Abstract:
A parafoil for operation at high altitudes, in low density air, or at low airspeeds, and methods for opening same. Some versions of the parafoil comprise flexible members connected to the parafoil canopy. When the parafoil canopy is in a stowed configuration, the members are deformed, storing elastic energy. When the canopy is released from its stowed configuration, the members spring back to their undeformed shapes, thereby opening or assisting with opening the canopy. The flexible member may also be attached to a base structure, which is attached to the payload. The members may comprise rods or hollow tubes that can be flexed using a fulcrum near the base structure, or a spacer plate, so that the ends connected to the canopy are restrained by a parachute bag containing the stowed or packed canopy. The parachute bag can be opened prior to or during detachment of the parafoil from the flight vehicle

Description:
INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS 
       [0001]    Any and all applications for which a foreign or domestic priority claim is identified in the Application Data Sheet as filed with the present application are hereby incorporated by reference under 37 CFR 1.57. 
         [0002]    This application is a continuation of U.S. patent application Ser. No. 15/065,828, filed Mar. 9, 2016, and entitled “Rigidized Assisted Opening System For High Altitude Parafoils,” which claims the benefit of priority under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 62/130,395, filed on Mar. 9, 2015, and entitled “Rigidized Assisted Opening System For High Altitude Parafoils,” and the benefit of priority under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 62/239,154, filed on Oct. 8, 2015, and entitled “Rigidized Assisted Opening System For High Altitude Parafoils,” the entire disclosure of each of which is incorporated herein by reference for all purposes. 
     
    
     BACKGROUND 
       [0003]    1. Field 
         [0004]    The present invention relates to a system to mechanically assist with opening a parafoil. More specifically, the present invention is related to assisting in the opening of a parafoil transitioning from a state where it is not flying to a state where it is flying, especially when that system is starting with little to no airspeed, starting in low density air, or both. Mechanically aiding in the opening of a parachute allows parafoils to inflate and fly in environments where they otherwise may not have been capable of opening and transitioning to flight reliably. Avoiding entanglement is also important during the period of low air speeds, in low density air (such as at high altitudes), or both, where there is no force of wind to hold the parachute fabric away from the payload and from entangling with itself. Thus embodiments of the present invention preferably serve a dual purpose both as a mechanism to assist in the opening of the parafoil envelope and as an anti-entanglement device holding the fabric, lines and payload away from each other so they cannot snag or tangle 
         [0005]    2. Description of the Related Art 
         [0006]    Note that the following discussion may refer to a number of publications and references. Discussion of such publications herein is given for more complete background of the scientific principles and is not to be construed as an admission that such publications are prior art for patentability determination purposes. 
         [0007]    The word parafoil is, appropriately, the combination of the words “parachute” and “airfoil”. A parafoil is essentially an inflatable wing combining the light weight and packability of a parachute with the cross-range, steerability and landability of an airfoil. A parafoil is often referred to as a parachute or a ram air parachute, and may be referred to as such herein. Parafoils comprise a fabric canopy and parachute lines. Parafoils have a much more complex opening and inflation dynamic than round parachutes do. Because the wing is typically inflated from the leading edge the inflation process happens in multiple stages. This opening dynamic is problematic at high altitudes. Because the air at high altitudes is thin, and the inflation ports of the canopy do not necessarily face the airstream, there is substantial risk when using parafoils at high altitude that they will fail to inflate for too long a period. At this point, once the canopy orients and finally does inflate, the airspeeds may be too high and the opening could destroy the parafoil or whatever is beneath it. 
       SUMMARY 
       [0008]    The present invention is a method of opening a parafoil comprising a canopy and a plurality of flexible members, the method comprising deforming the flexible members, thereby storing elastic potential energy in the flexible members, wherein a top end of each flexible member is connected to the parafoil canopy; securing the parafoil canopy and the deformed flexible members in a stowed configuration; attaching the parafoil to a flight vehicle; detaching the parafoil from the flight vehicle; releasing the parafoil canopy and the flexible members; and the flexible members returning to their undeformed shape, thereby at least partially deploying the parafoil canopy. The base end of each flexible member is preferably connected to a base member, optionally via a hinge, with the base member connected to a payload. The method optionally comprises one or more suspension lines, but not all suspension lines, supporting the weight of the payload during flight of the flight vehicle, the suspension lines connecting the base member and the canopy. The deforming step preferably comprises bringing the top ends of the flexible members together, the flexible members bending around a plate or fulcrum disposed between the top ends and the base ends. After the releasing step, the flexible members preferably spread apart from each other past a vertical orientation, at which point gravity preferably continues to spread apart the flexible members until the parafoil canopy is completely deployed. The deforming step preferably comprises folding the parafoil canopy and the securing step comprises disposing the folded parafoil canopy in a parachute bag. The detaching and releasing steps are optionally performed at an altitude greater than approximately 25,000 feet, or greater than approximately 50,000 feet. The releasing step is optionally performed before or approximately simultaneously with the detaching step. 
         [0009]    The present invention is also a parafoil comprising a canopy; a base member connected to the canopy via a plurality of suspension lines; and a plurality of flexible members attached to the canopy. The flexible members are preferably attached to the base member, optionally via a hinge. The base member optionally comprises a fulcrum for bending each flexible member; alternatively, the parafoil comprises a plate disposed between the base member and the canopy for bending the flexible members. Each flexible member optionally comprises a hollow tube, in which case each flexible member optionally comprises a telescoping end attached to the canopy or a suspension line disposed within each flexible member. 
         [0010]    Objects, advantages and novel features, and further scope of applicability of the present invention will be set forth in part in the detailed description to follow, taken in conjunction with the accompanying drawings, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The accompanying drawings, which are incorporated into and form a part of the specification, illustrate the practice of embodiments of the present invention and, together with the description, serve to explain the principles of the invention. The drawings are only for the purpose of illustrating certain embodiments of the invention and are not to be construed as limiting the invention. In the figures: 
           [0012]      FIG. 1  is a diagram of a deployed parafoil according to a first embodiment of the present invention. 
           [0013]      FIG. 2  is a diagram of the wing tip supports of parafoil of  FIG. 1  in their stowed configuration. 
           [0014]      FIG. 3  is a diagram showing deployed wing tip supports. 
           [0015]      FIG. 4  is a diagram detailing the base structure of the parafoil of  FIG. 1 . 
           [0016]      FIG. 5  details the hinge bracket attachment of the wing tip supports to the base structure. 
           [0017]      FIG. 6  shows telescoping wing tip supports. 
           [0018]      FIG. 7  is a perspective view of a deployed parafoil according to a second embodiment of the present invention. 
           [0019]      FIG. 8  is a front view of the deployed parafoil of  FIG. 7 . 
           [0020]      FIG. 9  shows suspension lines and wing tip support of the parafoil of  FIG. 7  in their stowed configuration. 
           [0021]      FIG. 10  is a detail of the base structure of the parafoil of  FIG. 7 . 
           [0022]      FIG. 11  shows a deployed parafoil in accordance with a third embodiment of the present invention. 
           [0023]      FIG. 12  shows rigidized and non-rigidized parachute suspension lines of the parafoil of  FIG. 11  in their stowed configuration. 
           [0024]      FIG. 13  shows the attachment structure at the top of the stowed configuration of the parafoil of  FIG. 11 . 
           [0025]      FIG. 14  shows an embodiment of a parafoil of the present invention comprising inflatable bladders or beams. 
           [0026]      FIG. 15  shows an embodiment of a parafoil of the present invention utilizing compressed gas to directly inflate the canopy. 
           [0027]      FIG. 16  shows an embodiment of a parafoil of the present invention comprising thrusters to help deploy the canopy. 
           [0028]      FIG. 17  shows an embodiment of a parafoil of the present invention comprising telescoping rods to help deploy the canopy. 
           [0029]      FIG. 18  shows an embodiment of a parafoil of the present invention comprising deployable beams to help deploy the canopy. 
           [0030]      FIG. 19  shows an embodiment of a parafoil of the present invention comprising a lattice of rigid members. 
           [0031]      FIG. 20  shows the parafoil of  FIG. 19  folded along its shortest dimension. 
           [0032]      FIG. 21  shows the parafoil of  FIG. 20  spiraled in the lengthwise dimension for stowage. 
           [0033]      FIG. 22  is a detail of the connection of the wing tip supports to the parachute bag. 
       
    
    
     DETAILED DESCRIPTION 
       [0034]    The present invention pertains to the assisting in the opening of a parafoil either during or prior to separating from a supporting structure while in low density air, starting with little air speed, or both. Embodiments of the present invention use stored energy to assist in the opening of a parafoil. Some embodiments of the present invention include spring loaded rods pushing open the parafoil envelope, hinged rods that use potential energy of their weight in a stowed configuration to open a parafoil, or rods that use a combination of stored potential energy and spring energy to open a parafoil envelope. Other embodiments of the present invention include utilizing inflatable bladders to spread the parafoil envelope, inflating the parafoil directly with compressors or compressed gas, using the weight of the mass suspended beneath the parafoil to force a mechanical arm to open the parafoil, using thruster mechanisms to push the envelope open, using springs to open the bottom of the parafoil envelope or using deployable split-tube booms to assist in the opening of the canopy. One embodiment of the present invention utilizes flexible rods connected to a base structure with hinges to assist in opening a parafoil. The rods can be flexed using a fulcrum near the base structure to a central point where they are preferably restrained at the base of the packed parafoil. When released the rods preferably spring out and fall away from the central structure, optionally assisted by gravity, opening the parafoil envelope prior to, during, or after the release of the parafoil from the supporting structure. This embodiment can be operated using flexed rods acting like springs, hinged rods assisted by gravity, or preferably, a combination of both. 
         [0035]    An embodiment of the present invention utilizes hinged flexible poles connected to a rigid base both supporting the poles and providing an attachment platform between a payload and a mechanism to lift the payload, such as a high altitude balloon. This embodiment is particularly useful for use with payloads having a mass greater than approximately 2,000 lbs., although it may be used with any payload. As shown in  FIG. 1 , supporting base structure  102 , also referred to as a “riser bracket”, provides the structural hub where the supporting vehicle, such as a high altitude balloon, connects to parafoil envelope  100 . A detail of base structure  102  is shown in  FIG. 4 . The connection to the balloon is preferably made via a release mechanism such as release hook  111 . Parachute lines  103  preferably attach using a mechanism such as attachment shackle  109 . The base structure attaches to a payload via attachment shackle  119  and payload support lines (not shown). Main structural beam  116  for all the structures preferably comprises an I-beam or any appropriate structure depending on the mass of the payload and specific structural specifications of the system. The release mechanism could attach to a flight vehicle, such as a high altitude balloon via a tether running from the release mechanism through the parafoil  100  to the flight vehicle. Release hook  111  preferably attaches to main structural beam  116  via structural rods  110 . Main structural beam  116  also preferably supports any other required equipment for operation of the parafoil, such as one or more control motors  118 . The structural rods and release mechanism are preferably aligned using cross brace  117 . The parafoil is preferably assisted in opening or is opened prior to release in an action referred to hereafter as “predeploy” by long flexible rods  101 , also referred to as “wing tip supports”. Centrally located wing tip supports  112  preferably support the nose and tail of the canopy during predeploy. In this embodiment the wing tip supports preferably comprise hollow poles which are aluminum, carbon fiber, or a combination thereof. The poles may be of any size, but in one embodiment they are 2.5″ in diameter, with a 0.065″ wall thickness. The tops of the wing tip supports preferably comprise aluminum to accommodate sliding of the plunger, as described below in reference to  FIG. 6 . The bottoms of the wing tip supports preferably comprise carbon fiber due to its lighter weight and higher strength. However, any combination, or any material by itself, may be used. 
         [0036]    Base  120  of each wing tip support is preferably fastened to main structural beam  116  via hinge bracket  114 , a detail of which is shown in  FIG. 5 . The hinge bracket preferably attaches to the beam via bolts through mounting holes  123 . The bracket may be angled to direct the wing tip support outward during the deployment process, which angle is preferably achieved via bend  124  in the bracket. The angle in the bracket preferably points the outside wing tip supports approximately towards the corners of the canopy when it is deployed. Angle  124  is preferably, but not limited to, approximately 20 degrees to achieve a substantially open canopy when deployed. Base  120  is preferably attached to the bracket via hinging mechanism  122  that allows it to rotate freely against the bracket. The initial angle of the wing tip support is preferably fixed by fulcrum  125  to a specific angle that will govern the spring load on the wing tip support when flexed. The angle will be determined by the size, geometry and material of the wing tip support as well as the configuration of the main structural beam and size of the parafoil. This angle is preferably, but not limited to, approximately 22 degrees. 
         [0037]    The top of the wing tip support preferably comprises a pole that is allowed to translate along the axis of wing tip support in a linear fashion as shown in  FIG. 6 . The moveable part of the wing tip support is referred to hereafter as a “plunger”. Plunger  127  slides in and out of the wing tip support by fitting inside it via sliding interface  126 . This sliding contact can be achieved using a linear bearing, a free-fit interface, or any other mechanism that allows the plunger to translate in and out with respect to the wing tip support. The plunger preferably attaches to the canopy at attachment eye  128  that is fixed with respect to plunger  127 . This linear freedom allows the canopy to fly in its natural shape. The design shape of the canopy is typically not identical to the actual shape of the canopy in flight, so some variability in the position of the wing tip support ends is preferable. 
         [0038]    The packed configuration of the parafoil can be seen in  FIG. 2 . When the parafoil canopy is packed the wing tip supports will be bent in around the fulcrum  125  to a central location at the tops  104  of the wing tip supports where they will be collected at the base of the parachute bag. Riser bracket  102  is where the hinge brackets are preferably located. Wing tip supports  101  are preferably flexed in and collected at the base of the parachute bag, similar to that shown in  FIG. 9 . The parachute bag, which is not shown in  FIG. 2 , is preferably just above the tops  104  of the wing tip supports, similar to the configuration shown in  FIG. 22 . 
         [0039]    When the stowed system shown in  FIG. 2  is ready to be deployed, a closure loop could be cut or otherwise opened, similar to the opening as described in the second embodiment below, releasing the wing tip supports to spring and fall open. After being opened the wing tip supports preferably spread out in a similar fashion to that shown in  FIG. 3 . Riser bracket  102  holds the bases of wing tip supports  101 . The parachute (not shown in  FIG. 3 ) is preferably connected to the wing tip supports, the weight of which will hold the parachute open. The geometry of the parachute in the open state is shown in  FIG. 1 . Riser bracket  102  holds parachute lines  103  and the bases of wing tip supports  101 . Parafoil envelope  100  is stretched out via the wing tip supports. 
         [0040]    In another embodiment of the invention, the parafoil is predeployed or otherwise assisted in opening using flexed rods on hinged bases, similar to the previous embodiment. In this embodiment of the invention the wing tip supports are held by retention cords while stowed, instead of flexed around a fulcrum. This embodiment of the invention is suitable for, but not limited to, payload masses between approximately 500 and 2000 lbs. In this embodiment of the invention payload  200  can be functionally recovered from a starting condition where the system has little starting airspeed or is in low density air. 
         [0041]    The system starts in a packed configuration as shown in  FIG. 9 . Payload  200  is suspended from structural platform or riser bracket  206 , preferably attached thereto via payload riser  207 . The riser bracket is preferably suspended from the parachute deployment bag  215  using the set of parachute suspension lines  223  which are taut by virtue of their lengths during ascent. Suspension lines  223  are preferably attached to parachute deployment bag  215  via rings  202 , which together preferably carry the structural suspension load of the system via structural strap  213  that preferably attaches the system to the balloon via connection device  214  (such as a structural shackle or carabiner). 
         [0042]    A detailed view of the attachment of wing tip supports  216  to parachute deployment bag  205  is shown in  FIG. 22 . A parachute container comprises a tubular parachute deployment bag that preferably houses the parachute in a typical “Proper Ram-air Orientation” PRO pack. The base of the bag preferably comprises fabric flaps  1001 , preferably comprising metallic grommets  1000 , used to hold the bag closed. Eyes  1002  on the top of wing tip supports  216  (or alternatively connected to the wing tip support plungers if used) are held together via closure loop  1004 , thereby maintain the wing tip supports under stress in their flexure configuration. Closure loop  1004  weaves through grommets  1000  and wing tip support eyes  1002 , preferably making a closed loop. That loop preferably both holds the wing tip supports in their flexed configuration and also holds the bag closed so the canopy cannot fall out. When the system is ready to deploy, closure loop  1004  is severed or otherwise released, opening the bag so that the canopy is free to open and allowing wing tip supports  216  to spring open due to their stored energy of flexure. The canopy is preferably connected to eyes  1002  inside parachute deployment bag  205 , and thus is predeployed or deployed as the wing tip supports spring open and the bag is opened. 
         [0043]    A detailed view of riser bracket  220  can be seen in  FIG. 10 . Payload risers  231  attach the payload to separable structural shackles  228 . The structural shackles connect to the riser bracket via “Y bridles”  227  connected to one or more riser bracket beams  221  via structural shackles  226 , which preferably equalize the front-to back load and ensure that offsets in payload center of gravity do not create control inputs to the parafoil. If the system were tethered to the ground prior to a flight it could be tethered via ground support straps  229 . Riser bracket beams  221  preferably hold any required support hardware such as an Aerial Guidance Unit  210 . The system can be suspended from a flight vehicle, such as a high altitude balloon, using a set of parachute suspension lines  223 . The remaining parachute suspension lines  222  are slack during ascent and taut after the parafoil is deployed. Wing tip supports  216  are preferably tethered to riser bracket beam  221  using restraint cords  225 , which restrict the wing tip supports from falling inwards towards the canopy when released. The restraint cord may alternatively be set such that the wing tip supports naturally sit with an outward angle and must be bent inwards during the parachute packing process, thereby creating outward spring energy when released. In this embodiment the wing tip supports comprise hollow aluminum  1 ″ diameter poles, although any material in any size may be used. The wing tip supports in this embodiment of the invention may employ plungers at the top of the wing tip supports, as described above, to more easily accommodate packing and a natural flight geometry. 
         [0044]    Once flying the system is preferably suspended under the parafoil as shown in  FIG. 7  and  FIG. 8 . Parafoil canopy  203  is preferably connected to riser bracket  206  via suspension lines  222 ,  223 . Wing tip supports  216  are preferably not active at this time. The system is preferably controlled in flight by aerial guidance unit  210 . The system may be coupled with a traditional reserve parachute  209  for added redundancy. 
         [0045]    Rings  202  are for attaching the parafoil to the base of the balloon during ascent. This transfers the load due to the payload through suspension lines  223  to the flight vehicle, such as a high altitude balloon. For predeploy, the parachute deployment bag can be opened by severing a loop that holds both the bag closed and the wing tip supports under stress due to their bending, allowing the parachute to spring open before the release of rings  202  from the balloon. The parafoil is then released from the balloon by the release of rings  202 . Alternatively, the parachute bag can be opened at approximately the same time as the release of rings  202  from the balloon. 
         [0046]    Another embodiment of the invention that allows a system to begin flight under a parafoil in situations where the system has little air speed, is in low density air, or both. This embodiment of the invention is suitable for, but not limited to, payloads having a mass less than approximately 500 lbs. In this embodiment of the invention select parachute suspension lines are rigidized (but still flexible) and flexed around a spreading plate to provide opening force. This embodiment of the invention does not comprise hinges or wing tip supports because the rigidized suspension lines are responsible for spreading the canopy.  FIG. 12  shows this embodiment of the invention in its packed form. Non-rigidized parachute suspension lines  311  and rigidized parachute suspension lines  310  connect to a payload via payload risers  312  which preferably converge to triangular structural mounting plate  313 . The rigidized suspension lines are preferably under stress, flexed outward by spreading plate  314 . 
         [0047]    This spreading plate can be restricted using short tethers rigged to triangular structural mounting plate  313  so the spreading plate isn&#39;t vertically displaced during stowage. In this embodiment rigidized suspension lines  310  each preferably comprises a suspension line passed through a rigid tube, such as a 0.375″ diameter hollow carbon fiber tube, having an inner diameter slightly larger than that of the suspension line. A select set of suspension lines is attached to the bottom of parachute deployment bag  309 . The structural load path goes through parachute deployment bag  309  and through structural strap  308  to connecting device  307  (such as a threaded connector, shackle or carabiner). 
         [0048]    A detail of the deployment bag and attachment structure at the top of the system is shown in  FIG. 13 . The load from the suspension lines is preferably carried through deployment bag  309  through straps sewn into the bag  320 . The top of the bag connects to attachment strap  308 , which preferably supports any equipment needed above the parachute system, such as an avionics box  322  and communication antenna  321  for actuating the release of the system. Above that hardware high side structural tether  316  preferably attaches to connection hardware  307  to connect the parachute system to a flight vehicle such as a high altitude balloon. 
         [0049]    The system is preferably released using a remote signal which activates a release mechanism that opens a deployment bag  309 . Once released the system will begin to fall and the tensioned, rigidized suspension lines  310  pull the parafoil open, assisting in the parafoil deployment. Shortly after releasing a combination of the airflow and the rigidized suspension lines will open parafoil canopy  300  to a state where it is flying, as shown in  FIG. 11 . Rigidized lines  310  preferably act as ordinary suspension lines from this point forward. Non-rigidized suspension lines  311  are preferably unaffected by this process. Spreader plate  314  is preferably configured such that the lines are oriented correctly in flight. Structural base assembly  304  connects the parafoil suspension lines to the payload during the descent in the same fashion as during ascent. Payload risers  312  connect the payload to the suspension lines. This system may be coupled with traditional reserve parachute  303  for additional redundancy. 
         [0050]    In any of the previous embodiments, once the wing tip supports (or rigidized lines) spring open and outward past vertical, the force of gravity can assist with them continuing to spread apart until the parafoil canopy is completely deployed. 
         [0051]    In a different embodiment of the invention, shown in  FIG. 14 , a series of inflatable bladders or beams  400  physically spread open parafoil canopy  401 . The beams optionally inflate using compressed gas to a pressure sufficient to physically push the canopy fabric out to its fully extended width so that inflation in flight can happen very quickly and efficiently. The beams optionally utilize the existing parafoil cross-ports (holes in the structural and non-structural ribs of the parafoil) to allow the use of inflatable beams without significant modifications to the parafoil. 
         [0052]    In another embodiment of the invention, shown in  FIG. 15 , compressed gas canisters  501 , or alternatively a compressor, directly inflate canopy envelope  500 . This process may optionally occur before, during or after the system&#39;s release from the balloon to establish the shape of the canopy before aerodynamic forces are high enough to cause the canopy to inflate by itself. Compressed air, for example, can be injected into the canopy interior providing the energy to push the canopy into an open state. Optional valved canopy inflation ports, such as fabric-flap type valves, may be used to allow flow into the cells but not out of them. 
         [0053]    In yet another embodiment of the invention, shown in  FIG. 16 , thrusters  600  are used to spread the canopy open during or immediately after release. Cold gas thrusters, chemical thrusters or any device capable of creating a linear force could be used to push canopy  601  into a deployed state. 
         [0054]    In another embodiment of the invention, shown in  FIG. 17 , telescoping rods  701  push canopy  700  into a deployed state. The telescoping rods can be deployed using internal bladders, by compressed gas acting directly on the interior surface of the telescoping rod, or by any type of mechanical spring or stored energy device. The telescoping rods are preferably nested while the canopy is not being used, allowing it to be small. When actuated the rods preferably create a continuous member spanning some or all of the canopy width. 
         [0055]    In a different embodiment of the invention, shown in  FIG. 18 , a parachute system employs deployable beams to spread out the parafoil fabric before, during or immediately after separation from a flight vehicle. Parafoil  800  can be stowed when not in use. When needed, deployable beam mechanism  801  deploys, thereby causing the parafoil to deploy. The deployable beam preferably comprises split-tube technology to allow a stowed, small beam to erect into a long rigid boom. The deployable beam optionally utilizes smart materials that change shape from a stowed condition to a rigid beam configuration when electricity, heat or both are applied. The rigid beams hold the canopy fabric open while the parafoil begins flying. 
         [0056]    In another embodiment of the invention, shown in  FIGS. 19, 20, and 21 , a framework of rigidly flexible members  901 ,  902  make a rigidized lattice inside the canopy to keep its shape while the system is in a condition where it has little airspeed, is in low density air or both. In this embodiment of the invention, flexible spanwise members  901  run spanwise from wingtip to wingtip of canopy  900 , and rigidly flexible cross members  902  run cordwise from nose to tail of canopy  900 . To stow the canopy it is preferably first folded across its shortest dimension, connecting the nose of the canopy to the tail, such that cross members  902  make a partial tube shape or loop as shown in  FIG. 20 , while the two spanwise members  901  meet up in parallel and are not yet bent. The final stage in stowing the canopy is twisting spanwise members  901  into a spiral, as shown in  FIG. 21 , with canopy  900  spiraled along with the rigidizers. This system may be held in the stowed configuration using a closure loop. When ready to deploy the closure loop would be cut or otherwise opened, allowing the rigidizers to spring the canopy into the final flight configuration. In this embodiment the flexible members preferably comprise 0.156″ diameter solid carbon fiber poles, although any material and size of pole, or hollow poles, may be used. 
         [0057]    Although the invention has been described in detail with particular reference to the disclosed embodiments, other embodiments can achieve the same results. Variations and modifications of the present invention will be obvious to those skilled in the art and it is intended to cover all such modifications and equivalents. The entire disclosures of all patents and publications cited above are hereby incorporated by reference.