Abstract:
A magnetically suspended door is described for the protection of spacecraft instrumentation exposed to space. The door is slid between an opened or closed position using electromagnets.

Description:
STATEMENT OF GOVERNMENT INTEREST 
     The conditions under which this invention was made are such as to entitle the Government of the United States under paragraph 1(a) of Executive Order 10096, as represented by the Secretary of the Air Force, to the entire right, title and interest therein, including foreign rights. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention is in the field of environmental covers for spacecraft instrumentation. 
     2. Description of the Prior Art 
     Satellites frequently use hatches/doors (hereafter referred to as doors) to protect instrumentation from the space environment when not in use. These protective doors are usually mechanically activated using various gears, hinges, springs, and other moving parts. The moving parts are subject to friction and wear out over time causing failure or malfunction of the protective door. There is a need for an environmental door with no mechanical or moving parts other than the door itself. 
     SUMMARY OF THE INVENTION 
     A magnetically suspended sliding door is described for use as an environmental cover for spacecraft instrumentation. The door is opened and closed using electromagnets and has no moving parts other than the door itself. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1--Side view of magnetically suspended sliding door. 
     FIG. 2--Front view of sliding door. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The side view of the magnetically suspended sliding door is shown in FIG. 1. In this edge-on view, the door 1 has canted, permanent magnets or strips of magnetized material 2 attached along the top and bottom edges of the door on both sides. Permanent magnets or strips of magnetized material (rails) 3 canted at a similar angle to the door strips are attached to the spacecraft structure 4. The structures the rails are attached to are themselves attached to the outer skin 5 of the spacecraft. The skin has an aperture 6 for exposing the instrumentation 7, e.g., optics, lasers, cameras, etc. to space. The polarity of the magnets are such that when the door is placed between the rails, the door magnets repel their opposing magnetic rails, thereby causing the door to be magnetically suspended. 
     Permanent magnets 8 are attached at each side edge of the door and centrally located. The door width is sufficient to shield the spacecraft instrument 7 it is designed to protect. The rails 3 are approximately twice the length of the door&#39;s width permitting it be in an opened or closed position by sliding from one side to the other. FIG. 2 shows a front view of the door in an open position exposing the instrument. The spacecraft outer skin 5 is not shown in FIG. 2; dashed lines indicate the aperture 6. An electromagnet 9 is located at each end of the sliding door&#39;s range of motion. Attraction/repulsion by these electromagnets acting on the permanent magnets 8 in the door edges causes the door to slide to the open or closed position. The range of motion is limited by stops 10 in front of the electromagnets. On either edge of the door where the permanent magnets 8 are attached, there is an optional groove 11 within which the top and bottom edges of the door fit to limit the range of motion perpendicular to the door&#39;s primary surface. This groove can be lubricated to allow the door to slide smoothly between the open and closed position.