But the aerospace contractors McDonnell Aircraft, who built the Gemini capsule, and Martin Marietta, who built the Titan launch vehicle, wanted a piece of the high-profile lunar action.
To get a foot in the door they proposed hurtling a modified Gemini capsule onto a simple lunar round trip where astronauts would do photo reconnaissance of potential Apollo landing sites. Launched on a Saturn IB booster, a liquid fueled Centaur upper stage would kick the Gemini onto a so-called free-return trajectory around the moon. No additional rocket power would be needed to swing back to a splashdown on Earth.
This idea ratcheted up to putting a Gemini into a highly elliptical lunar orbit. The capsule would swoop only 10 miles above target Apollo landing sites. The space choreography was tricky. The Gemini capsule would be launched first on its military Titan booster. A few minutes later a second Titan would launched a so-called transtage that had the rocket power to head to the moon and back. The astronauts would dock their Gemini nose-first with the transtage and fire up its engine.
A big proponent of the Gemini moon mission, astronaut Pete Conrad convinced NASA to allow him to used the Agena stage they practiced docking with to boost himself and co-pilot Richard Gordon to a record-breaking altitude of 850 miles in 1966. This was a demonstration of how a Gemini moon mission would unfold.
The most far-out idea of all was the proposal to land two astronauts on the moon in a modified Gemini capsule. Proponents argued that the direct landing on the moon was simpler than the Apollo plan that called for a separate orbiter and lander that would need to rendezvous and dock above the lunar surface. A brawny Saturn V booster would still be needed to send the Gemini capsule moonward, mounted atop nested rocket motors and deployable landing legs.