Bruce T. Lundin of the Lewis Research Center reported to members on propulsion requirements for various modes of manned lunar landing missions, assuming a 10,000-pound spacecraft to be returned to earth. Lewis mission studies had shown that a launch into lunar orbit would require less energy than a direct approach and would be more desirable for guidance, landing reliability, etc. From a 500,000 foot orbit around the moon, the spacecraft would descend in free fall, applying a constant-thrust decelerating impulse at the last moment before landing. Research would be needed to develop the variable-thrust rocket engine to be used in the descent. With the use of liquid hydrogen, the launch weight of the lunar rocket and spacecraft would be 10 to 11 million pounds.
If the earth orbit rendezvous concept were adopted, using Saturns to launch Centaurs for the lunar landing mission, nine Saturns would be needed to boost nine Centaurs into earth orbit for assembly to attain escape from earth orbit; three more Centaurs would have to be launched into earth orbit for assembly to accomplish the lunar orbit and landing; two additional Centaurs would be needed to provide for return and for the payload. The total of 14 Saturn/Centaur launches would be a formidable problem, not even considering the numerous complex rendezvous and assembly operations in space. The entire operation would have to be accomplished within two to three weeks because of the limitations on storing cryogenics in space.
Research would be needed on propulsion problems; on reliable, precisely controlled, variable-thrust engines for lunar landing; on a high-performance, storable-propellant, moon-takeoff engine; on auxiliary power systems; and on ground operations. Reduction of the ultimate payload weight was extremely vital, and more accurate information was needed on power and weight requirements for life support, capsule weight and size, and the exact scientific payload.
Lundin felt that a decision on whether to use the Saturn or Nova approach should be made as soon as possible since it would affect research and intermediate steps to be taken.