Trouble began on the sixth day of the flight, November 17. The capsule developed an atmospheric leak, the pressure first dropping from 760 to 380 mm of Mercury. With the drop in cabin pressure all the animal test subjects died. It would have killed any Cosmonaut not wearing a spacesuit.
The first attempt for a Zond 4 follow-up launched on April 22. It failed when the Launch Escape System sent an erroneous abort command at T+260 seconds and shut down the Proton booster’s second stage. The escape rocket fired and pulled the descent module to safety.
When we left the Soviet Union they had somewhat successfully landed a probe on Venus and they had completed the automatic docking of two Soyuz 7K-OK spacecrafts. However they did not reach their goal of a circumlunar flight in time for the 50th anniversary of the glorious revolution.
After 1957, the Soviets became accustomed to achieving “world firsts” in space accomplishments. Nevertheless, 10 years later they were not confident that they could pull off the world’s first fully automatic rendezvous and docking of two un-piloted Soyuz spacecraft. At the time the chance for success was estimated at only 50/50.
“It’s a terrible scene. Komarov burned up. All the instruments burned. We must quickly find out what prevented the main parachute from unlatching.” Chief Designer Mishin after he arrived at the Soyuz 1 crash site.
“I was the last one to see him alive and I told him ‘See you soon!’” Yuri Gagarin, recalls bidding farewell to his friend Kamarov in Soyuz 1.
With the success of Kosmos 146 and in spite of the failures of the first three 7K-Ok’s it was now time to plan for a Soyuz manned mission. The planned involved the launch and docking of two piloted Soyuzes. Soyuz 7K-OK production model number 4 was assigned the role of the active vehicle. The active vehicle was supposed to carry one cosmonaut into earth orbit. Twenty-four hours later, vehicle No. 5 (the passive vehicle) carrying three cosmonauts would be inserted in orbit. After rendezvouing, two cosmonauts from vehicle No. 5 would transfer through open space to vehicle No. 4.
Chief Designer Mishin proposed a two-launch “stopover” scenario for the piloted flight to the moon. This was similar to one of NASA’s earth orbit rendezvous modes to reach the moon. The gist of the plan was, the UR-500K would insert the 7K-L1 into orbit with no crew. Then the R7 derivative Semyorka would launch the 7K-OK carrying two cosmonauts. If everything went well on the two vehicles, they would dock, and the cosmonauts would transfer from the 7K-OK to the 7K-L1 via spacewalk. Then they would set out for the Moon, and, after flying around it, they would return to Earth.