Abstract:
A rail-captive sled for deploying payloads into outer space from a space launch vehicle. The sled is driven by a piston, powered by residual tank pressure from a tank native to the space launch vehicle. The rails are arranged parallel and adapted to a cross-sectional shape of a payload, such as small satellites or cubesats. The sled is a box frame sled with an adaptation to receive the piston. The rails may be attached to the residual pressure tank, with the piston in the residual pressure tank and aligned to the rails, or the pressure may be drawn from tank plumbing to a cylinder specific to the piston. The rails have a releasable closure to avoid unplanned egress of the payload, and the closure locks in the open position once released. The piston may be constrained by a direct constraint or by the closure via the payload.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional patent application Ser. No. 62/007,836 filed Jun. 4, 2014 by the same inventors, the contents of which are incorporated herein by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
     This invention was made with government support under contract FAA8650-12-C-7274 awarded by DARPA/AFRL. The government has certain rights in the invention. The research in this document is being developed by Ventions, LLC with funding from the Defense Advanced Research Projects Agency (DARPA). Distribution Statement A: Approved for Public Release, Distribution Unlimited. 
    
    
     FIELD OF ART 
     The present invention relates to deployment mechanisms for deploying satellites from launch vehicles in outer space. The present invention more particularly related to deploying very small satellites, such as pico-satellites or cubesats using residual tank pressure from tanks onboard the launch vehicle. 
     SUMMARY OF THE INVENTION 
     Briefly described the invention includes a deployment mechanism for deploying very small satellites (hereinafter “cubesats”) from a launch vehicle. The deployment mechanism is piston-driven using residual tank pressure for a fuel, oxidizer, or pressurant gas onboard the launch vehicle along a set of rails using a captive sled. 
    
    
     
       DESCRIPTION OF THE FIGURES OF THE DRAWINGS 
       The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and 
         FIG. 1  is a side elevation view illustrating an exemplary embodiment of the pneumatic cubesat payload deployment system, according to a preferred embodiment of the present invention; 
         FIG. 2  is a partial right side elevation view illustrating an exemplary embodiment of the pneumatic cubesat payload deployment system of  FIG. 1 , according to a preferred embodiment of the present invention; 
         FIG. 3A  is a detail right side elevation view illustrating an exemplary embodiment of the pneumatic cubesat payload deployment system of  FIG. 1 , according to a preferred embodiment of the present invention; 
         FIG. 3B  is a detail cross-sectional view illustrating an exemplary detail of the exemplary embodiment of the pneumatic cubesat payload deployment system of  FIG. 1 , according to a preferred embodiment of the present invention; 
         FIG. 4  is a perspective view illustrating an exemplary embodiment of the pneumatic cubesat payload deployment system of  FIG. 1 , according to a preferred embodiment of the present invention; 
         FIG. 5  is a detail of the perspective view illustrating an exemplary embodiment of the pneumatic cubesat payload deployment system of  FIG. 1 , according to a preferred embodiment of the present invention; 
         FIG. 6  is a perspective view illustrating an exemplary embodiment of the pneumatic cubesat payload deployment system of  FIG. 1  with cubesats loaded, according to a preferred embodiment of the present invention; 
         FIG. 7  is a perspective view illustrating an exemplary embodiment of the pneumatic cubesat payload deployment system of  FIG. 1  with cubesats loaded, according to a preferred embodiment of the present invention; 
         FIG. 8  is a top plan view illustrating an exemplary embodiment of the pneumatic cubesat payload deployment system of  FIG. 1  with the door removed, according to a preferred embodiment of the present invention; 
         FIG. 9  is a top plan view illustrating an exemplary embodiment of the pneumatic cubesat payload deployment system of  FIG. 1  with the door present and closed, according to a preferred embodiment of the present invention; and 
         FIG. 10  is a top plan view illustrating an exemplary embodiment of the pneumatic cubesat payload deployment system of  FIG. 1  with cubesats loaded, according to a preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a side elevation partial x-ray view illustrating an exemplary embodiment of the pneumatic cubesat payload deployment system  100 , according to a preferred embodiment of the present invention. While the examples herein are presented in regard to cubesats, various small satellite configurations may be deployed by the present invention with adaptation to the various shapes and sizes of the various small satellites. The pneumatic cubesat payload deployment system  100  includes rails  102  slidingly supporting sled  118  that is driven by residual pressure in tank  104  acting on hollow piston  108  inside tank  104 . Piston  108 , O-ring seals  112 , and end cap  110  are inside tank  104 . Tank  104  is supported on the launch vehicle structure  114 . Rails  102  (two of four in this view, one of two visible labeled) extend from tank interface connectors  116  on tank  104  toward releasably latchable door  124 . Rails  102  captively and slidingly support sled  118  to slide from proximate the tank  104  to the door  124  and be retained at that point. Rails  102  have cross-brace supports  122  for structural stability. Payload fairing standoff  126  supports the rails  102  during launch. 
     The door  124  is launched in the closed position, as shown, with cubesats  602 ,  604  and  606  (see  FIG. 6 ) arranged along and between rails  102 . Cubesats  602 ,  604  and  606  are pushed along rails  102  by sled  118 , through the door  124  and into outer space. In a preferred embodiment, door  124  is biased open, but is latched closed by a releasable latch  410  (see  FIG. 5 ) which is released by a control system to initiate deployment. In another embodiment, the door  124  is biased closed (by a spring, for example), and may be opened by the force of the cubesats  602 ,  604  and  606  being deployed overcoming the bias. The cubesats  602 ,  604  and  606  deploy out open door  124  (shown closed). In a preferred embodiment, pressure from tank  104  is applied via piston  108  before, during, and after launch. The force of piston  108  may be applied through the sled  118  to the cubesats to the door  124 . The door  124  is releasably latched closed against the force transmitted through the cubesats  602 ,  604  and  606 , and releasing the latch causes the door  124  to fly open and the cubesats to deploy into outer space. In another embodiment, the piston  108  may also be latched until deployment. One advantage of the present invention is that a pneumatic piston  108  attached to a pressurized tank  104  has a very flat force-vs-time curve through the stroke, particularly compared to a metal spring, thus reducing the peak deployment forces on the payload. Any pressurized source on board the launch vehicle  802  (see  FIG. 8 ) may be used, including attitude control system fuel or pressurant gases for other purposes. Another advantage is that heavy mechanical deployment actuators are eliminated and replaced by an otherwise wasted resource, i.e. residual pressurized gas available at the end of the engine burn of a launch vehicle  802 . 
     In another preferred embodiment, the piston  108  is latched against applying pressure to the sled  118  until it is time to deploy the cubesats  602 ,  604  and  606 , when both piston  108  and door latches are released. In such an embodiment, the cubesats  602 ,  604  and  606  are preferably loaded before the tank  104  is pressurized, thereby providing a more benign ground handling environment that minimizes the chance of damage during loading. In yet another embodiment, piston  108  is not located within the tank  104 , but is connected to the tank  104  via conduit, and a solenoid controlled valve in the conduit, for example, can be used to initiate deployment. 
     The interface between the sled  118  and the piston  108  will be described in more detail below. 
       FIG. 2  is a partial right side elevation view illustrating an exemplary embodiment of the pneumatic cubesat payload deployment system  100  of  FIG. 1 , according to a preferred embodiment of the present invention. The interface between the sled  118  and the piston  108  includes an upper piston  108  chamber  120  above the piston head  212  into which a sled pin  206 , such as a set screw, protrudes from a hub  408  (see  FIG. 4 ) in the center of the bottom sled frame  202  to contact the top of the piston head  212 . Sled  118  includes the four-sided, four cornered bottom sled frame  202  (one side visible in this view) having right circular cylindrical supports  204  (two visible in this view) extending normal to the bottom sled frame  202  from each corner and engaging and supporting a sled seat  210 , upon which a cubesat  606  may rest. The corners of the bottom sled frame  202  and the sled seat  210  slidingly engage two inner edges  306  of the rails  102 . Hollow piston  108  having a cylindrical wall  106  (shown in cross section) and a piston head  212  is sealed in the tank  104  using a sliding O-ring seal  208 . In a particular embodiment, an additional two set screws (not shown) may be arranged in opposed horizontal position in piston  108  to clamp sled pin  206 . 
     In another embodiment of the invention, the sliding o-ring seal  208  is replaced by a static face seal to prevent propellant leakage up to the point that the payload is ready to deploy. At the payload deployment juncture, the seal pre-load is released and a controlled gap between the piston  108  and its guide bore in the tank  104  is used to slow tank venting to the point that there is enough latent pressure to move the piston  108  forward. 
       FIG. 3A  is a detail right side elevation view illustrating an exemplary embodiment of the pneumatic cubesat payload deployment system  100  of  FIG. 1 , according to a preferred embodiment of the present invention. Connectors  116  connect rails  102  to tank protrusions  302  (one of two labeled). Rails  102  are coupled to supports  304 . Bottom sled frame  202  rests on supports  304  when piston  108  is not extended. Bottom rail frame  316  is connected to supports  304  and to rails  102  and has a central opening for receiving a top portion of piston  108 . Piston  108  is sealed, at its junction with the tank  104 , by a sliding O-ring seal  208  having O-ring  310 . Sled pin  206 , illustrated as a set screw, is secured in bottom sled frame  202  within set screw cavity  316 . In operation, piston  108  moves upward  308  pushing sled  118  via sled pin  206  to deploy cubesats  602 ,  604  and  606 . 
       FIG. 3B  is a detail cross-sectional view illustrating an exemplary detail of the exemplary embodiment of the pneumatic cubesat payload deployment system  100  of  FIG. 1 , according to a preferred embodiment of the present invention. Rail  102  has an L-shaped cross section, as shown, and a corner of bottom sled frame  202  is received in inner corner of the L by rail surfaces  306 . Cylindrical support  204  preferably does not engage the rails  102 . 
       FIG. 4  is a perspective view illustrating an exemplary embodiment of the pneumatic cubesat payload deployment system  100  of  FIG. 1 , according to a preferred embodiment of the present invention. Bottom sled frame  202  can be more clearly seen to include cross members  404  and  406  meeting at central hub  408  and three of the four cylindrical supports  204  can be seen. Sled seat  210  can be seen to have an interior support structure  412 , making the sled  118  as a whole a dimensionally stable box that can maintain shape and structural integrity during launch and deployment. The sizing of the sled  118  and the spacing between rails  102  is responsive to dimensional standards established for cubesats  602 ,  604  and  606 . In various embodiments, various other standards for other types of small satellites may be used. Releasable latch  410 , which may be, for example, a bolt cutter, is shown mounted on door  124 . 
       FIG. 5  is a detail of the perspective view illustrating an exemplary embodiment of the pneumatic cubesat payload deployment system  100  of  FIG. 1 , according to a preferred embodiment of the present invention. Spring-loaded hinge  502  couples door  124  to rails  102 . Hinge  502  contains a pin-détente locking mechanism to lock the door  124  in the open position after the latch  410  is released, preventing interference with the cubesat  602 ,  604  and  606  deployment. Releasable latch  410  may be used to additionally secure the door in a closed position, as discussed above. Pins  506 , which are mounted to opposing sides of door  124  at ends opposing the hinges  502 , enter sockets  804  (see  FIG. 8 ) in the tops of rails  102  to enable using the door  124  to provide additional structural stability during launch. 
       FIG. 6  is a perspective view illustrating an exemplary embodiment of the pneumatic cubesat payload deployment system  100  of  FIG. 1  with cubesats  602 ,  604  and  606  loaded, according to a preferred embodiment of the present invention. Cubesat  606  rests on sled seat  210 , cubesat  604  rests on cubesat  604 , and cubesat  602  rests on cubesat  604 . In a preferred embodiment, pressure is applied to piston  108  to force cubesats  602 ,  604  and  606  together and to force top surface  610  of cubesat  602  against door  124  along the truss sides  608  (one of two labeled). This same embodiment may be used to deploy one double-length cubesat (not shown, but like a combined cubesat  606  and  604 ) and one single length cubesat  602 , or to deploy one triple-length cubesat (not shown, but like combined cubesats  602 ,  604  and  606 ). In another preferred embodiment, the piston  108  is also latched until deployment. 
       FIG. 7  is a perspective view illustrating an exemplary embodiment of the pneumatic cubesat payload deployment system  100  of  FIG. 1  with cubesats  602 ,  604  and  606  loaded, according to a preferred embodiment of the present invention. The reverse side of pneumatic cubesat payload deployment system  100  is shown, as compared to  FIG. 6 . Tank  104  is omitted, making the interior supports  702  in bottom rail frame  316  more easily viewed. 
       FIG. 8  is a top plan view illustrating an exemplary embodiment of the pneumatic cubesat payload deployment system  100  of  FIG. 1  with the door  124  removed, according to a preferred embodiment of the present invention. Tank  104  is connected to launch vehicle  802 . Both spring-loaded hinges  502  can be seen. Latch sockets  804  (one of two labeled) can be seen in the tops of two of the rails  102 . Looking down, the interior support structure  412  of sled seat  210 , as well as the cross members  404  and  406  and hub  408  of the bottom rail frame  210  can be seen. The top ends of the cylindrical sled supports  204  are visible, as are the spring-loaded hinges  502  and latch sockets  804 . The top of sliding O-ring seal  208  can also be seen. 
       FIG. 9  is a top plan view illustrating an exemplary embodiment of the pneumatic cubesat payload deployment system  100  of  FIG. 1  with the door  124  present and closed, according to a preferred embodiment of the present invention. The drawing is otherwise the same as  FIG. 8 . The releasable latch  410  is not shown in this view. 
       FIG. 10  is a top plan view illustrating an exemplary embodiment of the pneumatic cubesat payload deployment system  100  of  FIG. 1  with cubesats  602 ,  604  and  606  loaded, according to a preferred embodiment of the present invention. Door  124  is omitted for clarity of the drawing. The top surface  608  of cubesat  602  is shown in the pre-deployment position. Cubesat sliders  1002  (one of four labeled) are part of the cubesat  602  and are configured to fit and slide within rails  102  (one of four labeled). The diagonally outward corner of each cubesat slider  1002  is rounded to reduce friction with the rails  102 . Those of skill in the art, enlightened by the present disclosure, will be aware of various strategies for reducing friction between the rails  102  and the cubesat sliders  1002  while maintaining constraint in the direction of travel and avoiding binding between the sliders  1002  and the rails  102 .