Burning up, blowing up or crash-landing is usually considered a bad thing for a space mission. But some of the most successful missions have ended when scientists deliberately steered them to their demise. For some spacecraft, such destruction was always part of the plan. Others had simply achieved their goals, budget outlays had run their course, the time had come to wind them down, and researchers realized that they had nothing left to lose by sending the probes on one last daredevil plunge.

View a slide show of five experiments pushed to the limits—and beyond.