The world had been fascinated with astronauts and spaceflight since well before the first crewed launches in 1961, when Yuri Gagarin, Alan Shepard, and John Glenn became household names. But when Alexei Leonov of the Soviet Union exited his spacecraft in March of 1965, a new era in spaceflight began. And when Ed White, clad in his gleaming space suit with the large American flag on his left shoulder, eased himself outside his Gemini IV spacecraft later that year, Americans too had a new space hero. They also learned a new acronym: EVA, short for extravehicular activity, more commonly known as "spacewalking."

Though few understood the tremendous risks White was taking in his twenty-two-minute spacewalk, Americans watched with immense pride and patriotism as White, tethered to the Gemini IV, propelled himself around the spacecraft with a pressurized oxygen-fueled zip gun. But White's struggle to fit his space-suited body back inside the claustrophobic Gemini spacecraft and close the hatch confirmed what NASA should have known: spacewalking wasn't easy.

More than fifty years and hundreds of spacewalks later, the art of EVA has evolved. The first spacewalks, preparation for walking on the moon, intended to prove that humans could function in raw space inside their own miniature spacecraft-a spacesuit. After the end of the lunar program, both the Americans and Soviets turned their focus to long-duration flights on space stations in low Earth orbit, and spacewalks were crucial to the success of these missions. The construction of the International Space Station-the most sophisticated spacecraft to date-required hundreds of hours of work by spacewalkers from many countries.

In Into the Void John Youskauskas and Melvin Croft tell the unique story of those who have ventured outside the spacecraft into the unforgiving vacuum of space as humans set our sights on the moon, Mars, and beyond.