Transistor Museum Oral History George Ludwig Explorer I Transistors Page 8

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)

g) Raytheon 2N329 (2). SCEL-designed high voltage power supply.

h) Raytheon) CK791 (1). Pulse blanking circuit.

i) Texas Instruments 903 (8). NRL-designed receiver.

j) Texas Instruments 905 (2). High power transmitter modulator driver.

Texas Instruments 905 (11). Timer and counter.

Texas Instruments 905 (60). Scaling circuits.

Texas Instruments 905 (16). Multivibrators, recorder control, and amplifiers.

Texas Instruments 905 (5). Playback amplifier.

k) Texas Instruments 926 (1). JPL-designed receiver IF amplifier.

This is the total transistor complement that was in Explorer III. There were a total of 120 transistors in the satellite by my count, 7 in the upper low power system, and 113 in my cosmic ray instrument cylinder.

I’d like to back up a moment, to when I first started learning about transistors. There was very little experience with transistors.

Oral History – George Ludwig

(Continued)

Remember that this was only about ten years after the junction transistor was first invented. Point contact transistors came earlier, but they would not have served very well for the satellites – they certainly would not have withstood the shock. I remember having only one book that treated transistor circuit design, and it was based entirely on network theory. In other words, it treated a transistor as a network from a very theoretical point of view. It was almost impossible, certainly for me, to design actual circuits from this, at least at that stage of my training. My greatest source of ideas for circuits that I could try out was Electronics magazine (1956 and 1957). They carried a series of articles – they were very active when the transistors were coming out, and they were feeding test circuits to the experimenters frequently. So, from time to time, various ideas for circuits would appear, and I would try them out – primarily some circuits for scalers.

By the time I started the satellite design, in March 1956, most of the transistors I mentioned above didn’t exist yet. The Philco surface barrier SB100 was fairly prominent at that time, and a bunch of the Electronics magazine circuits called on the use of those transistors. So, I got a bunch of them and "breadboarded" some scaler circuits.

Go To Ludwig Oral History, Page 9

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