The RX-M's design was taken from rocket illustrations that appeared in an article in the January 17, 1949 issue of "Life" magazine. The interior structure of the spaceship's larger second stage is shown as having a long ladder that the crew must climb; it runs "up" through the RX-M's fuel compartment, which has on all sides a series of narrow fuel tanks filled with various propulsion chemicals. By selecting and mixing them together in various proportions, different levels of thrust are attainable from the RX-M's engines. The crew ladder ends at a round pressure hatch in the middle of a floor bulkhead that leads to the crew's upper living and control compartment.