Abstract:
A pincer system is comprised of an array of pincers. Each pincer includes an inner disk having legs that are pushed downwards onto a pliable material to cause protuberances, while an outer disk is rotated to simultaneously squeeze the extruded material between its legs and those of the stationary inner disk. Tracks provide for slideable movement of the individual pincers. The system, carrying an attached micro-satellite, translates across a pliable material covering a spacecraft by coordinating the movement of the pincers with their grasping of the pliable material. This abstract is provided to comply with the rules requiring an abstract, and is intended to allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

Description:
STATEMENT OF GOVERNMENT INTEREST 
   The invention described herein may be manufactured and used by or for the Government of the United States for all governmental purposes without the payment of any royalty. 
   BACKGROUND OF THE INVENTION 
   The present invention is related to a method and apparatus for performing maintenance and repair on the outer surface of a satellite while the satellite is in orbit. More particularly, the present invention is comprised of movable pincers for latching onto the pliable protective fabric covering the satellite and moving the invention across the fabric, whereby the invention can carry and transport a proximity repair micro-satellite across the fabric to a location requiring repair or maintenance. 
   Satellites begin to deteriorate after launch, whereupon they are exposed to the deleterious effects of cosmic radiation, solar winds and electro-magnetic radiation while passing through the Van Alen belt. Over time, flecks of space debris may damage the satellite&#39;s surface. Continued damage may ultimately corrupt the satellite&#39;s hardware and electronic systems. Since there are no means to effect repairs or perform maintenance, satellite components will inevitably begin to malfunction or fail entirely. Depending on the system, the foregoing could render a satellite useless. Thus, for want of a minor repair or routine maintenance, a multi-million dollar satellite could be rendered useless and reduced to orbiting space junk. 
   Multi-layered insulation (hereinafter called “MLI”) is a manufactured material used to cover nearly the entire body of objects placed in orbit, i.e., satellites, and is presently the only known means of providing limited protection to such objects. MLI reflects harmful incident radiation, and also insulates the object from the cold of outer space by using multiple radiation-heat transfer barriers to retard the flow of energy that would otherwise cause damage. Beta cloth is one example of an MLI. It is an inorganic, fiberglass woven cloth impregnated with Teflon® polytetraflouroethylene resin (Teflon is a registered trademark owned by DuPont), and perforated to prevent ballooning. As an outer cover, the Beta cloth MLI has a nominal thickness of 0.008 inches and is rated with a tensile strength of about 90 lb/inch against warping. Its minimum shear strength is 1.8 pounds and it can maintain the foregoing tensile and shear strengths at a temperature of up to 400° F. However, regardless of its composition, MLI is not impermeable, and damage to the satellite nonetheless occurs. Maintenance of an orbiting satellite would also enhance its longevity. 
   The XSS Micro-satellite series is the Air Force Research Laboratory&#39;s sequence of on-orbit experiments to develop a logistics and servicing capability for orbiting satellites. As the name would imply, micro-satellites (hereinafter referred to as “nanosats”) are small, agile and compact. They are fully equipped with on-board avionics, propulsion and high-resolution cameras allowing a highly maneuverable nanosat to perform close-proximity inspection. It is the intent of aerospace leaders to expand the capability of such nanosats to include task-specific resources and tools, thereby providing it with the capability to perform maintenance and repair. Such modification of nanosats would permit them to extend the life and performance of an orbiting satellite at substantially less cost, and in less time, than by preparing and launching a replacement satellite from the earth. 
   Whatever the specific form or composition of the MLI, this protective fabric should provide a medium having sufficient pliability for the present invention to grasp onto and provide transport for a nanosat across the exterior of an orbiting satellite, as will be hereinafter discussed in detail. 
   Despite the availability of MLI as a means of protection for satellites, there is still a need in the art for means to perform exterior maintenance and repair while the satellite is in orbit. The present invention provides means for transporting a nanosat capable of performing maintenance and repair, across the MLI covering an orbiting satellite. The present invention thus fulfills the aforementioned need in the art. 
   SUMMARY OF THE INVENTION 
   Briefly, the present invention is comprised of a pincer system for physically attaching to and maneuvering over the pliable protective material covering a satellite, without damaging the material. A proximity-repair nanosat is carried by the pincer system over the material, allowing the nanosat to locate, assess and/or repair damage to a satellite&#39;s protective covering material, the satellite surface underlying the protective material, or its exterior components. 
   An array of pincers is slideably attached to tracks, wherein the tracks allow independent translation of the pincers along the pliable material&#39;s surface. Locomotive means for the pincers are contained in the tracks. In one embodiment, each pincer is comprised of a set two nested disks adapted to simultaneously pinch and twist the pliable protective material covering a satellite and thereby grasp it, without damaging the material. The array of pincers, and thus the entire apparatus and the attached nanosat, is maneuvered across the protective material by coordinating the translation of the pincers along their respective tracks with their grasping of the protective material. 
   Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, and illustrating by way of example the principles of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustrates a satellite undergoing inspection and repair by a nanosat traversing the satellite&#39;s protective covering by means of a pincer system of the present invention. 
       FIG. 2  illustrates a bottom view an embodiment of a pincer system of the present invention that includes four pincers running on a dual track configuration. 
       FIG. 3  is a partially sectioned front view a two-disk pincer usable as part of the pincer system shown in  FIGS. 1 and 2 . 
       FIG. 4  is a cross-sectioned front view of the pincer shown in  FIG. 3 , particularly showing the shaft and its operative relationship with the inner and outer disks. 
       FIG. 5  is an isometric view of the outer disk of the pincer shown in  FIG. 3 . 
       FIG. 6  is an isometric view of the inner disk of the pincer shown in  FIG. 3 . 
       FIG. 7  is a bottom view of the outer disk of the pincer shown in  FIG. 3 . 
       FIG. 8  is a front view of the outer disk of the pincer shown in  FIG. 3 . 
       FIG. 9  is a bottom view of the inner disk of the pincer shown in  FIG. 3 . 
       FIG. 10  is an isometric view of the inner disk and outer disk of the pincer shown in  FIG. 3 , in their open operative position. 
       FIG. 11  is an isometric view of the inner disk and outer disk of the pincer shown in  FIG. 3 , with the outer disk being rotated clockwise towards its engaged, grasping operative position. 
       FIG. 12  is an isometric view of the inner disk and outer disk of the pincer shown in  FIG. 3 , with the outer disk rotated into full engagement with the stationary inner disk. 
   

   DETAILED DESCRIPTION 
   Turning to the drawings,  FIG. 1  illustrates pincer system  11  of the present invention, in conjunction with nanosat  13 , undertaking an inspection and repair on orbiting satellite  15 . Nanosat  13  is a micro-satellite having resources and tools for inspecting space vehicles, performing maintenance on them and, depending on the extent of the damage, also making repairs. Satellite  15  is covered by pliable multi-layered insulation  17 , hereinafter called “MLI”  17 . Tear  19  in MLI  17  evinces damage to the underlying structure of satellite  15 . Nanosat  13  can be removably attached to pincer system  11 . Pincer system  11  is shown traversing MLI  17  while carrying nanosat  13  to tear  19  in MLI  17 . 
     FIG. 2  is a bottom view of pincer system  11 , showing its underside, i.e., the part of system  11  in contact with MLI  17 . Pincer system  11  includes track assembly  21 , comprised of tracks  23  and  25 , together with pincers  27 ,  29 ,  31  and  33 . Pincers  27  and  29  are slideably mounted on track  23 , while pincers  31  and  33  are slideably mounted on track  25 . Tracks  23  and  25  are attached where they intersect; they neither rotate nor translate with respect to each other. Although shown as being perpendicular, the angle of intersection between tracks  23  and  25  may be varied to suit particular circumstances. Pincers  27 ,  29 ,  31  and  33  may each be individually moved relative to their respective tracks by means of a worm gear, a chain and sprocket (neither of which are shown) or other means of locomotion well known to those skilled in the mechanical arts. Pincers  27 ,  29 ,  31  and  33  are each capable of alternately grasping and releasing MLI  17 , as will subsequently be explained in detail. 
   Pincer system  11  can be moved across MLI  17  to any location by using the ability of a selected pair of pincers to alternatively grasp and release MLI  17 , with the locomotive means engaging the grasping pincer to force translation of the track relative to the grasping pincer. The foregoing is best explained by the following example. 
   To move towards tear  19 , pincer system  11  would first move to the right and then upwards (or first upwards and then to the right). To move to the right, pincer  29  initially grasps MLI  17 , while pincer  27  is not grasping MLI  17  (the neutral mode). Pincers  27 ,  31  and  33  remain in the neutral mode while pincer system  11  is moving to the right. The locomotive means for track  31  is actuated to engage pincer  29  and pull track  23  through pincer  27  to the right until pincer  29  abuts track  25  (or a lesser distance if desired). 
   To proceed further to the right, pincer  27  (or pincers  31  and  33 ) are engaged to grasp MLI  17 , while pincer  29  is placed in the neutral mode and moved by the locomotive means to the right, until it reaches end  37  of track  23  (or a lesser distance if desired), whereupon it grasps MLI  17  and pincer  27  (or pincers  31  and  33 ) are placed in the neutral mode. The locomotive means for track  23  is actuated to engage pincer  29  and again pull track  23  through pincer  29  until pincer  29  abuts track  29 . The foregoing sequence is repeated until pincer system  11  is translated the desired distance to the right. 
   Translation of pincer system  11  relative to MLI  17  to the left would be achieved using the same sequence of steps with pincer  27  acting in concert with track  23 , with pincer  29  (or pincers  31  and  33 ) acting to keep track assembly  21  stationary while pincer  21  is being moved in the neutral mode. Translation up, i.e., towards tear  19 , is achieved using the aforementioned sequence of steps with pincer  33  acting in concert with track  25 , with pincer  31  (or pincers  27  and  29 ) acting to keep track assembly  21  stationary while pincer  33  is being moved in the neutral mode. Translation down would be achieved using the aforementioned sequence of steps with pincer  31  acting in concert with track  25 , with pincer  33  (or pincers  27  and  29 ) acting to keep track assembly  21  stationary while pincer  31  is being moved in the neutral mode. 
   Alternative track assemblies can be employed to enable nanosats to navigate around sharp corners on a spacecraft. Moreover, use of flexible, nonlinear tracks in conjunction with the pincers of the present invention could provide the ability to transport a nanosat over an uneven surface. 
     FIG. 3  is a partially sectioned front view of pincer  27 , a pincer of the present invention. Pincer  27  includes housing  40 , which is slideably attached to track  23  (not shown) by means of brackets  41 . Housing  40  is also attached to the locomotive means (not shown) for track  23 , which provides for translation of pincer  27  along track  23 . Pincer  27  includes disks  42  and  44 .  FIG. 4  is a cross-sectioned front view of pincer  27 , with housing  40  removed.  FIG. 5  is a perspective view of disk  42  and  FIG. 6  is a perspective view of disk  44 .  FIGS. 7 and 8  respectively show bottom and front views of disk  42 .  FIG. 9  is a bottom view of disk  44 . 
   As shown in the aforementioned figures, disk  42  includes six legs  46  that are equidistantly spaced apart from one another, with each leg having a foot  48 . Disk  44  includes six legs  50  that are equidistantly spaced from one another, with each leg having a foot  52 . Although six legs are shown for each disk, it should be noted that the present invention will function in a manner consistent with the teachings herein where there are more or fewer legs per disk. As illustrated by the perspective view provided by  FIG. 10 , disk  44  is nested within disk  42 .  FIG. 10  shows disks  42  and  44  in their completely open, neutral position, i.e., not grasping MLI  17 . 
   To engage, or grasp, MLI  17 , feet  52  are pressed down into MLI  17 , causing protuberances of the material around the feet. As shown in  FIG. 11 , disk  42  is then rotated clockwise relative to stationary disk  44 .  FIG. 12  shows disks  42  and  44  in the fully engaged position, with each of legs  46  brought into near abutment with the corresponding leg  50  that opposes it and thereby limits its rotation. This near abutment captures and squeezes the extruded portion of MLI  17  between legs  46  and  50  (it is not complete abutment only because the extruded portion of MLI will lie between legs  46  and  50 ). Both disks  42  and  44  can be further rotated together after they have secured MLI  17  between their respective opposing legs to form a stronger hold on the fabric. 
   The remaining parts of pincer  27  cooperate to obtain the aforementioned pressure of feet  52  against MLI  17 , and the of rotation of disk  42  relative to stationary disk  44  in order to effect their engagement. More particularly, rubber pads  60  of housing  40  are first moved into contact with MLI  17  while disks  42  and  44  are in an open state. The opposing resistive force of underlying satellite  15  acts against pads  60 . Spring  62  is captured between annular retaining collar  64  and annular spring retainer  66 . Housing  40  is mounted on retaining collar  64 . Thus, housing  40  is free to move upward until the initial distance between retainer  66  and stop block  68  has been taken up, whereupon the compressive spring force opposes further upward travel. The resistive force of underlying satellite  15  prevents the further downward travel of pads  60 , and exposes feet  48  and  52 , allowing them to come into contact with MLI  17 . 
   As shown in  FIG. 4 , retaining sleeve  69  sits between retaining collar  64  and spring retainer  66 . Shaft  70  passes through an annular hole in the center of spring retainer  66 , through a cylindrical bore in retaining sleeve  69 , through an annular hole in the center of retaining collar  64 , and through annular hole  72  in the center of disk  42 . Shaft  70  includes races  76  that accommodate ball bearings  78 . The foregoing openings, together with ball bearings  78 , allow the axial rotation as well as the vertical translation of shaft  70  relative to retaining collar  64 , spring retainer  66  and retaining sleeve  69 . Retaining sleeve  69 , retaining collar  64  and disk  42  are bracketed to each other. Disk  42  is thus also free to rotate about, and translate vertically relative to, the axial axis of shaft  70 . Retaining collar  64  also includes grooves  79 . 
   Camshaft  80  includes cam  82 . Shaft  70  includes shaft top  84  and shaft bottom  86 . Shaft bottom  86  rests in annular cavity  88  in the top of disk  44 . Cam  82  and shaft top  84  are mechanically engaged and shaped such that the rotation of camshaft  80 , and therefore cam  82 , creates a downward force on shaft top  84 , shaft  70 , and disk  44 . This results in disk  44 , and thus feet  52 , being slowly pressed against MLI  17 , causing the material to form protuberances about feet  52 . 
   As camshaft  80  is rotated, disk  42  is simultaneously rotated by force applied by metal tabs (not shown) inserted into grooves  71 . Disk  42  is rotated clockwise approximately 32°, until its legs  46  abut legs  50  of stationary disk  44 , thereby capturing the protuberances occurring around feet  52 . As previously noted, both disks  42  and  44  can be subsequently rotated together to strengthen their hold on the extruded MLI  17 . 
   It is to be understood that the preceding is merely a detailed description of an embodiment of this invention, and that numerous changes to the disclosed embodiment can be made in accordance with the disclosure herein without departing from the spirit or scope of the invention. The preceding description, therefore, is not meant to limit the scope of the invention. Rather, the scope of the invention is to be determined only by the appended claims and their equivalents.