NASA’s Parker Solar Probe is shown here mated to its third stage rocket motor on July 16, 2018, at Astrotech Space Operations in Titusville, Florida. In addition to using the largest operational launch vehicle, the Delta IV Heavy, Parker Solar Probe will use a third stage rocket to gain the speed needed to reach the Sun, which takes 55 times more energy than reaching Mars.
NASA/Johns Hopkins APL/Ed Whitman
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