Echoes of the Rocket Age: Remembering Simi Valley’s Sonic Past
(CLAIR | Simi Valley, CA) — From the 1960s through the 1980s, Simi Valley lived with a sound unlike any other American town — the sustained, mechanical roar of rocket engines under test.
The source was the Santa Susana Field Laboratory, a 2,800-acre complex carved into the hills between Simi Valley and Chatsworth, roughly five miles from the valley floor. There, engineers from Rocketdyne and Atomics International ran thousands of tests on engines built for the Apollo program, the Space Shuttle, and the nation’s missile defense systems.
Each firing produced enormous acoustic energy — sound levels above 150 decibels at the test stands, enough to register for miles. By the time those waves reached the neighborhoods below, the sound had become a deep, steady vibration: low-frequency pressure that made windows rattle, and the ground rumble. Residents described it as both powerful and strangely ordinary — a noise that had always been part of Simi city life.
The sound was often followed by sight. A thick white cloud would rise from top of the hill, billowing slowly into the sky before thinning out and fading away. It wasn’t smoke, but vapor — water used to cool and suppress the engines’ exhaust mixing with residual fuel. The plumes could stretch hundreds of feet high, visible from backyards and schoolyards across the valley. To anyone who lived here, that view — the hills and a single column of white climbing into clear air — was unmistakable.
It wasn’t frightening so much as constant. The roar came without warning, rolled for a few seconds, and stopped as cleanly as it began. Then came the silence — a hollow calm that reminded everyone how loud it had been.
At the same site, scientists were also pursuing nuclear research. In 1957, Atomics International’s Sodium Reactor Experiment delivered power to Moorpark, making it the first city in the United States to receive electricity from a commercial nuclear reactor. Two years later, the same reactor suffered a partial meltdown, releasing radioactive gas into the air — an incident the public wouldn’t learn about for decades.
Through it all, the testing continued. The sound and the clouds became part of daily life in Simi Valley — part nuisance, part marvel, entirely routine.
By the early 1990s, the tests stopped. The site closed and entered a long-term cleanup process, now overseen by Boeing, NASA, and the Department of Energy. The canyon is quiet these days. Most of the test stands have been dismantled or destroyed.
