Preliminary design notes on a low F-number EMR

Conceptual design studies were completed on a new Electrostatic Membrane Reflector, EMR. This new model incorporates both a preformed, curved membrane reflector and membrane control surface. This improved model is the second step toward a high precision large space antenna that could eventually exhibit a performance in terms of aperture diameter to surface quality exceeding 1,000,000. Design trades indicate that the goal of a low ratio of focal length to aperture diameter (f sub n) can be achieved while operating in a humid sea-level environment. A nominal surface quality of 1.0 mm (RMS) is possible using available off-the-shelf commercial membranes. Both the membrane reflector and control electrode surface are fabricated from 12 gore segments and attached to the available 12 sided, 4.88 m diameter rim. The preferred conceptual design has a f sub n = 1.0. The 4.88 m aperture is performed with a centerline displacement of 0.306 m. The nominal spacing between the membrane reflector and the electrode control surface is 50.8 mm. The centerline membrane displacement from its performed to its tensioned, smooth shape is about 3 mm. The membrane tensioning is achieved by application of an electrostatic pressure of 2.6 N/sq cm and a voltage of about 38 kV.