Plant’s Big Rumble Comes at a Bad Time for Residents : Test firings: The sound of a rocket engine at Rockwell lab near Chatsworth unnerves many already jittery over news of events in the Persian Gulf War.

Former Thousand Oaks City Councilman Larry Horner and his wife, Betty, were watching television news coverage of the war in Iraq when a great rumbling sound suddenly filled the air.

“We were frightened to death,” Betty Horner said. “We thought it was airplanes.”

The Horners were not alone. Ventura County sheriff’s officials said they received more than 200 phone calls from residents Thursday after a 7:50 p.m. rocket engine test at Rockwell International’s Santa Susana Field Laboratory in the hills just west of Chatsworth.

The test firing of an Atlas engine, used to launch satellites into space, lasted 40 seconds and caused rumbling and shaking that could be heard and felt by residents throughout eastern Ventura County and in parts of western Los Angeles County.

“The whole switchboard lit up,” Ventura sheriff’s dispatcher Susie Allaire said. “People thought planes were flying overhead. They were afraid.”

Betty Horner, for one, was not surprised.

“I guess everybody’s a little jumpy because we have the war on television,” she said. “And that’s what we were thinking about last night.”

Allaire said the Ventura sheriff’s office near Simi Valley usually receives a few calls from residents during and after testing at the lab, but nothing like the number received Thursday night.

“People are always calling in, saying, ‘Was that an earthquake?,’ ” she said. “But in this case, because of the war, people are getting paranoid.”

Pat Coulter, a spokesman for Rocketdyne, said the company received about 20 calls from nearby residents.

“We certainly apologize to anybody that may have been concerned about the noise,” Coulter said. “Because of the sensitivity to what is going on . . . with the war, we want to do everything we can to be respectful to the community. We certainly understand how the community feels.”

Coulter said Thursday’s test had been scheduled weeks ago. Rocketdyne, as usual, gave prior notice of the test to the Ventura County Fire Department, which notified the Sheriff’s Department.

Coulter said most calls received by Ventura County authorities came from Thousand Oaks, Westlake and Agoura Hills. He said residents in these communities are not as accustomed to the rumbling and shaking that comes with the firing of rocket engines at the Rocketdyne plant as those who live in Simi Valley.

“I heard it at my home in Agoura Hills,” Coulter said. “It just happened that the wind was blowing in that direction. There is no way of predicting where the sound is going to come down.”

Coulter said a similar rocket engine test planned for Friday evening was rescheduled for this afternoon because of the commotion from Thursday’s test. He added that Rocketdyne is holding an open house today for the general public, beginning at 8 a.m. and continuing until about 4 or 5 p.m. He said visitors on the grounds at the time of the engine tests, which has notbeen determined, will be permitted to view it.