Gemini-8 (or officially "Gemini-VIII")
Disastrous space mission that resulted in the deaths of Charles "Pete" Conrad and Richard Gordon in 1968.
Launched on March 7th, as the third test of the "Agena" docking system, soon after docking Conrad and Gordon discovered that they were in a heavy roll. A faulty thruster in their OAMS system was locked in the "on" position.
Rotating at over a revolution per second, Conrad was unable to shut down the OAMS system before passing out. Their spacecraft continue to roll faster until fuel for the thruster finally ran out.
The spacecraft now totally out of control was rotating at over three revolutions per second and Conrad and Gordon's medical monitors showed their heartrates skyrocketing. Thirteen minutes after passing out, Gordon died of what was believed heart failure or choking. Conrad died two minutes after that.
Upon news of their death on March 8th, President Johnson held their state funerals in Washington. "Gemini-8" remained active for another two weeks, before the spacecraft's systems finally failed. NASA ended monitoring after that.
Launched into a high orbit, the spacecraft remained in space for another six years, before finally re-entering the atmosphere in December 1974. Unguided and still attached to its service components, it disentegrated in the upper atmosphere over southern Africa.