APOLLO VENUS!

Today's post is a pull from Wikipedia- I couldn't resist because it's just so cool. As NASA was staring down the end of the Apollo missions, the Apollo Applications Office was considering a plan that had been under study for years- Apollo Venus. The idea was to send a "wet workshop"- an SIVB stage which could be used as a space station once empty- out to loop around Venus with a crew in a Command Module. The science intended in this mission would soon be carried out by robotic probes, but how cool would a manned flight past Venus be?

From Wikipedia: The proposed mission would use a Saturn V to send three men to fly past Venus in a flight which would last approximately one year. The S-IVB stage would be a 'wet workshop' similar to Skylab, first using the S-IVB engine to launch the mission on course to Venus, and then vented of any remaining fuel to serve as home for the crew for the duration of the mission. The Apollo SM engine would be used for course corrections on the way to Venus and back to Earth, and for a braking burn before the Command Module re-entered Earth's atmosphere. In order to free up more space in the Spacecraft Lunar Module Adapter for the docking tunnel connecting the CSM to the S-IVB, the SPS engine on the Service Module would be replaced by two LM engines. These would provide similar thrust with shorter nozzles, and would also give the mission the added safety of redundant engines.
Precursors to the Venus flyby would include an initial orbital test flight with an S-IVB 'wet workshop' and basic docking adapter, and a year-long test flight taking the S-IVB to a near-geostationary orbit around the Earth.
One oddity of the Venus flyby mission is that, unlike trips to the Moon, the CSM would separate and dock with the S-IVB stage before the S-IVB burn, so the astronauts would fly 'eyeballs-out', the thrust of the engine pushing them out of their seats rather than into them. This was required because there was only a short window for an abort burn by the CSM to return to Earth after a failure in the S-IVB, so all spacecraft systems needed to be operational and checked out before leaving the parking orbit around Earth to fly to Venus.