SOLAR SAILS ARE PROPELLED BY THE FREE AND ABUNDANT MOMENTUM AFFORDED BY SUNLIGHT. PROPULSION AND NAVIGATION ARE ACHIEVED BY DIRECTING REFLECTED OR TRANSMITTED LIGHT AWAY FROM THE NATURAL DIRECTION OF SUNLIGHT. THE MAGNITUDE AND DIRECTION OF THIS RADIATION PRESSURE FORCE DEPENDS ON FACTORS SUCH AS THE LIGHT DEFLECTION ANGLE THE ANGLE OF THE SAIL WITH RESPECT TO THE SUN AND THE DISTANCE FROM THE SUN. SAIL AREAS SPANNING HUNDREDS OF SQUARE METERS HAVE BEEN ENVISIONED FOR NEARLY 100 YEARS FOR A WIDE RANGE OF SPACE MISSIONS THAT ARE NOT PRACTICAL FOR CHEMICAL ROCKETS. IF THE MOMENTUM TRANSFER EFFICIENCY IS HIGH AND THE MASS PER UNIT AREA OF THE SAIL IS SMALL LARGE VELOCITY CHANGES MAY BE ACHIEVED OVER TIME OWING TO A CONTINUOUS ACCELERATION. THE CONVENTIONAL MEANS OF COLLECTING AND REDIRECTING SUNLIGHT WHICH MAKES USE OF A METAL-COATED POLYIMIDE FILM IS SUB-OPTIMAL AND UNSTABLE BECAUSE THE VERY LARGE AND VERY THIN SAIL MUST BE RAPIDLY SLEWED AWAY FROM THE SUN LINE FOR NAVIGATIONAL PURPOSES. WHAT IS MORE STABILITY RIGGING AND ATTITUDE CONTROL DEVICES ADD MASS TO THE SAILCRAFT THEREBY REDUCING THE ACCELERATION. IN PRINCIPLE THESE LIMITATIONS MAY BE OVERCOME BY REPLACING THE REFLECTIVE SAIL WITH A DIFFRACTIVE ONE. OUR OBJECTIVE IS TO SURMOUNT THESE SHORTCOMINGS BY ENGINEERING OPTICAL FILMS USING METAMATERIAL PRINCIPLES.