I find that the biggest thing that is often mistaught/misunderstood is orbital mechanics. You dont get to the moon by aiming directly at the moon. You dont get to mars by aiming directly at mars.
Watching lil einsteins with my kid the other day. and in episode one they say "we've left gravity!" as they travel to space. Which clearly is not how it works.
I think the falling past the edge of the world repeatedly really helps people get a grasp on how orbit works. and once you get that concept down, you can move the sphere of influence to the sun and get space travel down.
Might depend on what grade "elementary" is. Kindergarden might struggle, but I bet 5th grade could handle it.