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An RF Sensor for Gauging Screen-Channel Liquid Acquisition Devices for Cryogenic PropellantsA key requirement of a low-gravity screen-channel liquid acquisition device (LAD) is the need to retain 100% liquid in the channel in response to propellant outflow and spacecraft maneuvers. The point at which a screen-channel LAD ingests vapor is known as breakdown, and can be measured several different ways such as: visual observation of bubbles in the LAD channel outflow; a sudden change in pressure drop between the propellant tank and LAD sump outlet; or, an indication by wet-dry sensors placed in the LAD channel or outflow stream. Here we describe a new type of sensor for gauging a screen-channel LAD, the Radio Frequency Mass Gauge (RFMG). The RFMG measures the natural electromagnetic modes of the screen-channel LAD, which is very similar to an RF waveguide, to determine the amount of propellant in the channel. By monitoring several of the RF modes, we show that the RFMG acts as a global sensor of the LAD channel propellant fill level, and enables detection of LAD breakdown even in the absence of outflow. This paper presents the theory behind the RFMG-LAD sensor, measurements and simulations of the RF modes of a LAD channel, and RFMG detection of LAD breakdown in a channel using a simulant fluid during inverted outflow and long-term stability tests.
Document ID
Document Type
Conference Paper
Zimmerli, Gregory A. (NASA Glenn Research Center Cleveland, OH United States)
Metzger, Scott (Vantage Partners, LLC Brook Park, OH, United States)
Asipauskas, Marius (Universities Space Research Association Cleveland, OH, United States)
Date Acquired
November 26, 2014
Publication Date
July 28, 2014
Subject Category
Spacecraft Propulsion and Power
Report/Patent Number
Meeting Information
Joint Propulsion Conference(Cleveland, OH)
Funding Number(s)
WBS: WBS 645454.
Distribution Limits
Public Use Permitted.
microwave sensor
cryogenic propellants
liquid acquisition device

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