Abstract:
A structure, e.g. a pop-up tent, usable in extremes of temperature, wind, and aridity. One side of the structure&#39;s fabric reflects heat, and the other absorbs heat. The structure is reversible, so that, depending which side is outside and which inside, the structure either rejects or absorbs ambient heat, making the structure cooler in hot environments, and warmer in cool environments. The structure can have a detachable base with a hollow chamber in which one can put thermally insulating fluid (e.g. water) to add further comfort, which also provides additional physical and thermal stability to the structure. An optional moisture collector is disposable inside to collect condensate for recycling, and the fabric of the structure can be hydrophobic to direct other condensate to the base and away from occupants.

Description:
STATEMENT OF GOVERNMENT INTEREST 
     The invention described herein may be manufactured and used by or for the Government of the United States of America for Governmental purposes without the payment of any royalties thereon or therefor. 
    
    
     FIELD OF THE INVENTION 
     The invention pertains to portable, habitable, structures, in particular tents, and particularly readily portable pop-up tents. 
     BACKGROUND OF THE INVENTION 
     Pop-structures are known, and are used to form tents that can be flattened and folded for easy transport, and can readily pop-up into the shape of a tent for ready deployment. However, such tents are not designed for comfort in areas that experience extreme variations in hot, cold, arid, and windy weather. For example, Afghanistan has nearly 300 sunny days per year, maximum temperatures of near 95° F. to lows around 20° F., and winds ranging from a constant 5 to 14 MPH, in a relatively arid climate in which rainfall averages less than 12 inches per year and wind chill can be near zero degrees Fahrenheit. Inexpensive pop-up shelters that can protect and provide comfort to users in such a climate would thus be of value to military troops deployed in such areas, campers and hikers, and even the local indigenous population. 
     Conventional tents deployed in cold weather tend to form warm vapor on inside tent surfaces, making conditions inside unpleasant, and losing water which, if retrievable, would be a benefit in arid areas. For example, on a typical evening in Afghanistan about one cup of water from exhaled air can condense on a tent wall surface and begin to drip on occupants, which can be a serious problem. In a tent built for two this could result in as much as 16 ounces of water being dripped onto occupants and gear making the environment cold, wet, and uncomfortable. 
     SUMMARY OF THE INVENTION 
     Accordingly, an object of the invention is provide a structure useable as a tent that is easily deployable and storable, and that also provides thermal comfort to those within the structure in extremes of hot and cold. 
     Another object is to prevent water condensation from dripping onto occupants and other contents within such a structure. 
     Another object is to enable recovery of water condensate within such a structure. 
     In accordance with these and other objects made apparent hereinafter, the invention concerns a structure, useable as a tent, having a cover and structural elements disposed therein to permit the cover to lay flat or stand erect. The cover has at least two layers, one of which reflects, and the other of which absorbs, ambient heat. Because of this, the structure can stand erect with either of the layers directed outwards, and the other inwards, which permits the structure to define an enclosed living space which is cooled or heated with respect to ambient depending on which layer is outwardly disposed. This also permits a user to readily deploy the structure, or fold it for easy storage. The structure can have a detachable base with a cavity fillable with fluid such as air or water, to give the structure added stability, particularly in high winds, and provide thermal inertia to insulate the enclosed space from the ground. The structure can also have a water collector that uses the Lotus Effect to collect condensate on the top of the enclosed space to prevent the condensate from dripping on an occupant, and to permit recapture and reuse of the water, a particular advantage in dry environments. 
     These and other objects, features, and advantages are further understood from the following detailed description of particular embodiments of the invention. It is understood, however, that the invention is capable of extended application beyond the precise details of these embodiments. Changes and modifications can be made to the embodiments that do not affect the spirit of the invention, nor exceed its scope, as expressed in the appended claims. The embodiments are described with particular reference to the accompanying drawings, wherein: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an elevational view of a pop-up shelter according to the invention. 
         FIG. 2  is a sectional view in the direction of lines  2 - 2  of  FIG. 1 . 
         FIG. 3  is a detail sectional view of the portion of  FIG. 2  encircled by lines  3 - 3 . 
         FIG. 4  is an elevational view in the direction of lines  4 - 4  of  FIG. 1 . 
         FIG. 5  is a sectional view in the direction of lines  5 - 5  of  FIG. 4 . 
         FIG. 6  is an elevational view in the direction of lines  6 - 6  of  FIG. 2 . 
         FIG. 7  is an elevational view of the same structure illustrated in  FIG. 6 , but of the opposite side of member  20 . 
     
    
    
     DETAILED DESCRIPTION 
     With reference to the drawing figures, wherein like numbers indicate like parts throughout the several views,  FIG. 1  shows a structure  10  having a cover  12 , preferably in the form of a fabric shell, into which is sewn, in any conventional manner about cover  12 &#39;s periphery, spring loops  14 . Cover  12  mounts on an optional base  16 , which may be detachable (n.b.  FIGS. 4 and 5 ). Spring loops  14  make member  10  a pop-up structure such that, by use of the outward force of spring loops  14 , and by pushing or pulling structure  10  in the vicinity of handle  18 , one can cause structure  10  to flatten or to deploy upright as shown in  FIG. 1 , and, more importantly, be reversible, that is one can deploy structure  10  with either side of cover  12  outwardly facing, and either side inwardly facing. The combination of cover  12  and spring loops  14  permit structure  10  to be folded and laid flat such that spring loops  14  can be disposed one on top of each other, and then the loops twisted, perhaps several times, in figure-eight patterns to fold structure  10  into a compact size suitable for easy storage in a relatively small space. Such pop-up structures are usable as quick-deployable tents, and structure  10  is illustrated as a tent. Structure  10  has a sealable vent opening  13 , and a door flap  15  to permit entry and exit. 
     With particular reference to  FIGS. 2 and 3 , cover  12  is seen in section, and seen to have a fabric base  30  on which are layers  31 ,  33 , one of which is thermally reflective, and one of which is thermally absorbent. Note that layers  31 ,  33  can also be in direct contact with each other. In practice, if structure  10  is in a cold environment, one would deploy structure  10  with the thermally absorbent (i.e., solar absorbtive) side outward to take in heat from the environment, which, in turn will heat through to the opposite side of cover  12 , thus warming the inside of structure  10 . Conversely, in a hot environment, one deploys structure  10  with the thermally reflective (i.e., heat reflecting) side of cover  12  outwardly disposed to reject solar heat and thus keep the inside of structure  10  cooler than would be possible without the reflective surface. 
     The material constituting cover  12  may be one of a number of fabric textile materials that can be metalized with a highly ultraviolet/infrared (UV/IR) reflective coating on one side and a black matte metallic coating on the other. The black matte coating does not necessarily have to be metallic but a metallic coating is preferable for enhanced thermal transmission of absorbed radiation to the interior of structure  10  when in the heating configuration indicated above. The solar heating configuration will have the black matte surface on the outside with the reflective surface on the inside. In this configuration solar black body radiation is absorbed, heating the shell and radiating inward to heat the interior of structure  10 . The reflective surface on the inside acts to collect and retain the heat reaching inside, and also acts to reflect and contain body heat radiated by the occupants of structure  10 . In the solar shading/cooling configuration structure  10  is reversed and the reflective coating is placed on the outside of structure  10 . In this manner 90-99% of solar radiation on hot sunny days can be reflected away from the structure allowing the interior to stay cooler than if no solar reflection were employed, thus keeping occupants cooler than in other conventional unconditioned spaces. 
     While many different composite fabric choices may be employed, a particularly advantageous choice for simplicity and durability is a light-weight Mylar/Kevlar/Mylar composite metal coated on one side with highly reflective aluminum or silver oxide, and coated on the other side with a black metal oxide such as Black-Chrome for solar radiation absorption. 
     An example of another composite material for cover  12  that can be used and metalized is APEN 18 laminate sailcloth distributed by Sailrite Enterprises, Inc., 4506 S. State Rd. 9, Churubusco, Ind. APEN-18 laminate sailcloth is a film on film laminate made of 100% EURO PEN fill and cross (45 degree) yarn with two layers of Mylar film. The EURO PEN modulus of elasticity is 2½ times higher than polyethylene (PET) (standard Dacron®) and since this modulus is a measure of a fiber&#39;s ability to resist stretching, structures made with EURO PEN fibers will stretch less and hold their designed shape longer in wind and repeated use conditions. 
     When structure  10  is in the heating configuration, the reflective and shiny inner fabric walls may also have a band of moisture absorbing fabric  19  running the circumference of cover  12 , preferably about six inches above the bottom ( FIG. 2 ). Moisture absorbing fabric  19  layer can be made from something as simple as pressed cotton layers alone or impregnated with silica/desiccant and will be useful in humid environments in which warm moist exhale from occupants encounters a cooler interior wall on cold nights and cloudy cold days and condenses out as water. This will help keep moisture from pooling on the tent floor and wetting occupants or contents as the beads travel down the tent wall. To help the moisture to slide down the walls of structure  10 , cover  12  could be coated with a hydrophobic, and preferably superhydrophobic, coating on both sides to repel water and help water slide down the tent walls toward moisture absorbing fabric  19  more readily. 
     If a Mylar-Kevlar-Mylar composite-pressed-glued-sandwich fabric is used for cover  12 , then the energy absorbing side of the Mylar can also be coated with a metalized aluminum-oxide substrate, which in turn is covered with: (1) a Black-Chrome coating, producing a 5% reflection and a 15% reflected radiance loss, for a total of 20% loss (80% Absorption) or (2) a Selective Absorption coating, for example the ALMECO-TiNOX coating of Almeco-TiNOX GmbH, producing a 5% reflection and a 5% reflected radiance loss, for a total of 10% loss or 90% absorption. 
     The energy rejecting side  31  or  33  (depending which way reversible structure  10  is opened) of cover  12  can be regular reflective Mylar film (90% reflectivity), which may be optionally coated with silicone to preserve surface finish. 
     Additionally, cover  12  may also be layered such that a polypropylene based non-woven perforated fabric (corresponding to base layer  30  of  FIG. 3 ) has a similar metalization  31 ,  33  on the heat rejecting side and absorbing side. In this embodiment, both metalizations can advantageously be the material whose product name is Temptrol, available from Innovative Insulation, Inc., 6200 W. Pioneer Parkway, Arlington, Tex. A TemptrolT radiant barrier reflects 95% of radiant heat. The TemptrolT in  FIG. 3  would be tinted black on one side and silver on the other (corresponding respectively to the heat absorbing and heat rejecting sides), with preferably an additional superhydrophobic coating on both sides to repel water. Reflectivity would be a bit less, but radiant heat rejection will be much greater, resulting in much lower temperatures inside the tent because the radiant heat from the roof will not be radiated into the tent when in the cooling orientation. Note that the superhydrophobic coating will cause the fabric to repel water to such a degree that natural rainfall will clean the outside surface of the tent as well. 
     Another fabric scheme having the same general structure as illustrated in  FIG. 3  can be made of Flashgro Reflective Fabric. Reflective Agricultural Flashgro is a highly reflective film with a metalized polyester surface and a tough woven poly backing material. Flashgro reflects both heat and light in an even dispersed pattern on one side and can be produced with black pigment on the other side for energy absorption. 
       FIGS. 4 and 5  show in more detail base  16 , which preferably is in the form of a flexible, impermeable, pad  35  which encloses a chamber  17  that one can fill with a fluid such as water, air, or the like to both thermally insulate the interior of structure  10  and provide a softer floor inside for sitting. On opposite sides of the periphery of pad  35  are zipper tracks  34  which mate with a corresponding zipper track (not shown) in cover  12  to permit ready attachment of base  16  to cover  12 . Although zippering members  12  and  16  together permits especially fast attachment, and especially good protection against ambient conditions outside structure  10 , particularly wind, any effective attachment scheme is useable, e.g. Velcro, snaps, tie-straps, or mating stake holes in cover  12  and base  16 . Other effective attachment schemes can be laces, belts, buttons etc. Zipper  34 ′ of cover  12  is preferably sewn into a flap  36  integrated into the edge (or periphery) of cover  12 . The flap  36  is preferably approximately 3-6 inches in width to allow for external sand-bagging should such be desired by the user with or without the use of base  16 . If one fills chamber  17  in base  16  with water and securely attaches base  16  to cover  12 , the entire structure  10  will not require any external anchors to hold structure  10  in place during high winds, and a water fill in chamber  17  will help moderate the temperature inside via thermal mass. When structure  10  is erected to absorb heat from the ambient, water in base  16  will also heat, retain the heat and then radiate the heat back toward the occupants after the sun goes down or when cloud cover blocks warming radiation. When structure  10  is erected to reject heat from the ambient, water in chamber  17  will tend to be cooler than the surrounding air as it will couple with the cooler ground upon which it is sitting; thus an occupant laying on base  16  will find body heat being pulled away faster than is possible when surrounded only by hot summer air, and thus be more comfortable when air temperatures are hot. 
     FIGS.  2  and  6 - 7  show a moisture collector  20  attached to the interior top of structure  10 , with a space  23  left therebetween. Collector  20  is of air permeable material, for example air permeable fabric formed into a closed surface to define an inner convex surface  38  and an outer concave surface  40 , with large and small openings  22  and  24 , respectively, at opposite ends. Such curvature is preferable because it forms a de facto funnel to catch condensate from the top of cover  12 , and collect the condensate in receptacle  26 , which preferably hangs by supports  28  from receptacle  20  below small opening  24 . Inner surface  38  of receptacle  20  is coated with a hydrophobic, and preferably superhydrophobic, compound to make use of the Lotus Effect. As warm wet air, such as air exhaled by occupants of structure  10 , rises up, vapor passes through the fabric of collector  20  into space  23  and comes in contact with the cool roof of structure  10 . This vapor then condenses and begins to form water droplets on the underside of the roof. When enough vapor has condensed the droplets coalesce into larger droplets that fall from the ceiling. These droplets are now too large to pass through the treated fabric (liquid vice vapor) and, because of the superhydrophobic surface treatment, the water is repelled from inner surface  38  of collector  20 . Friction with collector  20  is low (reduced droplet contact area) and the droplets shed and travel down inner side  38  of collector  20  due to gravity and exit bottom center via hole  24  where it drips into receptacle  26  for collection. In this manner, as much as 16 ounces of fresh water may be collected and recycled per day. Tubing (not shown) may also be used in place of a cup and the water routed out of the tent if reuse is not desired. The fabric of collector  20  may be attached to the roof of structure  10  in any number of ways that include but are not limited to zippers, Velcro, snaps, ties, etc. An example of such a superhydrophobic fabric/coating arrangement for collector  20  would be cotton coated with a particulate silica sol solution of co-hydrolyzed TEOS/fluorinated alkyl silane with NH3-H2O. PET (Polyethylene), vinyl, polyester and wool coated with the same mixture will also result in stable superhydrophobic surfaces with water contact angles over 170 degrees and droplet sliding angles below 7 degrees to most effectively shed water to a collection reservoir. The condensate collecting superhydrophobic water recovery system could also be manufactured using TemptrolT Radiant Curtain coated on inner surface  38  in the manner described above, with a reflective coating placed on outer surface  40  to reflect the heat of the occupants back toward them. Note that the overhead size and coverage area of opening  22  of collector  20  can be selected to collect condensate from as large a portion of structure  10 &#39;s roof as desired. Obviously, a larger flatter roof would entail the need for a larger collector  20  with a larger opening  22  across the top/roof area of structure  10 . 
     The invention has been described in what is considered to be the most practical and preferred embodiments. It is recognized, however, that obvious modifications to these embodiments may occur to those with skill in this art. Accordingly, the scope of the invention is to be discerned from reference to the appended claims, wherein: