2 Killed in Rocketdyne Explosion : Test: The men die instantly from the chemical blast at the Simi Hills lab. A third worker is seriously injured. The cause is not known.

Two men were killed instantly and a third seriously injured Tuesday morning when a chemical explosion ripped through Rockwell International’s rocket engine test site on a rugged plateau in the Simi Hills.

The 9:13 a.m. blast at the Santa Susana Field Laboratory--so powerful that some nearby residents mistook it for an earthquake--did not ignite any buildings at the guarded, 2,700-acre hilltop facility.

It did, however, touch off a brush fire in the boulder-strewn chaparral surrounding the plant. The fire blackened 15 acres and was extinguished in an hour, authorities said.

The explosion’s victims were preparing for a controlled burn of a catalyst used in solid fuel rocket motors when something went wrong, said Rockwell spokesman Paul Sewell. The three Rockwell employees were standing near an outdoor 10-by-12-foot steel test stand at the time of the blast, he said.

“It was not supposed to explode,” Sewell said.

The cause of the blast at Rockwell’s Rocketdyne division was not immediately clear, and an investigation by fire officials and work place safety investigators continued. Although officials were still reviewing company records, Tuesday’s accident is believed to be the first fatal accident in the plant’s 47-year history.

The two men killed were identified as Larry A. Pugh, 51, a Thousand Oaks engineer who had worked for Rockwell since 1977, and Otto K. Heiney, 53, of Canoga Park, who had been an engineer with the company for 10 years. A Rockwell official was en route to Florida on Tuesday afternoon to deliver the news to Heiney’s wife.

“These were co-workers, these were friends and people we all knew very well,” Sewell said. “And we tremendously hate to see them lost.”

The injured worker, Lee Wells, 62, of Newbury Park was taken to Simi Valley Hospital, and later airlifted to the burn center at the Sherman Oaks Community Hospital.

Wells, a chief test mechanic for Rockwell’s Rocketdyne division, suffered second- and third-degree burns over 20% of his body, mostly on the left side of his head, neck and arms.

“He said he was blown back 5 feet, and he hit the hill,” said Dr. Richard Grossman, director of the burn center. “He has cuts on his face. It was probably from some kind of metal.”

Bill Fick, a friend and neighbor, described Wells as a devoted and highly skilled Rockwell employee.

“I’m upset and a little shocked, because he’s such a cautious guy, real clean, careful,” Fick said. “He’s very mechanically inclined. I knew he worked with rocket engines and testing, but I had no idea that he worked with chemicals.”

Fick said he is confident that Wells will fully recover.

“He’s a tough old goat,” Fick said. “He’ll battle through this.”

Grossman said Wells, a 32-year Rockwell employee, had worked with the two men who were killed for 15 years.

Two unidentified Rockwell workers who participated in the test escaped injury in Tuesday’s accident.

Sewell said the experiment involved 10 pounds of glycidal azide polymer and nitrocellulose, chemicals used to enhance the ignition of solid and liquid propellants used in rocket engines. He said the material was to be burned to determine its characteristics so it could be properly packaged, labeled and transported.

Ordinarily, the test burn would be triggered electronically by technicians standing a safe distance away, Sewell said. “They were all near the (test stand) when the accident occurred,” he said.

The accident is being investigated by Rockwell, Cal/OSHA and Ventura County fire officials. Ventura County sheriff’s officials said that the U.S. Air Force was also involved in the investigation.

“We’re going to find out the cause of the accident,” Sewell said.

The Santa Susana Field Laboratory is perhaps best-known as a rocket engine test site for the U.S. Air Force and the National Aeronautics and Space Administration. The facility has been in operation since 1947, when it was opened by Rocketdyne’s predecessor, North American Aviation.

Rockwell has tested engines for virtually every U.S. rocket program, including the space shuttle and the first manned flight to the moon. Current work includes testing of Atlas and Delta rocket engines that propel communication satellites into space, and the development of hardware for NASA’s space station project.

The last publicized accident to occur at the lab site was on Aug. 25, 1988. In that accident, a 52-year-old engineer lost his hand in an explosion that occurred while he was mixing a small quantity of solid propellants used to make rocket fuel. A similar accident occurred in 1985 at Rockwell’s Canoga Avenue plant involving a research chemist who was severely burned while mixing solid propellants.

Despite Tuesday’s accident, officials at Rockwell, which employs 742 people at the Santa Susana Lab, did not call for an evacuation. No buildings were damaged and the 15-acre brush fire ignited by the blast was quickly extinguished by Rockwell’s own fire department working with crews from the Ventura and Los Angeles county fire departments.

Several residents of the Summit mobile home park on Woolsey Canyon Road, down the hill from the lab, said they thought the explosion was an earthquake because it shook their walls slightly.

“We heard a boom and the windows rattled a bit,” said Melissa Barros, 32, who was staying with her sister in a double-wide mobile home overlooking the San Fernando Valley.

Down the street, Barbara Cole said she heard a “little pop” and thought it was an aftershock or the rising heat causing her metal awning to bend.

“I saw helicopters and thought they must be looking for something,” she said. “But there’s always helicopters and planes flying over. I never thought it was Rocketdyne.”

None of the hilltop mobile home residents saw smoke from the small brush fire, but Kurt Horstman, 30, said he noticed an acrid smell shortly after the explosion.

“It did smell pretty bad, but that’s about it,” he said.

Holly Huff, a 22-year resident of nearby Black Canyon Road and leader of a neighborhood effort to learn more about Rockwell’s Santa Susana operations, said she is eager to know the exact cause of Tuesday’s accident.

“Of course a million things go through your mind when Rocketdyne’s been part of your whole life,” she said. “What were they doing? What were the chemicals doing? What were they mixing them for?”

Times staff writers Mary Pols and Jeannette Regalado and correspondents Julie Fields and Scott Hadly contributed to this story.

* UNDER PRESSURE: Lab has played role in U.S. rocket history. A8