The purpose of the invention was to increase the operational power levels of power loads as well as improve the overall reliability and safety of existing systems. Using water (H2O), table salt (NaCl) or some other form of salt, and a matching network, an RF power load can be built to absorb transmitted power levels in the 10s or 100s of kilowatts, where the water absorbs the power. The only byproduct is the barely detectable heating of the water bath.

Current state-of-the-art power loads are large and cumbersome for the given power level handling capability. These power loads are normally made up of carbon piles that have a characteristic impedance of 50 ohms. The very-high-power modules are water-cooled (cooling of the carbon pile) and are much larger than this H2O power load. The current power loads are prohibitively high in cost and maintenance.

The main components of the architecture are H2O, NaCl, impedance matching circuitry (a precise value of inductance for a given frequency), a predetermined length of coax, and two metallic rods immersed into the H2O/NaCl mixture. The coax and matching circuitry is frequency dependent, using well established mathematical formulas to determine values. To build the H2O load, any amount of water can be housed in a non-metallic container [in this case, a 55-gallon (≈208-L) plastic drum]. An amount of NaCl is mixed with the water to achieve an AC (at the frequency of interest) resistive value in the vicinity of 50 ohms. A predetermined length of coax is then inserted into the circuit to achieve a capacitive load at the frequency of interest. Then, a value of inductance is determined to achieve the 50-ohm characteristic impedance required by most power transmitters. After the correct impedance is achieved, the H2O power load is ready for operation.

The H2O power load, once tuned using the salt, coax, and inductance, has the high-power radio frequency absorbed by the water with the only byproduct being an increase in the temperature of the water. This is a method to very cheaply obtain the same, or even larger, power levels with relatively low risks associated with power absorption.

This work was done by William Sims and Donald Chavers of Marshall Space Flight Center, and James Richeson of ICRC. For more information, contact Ronald C. Darty, Licensing Executive in the MSFC Technology Transfer Office, at This email address is being protected from spambots. You need JavaScript enabled to view it.. Refer to MFS-32439-1.

NASA Tech Briefs Magazine

This article first appeared in the November, 2015 issue of NASA Tech Briefs Magazine.

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