A Transistor Museum Interview

with Dr. George Ludwig

The First Transistors in Space - Personal Reflections by the Designer of the Cosmic Ray Instrumentation Package for the Explorer I Satellite


Oral History – George Ludwig



So you worked on a series of Explorer satellites?


Well, I worked on this package originally for Vanguard.  Then after Sputnik was launched in October, 1957 there was a big flurry of activity, and approval was given to the Army for going ahead with a launch with the Jupiter C.  Again, there is a long history behind this.  Even before the Sputnik launch, Van Allen and I had worked with the people in Huntsville Alabama in designing a version of our instrument that would fit onto the Jupiter C launch vehicle.  When Sputnik was launched and the Army finally received the go-ahead, then I switched our instrument to the Army’s program.  Well, they wanted an initial launch that was extremely high reliability, with absolute minimum risk, the greatest redundancy, and so on.  So we extracted a part of my instrument, combined it with two continuously operating beacons and some micrometeorite detectors, and put those on Explorer I.  That satellite did not have a device for recording the data in orbit, and so we depended on only the data as the satellite passed over the network of ground stations (most of them were roughly along 85 degrees west longitude).  That signal carried data from my electronics, the data from two micrometeorite detectors, and three different temperature measurements.



Oral History – George Ludwig



To back up, I had designed the full cosmic ray package, including its onboard tape recorder, for Vanguard.  Then the switch was made to the Army.  We made a simpler package using part of my electronics for Explorer I, and then flew the full package in Explorer IIIActually we attempted to launch it as Explorer II, but that one did not go into orbit.. 



Was the Explorer I the first earth satellite to carry transistor electronics?


In my original interview I said that it was.  Since then, I researched the question and found that, although the Soviets did not use transistors in Sputnik I, Sputnik II, launched in November 1957, did use a few transistors in one of its instruments.  Of course they had a much larger launch capacity and could carry vacuum tubes and their required batteries.  The Explorer I launch occurred on January 31st local time, which was actually February l Greenwich time, of 1958.  It was the first all-transistor satellite.  (Curator’s note:  See reference [5] for a more detailed discussion of Sputnik 1 and 2 -  there is a reference to the use of  semiconductor triodes on Sputnik 2, although there is not much published information on Soviet early transistor technology).



Go To Ludwig Oral History, Page 6


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