Transit, the US Navy’s Navigation Satellite System was conceived at the Applied Physics Laboratory in 1957 by observing the Doppler shift while tracking Sputnik I. As spacecraft development proceeded there was concern about the ability of batteries to maintain the hermetic seal over a 5‐year operational life requirement; therefore, alternate energy sources were investigated. The radioisotope thermoelectric generator (RTG) concept was pursued and resulted in the launch of SNAP 3s, providing partial power on both Transit 4A and 4B. SNAP 9s provided full power on three Transit 5BNs. All launches occurred in the early 1960s. When the U.S. conducted the high altitude nuclear test from Johnson Island, several spacecraft were lost due to artificial enhancement of charged particles in the Earth’s magnetosphere resulting in rapid degradation of solar cell power production. This led to the decision to have both an RTG and Solar cell/battery design for Transit power systems; hence, a new RTG design, with a separable heat source and radiative coupling to the thermoelectric elements, was flown on TRIAD. This pioneering effort provided the impetus for future RTGs on interplanetary spacecraft. This paper describes the origin and purpose of the Transit program and provides details on the five satellites in that program that were powered by the first American RTGs used in space. The rationale and some of the challenges inherent in that use are also described.


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    Title :

    RTGs on Transit


    Contributors:

    Conference:

    SPACE TECHNOLOGY AND APPLICATIONS INTERNATIONAL FORUM-STAIF 2007: 11th Conf Thermophys.Applic.in Micrograv.; 24th Symp Space Nucl.Pwr.Propulsion; 5th Conf Hum/Robotic Techn & Vision Space Explor.; 5th Symp Space Coloniz.; 4th Symp New Frontrs & Future Con ; 2007 ; Albuquerque, New Mexico (USA)


    Published in:

    AIP Conference Proceedings ; 880 , 1 ; 195-204


    Publication date :

    2007-01-30


    Size :

    10 pages





    Type of media :

    Conference paper


    Type of material :

    Electronic Resource


    Language :

    English



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