Just two men stood on the dusty surface of the moon after the first lunar landing in July 1969. But thousands and thousands of others — from scientists and technicians to clerks and doctors — worked long hours to make the voyage of Apollo 11 astronauts Neil Armstrong and Buzz Aldrin possible. Wallace Johnson, 93, of Alameda, played his part at a pivotal time when the future of America’s space program was in doubt. On Jan. 27, 1967, a flash fire killed astronauts Virgil “Gus” Grissom, Ed White and Roger Chaffee as they trained, leaving NASA administrators questioning whether the challenge offered by President John F. Kennedy of landing a man on the Moon — and bringing him safely home again — could be met. A few days later, Johnson got a call from his employer, North American Aviation, which had developed the command module in which the men died. The aerospace manufacturing company wanted Johnson, a pilot, to help figure out what went wrong. Johnson was fitted with a flight suit and helmet and sent inside another module at its plant in Downey, in Southern California. “We did everything we thought that they should have done to get out, trying to find out exactly what kind of timeline, the sequence of events that occurred,” said Johnson, who was picked for the job because he was an electronics and navigation systems expert. “What really happened?” The fire led to a congressional investigation and prompted the suspension of manned Apollo flights for 20 months. According to the findings, an electrical malfunction sparked the blaze which spread quickly because of the pure oxygen inside the cabin.The door hatch also could not be opened because of the internal pressure of the cabin, which prevented a rescue of the three astronauts. Johnson still boasts the wiry frame that allowed him to easily slip into one of the three seats in the module, where the tight quarters — it measured just about 13 feet in diameter and 11 feet long — made movement difficult for the astronauts. When he speaks in his soft Texas drawl, his voice is measured and his statements are matter-of-fact, as he if was working his way through a flight checklist. Johnson said he knew he was witnessing history during those days of NASA’s “Golden Age,” when families huddled around TV sets to watch rocket launches and TV shows such as “Lost in Space” and “Star Trek” teased that someday journeys to the stars might be commonplace. “It was such an exciting job,” said Johnson, who lives in a Shoreline Drive apartment facing Robert W. Crown Memorial State Beach. “I was very lucky. Everything just fell right into place for me.” Johnson’s tasks inside the command module often involved figuring out where was the best place to locate switches and other components so that astronauts could easily reach them. He also spent hours honing the capsule’s re-entry program — which had to be perfect, otherwise it could burn as it entered the Earth’s atmosphere — as well as what was needed for docking and rotating spacecraft, maneuvers that were necessary if a moon landing was to succeed. The information was then funneled to the astronauts, who then practiced and tweaked the procedures.