TED-Ed Lesson: In 1961, Yuri Gagarin piloted a spacecraft in humanity’s first manned space flight. A week later, Bell Aerosystems debuted a gas-powered rocket pack that could fly 35 meters in 13 seconds. Unfortunately, engineers knew this short flight was all the rocket pack could muster. So why was a massive spacecraft easier to send flying than a single pilot? Richard Browning investigates.