This was the first of three “second generation” interplanetary probes (two flyby probes and one impact probe), designed to reach Mars, prepared by the Soviets for the late 1962 launch period.

Because of the repeated failures of the Blok L upper stage during deep space missions, engineers elected to outfit the stage for the Mars missions with supplementary control and measurement equipment. As a result, most of the scientific instruments were deleted from the Mars spacecraft. The three missions were primarily technological test flights rather than scientific missions.

In this case, the Blok L interplanetary stage failed again. Just 17 seconds after trans-Mars injection ignition, the turbopump of the main engine (the S1.5400A1) exploded, destroying the payload. The problem was traced to leaking lubricant. As many as 24 fragments were later tracked in a 923 X 112 mile (1,485 × 180 kilometer) orbit at 64.8 degree inclination, the largest of which reentered on Oct. 29, 1962.

The original probe was designed to fly by Mars on June 17, 1963.


Siddiqi, Asif A. Beyond Earth: A Chronicle of Deep Space Exploration, 1958-2016. NASA History Program Office, 2018.

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