Kerbolar Probe Challenge:
Primary: Build a replica of the Parker Solar Probe. Don't forget your heat shield!
Secondary: Place your probe into a Kerbolar orbit with an apoapsis below 1Gm.
Jeb: Take advantage of Eve gravity assists to lower your probe's orbit as much as possible.
Val: Use a Jool gravity assist to establish a low Kerbolar periapsis, then gravity assist off Eve and Kerbin to lower your apoapsis.
How looooow can you gooooo?