Shepard was hit with Ménière’s disease, an inner-ear disorder that caused sporadic moments of nausea and extreme dizziness. Naturally, NASA couldn’t send someone prone to those side effects into space, so Shepard was forced to accept a desk job, which he loathed. For nearly six years, he frustratingly sat by and watched other astronauts take flight. However, in 1968, much-needed relief came. Photo Credit: NASA/Flickr