Although NASA had been working on the Apollo program during much of Gemini, they required a much more powerful booster than Gemini’s Titan II missile. Thankfully, von Braun’s NASA team had been working on this for years. These new super-boosters would become the Saturn family of rockets. The most important, and the only rocket to transport humans to the moon, was Saturn V. This super heavy-lift rocket weighed 50 times more than the early Mercury boosters, packed 7.9 million pounds of thrust and came in 60 feet taller than the Statue of Liberty. To this day, it remains the tallest, heaviest and most powerful rocket ever used. NASA also needed to develop a new spacecraft to sit atop the Saturn V – one capable of landing on the moon. This Apollo spacecraft was designed to house three astronauts for over two weeks, and contained a detachable, four-legged Lunar Module that would transport two astronauts to the moon’s surface. But the Apollo program got off to a tragic start. With Apollo 1 due to launch on February 21, 1967, a full takeoff rehearsal had been scheduled for four weeks before. At 1:00 p.m. on January 27, astronauts Virgil Grissom, Ed White and Roger Chaffee were strapped into their seats. The spacecraft’s hatches were sealed, and the capsule was pressurized and pumped with pure oxygen. They began running through the huge preflight checklist, while ground crews labored to fix some minor technical issues. But at 6:30 p.m., ground control noticed a surge in voltage. Over the radio, they heard an astronaut shout, “We’ve got a fire in the cockpit!” There were howls of pain, and then everything went silent. The pressurized cabin and complex hatch made rescue impossible. A later investigation suggested that a short circuit in a bundle of wires had ignited a fire, which spread quickly inside the capsule’s pure-oxygen atmosphere. Carbon monoxide and black smoke suffocated the crew. The Mercury and Gemini missions hadn’t lost a single astronaut, but a simple rehearsal for Apollo’s first mission had killed three. The fire shook NASA and the American nation deeply. With sixteen successful manned missions, complacency had set in at NASA, and the public had started to believe spaceflight wasn’t dangerous. That changed after the Apollo 1 deaths. NASA stepped up its safety, reliability and quality control commitments, and created a list of 8,000 potential safety problems that needed to be tackled. They made 1,300 changes to the spacecraft alone. The Apollo program was still on.