Complex sentence: The balloons are superpressure balloons filled with helium, stand across and tall when fully inflated, and carry a custom air pump system dubbed the "Croce" that pumps in or releases air to ballast the balloon and control its elevation.
Split into simpler sentences: The balloons are superpressure balloons filled with helium, standing across and tall when fully inflated. They carry a custom air pump system dubbed the "Croce" that pumps in or releases air to ballast the balloon and control its elevation.