Military industrial giant Rocketdyne has been reeling in the last few weeks from a barrage of negative publicity about pollution problems at its Santa Susana Field Laboratory. Sen. Barbara Boxer has demanded a more stringent cleanup at the San Fernando-Simi-valleys straddling site. And Channel 2 News produced a four-part expose on the contamination, albeit one that largely covered territory mined earlier by Offbeat. But what really caught our attention was the admission by a NASA official that the pollution at and around the lab stemmed in part from military testing. At a public task force meeting concerning the laboratory cleanup, the NASA official said that 77 percent of the 21,509 engine tests conducted from 1954 to 1983 at the Santa Susana Field Laboratory were for the Department of Defense. Rocketdyne officials had accused this reporter of lying last year when we disclosed that the company was a major supplier of America's nuclear arsenal. Now we learn that not only were engines for the nuclear-tipped Navaho, Atlas and Jupiter missiles tested at the Rocketdyne site. The process involved hosing down the engines with 1.73 million gallons of the extremely poisonous solvent TCE. The runoff was funneled into a pond; about a third of it eventually seeped into the soil, contributing to the contamination problems at the site today, according to the NASA official.