The Advanced Space Suit carries consumable cooling water maintained at ambient pressure within a soft-walled, flexible reservoir. To ensure uninterrupted thermal control it is critical to monitor the volume of water remaining, but no known sensor is suitable for this task. Existing measurement techniques are unacceptably sensitive to the motion and varying geometry of the reservoir in micro-gravity, or to electromagnetic interference within the suit environment. We will develop a simple, compact, low power sensor that accurately measures the volume of fluid in any soft-walled bladder. Our innovative sensing technique will provide an accurate measurement that is insensitive to gravity, the motion, and geometry of the reservoir, the presence of air, and electromagnetic interference.