NASA’s Parker Solar Probe will achieve a heliocentric velocity of 200 km/s (nearly 500,000 mph) and skim just 6.0 million km (3.7 million miles) above the Sun’s surface, far closer than Mercury. It will endure 1400° C behind an innovative carbon-fiber heat shield. In the mission’s two dozen passes through 2025, flybys of Venus will decelerate it to bring its perihelion closer to the Sun. Scheduled for launch July 31, 2018 on a Delta IV Heavy. More details.