NASA researchers collaborating with NASA contractor personnel have developed an audio system specifically designed for space suit applications. The audio system developed includes array microphones and speakers that are fix-mounted in the space suit, a digital signal processor (DSP), and other associated signal-processing components. This audio system has been designed to improve the signal-to-noise ratio of existing noisy suit subject audio leaving the suit by 23dB to enable human-robotic verbal interaction. The audio system was validated in a laboratory environment (TRL-4) using both a pressurized ILC Dover, Inc., “I” suit and Hamilton Sundstrand Mark-III suit at Johnson Space Center (JSC) in June 2003. The audio system was validated in an outdoor relevant environment (TRL-5) using a pressurized Hamilton Sundstrand Mark-III suit at Johnson Space Center (JSC) in February 2004. The technology is also being tested to eliminate the Communications Carrier Assembly (CCA) or “Snoopy cap” worn by astronauts during extra-vehicular activity (EVA).

We describe digital beam deflectors (DBDs) based on liquid crystals (LCs). Each stage of the device comprises a polarization rotator and a birefringent prism deflector. The birefringent prism deflects the beam by an angle that depends on polarization of the incident beam. The prism can be made of the uniaxial smectic A (SmA) liquid crystal or a solid crystal such as yttrium orthovanadate (YVO4). SmA prisms have high birefringence and can be constructed in a variety of shapes, including single prisms and prismatic blazed gratings of different angles and profiles. Rotation of linear polarization is achieved by an electrically switched twisted nematic (TN) cell. A DBD composed of N rotator-deflector pairs steers the beam into 2 to the power N directions. As an example, we describe a four-stage DBD deflecting normally incident laser beam within the range of ±56 mrad with 8 mrad steps. Redirection of the beam is achieved by switching the TN cells. To achieve the fast (0.5 millisecond) response time of the TN cells, we employed the so-called dual-frequency nematic LCs with a special addressing scheme that features amplitude and frequency modulated driving voltage.