Sam Francis, co-founder of the Sippican Corp., played a critical role in the development of NASA's Lunar Excursion Module in the 1960s. Yesterday, he spoke of "a very sad day for us all," but also talked about what people in the space program know is inevitable. "This is hard to say, but we've done surprisingly well to go this long without having it happen again," he said. People get used to successful shuttle missions, but the truth, he said, is that "every flight is an experiment." "If we as a nation want to explore space and gain the things we can from it," Mr. Francis said, "the issue is to work hard to reduce incidents like this.But you're not going to eliminate them." "We need to go," he insisted. Why? "Learning.The environment in space is one you cannot duplicate and one where you learn all kind of things about how life works." The fact that "everyone is a party to the learning" is what deepens our emotional attachment to the astronauts, Mr. Francis said. Of the debate over manned versus unmanned flights, he said, "Unfortunately, with a lot of things you want to do, you have to have a human being who can change things on the spot."