Solid propellant grain

Abstract

A solid rocket propellant grain having rocket propellant and a membrane in contact with the rocket propellant. The membrane includes a highly heat conductive pattern which affects the propellant burning rate through localized conductive heat transfer from the combustion zone and into the uncombusted propellant. Different geometries for the thermally conductive pattern produce different combustion results.

We claim: 
     
       1. A solid propellant grain comprising:
 a propellant having an interior, 
 a polymer sheet having at least one surface and having a thermally conductive pattern disposed on said at least one surface, said polymer sheet and said thermally conductive pattern being in contact with said propellant wherein said thermally conductive pattern transfers heat from a combustion zone through the interior of the propellant to increase the rate of combustion and provide greater propulsion, wherein said thermally conductive pattern comprises a metal. 
 
     
     
       2. The solid propellant grain of  claim 1  wherein said polymer sheet is embedded in said propellant. 
     
     
       3. The solid propellant grain of  claim 1  wherein said polymer sheet having said thermally conductive pattern is embedded in the propellant in the shape of a cone to create a conical combustion zone in the propellant. 
     
     
       4. The solid propellant grain of  claim 1  wherein said polymer sheet having said thermally conductive pattern is embedded in the propellant in the shape of a parabola to create a parabolic combustion zone in the propellant. 
     
     
       5. The solid propellant grain of  claim 1  wherein said polymer sheet having said thermally conductive pattern is embedded in the propellant in the shape of a spiral to create a spiral combustion zone in the propellant. 
     
     
       6. The solid propellant grain  claim 1  wherein said polymer sheet is wrapped around the outside of said propellant such that heat from combustion will be transferred along the outer periphery of said propellant. 
     
     
       7. The solid propellant grain of  claim 1  wherein said polymer sheet is flexible. 
     
     
       8. The solid propellant grain of  claim 1  wherein said polymer sheet comprises a polyimide sheet. 
     
     
       9. The solid propellant grain of  claim 1  wherein said polymer sheet comprises a polyester sheet. 
     
     
       10. The solid propellant grain of  claim 1  wherein said polymer sheet and thermally conductive pattern comprises in total a metallic foil. 
     
     
       11. The solid propellant grain of  claim 1  wherein said thermally conductive pattern is formed by etching a metallic foil on said sheet. 
     
     
       12. The solid propellant grain of  claim 1  wherein said solid propellant grain comprises a plurality of polymer sheets, each polymer sheet having two surfaces and a thermally conductive pattern on at least one surface of said sheet. 
     
     
       13. The solid propellant grain of  claim 1  wherein said heat conductive pattern is vertically oriented in said propellant. 
     
     
       14. The solid propellant grain of  claim 1  wherein said sheet has a vertical axis and said heat conductive pattern is vertically oriented and symmetrical about the vertical axis of said sheet. 
     
     
       15. The solid propellant grain of  1  wherein said polymer sheet has a vertical axis and said heat conductive pattern is vertically oriented and symmetrical about the vertical axis of the polymer sheet and said propellant. 
     
     
       16. A rocket propellant grain comprising:
 a rocket propellant grain having a vertical axis that aligns with a vertical axis of a rocket, and 
 a polymer sheet having at least one surface and having a heat conductive pattern disposed on said at least one surface wherein said heat conductive pattern is symmetric about a sheet axis and comprises a metal; 
 wherein said sheet axis aligns with the vertical axis of the rocket propellant grain and said heat conductive pattern being in contact with said rocket propellant grain such that the heat conductive pattern affects the rocket propellant grain burning rate though localized heat transfer from the combustion zone into the uncombusted rocket propellant grain. 
 
     
     
       17. A method of forming a solid propellant grain comprising:
 forming a thermally conductive pattern comprising a metal on a polymer sheet, 
 positioning the polymer sheet in a mold such that said thermally conductive pattern is configured to transfer heat from a combustion zone through an interior of said solid propellant grain, and 
 casting propellant in the mold so that the polymer sheet is embedded within the propellant and the thermally conductive pattern on the polymer sheet is in contact with said propellant. 
 
     
     
       18. The method of forming a solid propellant grain of  claim 17  wherein the thermally conductive pattern is formed symmetrically about a vertical axis of said polymer sheet. 
     
     
       19. A method of increasing the mass flow rate and thrust of an end-burning solid rocket motor, the method comprising:
 forming a thermally conductive pattern comprising a metal on a polymer sheet, 
 positioning the polymer sheet in a mold such that said thermally conductive pattern is configured to transfer heat from a combustion zone through an interior of said solid propellant grain, and 
 casting propellant in the mold so that the polymer sheet is embedded within the propellant and the thermally conductive pattern on the polymer sheet is in contact with said propellant. 
 
     
     
       20. The method of increasing the mass flow rate and thrust of an end-burning solid rocket motor of  claim 19  wherein the thermally conductive pattern is formed symmetrically about a vertical axis of said polymer sheet.