Transistor Museum Oral History George Ludwig Explorer I Transistors Page 16

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

(Continued)

It stayed there for a while, and then dropped to zero (all pulses present). That signified that the scalers were no longer being triggered. And then, sometime later, it rose again to 128 counts per second, stayed there for a while, and then transitioned down to the normal cosmic ray background rate. Upon seeing the transitions, Carl Mcllwain made a quick run of a similar Geiger counter in a test setup in front of an X-ray machine, where he flooded it with high intensity radiation and verified that that was how the tube would behave. So, from those pieces, we had the discovery of the "Radiation Belts."

When was Explorer III launched and how long did it last?

It was launched on 26 March, 1958, at 17:38 Universal Time. We obtained data from the onboard tape recorder for 44 days. I think the total power was something like 38 milliwatts, tape recorder and all, and that was long enough to give us a pretty good mapping of the radiation belts.

Did you continue with your graduate work at Iowa?

While I was in graduate school (at Iowa), I developed the instruments for a total of eight payloads.

Oral History – George Ludwig

(Continued)

Explorer I was successful, Explorer II failed to achieve orbit, Explorer III was successful, IV was successful – that was the so-called Argos experiment payload. Explorer V was a carbon copy of IV, but it failed to go into orbit. Explorer VII was the Juno I payload that carried our cosmic ray instrument along with others. There was an earlier launch attempt of Explorer VII called Payload 16, but it failed to go into orbit. Then, finally, my PhD thesis was based on the design of a complete satellite – shell and everything – at the University of Iowa. For that satellite I produced a thick manual which was used by students at the University as a guide for designing satellite payloads for a number of years. I completed my studies and research, and received my PhD degree in August 1960.

Considering the broad variation in the performance characteristics and reliability of the early transistors you used in building these satellite instruments, what types of failures did you see?

For the eight that I worked on, half of the launches were fully successful and half failed. None of the instruments failed on any of the payloads that I’ve ever built.

Go To Ludwig Oral History, Page 17

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