“The main trouble with the Mercury capsule was that most system components were in the pilot’s cabin; and often, to pack them in this very confined space, they had to be stacked like a layer cake and components of one system had to be scattered about the craft to use all available space. This arrangement generated a maze of interconnecting wires, tubing, and mechanical linkages. To replace one malfunctioning system, other systems had to be disturbed; and then, after the trouble had been corrected, the systems that had been disturbed as well as the malfunctioning system had to be checked out again.” James Chamberlin
This brings us to Project Gemini. Gemini started after Apollo had begun, in part to answer a crucial question for Apollo. Was rendezvous and docking in orbit a feasible basis for a manned lunar landing mission?
Mariner 4’s primary objective was to conduct closeup scientific observations of Mars and to transmit these observations to Earth. Additional goals included performing field and particle measurements in interplanetary space, and providing experience and knowledge of engineering capabilities for interplanetary flights of long duration…
From the Control center Yuri Gagarin’s kept the crew informed on everything taking place on the now deserted launching site. Finally the command was given: “Stand by!” Now, It would be a matter or minutes before the launch. Commands followed in quick succession. The flight recorder was switched on, the engines started up. There was not much noise at first. But, after the command “Main Engine” the noise and the vibration grew stronger. The final command came at 07:30 UT “Start!”