Von Braun envisioned these expeditions as very large-scale undertakings, with a total of 50 astronauts traveling in three huge spacecraft (two for crew, one primarily for cargo), each long and in diameter and driven by a rectangular array of 30 rocket propulsion engines. Upon arrival, astronauts would establish a permanent lunar base in the Sinus Roris region by using the emptied cargo holds of their craft as shelters, and would explore their surroundings for eight weeks. This would include a expedition in pressurized rovers to the crater Harpalus and the Mare Imbrium foothills.