The earliest known liquid rocket motor tests near the present site of JPL were done between October 1936 and January 1937 in the Arroyo Seco by a group of Caltech graduate students, under the guidance of Theodore von Kármán, the first director of JPL. This image was taken on November 28, 1936, and is one of several photos of the test series. Although a bit fuzzy, it shows the motor producing thrust, as evidenced by the two-foot flame being emitted from the rocket nozzle.

For more information about this series of tests, see the November 1998 Historical Photo of the Month, which features a labeled drawing by graduate student Frank Malina of a similar test configuration, or contact the JPL Archives.