2 Killed in Explosion at Rocketdyne in Simi Hills : Test site: A third man is seriously hurt. The blast, set off during work with rocket fuel, starts 15-acre brush fire.

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

The 9:13 a.m. blast at Rockwell International’s Rocketdyne Division plant--so powerful that some nearby residents mistook it for an earthquake--did not ignite any buildings on the guarded, 2,700-acre 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 cause of the blast at the 47-year-old lab was not immediately clear, and an investigation by fire officials and workplace safety investigators continued.

Rockwell spokesman Paul Sewell said the two Rockwell engineers who were killed were preparing a controlled burn of a catalyst used in solid fuel rocket motors on an outdoor test stand when the accident occurred.

The two men, who are believed to have died instantly, were identified as Larry A. Pugh, 51, of Thousand Oaks, and Otto K. Heiney, 53, of Canoga Park.

“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 taken by helicopter to the Burn Center at 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, with high-intensity explosive burns on the left side of his head, neck and arms.

“He said he was blown back five 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.”

Grossman said Wells, a 32-year Rockwell employee, had worked for 15 years with the two men who were killed. Two other workers, who also were not identified, escaped injury in the accident.

The Rocketdyne facility--which sprawls over an area so rugged that it has been used as a backdrop for Westerns--lies about 30 miles northwest of Downtown Los Angeles. It is perhaps best known as a rocket engine test site for the U.S. Air Force and the National Aeronautics and Space Administration, but nuclear research also has been done there.

Known as the Santa Susana Field Laboratory--or “Santa Sue,” in company parlance--the facility has been in operation since 1947, when it was opened by Rocketdyne’s predecessor, North American Aviation.

Its first mission was to dismantle and analyze a V-2 rocket like those the Germans had used to terrorize England during World War II. Since then, its employees, which currently number 742, have 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 communications satellites into space.

Safety has long been a concern at the plant, but other incidents there have chiefly involved problems with nuclear testing and environmental contamination.

For example, in 1959--in the early years of a nuclear research project that lasted through the 1980s--there was a partial meltdown of a small nuclear test reactor at the facility. Company officials later said the incident posed no danger to workers or the public.

And in 1989, public disclosure of lingering, low-level contamination from past nuclear projects prompted a public furor that led Rocketdyne to halt nuclear research at the site the following year.

In the energy research area of the site, the Department of Energy is funding a multimillion-dollar cleanup of buildings, soil and ground water tainted by chemicals and radiation. And in the rocket testing area, Rocketdyne is engaged in a long-term cleanup of ground water contaminated with chemical solvents used to rinse rocket engines.

But Tuesday’s accident is believed to be the first involving fatalities in the plant’s history, officials said.

According to Sewell, the experiment that set off the explosion involved 10 pounds of glycidal azide polymer and nitrocellulose, chemicals used to enhance the ignition of solid and liquid propellants in rocket engines. The material was to be tested to determine its characteristics so it could be properly packaged, labeled and transported, he said.

Ordinarily, the test explosion would be triggered electronically by technicians standing a safe distance away, Sewell said. He added that he did not know how far the victims were from the source of the blast.

“They were all near the (test stand) when the accident occurred,” he said.

Sewell 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 also was involved in the investigation.

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

Initially, the plant’s private fire department responded, but other agencies were called for assistance when the explosion ignited brush in the surrounding hills.

The blaze was put out by firefighters from Ventura and Los Angeles counties, along with Rocketdyne firefighters.

Meanwhile, nearby homeowners spent the morning wondering what had happened. At the Summit mobile home park on Woolsey Canyon Road, down the hill from the lab site, several residents said they thought the explosion was an earthquake because it had so shaken their walls.

“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 heat bending her metal awning.

“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 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.

Times staff writers Shawn Hubler, Mack Reed, Mary Pols and Jeannette Regalado and correspondents Julie Fields and Scott Hadly contributed to this story.

Plant Blast

An explosion ripped through Rockwell’s Santa Susana Field Laboratory on Tuesday.

Areas I-III: Used for rocket testing by NASA and other agencies.

Area IV: 230-acre site now leased by the U.S. Department of Energy, which contracts with Rockwell to operate its Energy Technology Engineering Center.

Plant profile

* Employees: About 750

* Size: 2,700 acres

* History: Established in 1947. Atlas ad Delta engines for Apollo missions and the space shuttle were built and tested here.

* Nuclear research: Rockwell used to operate test reactors and manufactured and recycled nuclear fuel for the Atomic Energy Commission and Department of Energy. Halted such research in 1989 after protests by neighbors and environmentalists. Rockwell is now undergoing a $40-million cleanup.