The ecliptic plane is the plane of the orbit of the Earth round the Sun. In a previous note the velocity requirements were examined for conventional rocket vehicles to enter reconnaissance orbits around the Sun in this plane.

Departure from the ecliptic plane obviously involves an increase in the velocity requirement. To some extent, all interplanetry voyages necessitate such motion, as the planets lie in planes inclined to the ecliptic. In this note, the extreme case of entry into orbits normal to the ecliptic will be considered.