feet, strong winds are present. In order to station keep in these strong winds, it is highly useful for the aircraft to have a low aerodynamic drag. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of the envelope of the present invention. 
         FIG. 2  is a side elevation of the envelope of the present invention. 
         FIG. 3  is a top elevation of the envelope of the present invention. 
         FIG. 4  is a front elevation of the envelope of the present invention. 
         FIG. 5  is a longitudinal cross-section of the envelope of the present invention illustrating the high and low pressure chambers. 
         FIG. 6  is an exploded view of the longitudinal cross-section of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1-4  illustrates envelope  2  for holding gas in a lighter-than-air aircraft. A payload  42  is supported by envelope  2 . Tethers  44  attach payload  42  to envelope  2 . 
     Envelope  2  includes an outer shell  4 . Outer shell  4  has an upper surface  6 , a lower surface  8 , a leading edge  10 , a trailing edge  12 , and opposing side surfaces  14 ,  16 . In one embodiment, outer shell  4  is symmetrical about a plane defined by leading edge  10  and trailing edge  12 . 
     Leading edge  10  and trailing edge  12  are each disposed between upper  6  and lower  8  surfaces. Opposing side surfaces  14 ,  16  extend between leading  10  and trailing  12  edges and upper  6  and lower  8  surfaces. 
     As may best be seen in  FIG. 3 , outer shell  4  also has an airfoil-shaped lateral cross-section. Also best seen in  FIG. 3 , in one embodiment, side surfaces  14 ,  16  are generally rectangular in shape. The generally rectangular shape may be truly rectangular or, alternatively, deviate from truly rectangular by extending beyond the boundaries of a perfect rectangle, as best seen in  FIG. 2 . The dashed lines represent the boundaries of a true rectangle  28 . It can be seen that, although the boundaries of shell  4  do not exactly match the boundaries of the true rectangle  28 , the boundaries are substantially close. 
       FIG. 5  is a longitudinal cross-section of envelope  2 . In one embodiment, envelope  2  further includes an inner wall  18 . Inner wall  18  divides outer shell  4  into a high pressure chamber  20  and a low pressure chamber  22 . High pressure chamber  20  is disposed adjacent a portion of leading edge  10 , upper surface  6 , and side walls  14 ,  16 . Low pressure chamber  22  is disposed adjacent trailing edge  12 , bottom surface  8 , a portion of leading edge  10 , upper surface  6 , and side walls  14 ,  16 . 
     In one embodiment, high pressure chamber  20  is disposed adjacent at least 50 percent of upper surface  6  and low pressure chamber  22  is disposed adjacent no more than 50 percent of upper surface  6 . In an alternative embodiment, high pressure chamber  20  is disposed adjacent at least 75 percent of upper surface  6  and low pressure chamber  22  is disposed adjacent no more than 25 percent of upper surface  6 . 
     In one embodiment, low pressure chamber  22  is disposed adjacent at least 50 percent of leading edge  10  and high pressure chamber  20  is disposed adjacent no more than 50 percent of leading edge  10 . In an alternative embodiment, low pressure chamber  22  is disposed adjacent at least 75 percent of leading edge  10  and high pressure chamber  20  is disposed adjacent no more than 25 percent of leading edge  10 . 
     In one embodiment, envelope  2  further includes a compressor  24  disposed between high pressure chamber  20  and low pressure chamber  22 . Compressor  24  is controlled to selectively force gas from low pressure chamber  22  to flow into high pressure chamber  20 . Although only one compressor  24  is illustrated, any number of compressors  24  may be used. 
     In one embodiment, envelope  2  further includes a valve  26  disposed between high pressure chamber  20  and low pressure chamber  22 . Valve  26  is controlled to selectively permit gas from high pressure chamber  20  to flow into low pressure chamber  22 . Although only one valve  26  is illustrated, any number of valves  26  may be used. 
       FIG. 6  illustrates an exploded cross-section of envelope  2 . In this illustration, envelope  2  includes high pressure chamber  20 , low pressure chamber  22 , compressor  24 , valve  26 , and an airfoil-shaped lateral cross-section ( FIG. 3 ). 
     High pressure chamber  20  has upper surface  6 , a lower interface  30 , a rear interface  32 , leading edge  10 , and opposing side surfaces  14 ,  16 . Opposing side surfaces  14 ,  16  are bounded by upper surface  6 , lower interface  30 , leading edge  10 , and rear interface  32 . In one embodiment, side surfaces  14 ,  16  of the high  20  and low  22  pressure chambers are together generally rectangular in shape. 
     Low pressure chamber  22  has upper surface  6 , lower surface  8 , leading edge  10 , trailing edge  12 , an upper interface  34 , a front interface  36 , and opposing side surfaces  14 ,  16 . Opposing side surfaces  14 ,  16  are bounded by lower surface  8 , upper surface  6 , upper interface  34 , leading edge  10 , trailing edge  12 , and front interface  36 . 
     Upper surfaces  6  of high  20  and low  22  pressure chambers are contiguous. Lower interface  30  and upper interface  34  are integral. Rear interface  32  and front interface  36  are also integral. All of which are best illustrated in  FIG. 5 . 
     The relative sizes of the high pressure  20  and low pressure  22  chambers is significant, but may be adjusted depending on the desired result. In one embodiment, upper surface  6  of high pressure chamber  20  is at least as large as upper surface  6  of low pressure chamber  22 . Alternatively, upper surface  6  of high pressure chamber  20  is at least three times as large as upper surface  6  of low pressure chamber  22 . In one embodiment, leading edge  10  of low pressure chamber  22  is at least as large as leading edge  10  of high pressure chamber  20 . Alternatively, leading edge  10  of low pressure chamber  22  is at least three times as large as leading edge  10  of high pressure chamber  20 . 
     In one embodiment, envelope  2  further includes vent valves  38 . Vent valves  38  allow gas to be exhausted from the high  20  and low  22  pressure chambers. 
     In addition, envelope  2  may further include a ram air duct  40 . Ram air duct  40  allows ambient air to be forced into low pressure chamber  22 . Ram air duct  40  may be further supplemented by a blower (not shown). 
     In one embodiment of using envelope  2 , only high pressure chamber  20  is inflated for launch. As envelope  2  ascends, expanding gas from high pressure chamber  20  fills low pressure chamber  22 . On station, a gas management system controls compressor  24  and valve  26  to manage the pressure and accommodate gas loss. As envelope  2  descends, gas is vented through vent valves  38  and ambient air is injected through ram air duct  40 . 
     The foregoing description is only illustrative of the invention. Various alternatives, modifications, and variances can be devised by those skilled in the art without departing from the invention. Accordingly, the present invention embraces all such alternatives, modifications, and variances that fall within the scope of the described invention.