The test ran from the Zond program from 1967 to 1970, which produced multiple failures in the 7K-L1's re-entry systems.

[4] Kosmos 146 was a Soviet test precursor to the Zond series, launched from the Baikonur cosmodrome aboard a Proton K rocket.

It was a successful mission that created false confidence just before a string of failures that would follow.

[2] By the time the spacecraft was launched, the United States had already deployed prototypes of their lunar vehicle (AS-201, AS-202, AS-203) in low earth orbit.

The United States flight tests came to a halt when the crew of Apollo 1 was killed by a fire in the command module two months before the launch of Kosmos 146.